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  • The influence of oxygen on thermal decomposition characteristics of epoxy resins cured by anhydride
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-18
    Xiaoxing Zhang, Yunjian Wu, Hao Wen, Guoxiong Hu, Zilai Yang, Jingsong Tao

    Anhydride cured epoxy resins are always used as pivotal solid insulation medium in many electrical equipment, which will decompose due to the high temperature caused by partial discharge and the presence of oxygen will aggravate this process. In order to explore the influence of oxygen on the thermal decomposition characteristics of epoxy resin cured by anhydride, simulation models are established in this paper. The ReaxFF force field is used to simulate the pyrolysis process of epoxy resin and the changes in production of small molecular gases (such as CO2, H2O, CO and CH2O), and C2, C3 are discussed. The results show that the oxygen will affect the main chain of the epoxy resin by introducing a carbon-oxygen double bond to the tertiary carbon atom attached to oxygen atom. Meanwhile, with the presence of oxygen, all the products' initial generation time will be earlier, the amount of CO2 will increase, the amount of H2O will go up dramatically while that of CH2O remain basically unchanged, the types and quantities of C2 and C3 products increase obviously, mainly reflected in the oxygenated products.

    更新日期:2018-08-18
  • Three-dimensional printing of PLA and PLA/PHA dumbbell-shaped specimens of crisscross and transverse patterns as promising materials in emerging application areas: Prediction study
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-18
    Jennifer Gonzalez Ausejo, Joanna Rydz, Marta Musioł, Wanda Sikorska, Henryk Janeczek, Michał Sobota, Jakub Włodarczyk, Urszula Szeluga, Anna Hercog, Marek Kowalczuk

    This paper presents ex-ante examination of advanced polymer materials to detect defects and define and minimize the potential failure of novel polymer products before they arise. The effect of build directions on the properties of dumbbell-shaped specimens obtained by three-dimensional printing from polylactide and polylactide/polyhydroxyalkanoate commercial filaments was investigated, as well as the hydrolytic degradation of these specimens at 50 °C and 70 °C. Taking into account previous studies, we have found further dependences of the properties of 3D printed species before and during abiotic degradation from the orientation of printing. The initial assumption that only the contact time with the 3D printer platform leads to an increase in the crystalline phase during printing turned out to be insufficient. Further investigations of individual parts of the dumbbell-shaped specimens showed that the size of the specimens' surface in contact with the platform also affected the structural ordering of the material.

    更新日期:2018-08-18
  • Fabrication of high-expansion microcellular PLA foams based on pre-isothermal cold crystallization and supercritical CO2 foaming
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-18
    Bo Li, Guoqun Zhao, Guilong Wang, Lei Zhang, Jie Gong

    Poly(lactic acid) (PLA) is a kind of bio-based and biodegradable polymers. PLA foams with high expansion ratio have great application potential in heat insulation, adsorption and other areas. However, due to its low melt strength and slow crystallization rate, linear PLA has poor foaming ability, so it is hard to prepare PLA foams with high expansion ratio. Although chain branching, blending, and other methods have been utilized to improve PLA's melt strength and foaming ability, they easily destroy PLA's biodegradability, cause chemical pollution, and raise production costs. In this study, a new supercritical fluid foaming process, based on pre-isothermal cold crystallization, was proposed to prepare PLA foams with high expansion ratio. To improve PLA's melt strength and foaming ability, a pre-isothermal treatment was applied to induce sufficient cold crystallization. According to the SEM results, the cold crystallization of PLA becomes more sufficient and the crystal morphology becomes more perfect with the pre-isothermal treating. The DSC and WAXD results confirm that, the pre-isothermal treatment remarkably promotes the PLA's cold crystallization, and endows the PLA sample higher crystallinity and more perfect crystalline structure. Moreover, the high-pressure rheology testing results indicate that the pre-isothermal treatment improves the PLA's melt viscoelasticity significantly. Finally, the foaming results show that the pre-isothermal treatment significantly enhances the PLA's foaming ability. With the pre-isothermal treatment, the PLA's maximum expansion ratio increases from 6.40-fold to 17.7-fold, and the uniformity of cellular structure is also improved obviously. The new process provides a green, flexible, and low-cost way to prepare fully biodegradable PLA foams with high expansion ratio.

    更新日期:2018-08-18
  • Performance comparison of flame retardant epoxy resins modified by DPO–PHE and DOPO–PHE
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-15
    Junjing Zhao, Xu Dong, Shan Huang, Xiujuan Tian, Liang Song, Qing Yu, Zhongwei Wang

    Two phosphorus-containing flame retardants, (bis(4-hydroxyphenyl)methyl)diphenyl phosphine oxide (DPO–PHE) and 1-(bis(4-hydroxyphenyl)methyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO–PHE) were synthesized and characterized. The two target compounds both were used as a flame retardant and a co-curing agent of 4,4′-diaminodiphenylsulfone of bisphenol A diglycidyl ether to prepare flame-retardant epoxy resins (EP/DPO–PHE and EP/DOPO–PHE). The thermal and flame-retardant properties of the thermosets were investigated by thermogravimetric analysis (TGA), limited oxygen index (LOI) measurement, and UL-94 vertical burning testing (UL-94). The results indicated that both flame retardants can improve the flame retardancy of epoxy thermosets. TGA results indicated that the char yields of EP/DPO–PHE–P-0.9 and EP/DOPO–PHE–P-0.9 thermosets were increased from 19.1% of EP/P-0 to 25.3% and 27.8%, respectively. Compared with that of EP/P-0, the LOI of the EP/DPO–PHE–P-0.5 thermoset increased from 23.7% to 30.1%, and the sample reached UL-94 V-0. Meanwhile, the LOI of the EP/DOPO–PHE–P-0.7 thermoset increased from 23.7% to 28.9%, and the sample reached UL-94 V-0. Cone calorimetry test, scanning electron microscopy of burning residues, and pyrolysis–gas chromatography/mass spectrometry indicated that both flame retardants mainly act through the gas–phase mechanism. In addition, no condensed-phase activity of DPO–PHE was observed, whereas the condensed-phase activity of DOPO–PHE was negligible. Immersion experiments showed that the water absorption activity of flame retardant epoxy resins fluctuates. Compared with DOPO–PHE, DPO–PHE was more effective as a higher flame-retardant and exhibited better characteristics for improving the Tg, thermal stability, and water absorption of modified resins.

    更新日期:2018-08-15
  • 更新日期:2018-08-15
  • UV degradation of styrene-butadiene rubber versus high density poly(ethylene) in marine conditions studied by infrared spectroscopy, micro indentation, and electron spin resonance imaging
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-12
    Miroslav Šlouf, Jan Pilař, Jiří Dybal, Ivana Šloufová, Danuše Michálková, Miroslava Lukešová, Oleg Zgadzai, Aharon Blank, Sergey K. Filippov

    UV irradiation and thermal degradation were studied in marine conditions for styrene-butadiene rubber (SBR) and high density poly (ethylene) (HDPE) containing a Tinuvin® 770 hindered amine stabilizer. Electron spin resonance imaging (ESRI) was used to monitor degradation process in various depths and compare the polymers in terms of robustness to UV irradiation. In addition, both oxidative degradation and mechanical properties were studied by microscale methods, such as infrared microspectroscopy (IR) and microindentation hardness testing (MHI), enabling us to compare the material changes locally, i.e. both at the exposed surfaces and inside the samples. In SBR/Tin770 system, Tinuvin®770 stabilizer failed to protect the polymer matrix against photooxidation as clearly seen from IR/ATR spectra. The Weather-Ometer (WOM) aging resulted in strong oxidative degradation of both non-stabilized and stabilized SBR and caused remarkable changes in three regions of IR/ATR spectra. The strong photooxidative degradation was also manifested through the micromechanical properties of SBR/Tin770 systems. The change of the local properties was the same (within the standard deviations) for both stabilized and non-stabilized samples, which confirmed negligible stabilization efficiency of Tinuvin® 770 in the SBR system. In contrast to the SBR systems, similar experiments showed very dramatic stabilization effects in the HDPE/Tin770 system. ESR and 2D spectral-spatial ESRI directly proved the different degradation behavior of the two types of the composites: whereas in the SBR composites fast degradation was observed, high density poly (ethylene) showed much slower degradation. We attributed such striking difference to the modification of Tinuvin® 770 hindered amine stabilizer after vulcanization during preparation of SBR rubber, which apparently eliminated most of its protective activity.

    更新日期:2018-08-13
  • Synthesis and characterization of novel poly(ethylene furanoate-co-adipate) random copolyesters with enhanced biodegradability
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-09
    Lazaros Papadopoulos, Andreas Magaziotis, Maria Nerantzaki, Zoi Terzopoulou, George Z. Papageorgiou, Dimitrios N. Bikiaris

    In this study, copolymers based on poly (ethylene furanoate) (PEF) and poly (ethylene adipate) (PEAd) were synthesized by melt polycondensation using 2,5-dimethyl furan dicarboxylate (DMFD), adipic acid (AA) and ethylene glycol (EG) in different proportions. The success of the reaction, crystallographic characteristics, molecular weight and thermal properties were determined with Nuclear Magnetic Resonance Spectroscopy (1H-NMR), Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The results confirm the successful synthesis of random copolymers, with high thermal stability, which exceeds 300 °C. Also, isodimorphic cocrystallization was concluded from both XRD patterns and DSC thermograms. The enzymatic hydrolysis rate of the copolyesters depended on comonomer ratio. Copolymers with 95 and 90 mol% of ethylene adipate (EAd) were completely degraded after 30 days.

    更新日期:2018-08-10
  • Rapid mass calorimeter as a high-throughput screening method for the development of flame-retarded TPU
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-10
    Aleksandra Sut, Elke Metzsch-Zilligen, Michael Großhauser, Rudolf Pfaendner, Bernhard Schartel
    更新日期:2018-08-10
  • Phosphorus flame retardants from isosorbide bis-acrylate
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-02
    Y.G. Daniel, B.A. Howell

    The increasing concern about the potential negative health effects of traditional organohalogen flame retardants have placed these compounds under increasing regulatory pressure around the world. There is a growing need to develop new, nontoxic, biocompatible or biodegradable flame retardant agents. Phosphorus compounds derived from renewable biosources offer great potential to meet this need. Isosorbide is a dihydroxy ether available from starch. It may be readily converted to the corresponding bis-acrylate ester. This compound undergoes Michael addition of phosphites to provide a number of phosphorus compounds which display good flame retardancy in DGEBA epoxy.

    更新日期:2018-08-02
  • High-efficiency glycolysis of poly(ethylene terephthalate) by sandwich-structure polyoxometalate catalyst with two active sites
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-02
    Pengtao Fang, Bo Liu, Junli Xu, Qing Zhou, Suojiang Zhang, Junying Ma, Xingmei lu

    Catalyst in the process on glycolysis of poly (ethylene terephthalate) (PET) wastes is a significant critical factor, which determine the efficiency and the cost of PET degradation. In this study, a kind of transition-metal-substituted polyoxometalates (POMs) Na12 [WZnM2(H2O)2(ZnW9O34)2] (M = Zn2+, Mn2+, Co2+, Cu2+, Ni2+) which have a sandwich-structure and more than two transition metal active sites show excellent catalytic performance in the glycolysis of PET under mild conditions. We investigated the effects of temperature, reaction time and catalyst amount on PET degradation and obtained the glycolysis optimal conditions. The PET could be fast and completely degraded at 190 °C for 40 min with low catalyst/PET molar ratio (0.018%) and high PET/Ethylene Glycol (EG) weight ratio (1:4), and the yield of bis(hydroxyethyl) terephthalate (BHET) is higher than 84.5%. After four-times recycling, the conversion of PET and the yield of BHET can still reach 100% and 84.5%. The exact structure of POMs Na12 [WZnM2(H2O)2(ZnW9O34)2] is confirmed by Single Crystal X-ray Diffraction (SC-XRD). Compared with traditional heteropolyacid catalysts, this catalyst possessed of at least two transition metal active sites, which lead to its an excellent catalytic capacity. The possible coordination activates mechanism for PET glycolysis is also proposed.

    更新日期:2018-08-02
  • Disulfide-containing polyamidoamines with remarkable flame retardant activity for cotton fabrics
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-08-01
    Amedea Manfredi, Federico Carosio, Paolo Ferruti, Jenny Alongi, Elisabetta Ranucci
    更新日期:2018-08-01
  • Effects of graphene on thermal oxidation of isotactic polypropylene
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-31
    A.L. Margolin, T.V. Monakhova, P.M. Nedorezova, A.N. Klyamkina, S.V. Polschikov
    更新日期:2018-07-31
  • Synthesis and flame retardant properties of cyclophosphazene derivatives containing boron
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-30
    Lianghui Ai, Shanshan Chen, Jinming Zeng, Ping Liu, Weishi Liu, Yonghong Pan, Dongfa Liu
    更新日期:2018-07-31
  • Inhibition of algae growth on HVDC polymeric insulators using antibiotic-loaded silica aerogel nanocomposites
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-29
    Shifang Yang, Zhidong Jia, Xiaogang Ouyang, Shihao Wang

    Algae contamination has been observed on high-voltage direct current transmission (HVDC) polymeric insulators in tropical and subtropical areas, and this has an impact on the outdoor insulation performance. In this paper, the antibiotic 4,5-dicholoro-2-octyl-2H-isothiazolone-one (DCOIT) was chosen to be loaded onto the porous silica aerogel through sol-gel and dip-molding methods; the nanocomposites were mixed with base silicone rubber to prepare the antibiotic polymeric insulator. The algae inhibition properties of the insulators were characterized by the damaged membrane rate, photosynthesis rate (SAT) and chlorophyll-a density (Chl) of the algae cells. The results showed that the antibiotic insulators were free from algae colonization and that the extermination process could be completed within 21 days. During the antibiotic treatment process, the specimen surface stayed hydrophobic because of the water repellent property of nano silica. Meanwhile, due to its excellent dispersibility and electrical resistivity, the volume conductivity and surface conductivity were slightly increased in the initial period within insulation margins. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of antibiotic-containing insulators was carried out, and the intermediate products in the treatment process were verified. After algae apoptosis, the functional group on the silicone rubber was returned to its initial condition before algae colonization. After application on-site for 1 year, the antibiotic-loaded insulators retained antibiological properties without algae spots upon their surfaces.

    更新日期:2018-07-30
  • Kinetics study of the fully bio-based poly(propylene succinate) synthesis. Functional group approach
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-30
    Paulina Parcheta, Janusz Datta

    Currently, the increasing importance of the bio-based chemical compounds development is visible in the polymer chemistry, chemical engineering and materials science. It is well-known that the various purity level and different contaminants characterize petrochemical-based compounds compared to their bio-based counterparts. Therefore, it is necessary to find out the contaminants impact on the bio-based monomers synthesis. One of the most important information about the reaction pathway gave the kinetics study. In this work, the fully bio-based poly (propylene succinate)s were synthesized under various temperature conditions via two-step polycondensation reaction. The kinetics studies were investigated with the use of a functional group approach. The first step of the polycondensation reaction was autocatalytic esterification reaction. During the second step, the polycondensation catalyst was used. For macromolecular structure characteristics and the progress of the chemical reaction monitoring, Fourier Transform Infrared Spectroscopy, Proton Nuclear Magnetic Resonance, and Gel Permeation Chromatography were conducted. The activation energy value of 38.5 kJ/mol was determined for the first step of the bio-based polyols synthesis. The results of the investigations verified that the activation energy for the bio-based poly (propylene succinate) synthesis revealed lower value than the same polyester synthesis based on the petrochemical monomers. Thermal analysis by TGA measurements allowed confirmed the high thermal stability of the prepared bio-based polyols equaled ca. 418 °C.

    更新日期:2018-07-30
  • Microstructure evolution of polyimide films induced by electron beam irradiation-load coupling treatment
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-25
    Shan-Shan Dong, Wen-Zhu Shao, Li Yang, Hui-Jian Ye, Liang Zhen

    Polyimide films are widely used in space with extreme environments, where high energy beam irradiation and corresponding coupling treatment could occur. The combined effect of high energy electrons (1.2 MeV) and high tensile stress (50 MPa) on the degradation behavior of polyimide films was studied by means of scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and mechanical testing. The degradation of polyimide films was evaluated by analyzing the microstructure and mechanical properties. The results indicated that the external tensile stress and irradiation coupling treatment resulted in the breakage of a larger number of chemical bonds and greater deterioration of the surface quality when compared with the irradiated polyimide samples. After irradiation-load coupling treatment, numerous micro-cracks were formed on the polyimide surface, facilitating the diffusion of oxygen into polyimide films and thus increasing the probability of free radical reactions. Moreover, the coupling treatment led to a more significant decrease in tensile strength and elongation of polyimide films by 10% and 35%, respectively. The mechanism of molecular chains' scission and crosslinking as well as correlations between molecular chains and mechanical performances were discussed. The obtained results indicated that the external tensile stress accelerates the degradation process during electron beam irradiation; thus, the tensile stress potentially seriously deteriorates polyimide film properties in irradiated environments.

    更新日期:2018-07-25
  • In-field aging process of high content SBS modified asphalt in porous pavement
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-24
    Raqiqa tur Rasool, Yao Hongru, Adeel Hassan, Shifeng Wang, Haiyan Zhang

    Highly modified asphalt (>6.0 wt% styrene butadiene styrene copolymer, SBS) has been extensively used for extending the durability of porous asphalt (PA) pavement. In depth knowledge of the in-field aging of different PA layers is needed because the natural aging of PA possessing around 20% voids content severely affects its properties. The field core samples were taken from sections of the Shanghai Highway which had aged 6 years and 9 years outdoors. The recovered modified binders from different layers (top, middle and bottom) of the PA were evaluated by chemical and rheological characterization. After undergoing outdoors aging, chemical characterization showed that the carbonyl and sulfoxide content of the modified binders had increased for the top layers. The intensities of peaks for bottom layers were lower, demonstrating that the top part of the PA was more exposure to real weather aging. Aging in the degradation of SBS, evaporation of lighter components, oxidation and condensation of the asphalt produces variations in the rheological properties of the recovered binders. Rheological characterization revealed that the highly modified binders continue to perform well even after 6 years and 9 years of outdoor aging.

    更新日期:2018-07-24
  • Synthesis, photodegradable and antibacterial properties of polystyrene-cinnamaldehyde copolymer film
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-24
    Umeka Nayanathara, Nilwala Kottegoda, Inoka Perera, Thilini Kuruwita Mudiyanselage

    Copolymerization of styrene (St) and different ratios of Cinnamaldehyde (Cin) from cinnamon oil and synthetic cinnamaldehyde were carried out by free radical polymerization, and were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC) analysis, and Gel Permeation Chromatography (GPC). Photodegradation of cinnamaldehyde incorporated copolymer (Poly (St-co-Cin)) films have been studied at outdoor weathering and under direct ultraviolet (UV) radiation. The extent of photodegradation was assessed by FTIR spectroscopy, percentage weight loss, surface analysis, average molecular weights and polydispersity indices. FTIR analysis confirms the photodegradable mechanisms of the copolymer films as Norrish Type I, Norrish Type II and photo-oxidation. Extreme weight loss was observed at outdoor weathering with 36.76% weight loss for 75% (w/w) cinnamaldehyde (natural-from cinnamon oil) incorporated copolymer (Poly(St-co-N-Cin)), and 45.58% weight loss for 75% (w/w) cinnamaldehyde (synthetic) incorporated copolymer (Poly(St-co-S-Cin)) with respect to 2.5% weight loss for polystyrene (PS) homopolymer for the period of 100 days. The average molecular weights of Poly(St-co-Cin) copolymers after outdoor weathering have drastically reduced compared to polystyrene. Scanning Electron Microscope (SEM) images clearly depict the fracture generation on Poly(St-co-Cin) films upon degradation. Embrittlement and color developments of the copolymer films with aging were noticeably evident. Furthermore, copolymers were tested positive for antibacterial activity against both gram negative and gram positive bacteria.

    更新日期:2018-07-24
  • Flame retardancy effect of combined ammonium polyphosphate and aluminium diethyl phosphinate in acrylonitrile-butadiene-styrene
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-23
    Vera Realinho, Laia Haurie, Joan Formosa, José Ignacio Velasco

    The present work investigates the fire retardancy mechanism of ammonium polyphosphate (APP) and aluminium di-ethyl phosphinate salt (AlPi) in an acrylonitrile-butadiene-styrene copolymer (ABS) by analysing the pyrolysis, flammability and fire behaviour. Evidences of synergy in flammability by combining both flame retardants were discussed and related to flame retardant mechanisms assessed by means of TGA and FT-IR analysis of the pyrolysis gases. Specifically, the ABS flame retardant formulation with a 12.5 wt% APP and 12.5 wt% AlPi (ABS-APP/AlPi) reached a UL-94 V-0 classification, unlike the ABS with 25 wt% APP (ABS-APP) and ABS with 25 wt% AlPi (ABS-AlPi) formulations, which completely burned. Under forced flame conditions, APP and AlPi showed, respectively, a main condensed and gas phase-based mode of action in the ABS matrix, whereas, a combined gas and condensed mode of action was identified when both additives were simultaneously incorporated. Also, the ABS-APP/AlPi formulation showed the higher reduction of the peak heat release rate (74%) and of the maximum average rate of heat emission (65%), obtained from cone calorimeter tests. As well as, a protective fire residue with an improved microstructure assed by SEM.

    更新日期:2018-07-24
  • Highly branched linear-comb random copolyesters of ε-caprolactone and δ-valerolactone: Isodimorphism, mechanical properties and enzymatic degradation behavior
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-21
    Tong Wu, Zhiyong Wei, Yingying Ren, Yang Yu, Xuefei Leng, Yang Li

    In this work, a series of highly branched linear-comb random copolyesters of ε-caprolactone (CL) and δ-valerolactone (VL) with high molecular weight and narrow distribution in various compositions were successfully synthesized. The composition-dependent microstructure, thermal and mechanical properties, and enzymatic degradation behavior of the resulting copolyesters were investigated systematically. The cocrystallization behavior was observed for the highly branched linear-comb random CL/VL copolyesters over the entire composition range, and a pseudo-eutectic point of isodimorphism occurred at about 50 mol% VL incorporated in copolymer. The obtained copolymers displayed lower Young's modulus, yield strength, and breaking strength, but higher elongation at break. Furthermore, the copolymers presented much higher degradation rate during enzymatic degradation process in comparison with parent homopolymers. More importantly, it was found that both mechanical properties and degradation behavior showed a similar pseudo-eutectic behavior of isodimorphism. Consequently, the correlation among of isodimorphism, mechanical properties, and degradation behavior depending on composition is highly significant, and the physical properties and degradation rate of the isodimorphic copolyesters could be continuously tailored by the feedstocks.

    更新日期:2018-07-21
  • Effect of biphenyl biimide structure on the thermal stability, flame retardancy and pyrolysis behavior of PET
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-19
    Zhi-Zheng Wu, Yan-Peng Ni, Teng Fu, Bo-Wen Liu, Wan-Shou Wu, Lin Chen, Xiu-Li Wang, Yu-Zhong Wang

    At present, developing a flame-retardant unit to solve the flammability and melt-dripping of poly(ethylene terephthalate) (PET) still is a key issue. To endow PET with good flame retardancy and low smoke releasing, a third monomer, N, N′-bis(2-hydroxyethyl)-biphenyl-3,4,3′,4′-tetracarboxylic diimide (BPDI) containing biphenyl biimide and without any traditional flame-retardant elements, is synthesized and incorporated to the main chain of PET to obtain the P(ET-co-BP)n copolyester via melt polymerization. The thermal stability, combustion and pyrolysis behaviors of the obtained copolyesters have been well investigated. Thermogravimetric analysis (TGA) results demonstrate that introducing BPDI into PET obviously improves its thermal stability and the forming ability of char residue. LOI, vertical UL-94 and cone calorimeter measurements have been applied to investigate the combustion behaviors of P(ET-co-BP)n. The results prove that P(ET-co-BP)n copolyesters containing biphenyl biimide show better fire safety, reflected by lower fire growth rate (FIGRA) and low smoke production. SEM and Raman results suggest that the char layers of P(ET-co-BP)n become denser and mainly consist of polyaromatic species with small and uniform microstructures. The pyrolysis behaviors of the copolyesters are investigated by Py-GC/MS, and the results showed that the biphenyl biimide structure units can lead to rearrangement reactions at high temperature, ultimately forming the phenanthrene ring structures during combustion. Without traditional flame-retardant elements like halogen and phosphorus, this novel PET copolyester is environmentally friendly and more safety.

    更新日期:2018-07-20
  • Long-term effect of silk paper used for wrapping of plasticized PVC objects: Comparison between ancient and model PVC
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-18
    Adeline Royaux, Isabelle Fabre-Francke, Nathalie Balcar, Gilles Barabant, Clémentine Bollard, Bertrand Lavédrine, Sophie Cantin

    The degradation kinetics of ancient and model plasticized PVC films placed in contact with silk paper as wrapping material used for PVC heritage objects was investigated during an artificial thermal aging consisting in a temperature cycle and under controlled relative humidity. The studied PVC had close plasticizer content at the beginning of the artificial aging treatment and both contain a phthalate plasticizer. As reference, the same materials were aged in absence of any contact material. Color changes, plasticizers loss and surfaces properties were assessed every month.The results show that the silk paper does not accelerate the PVC degradation rate. Indeed, color changes and plasticizer loss are similar whether the contact material is present or not. However for both PVC, the silk paper slows down the migration of an additive. Even if these additives are present in a very low proportion, their migration modifies significantly the material aspect as they accumulate at the PVC surface. The silk paper has thus a protective effect during the storage of PVC objects.In addition, this study shows that the speed of aging of the ancient PVC is faster than that of the model PVC, revealing the role of the initial state of degradation.

    更新日期:2018-07-18
  • In-situ investigation of temperature evolution of drippings via an optimized UL-94 instrumentation: Application to flame retarded polybutylene succinate
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-17
    Chi Hu, Gaëlle Fontaine, Pauline Tranchard, Thierry Delaunay, Marion Collinet, Sophie Marcille, Serge Bourbigot

    Incorporation of 10 wt% 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in polybutylene succinate (PBS) showed a significant improvement of fire behavior at the UL-94 test (3.2 mm): (i) V-0 rating and no ignition of the bar for PBS/DOPO with dripping but with no ignition of the cotton whereas (ii) no classification for neat PBS with dripping and with ignition of the cotton. To fully understand these two different phenomena, an optimized UL-94 instrumentation was developed. Thermocouples embedded in the bar measures heat gradient and infrared (IR) camera equipped with a specific filter permits estimating heat gradient in the bar and surface temperature of the falling drop respectively. The main advantage of this optimized designed UL-94 instrumentation is to get measurement in situ and in dynamic. For the first time, this instrumentation has successfully captured the temperature evolution of a falling drop during a UL-94 test. It was shown that the drops of neat PBS exhibits a constant temperature of 453 ± 10 °C when detaching the bar. However the drops' temperature of PBS/DOPO varied during the UL-94 test when they detach the bar: the drops formed at around 403 ± 10 °C at the end of the first ignition, whereas at the end of second ignition they detach the bar at about 313 ± 15 °C. Neat PBS exhibited temperature at least 50 °C higher than PBS/DOPO when the drops touched the cotton: 435 ± 5 °C for neat PBS at the end of first ignition vs. 385 ± 10 °C for the PBS/DOPO at the end of first ignition vs. 295 ± 15 °C for the PBS/DOPO at the end of second ignition. This can explain why the drops of PBS can ignite the cotton whereas those of PBS/DOPO cannot. Additionally, IR camera images indicate the change of rheology by incorporation of DOPO into PBS. A measurement of viscosity by the rheometer showed that PBS/DOPO has lower viscosity than neat PBS.

    更新日期:2018-07-18
  • Accelerated weathering study of extruded polyethylene/poly (lactic acid)/chitosan films
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-10
    L.L. Lizárraga-Laborín, J.M. Quiroz-Castillo, J.C. Encincas-Encinas, M.M. Castillo-Ortega, S.E. Burruel-Ibarra, J. Romero-García, J.A. Torres-Ochoa, D. Cabrera-German, D.E. Rodríguez-Félix

    Polyethylene/poly (lactic acid)/chitosan films, with and without poly (ethylene-g-maleic anhydride) (PEgMA) as compatibilizer, were prepared by extrusion and the degradation behavior under different times of standard weathering conditions was analyzed. The materials were characterized by means of infrared spectroscopy, scanning electron microscopy, tensile strength, differential scanning calorimetry and thermogravimetric analysis. It was demonstrated that blends of synthetic and natural polymers have a higher susceptibility to degradation in comparison to neat polyethylene and poly (lactic acid) films. Additionally, it is found that the incorporation of PEgMA into the extruded films apparently favored the polymer degradation, as it deduced from the fall of the mechanical properties when the films are exposed to accelerated weathering simulation.

    更新日期:2018-07-12
  • Synthesis of fully bio-based and solvent free non-isocyanate poly (ester amide/urethane) networks with improved thermal stability on the basis of vegetable oils
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-11
    Abdolreza Farhadian, Abbas Ahmadi, Ismail Omrani, Ahmad Babaei Miyardan, Mikhail A. Varfolomeev, Mohammad Reza Nabid

    The purpose of this study is to synthesize non-isocyanate poly (ester amide/urethane) networks, based entirely on vegetable oil through a green method, i.e., without solvent and having any rigid and aromatic structures to improve their thermal stability. For this purpose, first, three amines were synthesized from castor oil and oleic acid. Second, carbonated sunflower oil (CSFO) was obtained by reaction of epoxidized sunflower oil with CO2 at atmospheric pressure. In the final step, CSFO easily reacted with bio-based amines by melt-blending without catalyst to give corresponding non-isocyanate poly urethane (NIPU) networks. The Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) techniques were applied to characterize the structural, thermal and physical features of NIPU networks. In addition, to determine the environmental stability the water absorption amount and the degradation percentage were calculated in the deionized water and phosphate saline buffer, respectively. These NIPU networks showed an excellent thermal stability (T5 wt% between 323 and 386 °C), low water absorption and degradation (4–10 and 1.04–1.40 wt% respectively). The results show the potential of this environmentally friendly strategy to preparing bio-based NIPU for high performances. Furthermore, the presence of an aliphatic ester group and their biodegradability nature may also make them proper for biological and/or biomedical applications.

    更新日期:2018-07-12
  • A review of experimental studies of the role of free-radicals in polyethylene oxidation
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-11
    Pierangiola Bracco, Luigi Costa, Maria Paola Luda, Norman Billingham

    This paper reviews current understanding of the role of free radicals in the oxidation of polyethylene induced by high-energy irradiation (gamma or e-beam). To evaluate the reactivity, stability and mobility of different macroradicals, their reactions after gamma irradiation of different polyethylenes (LDPE, LLDPE, VLLDPE, HDPE, UHMWPE) are considered. Macroradicals are formed in all phases of PE (crystalline, amorphous and interphase). Their overall determination is possible only if both irradiation and detection are carried out at 100 K, or below. At this temperature, the most abundant macroradical formed is the secondary alkyl macroradical (R’’°). On gradually raising the temperature, the macroradicals decay with formation of vinylene double bonds and molecular hydrogen. At room temperature, the macroradical concentration is about 4% of the original quantity at 100 K for LDPE and around 15% for HDPE. In HDPE and UHMWPE; the macroradicals are mainly present in the crystalline phase and in short times (hours) they migrate to the amorphous phase. In LDPE and LLDPE macroradicals are mainly allylic, present in minimal amounts at the crystalline-amorphous interphase. In the nearly fully amorphous VLDPE no residual macroradicals can be detected at room temperature. The mobility of R’’° is variable and is a function of the mobility of the polymer backbone, slow in the crystalline phase, relatively fast in the amorphous phase. Kinetic stability, or persistence, is often more important than thermodynamic stability in determining radical lifetimes, in particular for radical processes in the solid phase. Alkyl macroradicals react with chain imperfections, additives and oxygen, in a cyclic process involving initiation, propagation and termination reactions. The initiation reactions form macroradicals by cleavage of the C-H bonds of PE, induced by irradiation or by photo- or thermal-scission of peroxides formed during processing of the polymer. Propagation involves the reaction of R’’° with vinyl or vinylidene double bonds, with the formation of a new radical, in competition with their reaction with oxygen to form various oxidation products (ketones, hydroperoxides acids, alcohols and esters). It is notable that the formation of ketones does not necessarily require decomposition of the hydroperoxides. In the presence of stabilizing additives, radicals react with the additive (ADH), with the formation of a more kinetically stable radical (AD°), which considerably decreases the propagation rate, but a termination reaction between R’’° and AD° may also be envisaged. It is observed that radiation-induced oxidation has a constant rate during irradiation. Post-irradiation, the oxidation occurs via transfer of the macroradicals from the crystalline phase and the interphase to the amorphous phase, where oxygen is available, and the rate decreases, approaching zero. The occurrence of termination is apparent. Termination must occur through the reaction of two macroradicals. The reaction between two R’’° is difficult, due to steric hindrance. The most probable reaction is that between peroxy macroradicals (ROO°), fixed in position on the polymer chain and R’’°, which migrate through the polymer bulk. This reaction is difficult to confirm experimentally because of the lack of reliable analytical methods for ROOR species in the presence of ROOH. The formation reactions of the different oxidation products are reported and the branching reactions occurring in thermal and photo-oxidation are also discussed.

    更新日期:2018-07-12
  • Partial discharge behaviour of biaxially orientated PET films: The effect of crystalline morphology
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-11
    Rong Tang, John J. Liggat, Wah H. Siew

    The relation between PD induced breakdown behaviour and crystalline and amorphous morphology of PET films used in photovoltaic devices has been explored and discussed in this work for the first time. Biaxially orientated PET films with and without BaSO4 filler were isothermally annealed at various temperatures before partial discharge (PD) breakdown tests of the films to investigate the crystalline morphology effect. Attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC) were used to study the changes of crystallinity and lamellar thickness of the samples. It was found that both PD resistances and PD lifetimes could be significantly improved when the samples were annealed at temperatures above 210 °C. On the other hand, improvements were much less in the annealing temperature region between 180 and 210 °C. This is because the thinner and less perfect lamellae formed by annealing at the lower temperatures are less effective at resisting either ion bombardment or electrical tree propagation. On the other hand, the formation of thickened and perfected lamellae produced at higher annealing temperatures can effectively increase the tortuosity of electrical tree propagation paths, thereby increasing the PD lifetimes.

    更新日期:2018-07-12
  • Improving the resistance to hydrothermal ageing of flame-retarded PLA by incorporating miscible PMMA
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-09
    R. Mangin, H. Vahabi, R. Sonnier, C. Chivas-Joly, J.-M. Lopez-Cuesta, M. Cochez

    Three flame-retarded systems based on PLA, PMMA and PLA/PMMA blend have undergone hydrothermal ageing. The miscibility of the blend as well as the crystallization behaviour of PLA were studied by DSC. The impact of ageing in terms of weight variations, melt viscosity, molecular weight distribution, morphology, and thermal degradation was investigated. Results showed that crystallization of PLA and significant hydrolysis phenomenon occurred during ageing. Flame retardant content determined by EDX and ICP revealed a loss of phosphorus during ageing, especially for flame-retarded PLA (91 wt% phosphorus loss after ageing). Incorporation of 50 wt% PMMA moderated the negative impacts observed. Fire properties evaluated using cone calorimeter revealed almost no impact of ageing on flame-retarded PMMA, contrary to flame-retarded PLA (increase of pHRR from 291 to 487 kW/m2). Flame-retarded blend shows intermediate properties. It revealed the positive effect of incorporation of PMMA in PLA, by limiting the water diffusion and by reducing the loss of phosphorus.

    更新日期:2018-07-10
  • Effect of nano-TiO2 immobilized antioxidant on ageing resistance behavior of thermoplastic vulcanizate exposed to UV/O3
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-09
    Hao Yang, Hui Zhang, Henglun Cheng, Baoqing Shentu

    Nano-TiO2 immobilized antioxidant was prepared to improve the ageing resistance of thermoplastic vulcanizate (TPV) exposed to UV/O3. TiO2 nanoparticles were firstly modified with 3-aminopropyltriethoxysilane (KH550) and then reacted with the antioxidant, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid (AG), through the acyl chloride reaction followed by the amidation. FT-IR, XPS and TGA measurements confirmed that the antioxidant (AG) was chemically immobilized onto the nano-TiO2 surfaces. TPV/TiO2-KH550-AG nanocomposites were prepared by melt mixing. SEM observation showed that TiO2-KH550-AG was homogeneously dispersed into the matrix of TPV. The UV/O3 ageing test of the samples was carried out in the environment with constant UV intensity of 1.40 mW/cm2 and ozone concentration of 100 ± 4 mg/m3. The ageing resistance behavior of the TPV/TiO2-KH550-AG nanocomposites was evaluated by the changes of surface morphology, mechanical properties and carbonyl index during the UV/O3 ageing test. It was observed that the TPV/TiO2-KH550-AG exhibited high stability during the process of UV/O3 ageing. The results revealed that the anti-ageing efficiency of TiO2-KH550-AG was superior to the mixture of the corresponding AG and modified TiO2, owing to the better dispersion and migration resistance of TiO2-KH550-AG.

    更新日期:2018-07-10
  • Comprehensive study on flame retardant polyesters from phosphorus additives
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-09
    Khalifah A. Salmeia, Ali Gooneie, Pietro Simonetti, Rashid Nazir, Jean-Pierre Kaiser, Alexandra Rippl, Cordula Hirsch, Sandro Lehner, Patrick Rupper, Rudolf Hufenus, Sabyasachi Gaan

    In this work we have performed a comprehensive study on synthesis, processing, detailed material characterization and preliminary assessment of toxicity of relatively new flame retardant (FR) additives as a key for developing environmentally friendly fire safe polyesters. Two 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based FR additives were synthesized using principles of green chemistry and incorporated via thermal processing in high temperature polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The green synthesis strategies included (i) the use of N-chlorosuccinimide as a sustainable chlorinating agent for DOPO and (ii) a solvent and catalyst free microwave-assisted synthesis. Atomistic molecular dynamics (MD) simulations were employed in order to calculate the solubility parameters of these additives so as to estimate their compatibility in the polyesters. Detailed rheological measurements of the polyester/FR blends were carried out and the results indicated a clear difference in all three additives tested. Based on these analyses, 6H-dibenz[c,e][1,2]oxaphosphorin,6-[(1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]oct-4-yl)methoxy]-, 6-oxide (DOPO-PEPA) exhibited the highest compatibility with both polyesters and their blends and showed the highest thermal-oxidative stability guaranteeing stable and steady processing at high temperatures. All polyester/FR formulations exhibited higher flame retardancy compared to the virgin polyesters in the small scale fire tests. The FR additives were evaluated for their potential toxicity using a well-established in vitro platform. Our results indicate no acute cytotoxic potential for all FRs analyzed in two different cell types (the human lung epithelial cell line A549 and macrophages derived from the monocytic cell line THP-1) and under the chosen experimental conditions.

    更新日期:2018-07-10
  • Enhanced catalytic glycolysis conditions for chemical recycling of glycol-modified poly(ethylene terephthalate)
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-06
    Linh Nguyet Thi Ho, Dieu Minh Ngo, Jaeyoung Cho, Hyun Min Jung

    Despite the significant influences of the rigid cyclic ring structure on the good thermal and mechanical characteristics of poly (1,4-cyclohexylenedimethylene terephthalate) (PCT), steric hindrance by the cyclohexylene group interferes with glycolysis, an important chemical recycling route for poly (ethylene terephthalate) (PET) derivatives. To confirm the effects of chemical structure on the reaction, bis(4-hydroxymethyl)cyclohexylmethyl terephthalate (BHCHT), a model compound for PCT, was synthesized and compared with bis(2-hydroxyethyl) terephthalate (BHET), a model compound for PET, in transesterification reactions under zinc catalytic conditions. The rate of transesterification of BHCHT was 1/3 of that of BHET, and this retarded reaction rate was dramatically increased by up to 4 times when a catalytic amount of alkoxy species was combined with the zinc catalyst. The conditions of alkoxide combined with the zinc catalyst were applied to the glycolysis of PCT; the glycolytic reaction rate was three times higher than that with the conventional zinc acetate and the glycolysis product was produced with 82% yield.

    更新日期:2018-07-08
  • Effect of hydrolytic degradation on the mechanical property of a thermoplastic polyether ester elastomer
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-06
    Cody M. Diaz, Xiang Gao, Agathe Robisson, Miranda Amarante, S. Sherry Zhu

    Polymers with a finite lifetime are of great interest for oil and gas industry. Thermoplastic elastomers (TPEs) combine the strength of thermoplastics with the flexibility of elastomers, a characteristic also potentially useful in oil and gas applications. We studied the hydrolytic degradation of a TPE of interest at elevated temperatures from both a mechanical and chemical perspective, and have demonstrated that the chemical degradation rates, the change in crystallinity and the storage modulus all follow the pseudo zero order kinetics with respect to varying time at three temperatures. Applying Arrhenius' empirical relationship to the determined rates gives rise to a temperature-dependent model that predicts the degradation behavior of the TPE outside of the experimental temperature range. Our results indicate that hydrolytic degradation leads to an increase of crystallinity (chemicrystallization) and a decrease of tensile strength and strain, and that the increase of crystallinity strongly correlates to the increase of the storage modulus. The polymer eventually deteriorates due to brittleness.

    更新日期:2018-07-08
  • Macromolecular modifications of Poly(etherketoneketone) (PEKK) copolymer at the melting state
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-07
    T. Choupin, B. Fayolle, G. Régnier, C. Paris, J. Cinquin, B. Brulé

    Macromolecular modifications of poly(etherketoneketone) (PEKK) copolymer prepared from diphenyl ether (DPE), terephthalic acid (T) and isophthalic acid (I) with a T/I ratio of 60/40 have been investigated above its melting temperature by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and rheological measurements to assess the evolution of PEKK matrix during composite consolidation step. We mainly focused in this study on anaerobic conditions, i.e. degradation under nitrogen or in lack of oxygen. During exposure, thermal degradation leads to an increase of weight average molar mass Mw and viscosity which is typical to crosslinking/branching mechanism as already observed for PEEK in the literature. However, thanks to GPC measurements, it appears that a chain scission mechanism occurs in the same time related to a constant number average molar mass Mn. Crosslinking kinetics are identified at several temperatures between 320 and 400 °C with rheological measurements from a kinetic scheme governing the crosslinking mechanism. At last, the influence of the crosslinking process on PEKK crystallization is investigated. The final crystallinity and crystallization kinetics decrease with crosslinking due to branching of macromolecular chains.

    更新日期:2018-07-08
  • Full substitution of petroleum-based polyols by phosphorus-containing soy-based polyols for fabricating highly flame-retardant polyisocyanurate foams
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-07-02
    Ming-Jun Chen, Xu Wang, Mei-Cen Tao, Xing-Ya Liu, Zhi-Guo Liu, Yan Zhang, Cheng-Shou Zhao, Jun-Sheng Wang

    To obtain a substitute for petroleum-based polyols and simultaneously solve the flammability problem of polyisocyanurate (PIR) foams, a novel phosphorus-containing soy-based polyol (PCSO) was firstly synthesized. Then, PCSO was used to fabricate biomass flame-retardant PIR foam (P-PIR) by fully replacing petroleum-based polyol. The morphology, compressive strength, thermal conductivity, thermal stability, flammability, and flame-retardant mechanism were studied for the developed PIR. The incorporation of PCSO results in a slight decrease in the compressive strength and an increase in the flame retardancy of PIR foam. To further improve the flame retardancy, a commercial phosphorus-containing polyol (BY30) and an expandable graphite (EG) were added in the P-PIR system. The test results show that the decompositon of PIR was hindered after 330 °C and the char residue was significantly improved. In addtion, the limiting oxygen index of PIR was significantly increased to 35%, and the peak of heat release rate and total heat release were dramatically decreased by 65% and 87%, respectively. A synergistic flame-retardant effect was achieved by combining the gas phase action of PCSO and BY30 with the condensed phase action of EG.

    更新日期:2018-07-03
  • Controlled degradation of polyisoprene and polybutadiene: A comparative study of two methods
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-30
    Pierre Berto, Stéphane Grelier, Frédéric Peruch

    Low molar mass carbonyl telechelic cis,1–4 polyisoprene (CTPI) and aldehyde telechelic cis, 1–4 polybutadiene (ATPB) were easily prepared by the controlled degradation of high molar mass 1,4-cis polyisoprene (PI) and 1,4-cis polybutadiene (PB) in a molar mass range of 5000–80 000 g mol−1. Two methods are compared: the direct one using only the periodic acid (H5IO6) to randomly cleave the chain and a second one where the chain are first epoxidized before being cleaved by the periodic acid. In both cases, a control of the final chain length was observed with nevertheless a better control of the final chain length, dispersity and chain-ends using the 2-steps procedure. Importance of the washing step in order to avoid side reactions on the carbonyl chain-ends is also discussed.

    更新日期:2018-07-01
  • Polylactic acid, maleic anhydride and dicumyl peroxide: NMR study of the free-radical melt reaction product
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-30
    Idejan P. Gross, Felipe S. Schneider, Miguel S.B. Caro, Thiago F. da Conceição, Giovanni F. Caramori, Alfredo T.N. Pires

    In this study, a detailed characterization was carried out of a product formed in the melt reaction of poly(lactic acid) PLA with maleic anhydride, initiated by dicumyl peroxide under the reaction conditions reported herein. The chemical structure of the reaction product was determined by 1H NMR and 13C NMR spectroscopy and by DEPT-135 and 13C-1H HSQC techniques. It was found that, under the conditions applied in this study, instead of the well-reported grafting of maleic anhydride onto the PLA, a product was formed from the reaction of two PLA macro-radicals, which probably occurs after the β-scission mechanism. The 13C NMR spectrum of the proposed reaction product was also calculated using the GIAO-DFT method and the result is in agreement with the experimental spectrum.

    更新日期:2018-07-01
  • Characterization of in-flame soot from balsa composite combustion during mass loss cone calorimeter tests
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-30
    G. Okyay, S. Bellayer, F. Samyn, M. Jimenez, S. Bourbigot

    Soot is one of the degradation products of material burning, having the fingerprints of the conditions in which it is formed. In this work, in-flame soot was probed from flaming combustion of balsa core and its sandwich composite at different heat flux scenarios during mass loss cone calorimeter tests. Soot probing was performed by thermophoresis. Electron microscopy was performed to analyze the size of the particulate media at multiscale. The size of the aggregates and the primary particles were found to be inherent to scenarios, i.e. materials specifications and heat flux rates. Nanoscale structure of in-flame soot was consistent with the results of thermogravimetric analysis of emitted-deposited soot. This semi-quantitative study contributes to soot observations in fire scenarios and constitutes the first application of soot probing by thermophoresis in a bench-scale fire scenario simulated by cone calorimetry. Technique shall be used in future to support emitted soot and smoke data.

    更新日期:2018-07-01
  • Enzymatic degradation of poly (butylene succinate-co-hexamethylene succinate)
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-30
    Siwen Bi, Bin Tan, James L. Soule, Margaret J. Sobkowicz
    更新日期:2018-07-01
  • Synthesis of an acrylate constructed by phosphaphenanthrene and triazine-trione and its application in intrinsic flame retardant vinyl ester resin
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-28
    Xiaoxiao Tao, Huajun Duan, Wenjing Dong, Xin Wang, Shuang Yang

    An intrinsic flame retardant vinyl ester TGIC-AA-DOPO constructed by phosphaphenanthrene and triazine-trione groups was successfully synthesized via the reaction between 1,3,5-triglycidyl isocyanurate (TGIC), acrylic acid and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The structure of TGIC-AA-DOPO was characterized in detail by fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The intrinsic P-N-containing flame retardant vinyl ester resin (IFR-VER) was prepared after diluting TGIC-AA-DOPO with styrene (st) and triallyl isocyanurate (TAIC). The flame retardancy, thermal properties and combustion behavior of IFR-VER were respectively investigated by a series of tests involving limited oxygen index (LOI) measurement, UL-94 vertical burning test, cone calorimeter test, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The results showed that the as-obtained resin system exhibited a dramatic improvement in flame retardance. In the case of 40 wt% TAIC in resin system, the LOI value achieved 31%, leading to the UL-94 V-0 rating. In addition, compared with the 901-VER, the peak heat release rate (pk-HRR), average of heat release rate (av-HRR), total heat release (THR) and average effective combustion heat (av-EHC) of the IFR-VER containing 40% TAIC diluent were decreased by 48%, 60%, 41% and 24% respectively. The diphase flame retardant effect of the prepared IFR-VER during combustion was demonstrated by the results of Py-GC/MS, FTIR, laser raman spectroscopy and scanning electron microscope (SEM).

    更新日期:2018-06-30
  • Thermal properties, phase morphology and stability of biodegradable PLA/PBSL/HAp composites
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-19
    Kartik Behera, Veluri Sivanjineyulu, Yen-Hsiang Chang, Fang-Chyou Chiu

    Blends/composites of poly (lactic acid) (PLA) with poly (butylene succinate-co-lactate) (PBSL) and hydroxyapatite (HAp) were successfully prepared by a conventional melt-mixing process. The thermal properties, phase morphology, crystal structure, and in vitro hydro-degradability of the prepared samples were characterized and compared. Thermogravimetric analysis confirmed that adding HAp increased the thermal stability of PLA/PBSL blends in both air and nitrogen environments. The activation energy for PLA thermal degradation increased with increasing HAp content in the samples. Scanning electron microscopy results showed that HAp was uniformly distributed within the composites. HAp also played a compatibilizer role for the PLA/PBSL blends, leading to evidently reduced size of dispersed PBSL domains. The Avrami crystallization analysis revealed that the n values of PLA in different samples ranged within 2.1–3.9, and the presence of HAp caused athermal nucleation process of PLA crystallization. The activation energy for non-isothermal crystallization of PLA decreased from 136 kJ/mol in neat state to 86 kJ/mol in PLA(70)/PBSL (30)/HAp (20 phr) composite. Melting behavior study revealed that the presence of HAp increased the original crystals stability of PLA in the composites. X-ray diffraction results confirmed that the crystal structures of PLA and PBSL remained in the blends and composites. Finally, in vitro hydrolytic degradation tests showed that the HAp addition facilitated the degradation of the prepared samples.

    更新日期:2018-06-22
  • Combined effect of UVA radiation and agrochemicals on the durability of agricultural multilayer films
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-20
    Demetres Briassoulis, Miltiadis Hiskakis, Philippos Tserotas

    New generation agricultural films combine multilayer technologies, with the latest developments in chemicals resistant UV stabilisers and possibly the incorporation of barrier layers against agrochemicals. The photo-degradation behaviour of a series of experimental multilayer (ML) films exposed to accelerated ageing in combination with agrochemicals, was analysed. It has been shown that the presence of a barrier layer (EVOH or PA) adversely affects the mechanical behaviour of ML films, because of the low ductility of these barrier layers, whose failure is propagating to the other layers leading to premature failure of ML film structures. ML films with barrier layer have shorter lifespan due to the rapid photo-degradation of the barrier layer. It was confirmed that these layers absorb the main part of the agrochemicals load, acting as effective barriers. Agrochemicals were shown to accelerate the detrimental effect of the UVA radiation on PA and EVOH layers causing premature failure of the barrier layers, compromising evenmore the mechanical strength and durability of the entire film. The presence of barrier layers such as PA (mainly) and EVOH in agricultural ML films is not recommended, as both their mechanical properties and photodegradation behaviour are adversely affected by the presence of low ductility barrier layers, deteriorated by the combination of UVA radiation and agrochemicals.

    更新日期:2018-06-22
  • Thermal properties of polyetherimide/polycarbonate blends for advanced applications
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-20
    Ignazio Blanco, Gianluca Cicala, Giulia Ognibene, Mario Rapisarda, Antonino Recca

    Polyetherimide (PEI)/Polycarbonate (PC) blends were prepared and their thermal behaviour was evaluated in the perspective of an improved processability, thus favouring the use as feeding material for a Fusion Deposition Modelling (FDM) 3D printing machine. PEI/PC blends obtained with a batch mixer were characterized by the means of Thermogravimetric (TG) and Differential Thermogravimetric (DTG) analysis and Differential Scanning Calorimetry (DSC). The parameters associated with the physical properties of the various blends were evaluated and compared with those obtained for the pristine polymers. Both thermal and spectroscopic analyses showed the formation of an immiscible blend, with some possible regions of partial miscibility, furthermore the glass transition temperature (Tg) values demonstrated that the presence of PC in the blend allowed an important lowering of the viscosity, thus meaning an improved processability. Finally, the TGA and DSC results were compared with those obtained for Ultem 9085 that is the standard PEI grade for FDM printing in advanced applications developed by Stratasys, Ltd.

    更新日期:2018-06-22
  • Application of self-templated PHMA sub-microtubes in enhancing flame-retardance and anti-dripping of PET
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-12
    Chang Wang, Liping Wu, Yamin Dai, Yuxi Zhu, Bijia Wang, Yi Zhong, Linping Zhang, Xiaofeng Sui, Hong Xu, Zhiping Mao

    Tubular one-dimensional poly (cyclotriphosphazene-melamine) (PHMA) sub-microtubes were conveniently synthesized from co-polymerization of hexachloro -cyclotriphosphazene and melamine. The SEM and TEM results showed PHMA sub-microtubes were opened at one end with diameters of 100–300 nm and lengths of 1–10 μm. The inner diameters of closed and open end were 10–30 nm and 50–100 nm, respectively. The PHMA sub-microtubes were melt blended with PET (PET/PHMA) to be used as an effective flame retardant. The flame-retardant and anti-dripping properties of PET/PHMA composites were evaluated by TGA, LOI, vertical burning, MCC and rheological test. The results confirmed the efficiency of PHMA in enhancing the self-extinguishing ability and inhibiting melt-dripping of PET. The morphological characteristics and graphitic structure of the charred residues were evaluated by SEM, Raman spectroscopy. Results demonstrated the formation of a compact protective carbon layer and a carbonaceous micro-structures, which acted as insulator against oxygen and heat.

    更新日期:2018-06-12
  • A novel organic-inorganic hybrid SiO2@DPP for the fire retardance of polycarbonate
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-07
    Yun-Xia Wei, Cong Deng, Ze-yong Zhao, Yu-Zhong Wang

    To enhance the fire retardance of polycarbonate (PC), a novel organic-inorganic hybrid particle containing phosphorus and silicon (SiO2@DPP) was synthesized through a facile hydrothermal reaction. Different measurements verified that the SiO2@DPP was prepared successfully. After incorporation of the SiO2@DPP into PC, it was found that the flame retardancy of PC was greatly affected by only small amount of SiO2@DPP. The PC containing only 0.8 wt% SiO2@DPP passed the UL-94 V-0 rating in vertical combustion test and had the limiting oxygen index (LOI) of 29.3%. Moreover, the dripping behavior of PC was also restricted in this case. In cone calorimetry test, the peak heat release rate (PHRR) and the peak smoke production rate (PSPR) of PC were correspondingly remarkably reduced by 41.6% and 15.4% in the presence of only 0.8 wt% SiO2@DPP. Moreover, the flame-retardant mechanism of the SiO2@DPP was also investigated in detail through different measurements. The results demonstrated that the phosphorus-containing substances and SiO2 left in the condensed phase and some structures containing phosphorus in gaseous phase had great contribution to excellent fire retardance of PC/SiO2@DPP. All these results demonstrate that the SiO2@DPP is an efficient organic-inorganic hybrid material for preparing fire-retardance PC.

    更新日期:2018-06-07
  • Water ageing of urethane dimethacrylate networks
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-06
    Benjamin Pomes, Isabelle Derue, Albert Lucas, Jean-François Nguyen, Emmanuel Richaud

    This work explores the process of water ageing of high-temperature high-pressure polymerized urethane dimethacrylate (UDMA) networks. UDMA samples polymerized under several pressures (0.1–300 MPa) and differing by the conversion degree of polymerization were aged in water at 37, 50 and 70 °C and followed by gravimetry. Diffusion was observed to obey Fick's law. The diffusion coefficient and water maximal uptake were observed to be almost independent of polymerization pressure, consistently with analysis of Dynamic Vapor Sorption data suggesting that external polymerization pressure has no effect on polymer affinity with water. This was ascribed to the fact that all materials have the same cohesive energy, as confirmed by ultrasonic measurements of elastic moduli. Polymerization pressure (used to improve conversion degree and mechanical properties) would thus have a minor influence on water ageing that is mainly triggered by polymer chemistry. When elevating the polymerization pressure, there is hence no compromise between the optimization of thermo-mechanical properties and the resistance to water ageing.

    更新日期:2018-06-06
  • Enhanced crystallization kinetics of bacterially synthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanate) with structural optimization of oxalamide compounds as nucleators
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-02
    Pengwu Xu, Ying Cao, Pei Lv, Piming Ma, Weifu Dong, Huiyu Bai, Wei Wang, Mingliang Du, Mingqing Chen

    Bacterially synthesized poly (3-hydroxybutyrate-co-3-hydroxyhexanate) (PHBH) has attracted much attention as biodegradable plastics and potential biomaterials. However, the crystallization rate of PHBH is very low, which limits its application in plastic field. Herein, oxalamide compounds (OXAn) with a formula of C6H5NHCOCONH(CH2)nNHCOCONHC6H5 (n = 2, 4, 8, 12) were tailor-made as nucleators to improve the crystallization behaviors of PHBH. The effect of aliphatic spacer length of OXAn, i.e., -(CH2)n-on the nucleation behavior was investigated. The OXAn would assemble into shish-like superstructures and PHBH crystals preferred to grow on the surfaces of the shish. The crystallization rate of PHBH/OXAn blends increased with the spacer length of OXAn up to n = 8 and then leveled off, which trend was consistent with the nucleation activity (Ψ) and the nucleation constant (Kg) of the OXAn. Meanwhile, the OXAn increased the nuclei density of the PHBH while inhibited its secondary crystallization, resulting in a superior and steady mechanical performance of PHBH materials. This work provides a scientific approach to design the optimal structure of OXAn as nucleators for PHBH materials, which may broaden the application range of PHBH materials.

    更新日期:2018-06-02
  • Poly-etherimide epoxy diamine blends: Conductivity and breakdown voltage measurements at room temperature
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-06-01
    N. Halawani, J.L. Augé, O. Gain, V. Griseri, G. Teyssèdre, S. Pruvost

    This paper presents an investigation on the current and breakdown voltage measurements in thermoset-thermoplastic blends based on an epoxy-amine/poly-etherimide phase separated material. Thermoset-thermoplastic separated blends could be a novel material for insulation applications and can be compared to epoxy/inorganic composites systems. Pure epoxy network as well as the blends with 10 wt% of PEI were studied in terms of conduction and transient currents. An ohmic behavior below the threshold field (Eth) and space-charge-limited conduction (SCLC) above Eth are pointed out. Contact emission phenomenon was investigated by means of Schottky model and seems to be valid for both materials. The addition of 5 and 10 wt% of PEI into the epoxy system showed an increase in the values of breakdown voltage with the increase of the PEI amount.

    更新日期:2018-06-02
  • Influences of diantimony trioxide on laser-marking properties of thermoplastic polyurethane
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-31
    Junfeng Cheng, Hao Li, Jiaqi Zhou, Zheng Cao, Dun Wu, Chunlin Liu

    The influences of diantimony trioxide (Sb2O3) on the laser-marking properties of thermoplastic polyurethane (TPU) are studied. The TPU/Sb2O3 composites are prepared by melt blending in a HAAKE mixer. A neodymium-doped yttrium aluminum garnet (Nd:YAG) pulsed laser beam of a wavelength of 1064 nm is used to scan the surfaces of the composites to create markings. Visual and microscopic analyses of the TPU/Sb2O3 composites after laser treatment show high-contrast black markings, depending on the Sb2O3 loading, Sb2O3 particle size, and laser-beam power. The laser-marking properties of the composite surfaces are analyzed by X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Furthermore, a mechanism for the laser-induced darkening of the TPU/Sb2O3 composites is proposed. The Sb2O3 particles absorb laser energy and convert it into thermal energy. This causes the surrounding TPU matrix to carbonize into amorphous carbon, forming black markings.

    更新日期:2018-05-31
  • Biobased copolyesters: Synthesis, structure, thermal and mechanical properties of poly(ethylene 2,5-furandicarboxylate-co-ethylene 1,4-cyclohexanedicarboxylate)
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-30
    Xiansong Wang, Qingyin Wang, Shaoying Liu, Gongying Wang

    A series of bio-based copolyesters, poly(ethylene 2,5-furandicarboxylate-co-ethylene 1,4-cyclohexanedicarboxylate)s (PEFCs) were synthesized from ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA) and 1,4-cyclohexanedicarboxylic acid (CHDA) through a two-step melt polycondensation procedure. The chemical structure, compositions and sequence distributions were determined by 1H NMR. The molecular weight, thermal properties, thermal stabilities, crystal structure and mechanical properties were investigated by GPC, DSC, TGA, WAXD, and tensile testing, respectively. All PEFCs showed the characteristic of random copolymer, and their composition could be controlled by the feed molar ratio of FDCA to CHDA. DSC results showed that PEFCs were amorphous, while increasing the content of the CHDA unit, the glass transition temperatures (Tg) of PEFCs decreased. Moreover, the thermal stabilities of all PEFCs remained unchanged. The tensile testing demonstrated that PEFC-30 was a toughened plastic with tensile modulus 801 MPa and elongation 667%.

    更新日期:2018-05-31
  • Anti-aging behavior of amino-containing co-condensed nanosilica in polyethylene
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-30
    Ming Lu, Peng Liu, Shimin Zhang, Wenjing Yuan, Siyin Ding, Feng Wang, Yanfen Ding, Mingshu Yang

    Physical loss of stabilizers by migration and extraction accelerates the degradation of polymer materials. In this work, amino-containing nanosilica with anti-aging properties was prepared simply by the co-condensation of tetraethoxysilane and N-(2-aminoethyl)-3-aminoproply-trimethoxysilane (AEAPS). AEAPS was used to introduce amino groups into silica nanoparticles and to act as a catalyst in this process. The co-condensed nanosilica (CCS) showed agglomerate structure similar to the typical fumed nanosilica (FS). The amino groups were distributed both on the surface and inside the nanoparticles. HDPE/CCS and HDPE/FS composites were prepared by melt blending. Thermogravimetric analysis and oxidative induction time showed that CCS has effectively improved the thermo-oxidative stability of HDPE. In the long-term accelerated thermo-oxidative aging and UV aging tests, HDPE/CCS composite showed superior stability to neat HDPE and HDPE/FS composite. The results of infrared spectroscopy and electron paramanetic resonance suggested that the HDPE/CCS composite manifested a special degradation mechanism involving the nucleophilic addition of amino groups to carbonyl species as well as the oxidation of amino groups on CCS by peroxides. The amino groups on CCS consumed carbonyl species and peroxides, and generated hydroxylamines and nitroxide radicals which were able to eliminate free radicals, thus restrained the degradation of HDPE.

    更新日期:2018-05-31
  • Oxidation reactions in kink banded regions of UHMMPE fiber-based laminates used in body armor: A mechanistic study
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-29
    Zois Tsinas, Amanda L. Forster, Mohamad Al-Sheikhly

    This work demonstrates the synergy between the thermo-mechanical and humidity induced degradation as well as the oxidation reactions in the kink-banded areas of ultra-high molar mass polyethylene (UHMMPE) fiber-based laminates used in body armor. For aged materials, the energy-dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) results reveal high concentrations of oxygen containing products, and the EPR results demonstrate the presence of the peroxyl radicals (RO2•) in the kink-banded areas. After one year of dark ambient storage, very long-lived RO2• radicals were observed primarily in the samples exposed to ageing conditions of elevated temperatures, humidity, and mechanical stress. The total percentage of crystallinity, as measured by differential scanning calorimetry, of the kink-banded fibers was unchanged, indicating that the degradation occurs primarily in the amorphous region, and may also involve recrystallization processes of the degraded chains. However, the most abundant orthorhombic crystalline phase decreases from 77% to 70%. This decrease in the orthorhombic structure leads to more diffusion of oxygen into the kink-banded region, enhancing the oxidation processes. No changes are observed in the monoclinic phase of the kinked fibers, which remained constant and constituted ∼2% of the total crystallinity.

    更新日期:2018-05-30
  • 更新日期:2018-05-25
  • Low molecular weight hindered amine light stabilizers (HALS) intercalated MgAl-Layered double hydroxides: Preparation and anti-aging performance in polypropylene nanocomposites
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-25
    Qian Zhang, Fabrice Leroux, Pinggui Tang, Dianqing Li, Yongjun Feng

    A low molecular weight hindered amine light stabilizer (HALS), contains 2, 2, 6, 6-tetramethyl piperidine functional group has been successfully prepared and intercalated into the interlayer region of Mg-Al layered double hydroxides (LDH) via a co-precipitation method to produce HALS-LDH. Furthermore, a series of HALS-LDH/PP nanocomposites were fabricated by dispersing HALS-LDH in poly(propylene) (PP) in a solvent casting route. Through the accelerated aging test method, the morphological properties, the thermal-oxidative degradation and photo-oxidative degradation behavior of HALS-LDH/PP composites were carefully investigated. The results show that the thermal stability of HALS in HALS-LDH was improved compared to that of HALS free of LDH dispersed into PP, and there is no negative effect on the crystallization behavior of PP after the addition of HALS-LDH. Besides, the HALS-LDH significantly enhances synergistically the thermal- and photo-stability of PP compared when LDH platelets CO3-LDH or HALS are used separately. Under the experimental conditions, a mass loading of HALS-LDH optimized as 4 wt % in respect to PP was found to exhibit an excellent anti-aging performance for potential applications.

    更新日期:2018-05-25
  • Fire-resistant natural fibre-reinforced composites from flame retarded textiles
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-24
    W. Pornwannachai, J.R. Ebdon, B.K. Kandola

    Thermoplastic composites were prepared by melt pressing fabrics from commingled natural (flax) –thermoplastic (polypropylene (PP) and poly lactic acid (PLA)) polymeric fibres. Fabrics were treated with a number of commercial flame retardants (FRs) used for textiles prior to composite preparation. Their flammabilities and mechanical performances have been evaluated in terms of FR types effective on each fibre type. The fire performances of the composite laminates evaluated using UL-94 showed that flax/PP control and all flame retarded composite samples failed the UL-94 test, except for one treated with organophosphonate FR. On the other hand all flame retarded flax/PLA samples achieved V0 rating. Cone calorimetric results obtained at 35 kW/m2 also showed that all FRs significantly reduced the flammability of the composites and that their efficiencies were more pronounced in flax/PLA than in flax/PP composites. The mechanical performances of composites evaluated in tensile, flexural and impact modes indicated that all flame retardants reduced the mechanical properties of the composites, with the extent of reduction dependent on the pH of the flame retardant solution used. The reduction in mechanical properties was more severe in flax/PLA composites than in flax/PP composites.

    更新日期:2018-05-25
  • Improving fire safety of epoxy filled with graphene hybrid incorporated with zeolitic imidazolate framework/layered double hydroxide
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-23
    Wenzong Xu, Xiaoling Wang, Yucheng Liu, Wu Li, Rui Chen

    In this work, a novel graphene (RGO) hybrid added with Zeolitic Imidazolate Framework/Layered Double Hydroxide (ZIF/LDH) was prepared to obtain a synergistic system (RGO-LDH/ZIF-67). Subsequently, RGO-LDH/ZIF-67 was mixed into epoxy resin (EP) by physical blending for the purpose of improving its fire safety. Based on a series of tests and analyses, it was found that RGO-LDH/ZIF-67 was beneficial to reducing the heat release of EP during its burning process. The peak heat release rate (PHRR) and total heat release (THR) of the composite with 2 wt% RGO-LDH/ZIF-67 were reduced to 464 kW m−2 and 37.9 MJ m−2, respectively. Simultaneously, the smoke production in its flame and flameless combustion were also reduced significantly. According to the char analysis of different composites, the main mechanism is discussed. This work provided a new type of modified RGO for improving the fire safety of EP.

    更新日期:2018-05-24
  • Facile synthesis of a novel hyperbranched poly(urethane-phosphine oxide) as an effective modifier for epoxy resin
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-22
    Chao Ma, Shuilai Qiu, Junling Wang, Haibo Sheng, Yi Zhang, Weizhao Hu, Yuan Hu
    更新日期:2018-05-23
  • Diffusion-limited oxidation of polyamide: Three stages of fracture behavior
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-22
    Xin-Feng Wei, Kai J. Kallio, Stefan Bruder, Martin Bellander, Hans-Henning Kausch, Ulf W. Gedde, Mikael S. Hedenqvist
    更新日期:2018-05-23
  • Simultaneous improvement of mechanical and fire retardant properties of synthesised biodegradable guar gum-g-poly(butyl acrylate)/montmorillonite nanocomposite
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-22
    Dharmendra K. Jena, Prafulla K. Sahoo

    A novel multicomponent biopolymer based nanocomposite was synthesised via graft copolymerization of butyl acrylate (BA) onto guar gum (GG) and montmorillonite (MMT) by using ammonium persulfate (APS) as a free radical initiator, in the presence of N,N′-methylene bisacrylamide (MBA) as a crosslinking agent. BA had been grafted onto GG chains and the participation of -OH groups of MMT in polymerization reaction was confirmed by FTIR spectra. XRD and TEM observations revealed that MMT was exfoliated and uniformly dispersed in guar gum-g-poly (butyl acrylate) (GG-g-PBA) matrix. The resultant nanocomposite showed remarkably improved thermal stability and mechanical properties. In addition, the excellent fire retardancy of nanocomposite results from the formation of compact and continuous char which not only hinders the migration of volatile decomposition products out of polymer matrix but also provides barrier for heat transfer evaluated by limiting oxygen index (LOI) and cone calorimetry test. The biodegradation of nanocomposite has been carried out for better commercialization and environmental concern.

    更新日期:2018-05-22
  • Biodegradable PHBH/PVA blend nanofibers: Fabrication, characterization, in vitro degradation, and in vitro biocompatibility
    Polym. Degrad. Stabil. (IF 3.193) Pub Date : 2018-05-21
    Rina Afiani Rebia, Sélène Rozet, Yasushi Tamada, Toshihisa Tanaka
    更新日期:2018-05-21
  • 更新日期:2018-05-18
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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