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  • Sulfathiazole derivative with phosphaphenanthrene group: Synthesis, characterization and its high flame-retardant activity on epoxy resin
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-13
    Peng Wang; Hang Xiao; Chao Duan; Bo Wen; Zongxin Li

    A sulfathiazole derivative with phosphaphenanthrene group (STZ) was successfully synthesized by covalently bonding DOPO and imine intermediate obtained from the condensation of sulfathiazole with p-hydroxybenzaldehyde. Its effect on the thermal, flame-retardant and mechanical properties of epoxy thermosets were comprehensively studied. The presence of STZ decreased the initial degradation temperature and glass transition temperature (Tg) of epoxy thermoset. STZ significantly improved the flame retardancy and fire safety of epoxy thermoset. With the addition of only 4 wt% STZ, the modified epoxy thermoset achieved an LOI value of 29.1% and V-0 rating in UL-94 test. Moreover, the peak heat release rate (PHRR) and total heat release (THR) in cone calorimeter test were decreased by 34.4% and 32.1% in comparison with those of pure epoxy thermoset. STZ showed high flame-retardant activity not only by releasing nonflammable gases and phosphorous radicals in the gas phase, but also by promoting the formation of dense and intumescent char layer with honeycomb-like hollow structure inside in the condensed phase. Because of the strong intermolecular action between STZ and epoxy macromolecular chain, the presence of STZ increased the tensile strength, while decreased the elongation at break of epoxy thermoset.

  • Synthesis of a novel phosphorus and nitrogen-containing flame retardant and its application in rigid polyurethane foam with expandable graphite
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-13
    Zhiyong Zhang; Dongsheng Li; Miaojun Xu; Bin Li

    A novel phosphorus and nitrogen containing flame retardant named 1,4-bis(Diethyl methylenephosphonate) piperazine (BDEMPP) was synthesized. The chemical structures of BDEMPP were determined by Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS). The flame retardant rigid polyurethane foams (FR-RPUFs) were prepared by one-pot and free foaming with incorporating BDEMPP/expanded graphite (EG) with polyether polyol and polymethylene polyphenyl isocyanate. The limit oxygen index (LOI), vertical burning (UL94) and cone calorimeter (CONE) test showed that the fire-retardant properties were improved due to the barrier effect of EG and residual char. With addition of 10 wt % EG and 15 wt % BDEMPP, RPUF/10EG/15BDEMPP passed UL94 V-0 with the LOI value of 25.7%. The thermogravimetric analysis (TGA) results revealed that the initial decompose temperature (T5%) of RPUF/10EG/15BDEMPP was decreased compared with pure RPUF. However, the yield of residual char was increased from 0.35% for pure RPUF to 30.52% for RPUF/10EG/15BDEMPP at 800 °C. EG and BDEMPP had a slight influence on density and compression strength. The density and compression strength of pure RPUF was 45.42 kg m−3 and 213 kPa. As for RPUF/10EG/15BDEMPP, the density and compression strength was 44.18 kg m−3 and 180 kPa. The morphology and composition of residual char were investigated. The results demonstrated that the intact, compact and thick residual char with abundant of phosphorus and nitrogen was formed to enhance the flame retardancy and smoke suppression.

  • Biomimetic scaffold fabricated with a mammalian trabecular bone template
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-08
    Inna Bulygina; Fedor Senatov; Rajan Choudhary; Evgeniy Kolesnikov; Sergey Kaloshkin; Ronja Scholz; Marina Knyazeva; Frank Walther; Natalya Anisimova; Mikhail Kiselevskiy
  • Effects of the proportion of two different cross-linkers on the material and biological properties of enzymatically degradable PEG hydrogels
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-03
    Siju Liu; Hong Cao; Renqi Guo; Heling Li; Cuifen Lu; Guichun Yang; Junqi Nie; Feiyi Wang; Nianguo Dong; Jiawei Shi; Feng Shi

    A series of enzymatically degradable PEG hydrogels with tunable degradability were prepared by changing the proportions of two cross-linkers, enzymatically degradable cross-linker matrix metalloproteinase (MMP) degradable peptide and non-degradable cross-linker PEG-dithiol, and the effects of the proportion of two cross-linkers on the other properties of PEG hydrogels were also investigated. As the content of the degradable cross-linker increased, their mechanical properties decreased, but their swelling rate gradually increased. LIVE/DEAD cell staining and CCK-8 assay indicated that PEG hydrogels have high biocompatibility and low cytotoxicity, and as the content of the degradable cross-linker increased, the proliferation of cells is more favorable. Furthermore, adipogenic differentiation and osteogenic differentiation assays showed that BMSCs 3D-capsulated in PEG hydrogels can proliferate and then differentiate into osteoblasts or adipocytes, and as the content of degradable cross-linker increased, calcium nodules and the number of fat cells increased. These results demonstrate that the proportions of two cross-linkers have an effect on the physical, chemical and biological properties of PEG hydrogels, and these PEG hydrogels could be used as tissue engineering scaffold materials.

  • Preparation and properties of room temperature vulcanized silicone rubber using triethoxy(2-(4-methylcyclohex-3-en-1-yl)propyl)silane as a novel cross-linking agent
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-03
    Yuehan Qian; Fuhao Dong; Lizhen Guo; Jiawen Guo; Hiba Shaghaleh; Yuqi Wang; Xu Xu; Shifa Wang; Shiwei Liu

    Limonene is an important subsidiary agricultural product obtained from orange peel that can also be prepared by microbial engineering, but its application degree of deep processing is relatively lower. By studying the application of limonene to silicone rubber, the application field of limonene has been expanded. Triethoxy (2-(4-methylcyclohex-3-en-1-yl)propyl)silane (LTES) was synthesized by a hydrosilylation reaction in the presence of Karstedt's catalyst using limonene and triethoxysilane as raw materials. FT-IR and 1H NMR were used to determine the structure of the product (LTES). Thereafter, a series of room temperature vulcanized (RTV) silicone rubbers was modified with the LTES cross-linking agent and hydroxy silicone oil under the catalytic action of dibutyltin dilaurate. The results showed that the tensile strength, elongation at break and heat resistance of the synthetic silicone rubber modified with LTES were significantly higher.

  • Thermal stability of ethylene copolymers with multi-alkenylsilsesquioxane comonomers synthesized by organometallic catalyst - Effect of copolymer structure
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-03
    Paweł Groch; Krystyna Czaja; Beata Sacher-Majewska

    This study was focused on thermal properties of ethylene copolymers with di-, tri- and tetra-alkenylsilsesquioxanes (POSS) synthesized by ansa-metallocene complex. Ethylene copolymers with multi-alkenyl POSS were characterized by different thermal behavior depending on the kind of POSS comonomer and its content, as well as the copolymer structure. The copolymers differed in the incorporation way of POSS into the polymer chain (linear and crosslinked structure), content of specific unsaturation groups, molecular weight, as well as heterogeneity of polymer chain compositions. It was found that the kind and content of unsaturation groups in E/POSS copolymers played a significant role in the thermal stability of the obtained hybrid materials determined in non-isothermal conditions. Thus, linear copolymers showed higher thermal stability in comparison with neat polyethylene and crosslinked copolymers. Thermal stability of copolymers under iso-thermal conditions (1500 h heating at 100 °C) of polymeric products was primarily determined by the kind and content of silicon-oxygen POSS cage incorporated into the polymer chain. Incorporation of alkenylsilsesquioxane with completely condensed POSS cage into the polymer chain caused significant improvement of thermal stability, even in case of crosslinked copolymers, in contrast to comonomers with incompletely condensed silicon-oxygen POSS cage.

  • Tailoring the toughness of sustainable polymer blends from biodegradable plastics via morphology transition observed by atomic force microscopy
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2020-01-02
    Feng Wu; Manjusri Misra; Amar K. Mohanty

    Super-toughened polylactide/polybutylene succinate/polybutylene adipate terephthalate (PLA/PBS/PBAT) ternary blends can be prepared by reactive extrusion in the presence of peroxide. However, the high peroxide contents always lead to lowered biodegradability and decreased flowability of the prepared materials. In this study, a strategy to prepare such super-toughened PLA ternary blends with a small amount of peroxide, by simultaneous phase transition and interfacial compatibilization, was demonstrated. Firstly, based on thermodynamic predictions, a core-shell PBS/PBAT structure was successfully prepared that worked as a toughening agent for PLA. Secondly, the viscosity ratio between PLA and PBS/PBAT was adjusted via the introduction of a small amount of peroxide because of the different reactive priority between peroxide and the polymers. Via transferring the co-continuous PBS/PBAT to droplet structure with optimum size and improving the compatibility between PLA and core-shell PBAT-PBS, two different super-toughened PLA ternary blends with high impact strength and melt strength were successfully prepared. The resulting ternary blends showed super toughness with significantly improved notched impact strength (∼530 J/m). The mechanism behind the morphology transformation is discussed based on the phase inversion theory with the help of relaxation time spectrum analysis and atomic force microscopy (AFM). The studies show that both the morphology transition of the different components and improved compatibility make contributions together to the improved mechanical properties. The research provides a new approach to improving the toughness of the polymer blends in reaction extrusion by tailoring the viscosity ratios between different components. The ternary blends developed are expected to be used widely in industrial applications.

  • 更新日期:2020-01-02
  • Flame retardant efficiency of modified para-aramid fiber synergizing with ammonium polyphosphate on PP/EPDM
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-31
    Kai Wu; Xiangyu Wang; Yuhan Xu; Weihong Guo

    This paper investigates the char forming effect of para-aramid fiber and the flame-retardant efficiency of para-aramid fiber synergizing with ammonium polyphosphate on polypropylene/ethylene propylene diene monomer. Para-aramid fiber was firstly modified by phosphoric acid, and then modified by 3-aminopropyltriethoxy. Para-aramid fiber and modified para-aramid fiber were characterized by field-emission scanning electron microscope, energy-dispersive analysis and Fourier transform infrared spectroscopy. Fourier transform infrared spectroscopy illustrated that P–O groups and Si–O groups appeared on the surface of modified para-aramid fiber. The intumescent flame retardants containing para-aramid fiber/ammonium polyphosphate or modified para-aramid fiber/ammonium polyphosphate was introduced into polypropylene/ethylene propylene diene monomer. The flame-retardant efficiency of polypropylene/ethylene propylene diene monomer composites were investigated by limiting oxygen index, UL-94 vertical burning and cone calorimeter test. The polypropylene/ethylene propylene diene monomer composite containing 34.5 wt% ammonium polyphosphate and 0.5 wt% modified para-aramid fiber achieved a UL-94 V0 rating with a limiting oxygen index of 28, as well as showed a 23.6% reduction of total heat release and a 47.0% reduction of total smoke release. The thermal stability of polypropylene/ethylene propylene diene monomer composites were investigated by thermogravimetric analysis. The residual char layers of polypropylene/ethylene propylene diene monomer composites were analyzed by field-emission scanning electron microscope. The tensile and tear strength of polypropylene/ethylene propylene diene monomer composites were also tested. After 1 phr modified para-aramid fiber was added, the tensile strength and tear strength increased by 33.3% and 35.9%, respectively. The results indicated that modified para-aramid fiber/ammonium polyphosphate/polypropylene/ethylene propylene diene monomer had better flame-retardant efficiency, thermal stability, smoke suppression and mechanical properties with the synergistic effect of P, N, Si elements.

  • Epoxy thermoset with enhanced flame retardancy and physical-mechanical properties based on reactive phosphaphenanthrene compound
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-30
    Shanglin Jin; Zhen Liu; Lijun Qian; Yong Qiu; Yajun Chen; Bo Xu

    A phosphaphenanthrene flame retardant, DCAD, was synthesized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), p-phenylenediamine and bio-based material cinnamaldehyde. After being incorporated into epoxy thermosets, DCAD can impose better flame retardancy and physical-mechanical properties to epoxy thermosets. 4%DCAD/EP achieved a LOI value of 35.6% and passed the UL94 V-0 rating, obviously decreased peak value of heat release rate, and generated the compact, stable and foam-like char layer during combustion. Through tracking by the gas-phase real-time infrared spectrum and observing the microscopic structures of residue, the higher flame retardancy of DCAD was attributed to the effectively quenching effect in gas phase and the high-quality charring effect in condensed phase. In addition, the N–H structures in reactive-type DCAD molecule can react with the epoxy groups of epoxy resin and two CC bonds in DCAD can form elastomer-like crosslink, resulting in that 4%DCAD/EP owned a raised impact strength of 25.74 kJ/m2 and did not decrease the glass transition temperature obviously in contrast to neat epoxy resin.

  • Epoxy resin flame retarded and toughed via flexible siloxane chain containing phosphaphenanthrene
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-23
    Qiuru Bao; Biwu Wang; Yuan Liu; Qi Wang; Zhongqiang Yang
  • Synthesis and crystal characterization of novel fulleropyrrolidines and their potential application as nitrocellulose-based propellants stabilizer
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-24
    Guang Li; Bo Jin; Zuohu Chai; Ling Ding; Shijin Chu; Rufang Peng

    Safe storage of nitrocellulose-based propellants has become challenging due to their requirements of extreme storage and operational environments. Thus, developing new high-performance stabilizers is urgently needed to improve the stability of propellants. With their excellent thermal stability and strong ability to clear free radicals, fullerene stabilizers for nitrocellulose-based propellants were synthesized using the Prato reaction. Their molecular structures were confirmed by 1H NMR, 13C NMR, FT-IR, UV–Vis, HRMS, and single-crystal X-ray diffraction. Their compatibility and stability in nitrocellulose were investigated using differential scanning calorimetry, methyl-violet, vacuum stability, and weight loss tests. Results indicated that the new fullerene stabilizers had excellent compatibility with nitrocellulose and their stability were better than the conventional stabilizers C2 and DPA. Moreover, their stability mechanism was investigated by electron paramagnetic resonance spectroscopy and FT-IR analysis. The results turned out that new fullerene stabilizers could absorb nitrogen oxides and effectively eliminate the nitroxyl radicals released from nitrocellulose decomposition. Therefore, these new multifunctional fullerene derivatives can be used as novel stabilizers and apply to single and double base propellants.

  • Photo-degradation of polyethylene under stress: A successive self-nucleation and annealing (SSA) study
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-20
    Qiang Liu; Shixiang Liu; Yadong Lv; Yajiang Huang; Miqiu Kong; Qi Yang; Guangxian Li

    Successive self-nucleation and annealing (SSA) technique based on calorimetry is utilized to reveal the effect of uniaxial tensile stress on the photo-oxidation of high density polyethylene (HDPE). Stress-induced acceleratory and inhibitory effects on HDPE are confirmed by analyzing the newly formed melting peaks at low temperatures and the gradually disappeared melting peaks at high temperatures on the SSA curves. The formation of short chains due to chain scission contributes to both the new higher melting peaks (thick lamellae) and lower melting peaks (thin lamellae) because of high mobility and thermodynamic preference, respectively. Besides, chain crosslinking also gives rise to the formation of low melting peaks due to the decrease in the crystallizable sequence lengths and dynamical constraints. Compared with Fourier Transform Infrared Spectrometry, Scanning Electron Microscopy and Small Angle X-ray Scattering, the SSA technique can more precisely and sensitively reflect the early multi-scale aging behavior of HDPE subjected to stress.

  • Pyrolysis of brominated polyethylene as an alternative carbon fibre precursor
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-18
    Bronwyn Laycock; Xiaoyu Wang; Ru-Fen Liu; Pratheep Kumar Annamalai; Jorja Cork; Chris Derstine; Michael Mills; Eric W. McFarland

    Polyethylene as a polymeric precursor for carbon fibre production has attracted much attention over recent years. Not only is it a low-cost commodity polymer, it has a higher theoretical carbon yield (at 86%) than polyacrylonitrile (at 67%) and is very readily melt processed into fibres. The challenge is to efficiently dehydrogenate and graphitize polyethylene fibres. This paper explores the use of bromine as a novel oxidant to functionalise polyethylene prior to carbonisation, leading to efficient cyclisation and carbonisation on heating. Through a process of low-temperature photo-induced liquid-phase bromination followed by dehydrobromination at moderate temperature and subsequent carbonisation to 800 °C, a carbonaceous product was obtained in high yield (>90%). The effects of a range of process conditions, as well as the use of different types of polyethylene and polyethylene blends, were explored.

  • Phthalonitrile prepolymer and PAN blends: New strategy for precursor stabilization and pyrolytic char yield enhancement
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-18
    Yu Shan Tay; Ming Liu; Jacob Song Kiat Lim; Hui Chen; Xiao Hu

    New polymer blends of polyacrylonitrile (PAN) and resorcinol-based phthalonitrile prepolymer (pPN) are studied as superior carbon precursors. pPN has a hyperbranch-like structure with multiple terminal nitrile groups available for chemical interactions. The addition of pPN into PAN significantly lowers the cyclization temperature by more than 15 °C during the oxidative stabilization stage which is unprecedented and highly desirable giving rise to a multitude of advantages during carbonization. The presence of pPN also leads to large synergy in char yield by due to the specific interaction between the nitrile terminal groups in the hyperbranch-like pPN and PAN chains. The char yield at 600 °C increased from 57.7% to a remarkable 69.0% when 10 wt% of pPN is added into PAN even though under the same condition the char yield of neat pPN itself is only 48.8%. Additional advantages of this new approach, i.e., large shrinkage reduction and property enhancement, are also observed in the carbonaceous materials obtained from the pPN/PAN blends. Raman spectra reveal that the carbon structure is retained when 10 wt% or less pPN is used.

  • Ageing of chemically modified poly(vinylidene fluoride) film: Evolution of triple carbon-carbon bonds infrared absorption
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-18
    V.E. Zhivulin; L.A. Pesin; E.A. Belenkov; V.A. Greshnyakov; N. Zlobina; M. Brzhezinskaya

    The paper presents the results of the combined investigation of changes in the poly(vinylidene fluoride) (PVDF) structure caused by chemical carbonization and subsequent long-term ageing, as one of the most promising ways to synthesize the 1D modification of chemically pure carbon, carbyne. For the first time, the ageing process of PVDF was monitored during extremely wide time-frame from 19 to 500000 min. The evolution of PVDF molecular structure was investigated experimentally by infrared and X-ray absorption spectroscopies. As a result, non-monotonic variation of triple carbon-carbon bonds infrared absorption in the course of long-term ageing was revealed, as well as new aspects of PVDF carbonization. The series of appropriate molecular complexes were modeled, for which characteristic frequencies and absorbance intensities in the IR spectra were simulated by the DFT-LDA method and applied to interpret the results of the experimental study.

  • In vivo degradation study of polyvinylidene fluoride/polybutylene succinate/modified organic montmorillonite nanocomposite films implanted in the gastrointestinal tract
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-18
    Chung-Feng Jeffrey Kuo; Hao-Yu Wang; Adhimoorthy Prasannan; Juin-Yih Lai; Jun-Sheng Wang; Hao-Ming Chang; Hsieh-Chih Tsai

    A duodenal barrier treatment implanted in gastrointestinal (GI) tract prevents the direct contact of food with the duodenal wall, which helps control the plasma glucose by manipulating the intestinal hormone and insulin secretion. Duodenal barrier material design has to withstand the stress of enterogastric peristalsis and be degradable to avoid damaging the intestinal tissue during its removal when the treatment finished. Most of the biodegradable polymer based implanted materials in the digestive tract were failed to withstand the erosion by gastric acid and intestinal juice. In this regards, composites from polybutylene succinate (PBS) shows weaker stability while used in digestive track, but it could improve towards less prone to sticking to the intestinal wall in the digestive tract through reduce the incidences of infection and inflammation while mixed with poly(vinylidene fluoride) (PVDF). Moreover, addition of nanosized additives like montmorillonite to polymer nanocomposites can offer versatile mechanical stability and sustainable degradation. Therefore, in this study, a polymer nanocomposite with degradability and high mechanical properties was prepared by blending (PVDF with biodegradable PBS and organic montmorillonite (OMMT). The nanocomposite with 3 wt% OMMT (PVDF90/PBS10/OMMT3wt%) exhibited the highest tensile strength of 62.61 MPa, which exceeds the tensile strength required for application to soft tissues (46.5 MPa) due to uniform distribution of OMMT. The result showed that the PBS films degraded much faster than the nanocomposite film did in the duodenum and stomach. The rates of weight loss of the nanocomposite in stomach and duodenum were 1.88% and 0.88%, respectively, which indicated that the degradation rate of the nanocomposite film is faster in the stomach than in the duodenum. The nanocomposite maintained a high tensile strength of 60.85 MPa after one month of implantation. Moreover, histological examination revealed mild inflammation of tissue and negligible adverse effects. The in vivo degradation test suggests that the PVDF/PBS/OMMT nanocomposite prepared in this study have the potential for application as a biodegradable duodenal barrier.

  • Simultaneously improving flame retardancy, water and acid resistance of ethylene vinyl acetate copolymer by introducing magnesium hydroxide/red phosphorus co-microcapsule and carbon nanotube
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-16
    Jichun Liu; Yunpeng He; Haibo Chang; Yingbin Guo; Hang Li; Bingli Pan

    In this work, a co-microcapsule of magnesium hydroxide (MH) and red phosphorus (RP) (denoted as M[MH&RP]) was synthesized using 4, 4′-diphenylmethane diisocyanate and melamine via one-step in-situ surface polymerization, which was subsequently introduced into ethylene vinyl acetate copolymer (EVA) as a flame retardant. The results indicate that the core-shell structured co-microcapsule displays increased thermal and thermo-oxidative stability as well as better dispersion in EVA. Flame retardancy of the EVA/M[MH&RP] composite improves significantly in comparison with the EVA/MH/RP composite due to formation of continuous and compact char layer on the surface of the composite. Moreover, this flame-retardant composite exhibits excellent water and acid resistance. The addition of a small amount of multi-walled carbon nanotube (MWCNT) further increases flame retardancy of the EVA/M[MH&RP] composite considerably and the flame-retardant EVA/M[MH&RP]/MWCNT composite has good mechanical flexibility and electrical insulation. This work has provided a simple method to prepare multi-functional flame-retardant EVA composite.

  • Influence of carboxylic acid content and polymerization catalyst on hydrolytic degradation behavior of Poly(glycolic acid) fibers
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-16
    K. Saigusa; H. Saijo; M. Yamazaki; W. Takarada; T. Kikutani

    Poly(glycolic acid) (PGA) is an aliphatic polyester with the simplest chemical structure. Since PGA is susceptible to hydrolysis, various researchers studied the factors affecting the hydrolytic degradation behavior of PGA. The factors include the higher-order structure, pH, ionic electrolyte etc. In this study, to clarify the mechanism for the hydrolysis of PGA fibers, effect of the carboxylic acid content on the hydrolytic degradation behavior was investigated through the quantitative evaluation of the amounts of the carboxylic acid end group and the PGA monomer (glycolide, GL) in the fibers. Evaluation of the hydrolysis of PGA fibers through the analyses of the molecular weight retention and tensile strength retention after immersing in the phosphate buffer solution at 37 °C revealed that the hydrolysis is governed by the carboxylic acid content in the PGA fibers. It was also found that the amount of GL generated during the melt spinning process is affected by the amount and type of polymerization catalyst. In addition, the experimental results of fundamental analysis suggested that the polymerization catalyst also decomposes the GL into glycolic acid or glycolic acid dimers to generate carboxylic acid, and the rate of decomposition varies depending on the type and amount of catalyst. Based on these results, it was concluded that there is an indirect effect of the type and amount of polymerizing catalyst on the rate of hydrolysis of PGA fibers.

  • Thermal ageing of PTFE in the melted state: Influence of interdiffusion on the physicochemical structure
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-14
    V. Henri; E. Dantras; C. Lacabanne; A. Dieudonne; F. Koliatene

    PTFE is one of the most used polymer for electrical insulation. For future aircraft, PTFE will be exposed to thermal constraints above its melting temperature. Its high melt viscosity allows PTFE to be operable but it will be subjected to thermal-oxidative ageing. PTFE presents two initial states, associated with its thermal history corresponding to the interdiffusion phenomenon. In the case of thermo-oxidative ageing in the melt, interdiffusion impairs the thermal stability by shifting the thermal degradation towards lower temperature. While interdiffusion reduces the thermal stability for long time ageing, strong physical interactions reduce the impact of degradation on the mechanical behaviour for short time ageing. Chemical ageing induced by degradation promotes recrystallisation of PTFE shorter chains; this crystalline phase modifies the β anelastic relaxation mode. The tan δ thermograms allows us to identify the β1 and β2 components of the anelastic effects of respectively the triclinic/hexagonal and hexagonal/pseudo hexagonal transitions observed by X-Rays Diffraction. Upon chemical ageing, the evolution of the β mode is mainly governed by the decrease in the β2 component corresponding to the pseudo-hexagonal phase.

  • Solid-state and time domain NMR to elucidate degradation behavior of thermally aged poly (urea-urethane)
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-11
    Kaori Numata, Atsushi Asano, Yasumoto Nakazawa

    We have demonstrated that solid-state and time-domain Nuclear Magnetic Resonance spectroscopy (NMR) techniques are effective in monitoring the degradation site of poly (urea-urethane). We prepared two types of commercial poly (urea-urethane), Urethane-A and Urethane-B, and aged them at 100 °C for up to 10000 h. We performed tensile strength tests and solid-state NMR experiments, in which 13C and 15N NMR spectra and T2 were collected. The tensile strength of Urethane-A decreased, increased and decreased again, whereas that of Urethane-B decreased at a lower rate with aging. Solid-state NMR experiments clearly showed that the degradation of Urethane-A was caused by molecular chain scission and cross-linking in its urea bonds, and that of Urethane-B occurred owing to molecular chain scission in its urethane bonds. T2 had three components, short T2 (T2S), intermediate T2 (T2I) and long T2 (T2L), whose fractions were xS, xI and xL, respectively. We have demonstrated that molecular chain scission in urea bonds decreases xS and increases xL, and that in urethane bonds increases T2I and T2L without changing all the T2 fractions.

  • Are we overestimating the permanence of cellulose triacetate cinematographic films? A mathematical model for the vinegar syndrome
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-10
    Ida R. Ahmad, Deborah Cane, Joyce H. Townsend, Cristian Triana, Luca Mazzei, Katherine Curran

    Among the earliest signs of degradation in cellulose triacetate cinematographic films is the generation of acetic acid due to hydrolytic deacetylation of the polymer, marked by an increase in the acidity of the films and emissions of acetic acid leading to a characteristic vinegar odour. We propose a mathematical model for predicting the onset of the vinegar syndrome which accounts for the autocatalytic effect of acetic acid on the deacetylation reaction. Model parameters are estimated from previously published experimental data from other research groups. These show free acidity changes in cellulose triacetate films subjected to accelerated ageing at temperatures of 70–100 °C. The model is validated against a different set of previously published experimental data of cellulose triacetate films aged at 21 °C and 35 °C, at 20, 35 and 50% relative humidity. The model demonstrates good quantitative agreement with the published experimental data. Predictions of film permanence at lower temperatures, similar to those present in the archives in which the films are typically stored, are made and compared with the predictions of film conservation guidelines. The results indicate that film permanence may be overestimated by existing guidelines, which do not account for autocatalysis in their modelling of the deacetylation rate. Our results suggest that cold storage, a common film conservation strategy, may be less effective at inhibiting degradation than previously thought. As cold storage typically requires film to be kept in confined spaces with limited air movement, conditions which promote autocatalysis, the inclusion of autocatalysis in our model is highly applicable to simulating this environment.

  • Ring-opening dispersion polymerization of L-lactide initiated by L-arginine in supercritical carbon dioxide
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-10
    Shiping Zhan, Zetao Wan, Yu Zhao, Jingchang Wang, Zhiyi Li

    The ring-opening dispersion polymerizations of l-lactide (L-LA) were carried out with ScCO2 as the green solvent, l-arginine (L-Arg) as an initiator and PCL-PDMS-PCL triblock copolymer as the stabilizer. The poly (l-lactide) (PLLA) products were obtained with a good disperse powders (9–22 μm), a higher number-average molecular weight (11700 g/mol), a better molecular weight distribution (PDI) (1.31) and a lower reaction temperature (150 °C). The synthesis mechanisms and synthesis procedures of the polymerization reaction were presented. The optimum reaction conditions were obtained under the pressure of 12 MPa and the reaction time of 48 h. The kinetic process of the reaction was discussed and the results showed that the reaction was controllable polymerization and a first order kinetic reaction.

  • Dripping and decomposition under fire: Melamine cyanurate vs. glass fibres in polyamide 6
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-10
    Analice Turski Silva Diniz, Christian Huth, Bernhard Schartel

    Manipulating the melt dripping of thermoplastics makes a fire scenario more or less dangerous. Yet, a detailed understanding of this phenomenon has remained a question mark in studies of the flammability of plastics. In this work, the individual and collective impacts of additives on the dripping behaviour of polyamide 6 (PA6) were studied. A set of materials compounded with melamine cyanurate (MCA) and glass fibre (GF) was investigated. Under UL 94 vertical test conditions, the dripping during first and second ignition was quantified and investigated in detail. The number, size and temperature of the drops were addressed, and the materials and their drops evaluated with respect to such aspects as their averaged molecular weight, thermal decomposition and rheological properties. PA6 with V-2 classification improved to V-0 with the addition of MCA, and achieved HB in the presence of GF. PA6/GF/MCA achieved V-2. Non-flaming drops of PA6/MCA consisted of oligomeric fragments. Flaming drops of PA6/GF showed a more pronounced decomposition of PA6 and an increased GF content. The dripping behaviour of PA6/GF/MCA can be understood as a combination of the influence of both additives. The results showed nicely that dripping under fire is neither a straightforward material property nor a simple additive influence, but the complex response of the material influenced by the interaction and competition of different phenomena.

  • 更新日期:2019-12-07
  • Nano-ZrO2 filled high-density polyethylene composites: Structure, thermal properties, and the influence γ-irradiation
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-04
    A.A. Nabiyev, A. Olejniczak, A. Pawlukojc, M. Balasoiu, M. Bunoiu, A.M. Maharramov, M.A. Nuriyev, R.S. Ismayilova, A.K. Azhibekov, A.M. Kabyshev, O.I. Ivankov, T. Vlase, D.S. Linnik, A.A. Shukurova, O. Yu Ivanshina, V.A. Turchenko, A.I. Kuklin

    High-density polyethylene (HDPE) composites with different amounts of ZrO2 nanoparticles (1–20 vol%) were prepared by high-pressure thermal pressing. The effect of γ-irradiation on their structural and thermal properties was investigated using small-angle neutron scattering (SANS), X-ray diffraction (XRD), Raman spectroscopy, infrared spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SANS analysis confirmed good dispersion of the nanoparticles in HDPE matrix. Upon exposure to γ-radiation only small changes in the lattice parameters and the crystalinity degree occurred for both HDPE and the nanocomposities. More significant changes for irradiated HDPE were observed in DSC-derived parameters, including the decrease in the melting point, and increase in crystalinity degree. This trend was even more pronounced for the nanocomposities. A possible explanation assuming resonant enchantment of polymer chain scission in the presence of ZrO2 nanoparticles is discussed. The extent of radiation-induced oxidation was essentially the same for pure HDPE and the nanocomposities, suggesting that the process is diffusion controlled. The thermal stability of the irradiated composites was somehow higher than that pure HDPE.

  • Effect of solid-state polymerization on the structure and properties of mechanically recycled poly(lactic acid)
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-03
    Freddys R. Beltrán, Esteban Climent-Pascual, María U. de la Orden, Joaquín Martínez Urreaga

    Poly(lactic acid) (PLA) is one of the most important alternatives to fossil-fuel based polymers due to its biodegradability and good properties. However, the growing production along with the increasing resistance to degradation of the newer grades could lead to waste management problem. The application of mechanical recycling, which could be the best valorization method for biodegradation-resistant PLA residues, is limited by the degradation of the polymer, which decreases its performance, so it is interesting to develop simple and acceptable methods to improve the recycled plastic. The aim of this work is to study the effect of thermal treatments of PLA residues (with two levels of degradation) on the structure and properties of recycled PLA. During thermal treatments, both polycondensation and degradation reactions take place, and the net result depends on the degradation level of the residue and the time and temperature of the treatment. In adequate conditions, polycondensation reactions increase the molecular weight of the residue and lead to significant improvements of the mechanical and thermal properties of the recycled plastic. These results suggest that thermal treatments represent a simple, cost-effective and environmentally friendly method to improve the recyclability of PLA and, hence, the environmental impact of this plastic.

  • Thermal properties and degradation of enantiomeric copolyesteramides poly(lactic acid-co-alanine)s
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-12-02
    Hideto Tsuji, Shotaro Sato, Noriaki Masaki, Yuki Arakawa, Yuta Yoshizaki, Akinori Kuzuya, Yuichi Ohya
  • Facile fabrication of fully biodegradable and biorenewable poly (lactic acid)/Poly (butylene adipate-co-terephthalate) in-situ nanofibrillar composites with high strength, good toughness and excellent heat resistance
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-28
    Tong Liu, Xinghan Lian, Lengwan Li, Xiangfang Peng, Tairong Kuang

    Fully biodegradable and renewable polymer materials have shown broad application prospects with minimal environmental degradation. In the current study, eco-friendly poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) in-situ nanofibrillar composites with hierarchical crystal architectures, high mechanical performance and excellent heat resistance properties were fabricated using the loop oscillating push-pull molding (LOPPM) technique and in-situ PBAT nanofibrils were used to induce highly oriented hybrid shish-kebabs. Benefiting from the flow-induced crystallization and abundant hybrid shish-kebabs, the overall crystallinity of LOPPM processed PLA/10 wt%PBAT sample increased by 4-fold than the conventional injection-molded (CIM) neat PLA sample. The present work indicated that the tensile strength, Young's modulus, elongation at break and impact strength of LOPPM processed PLA/10 wt%PBAT were higher than the CIM-processed PLA by 36.2%, 12.5%, 181.8% and 253.7%, respectively. The vicat softening temperature was elevated from 59.6 °C to 104.8 °C, and the thermostability also enhanced due to the construction of hybrid shish-kebabs. Strong, tough and heat-resistant PLA/PBAT in situ nanofibrillar composites exhibited outstanding properties for use under more demanding circumstances and are environmentally friendly.

  • Synthesis, crystallization behavior and mechanical properties of novel biobased Poly(octamethylene succinate)
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-27
    Yaqing Shang, Xiaojing Li, Zhiguo Jiang, Zhaobin Qiu

    In this research, a novel relatively long chain aliphatic polyester poly(octamethylene succinate) (POS) with a high weight-average molecular weight of 1.05 × 105 g/mol was synthesized from succinic acid and 1,8-octanediol via a melt polycondensation method. POS was a semicrystalline polyester with a glass transition temperature of −53 °C and an equilibrium melting point temperature of 72.5 °C. With an increase in crystallization temperature, the overall crystallization rate and spherulitic growth rate of POS gradually decreased. Due to its high molecular weight and relatively long chain chemical structure, POS displayed relatively good mechanical properties with the Young's modulus, tensile strength, and elongation at break being 526 ± 8 MPa, 12.0 ± 0.3 MPa, and 165 ± 24%, respectively, thereby making it a potential candidate to find end use as a packing material.

  • The effect of introduction of filament shift on degradation behaviour of PLGA- and PLCL-based scaffolds fabricated via additive manufacturing
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-24
    Ewa Walejewska, Joanna Idaszek, MarcinHeljak, Adrian Chlanda, Emilia Choinska, Vasif Hasirci, Wojciech Swieszkowski

    The degradation rate of polyester scaffolds has been emphasised as one of the main areas of concern in bone tissue engineering. In ideal conditions, the degradation of polymeric constructs should match regeneration of the injured tissue. Thus, there is an imperative need to strictly define and understand determinants influencing the degradation rate of scaffolds. In this study, we focused on the effect of filament shift introduction on degradation behaviour of the polymeric-based scaffolds. The poly(l-lactide-co-glycolide) (PLGA), poly(l-lactide-co-ε-caprolactone) (PLCL) and their tricalcium-phosphate-loaded (TCP) composites containing 20 and 40 wt% of filler, were utilized to fabricate constructs using modified fused deposition modeling (FDM). The scaffolds were designed with filament lay-down pattern of 0°/90° and with or without the modifications of filament distance in n+2 layer, shifted and non-shifted constructs were obtained, respectively. To investigate the degradation profile, the change of mass, pH, water absorption and initial molecular weight (Mw0) loss was observed during the degradation study in phosphate buffered saline (PBS) at 37 °C for up to 48 weeks. The scaffold morphology was evaluated utilizing scanning electron microscopy (SEM) and the visualization of the topography was performed utilizing atomic force microscopy (AFM). Surface area to volume ratio (SVR) and porosity were determined using micro-computed tomography (μCT). The fluid flow simulations were used to define the permeability of two investigated groups of scaffolds. The results of this study clearly demonstrate the accelerating effect of filament shift introduction on degradation behaviour in the scaffolds with similar porosity and SVR. The decrease of Mw0 was significantly higher in case of all shifted samples. We assume that faster degradation of shifted constructs may be attributed to their tortuosity, making them less permeable and prone to the degradation, as the result of the accumulation of acidic products in the tortuous architecture of the samples. Thus, the effect of introduction of filament shift into scaffold architecture comprise an attractive approach to influence the degradation rate in case of bone regeneration with the use of polyesters scaffolds.

  • Thermal degradation mechanism of a cured acetylene/aldehyde functional benzoxazine with high thermal stability
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-22
    Yi Xu, Pengcheng Li, Liying Li, Jie Dai, Qichao Ran, Yi Gu

    A cured mono-benzoxazine (PHB-apa) with both acetylene and aldehyde functional groups exhibits excellent heat resistance. The thermal degradation process of this polybenzoxazine was studied in this work. The pyrolysis temperature range and major thermal degradation products were determined by TGA-FTIR analysis. The stepwise-temperature Py-GC/MS was employed to identify the structures and the contents of the pyrolysis products at different temperature stages. Transformation of chemical structures of the polymer bulk during the pyrolysis process was speculated. The results suggest that the concerted reaction of the aldehyde groups and the polymerization of the acetylene groups form special crosslinking structures that can effectively prevent the release of the amines and the phenols.

  • A useful method for thorough dehydrochlorination of Poly(vinylidene chloride-co-vinyl chloride) using Zinc(II) oxide
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-22
    Tomohiko Okada, Satoru Sutoh, Kohtaro Sejima, Hiroki Tomohara, Shozi Mishima
  • 更新日期:2019-11-22
  • Synthesis of a novel liquid phosphorus-containing flame retardant for flexible polyurethane foam: Combustion behaviors and thermal properties
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-19
    Feng Zhou, Tao Zhang, Bin Zou, Weizhao Hu, Bibo Wang, Jing Zhan, Chao Ma, Yuan Hu
  • Relationship between morphological changes and mechanical properties in HDPE films exposed to a chlorinated environment
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-18
    K. Majewski, S.C. Mantell, M. Bhattacharya

    The effect of an oxidative environment on HDPE morphology and mechanical performance were studied. Extruded HDPE film samples of thickness (∼70 μm) (as-extruded and heat treated) were exposed to 5 ppm chlorinated water at 70 °C for up to 1250 h. As extruded samples had an initial crystallinity of 75% and heat treated samples an initial crystallinity of 83%. The initial molecular weight for all samples was approximately 200 kg-mol−1. Changes in morphology and mechanical properties as a function of exposure time were evaluated. The most significant changes occur after 500 h exposure. Fourier-Transform Infrared Spectroscopy (FTIR) spectrum data indicate an increase in the carbonyl functional groups with increased exposure time. As the exposure time increased, the molecular weight (Mw) of the samples decreased, with the as extruded samples being consistently less than that of the heat treated samples. Crystallinity increased nearly linearly with exposure time. XRD data reveal that the interlamellar spacing decreases significantly between 500 and 750 h exposure, from 102 A∘ to 85 A∘. Mechanical test data show a similar trend with tensile strength and strain at break. After exposure time of 500 h the samples become increasingly brittle. The combined morphology and mechanical data demonstrate, independent of exposure time, that there is a critical combination of molecular weight (<85 kg-mol−1) and interlamellar spacing (<85A∘) corresponding to the transition from ductile to brittle behavior.

  • Accelerated biodegradation testing of slowly degradable polyesters in soil
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-18
    Jana Šerá, Lynn Serbruyns, Bruno De Wilde, Marek Koutný

    According to the impending EU regulations, all polymer products used in agriculture and applied into soil must be biodegradable to prevent their accumulation in the environment. However, some of these products must serve their purpose for months up to years before their degradation and mineralization is desirable. Current international standards describing the biodegradability in soil are more directed towards materials that undergo relatively fast biodegradation, which hampers the development and certification of slowly biodegrading polymeric materials. Here, an accelerated soil biodegradation test is proposed, where by increasing the incubation temperature from 25 °C to 37 °C, up to about 4-fold increase in the biodegradation rate is achieved. The polymers tested include TÜV AUSTRIA Belgium certified polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polybutylene adipate-terephthalate and polylactic acid blend (PBAT/PLA) and an experimental polyester network (ICL-PN). The biodegradation rates of the given polymers at the two temperatures was examined by carbon dioxide evolution. Independent testing was done in two independent laboratories and the results were compared. The biodegradation of the materials was further assessed by electron microscopy and the microbial community present was analyzed by next-generation sequencing. Criteria were proposed for the accelerated test method, which include that the polymers eligible for the accelerated test should not manifest any phase transition, like e.g. a glass transition, in the interval from 25 °C to 37 °C. The proposed accelerated test can be helpful in the development of polymeric materials with a functional life of several years and with ultimately quantitative biodegradability.

  • Construction of flame retardant coating on polyester fabric with ammonium polyphosphate and carbon microspheres
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-18
    Ruihong Qin, Yinghao Song, Mei Niu, Baoxia Xue, Liyuan Liu

    In this study, ammonium polyphosphate (APP) was coated on the surface of carbon microspheres (CMSs) to synthesize the CMSs-APP (CA) three-in-one intumescent flame retardant (IFR). Then, CA was coated the surface of polyester fabric (CAP) by flame retardant finishing method to improve the flame retardant of polyester fabric. Morphology, thermal, flame retardant and other properties of CAP was characterized by SEM, TG, LOI, UL94 and CONE. The results show that when two layers of flame retardant (CMSs-APP) coated on polyester fabric (CAP2), the LOI value of CAP2 was 28.1% and the burning rating reached B1 class with no droplet drop during the UL94 test. The residue char has increased by 22.2%. The CA coating significantly reduced the heat release rate (HRR) and total heat release (THR) of the polyester fabric, with the HRR reduced by 51.0%, and produced a more stable and compact carbon layer during combustion. Moreover, the coated polyester fabric has excellent washing durability. Overall, CA flame retardant was coated the surface of polyester fabric endowed the polyester fabric with good flame retardant, broadening its scope of application.

  • Remarkable improvement of organic-to-inorganic conversion of silicone rubber at elevated temperature through platinum-nitrogen catalytic system
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-17
    Tian Liu, Xingrong Zeng, Xuejun Lai, Hongqiang Li, Yanlin Wang

    Organosilicon materials with high capacity of organic-to-inorganic conversion at elevated temperature are always favorable in the field of high-temperature-resistant materials, flame retardant materials, chemical engineering and functional materials in electrical engineering. In this work, it was found out that the platinum-nitrogen catalytic system could obviously enhance the organic-to-inorganic conversion efficiency of silicone rubber (SiR) at elevated temperature. The residual rate of Pt/N/SiR (SiR containing 0.33 phr Karstedt's catalyst (Pt) and 2 phr nitrogenous silane (N)) at 1000 °C was significantly improved from 3.0% to 44.8% in comparison with SiR and its thermal stability was also enhanced. DLS, TEM and UV–vis absorption spectrometry revealed that the platinum in Karstedt's catalyst would aggregate at elevated temperature and deteriorate its catalytic activity for organic-to-inorganic conversion of SiR. And the addition of nitrogenous silane can efficiently inhibit the aggregation and retain the high catalytic efficiency of platinum. A thorough TG-FTIR study, together with SEM/EDX and XPS analyses suggested that the platinum-nitrogen system might suppress the intramolecular cyclic transition and enhance the radical coupling between polymer chains of SiR during thermal degradation, which resulted in the high capacity of organic-to-inorganic conversion of Pt/N/SiR at elevated temperature.

  • Understanding the mechanism of ageing and a method to improve the ageing resistance of conducting PEDOT:PSS films
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-14
    Sujitkumar Bontapalle, Susy Varughese

    Accelerated thermal ageing studies were carried out on poly(3,4ethylenedioxythiophene): poly(styrene sulfonate)(PEDOT:PSS) thin films upto 150 °C to predict its life-time. The effect of thermal ageing on the chemical structure and the electronic structure is investigated. Changes in the conductivity of PEDOT:PSS films with ageing are studied along with UV–Vis, ATR-FTIR, Raman spectroscopy and AFM analysis. Conductivity at different temperatures shows an exponential decrease with time in the case of PEDOT:PSS (1.6PSS). Based on this data, the life-time of PEDOT:1.6PSS thin films at ambient conditions is predicted. The analysis of changes in the chemical structure using FTIR spectroscopy and the corresponding changes in the electronic structure using UV–Vis data shows changes in the polaronic states during ageing. Corresponding changes in the Raman spectroscopy data show oxidized-neutral transitions occurring during ageing which results in the conductivity changes. It is observed that unidirectional shearing of PEDOT:1.6PSS dispersion during film formation improved the thermal ageing characteristics. The ageing resistance of these films became comparable to that of PEDOT:2.5PSS films with higher PSS ratio. AFM studies show the effect of ageing on the surface morphology of films and shearing of films during formation can result in better ageing resistance and stable morphology.

  • Determination of chemical decay mechanisms of Parylene-C during X-ray irradiation using two-dimensional correlation FTIR
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-11
    Matthew J. Herman, Michael W. Blair

    Parylene (poly-p-xylylene), and its family of halogenated variants, have a long history for application as protective coatings and dielectric barriers. Among them, Parylene-C is the most popular due to its high impermeability to moisture, resistance to corrosive environments, and its vapor deposition polymerization, which is self-initiated and unterminated creating an extremely pure polymer coating. In order to apply these advantageous material characteristics in an environment containing ionizing radiation the effects of irradiation on the chemical stability of the polymer throughout the lifetime of the material needs to be further understood. In this work, Fourier-transform infrared (FTIR) and two-dimensional correlation (2D-COS) spectroscopies were used to monitor the structural changes in a ∼25 μm freestanding film of Parylene-C after subjection to X-ray irradiation. Samples were exposed to X-ray doses up to 100,000 Gy in atmospheric conditions, and IR spectra were measured after each 500Gy dose. Using 2D-COS it was possible to gain insight into the chemical stability and temporal mechanisms of the chemical reactions accompanying X-ray radiation of Parylene-C. Oxidation was observed by the production of a new species absorbing in the IR at 1697 and 1740 cm−1. Additionally, skeletal stretching of the aliphatic back bone were positively correlated to C–O oxidation products found in the region of 1425–1100 cm−1. The present work is confirmation that Parylene-C does experience chemical degradation from x-ray dose caused by oxidation of the polymer structure.

  • Heterophasic ethylene-propylene copolymers: New insights on complex microstructure by combined molar mass fractionation and high temperature liquid chromatography
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-11
    Sifiso Innocent Magagula, Anthony Ndiripo, Albert Johannes van Reenen

    The present study investigates the changes in the microstructure of heterophasic ethylene propylene copolymers (HEPCs) with increasing ethylene content, before and after visbreaking. Three samples obtained from commercial gas process reactors at Sasol Polymers at varying times after the addition of the ethylene comonomer are further visbroken to produce three more samples. Bulk sample analyses indicate that the ethylene-rich rubber phase which is essential in aiding peroxide mobility during visbreaking as observed in narrower dispersities and lower peak molar masses with increasing ethylene content. Further investigations of the microstructure via offline coupling of preparative molar mass fractionation (pMMF) to advanced analytical techniques such as solvent gradient interaction chromatography (SGIC) reveal that ethylene-rich copolymer chains are not significantly affected by the peroxide as the polypropylene homopolymer. Consequently, the polypropylene (PP) homopolymer and polypropylene-rich fractions with high molar mass diminish after visbreaking. Furthermore, the increase in ethylene content was observed to reduce the impact of the peroxide on the fraction quantities before and after visbreaking implying that visbreaking affects more the polyolefin chains with more PP segments and less those with more ethylene comonomer.

  • Nitrogen/sulfur-containing DOPO based oligomer for highly efficient flame-retardant epoxy resin
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-11
    Peng Wang, Lei Chen, Hang Xiao, Tonghui Zhan

    Improving the flame retardancy of epoxy resin will greatly expand its application in the fields requiring flame retardancy. Herein, a nitrogen/sulfur-containing DOPO based oligomer (SFG) for highly efficient flame-retardant epoxy resin was successfully synthesized via a facile one-pot method with DOPO, sulfaguanidine and p-phthalaldehyde. The incorporation of SFG accelerated the cross-linking reaction of epoxy system and improved the tensile strength, flame retardancy and fire safety of epoxy thermoset. SFG showed high flame-retardant efficiency due to the synergism among nitrogen, sulfur and phosphorus. With only 0.38 wt% phosphorus content, the corresponding epoxy thermoset achieved an LOI value of 32.8%, passed UL-94 V-0 rating and possessed lower fire growth rate and total heat release in cone calorimeter test in comparison with neat thermoset. SFG exerted dual flame-retardant effect not only by diluting oxygen and combustible volatiles and quenching active radicals, but also by promoting the formation of thermal insulating char layer with honeycombed cavity inside. Moreover, the appearance of blowing out phenomenon during combustion was disclosed that the intensive release of gases blew out the flame based on the dilution and quenching effects when the inner gas pressure was sufficient to break through the char layer.

  • Role of water in degradation of nitroplasticizer
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-09
    Dali Yang, Duan Z. Zhang

    The role of water in degradation of nitroplasticizer (NP) was studied using a set of NP samples aged inside confined containers between room temperature and 70∘C with their water concentrations monitored during the aging course. For the first 42 days at the temperatures at 55∘C and below, simple Fickian diffusion dominates the monotonic decreases of the water concentrations with time. After about 60–80 days depending on temperatures, diffusion alone can no longer explain the water decreases, despite no significant NP degradation detectable using the FTIR spectroscopy. Starting at about 80–160 days, also depending on temperatures, the measured water concentrations fluctuated around mean values that decrease with increasing temperature, and the onset of NP degradation was detected using FTIR and TGA. It was found that NP contains an irreducible amount of water on the order of a few hundred ppms, which decreases with increasing temperature. Pristine NP does not exist with a water concentration lower than this amount. The diffusivity, the irreducible amount of water in NP, and the mean water production rate due to NP degradation are calculated from the water concentrations of the first aging stage and the mean water concentrations during the onset of NP degradation. They all change with the temperature following Arrhenius laws with different prefactors and activation energies. This study shows that trace water formation is an intrinsic property of the NP while it ages with the mechanistic details to be resolved.

  • Wet spun polyacrylonitrile-based hollow-mesoporous carbon fiber: Stabilization, carbonization and its basic properties
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-11-08
    Bing Zhang, Chunxiang Lu, Yaodong Liu, Shuxia Yuan

    Due to its unique structure, hollow-mesoporous carbon fibers would enlarge the applications of hollow fiber in the areas operating in the harsh environment. In this paper, polyacrylonitrile (PAN) -based hollow-mesoporous carbon fibers (HMCFs) with various carbonization temperatures were firstly fabricated by heat treatments including stabilization and carbonization with the hollow-mesoporous precursor fibers preparing with blending alkali lignin (AL). Unlike previously, a small amount of residue of AL (less than 1%) in the hollow-mesoporous fiber (HMF) would reduce the degree of cyclization although the activation energy of cyclization reaction reduces, and thus accelerate the thermal decomposition of HMF which shows a lower carbon yield eventually compared with PAN. The oxidative stability of fibers improves a lot when HMF is transformed into HMCF which is beneficial to use it in the poor conditions. This work explains the effects of residue of AL existing in the precursor fiber on the processes of stabilization and carbonization of HPCMs, and the relationships between basic properties of HMCFs including physical structure, chemical composition and relevant properties and carbonization temperature. It provides a new insight to fabricate HMF into HMCF by the heating treatments of stabilization and carbonization with the existence of AL.

  • Synergistic effect of ammonium polyphosphate and α-zirconium phosphate in flame-retardant poly(vinyl alcohol) aerogels
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-31
    Yong Luo, Delong Xie, Yifan Chen, Tao Han, Renjie Chen, Xinxin Sheng, Yi Mei

    To overcome the flammability and melt dripping issues of poly(vinyl alcohol) (PVA) aerogel, a combination of ammonium polyphosphate (APP) and α-zirconium phosphate (α-ZrP) was used to enhance the flame retardancy of PVA aerogels, which were fabricated using a simple mixing and freeze-drying approach. Results obtained from transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirm that α-ZrP was successfully exfoliated by ultrasonic stripping. The effects of the exfoliated α-ZrP nano-plates on the microstructure, composition, flame retardancy, fire behavior of the aerogels was investigated using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), limiting oxygen index (LOI), UL-94 vertical burning, and cone calorimetry test. It was found that the incorporation of α-ZrP improved the 3D network structure of the PVA aerogel. The results showed that a sample with 2 wt% α-ZrP and 13 wt% APP could reach the maximal LOI value of 43.1%, achieved the UL-94 V-0 rating, and the peak heat release rate (PHRR) and total heat release (THR) of the sample reduced by 82.6% and 76.3%, respectively. Thermogravimetric analysis (TGA) revealed that α-ZrP improved the thermal stability of PVA-APP system. The residues analysis revealed that α-ZrP accelerated the formation of a compact and graphitization structure of residues and catalyzed the charring of PVA during burning.

  • Mechanical, rheological and anaerobic biodegradation behavior of a Poly(lactic acid) blend containing a Poly(lactic acid)-co-poly(glycolic acid) copolymer
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-31
    Kosar Samadi, Michelle Francisco, Swati Hegde, Carlos A. Diaz, Thomas Trabold, E. Dell, Christopher L. Lewis

    The goal of this work is to examine the thermal, rheological, mechanical and thermophilic anaerobic biodegradation performance of PLA blends containing a highly degradable polymer. Here random copolymers consisting of Poly(l-lactic acid) (PLLA) and Poly(glycolic acid) (PGA) structural units (75:25 M ratio) were synthesized at three different molecular weights (Mw = 16, 58 and 113 kg mol−1) and melt blended with a high molecular weight PLA homopolymer. The glass transition temperature (Tg) of poly(lactic acid-co-glycolic acid) (PLGA) was lower than that of PLA and increased with copolymer molecular weight. A single Tg intermediate to that of the two blend constituents was observed suggesting miscibility. Polymer blends showed enhanced methane production at early stages of anaerobic degradation with the rate increasing with increasing PLGA content and decreasing PLGA molecular weight. Blends exhibited a decrease in modulus and tensile strength as compared to pure PLA. Likewise, a decrease in ductility for all but the lowest molecular weight copolymer containing blend was observed. The zero-shear viscosity of polymer blends scaled predictably with PLGA content and exhibited reduced sensitivity to shear-rate. It is envisioned that this strategy could be applied for those applications where recycling is prohibitive such as at universities, hospitals and stadiums where mixed waste streams containing plastics and other waste types, such as food and paper, can be anaerobically co-digested and the resulting biogas used as fuel.

  • Castor oil-derived monomer ricinoleic acid based biodegradable unsaturated polyesters
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-30
    P. Rajalakshmi, J. Margaret Marie, A. John Maria Xavier
  • Crystallization and hydrolytic degradation behaviors of poly(l-lactide) induced by carbon nanofibers with different surface modifications
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-25
    Xin-zheng Jin, Xu Yu, Cheng Yang, Xiao-dong Qi, Yan-zhou Lei, Yong Wang
  • Biodegradation of plastics in soil: The effect of temperature
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-24
    Alessandro Pischedda, Maurizio Tosin, Francesco Degli-Innocenti

    The assessment of the intrinsic biodegradability of plastic materials is made under optimized environmental conditions in order not to limit the microbial growth and activity and follow the biodegradation process until completion. In particular, biodegradation tests are carried out at constant temperature in the range between 20 and 28 °C in order to favour the growth of mesophilic microorganisms. On the other hand, if the purpose is to predict the environmental fate of consumer or professional products made with biodegradable plastics after accidental or deliberate release into the environment, then the biodegradation rate attainable under less optimal conditions should be estimated. In this work pellets of a commercial biodegradable plastic material were tested for soil biodegradation at 28, 20, and 15 °C. The CO2 evolution was followed for more than one year using the ASTM D 5988–18 test method. The mineralization rates (mg C/day, i.e. the amount of organic carbon converted into CO2 per day) were determined by applying a linear regression from day 140 onwards on the organic carbon depletion curves, when the biodegradation reaction was constant. The specific mineralization rates, i.e. the rate per surface area unit (mg C/day/cm2) were determined by dividing the mineralization rates by the available surface areas of the pellets tested. A thermal performance curve (TPC) was obtained by plotting the specific mineralization rates against the respective temperatures. The TPC curve was perfectly described by an exponential model that was in agreement with the Arrhenius equation. This suggests that biodegradation is dominated by simple thermodynamic effects in the tested temperature ranges (15–28 °C). The apparent activation energy of the biodegradation reaction was 108.7 kJ/mol. Using the TPC, it was possible to estimate the time needed for total mineralization of a product made with the test material with a given surface area when exposed to different temperatures. Clearly, the effective biodegradation rate was affected by other environmental factors (e.g. nutrients, pH, gas exchange, etc.) besides temperature. The current work indicates that temperature, an important environmental factor, affects biodegradation rates, in accordance with the Arrhenius equation. The observation that the apparent activation energy of the biodegradation reaction does not vary with temperature in the tested temperature range indicates a persistency in the metabolic activities of the involved mesophilic microbial communities.

  • Influence of the crystalline structure on the fragmentation of weathered polyolefines
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-23
    F. Julienne, F. Lagarde, N. Delorme

    Blown-extruded low density polyethylene (LDPE) and polypropylene (PP) films were submitted to accelerated weathering in water in order to identify their fragmentation mechanism and to compare the fragments number, size and shapes generated for long irradiation time. The study of the chemical modification during weathering was performed by following the progressive oxidation (FTIR, contact angle), increase of crystallinity (DSC) and surface rigidity (AFM) for the two polymers. It was demonstrated that although the kinetics of degradation is faster for PP than for LDPE films, the same fracture mechanism namely slow crack propagation is observed for both polymers. The analysis of the cracks structures on the surface of the films by AFM indicates that the crack initiation and propagation strongly depends on the crystalline morphology of the polymer. Indeed, for both material cracks propagation mainly occurs in the direction perpendicular to the extrusion direction explaining the elongated shape observed for the LDPE fragments. However, for PP film, the presence of spherulite structures induced the initiation of cracks in other directions (between the lamellae) leading to the formation of an increased number of fragments significantly smaller and with non-elongated shape compared to LDPE. To our knowledge this study is the first to directly link the size, shape distributions of plastics fragments to the crystalline morphology of the weathered polymers. These results point out the importance of taking into account the crystalline morphology to predict plastic fate in the environment.

  • Application of small punch test to lifetime prediction of plasticized polyvinyl chloride wire
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-23
    Yasutomo Koga, Yoshihiko Arao, Masatoshi Kubouchi

    In this study, it was investigated that the validity of small punch (SP) test for the lifetime prediction of polyvinyl chloride (PVC) resin used as an electric insulation material for the electric cable. The degradation behavior of PVC resin under the accelerated high-temperature condition was analyzed using Fourier transform-infrared spectroscopy (FT-IR), tensile testing, and SP testing. The activation energies and estimated lifetime obtained from the Arrhenius method were compared. The peak ratio of the carbonyl group obtained by FT-IR, the elastic modulus obtained by tensile testing, and the apparent elastic modulus obtained by SP testing were used as indicators for lifetime estimation, and the logarithm of these values showed a linear correlation with exposure time. The activation energy obtained from the elastic modulus using SP testing was the smallest and the predicted lifetime was the shortest among all mechanical properties in this research. It indicates that SP testing is sensitive to the degradation. This is because the stress at the surface becomes maximum for SP testing, and the degradation occurs at the surface of the materials by priority degradation. SP testing is an excellent minimally destructive lifetime prediction method for detecting of early-stage degradation.

  • Hydrothermal ageing of graphene/carbon nanotubes/epoxy hybrid nanocomposites
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-23
    C. Arribas, M.G. Prolongo, M. Sánchez-cabezudo, R. Moriche, S.G. Prolongo

    The hydrothermal ageing of hybrid nanocomposites formed by carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) incorporated into an epoxy matrix was studied. In order to avoid the weak interface, amine functionalized GNPs were used which are reactive with the epoxy matrix. The content of CNTs was 0.1 wt% and the GNPs content ranged from 5 to 12 wt%. The isothermal water absorption was measured until very long times (almost two years). Reduction of water absorption with the addition of either carbon nanotubes or graphene nanoplatelets has been found independently of the ageing time. The results can be described by a two-stage diffusion model with the first and second stages being diffusion and matrix relaxation controlled respectively. The obtained diffusion coefficient for the neat epoxy thermoset is higher than those of nanocomposites, which decreases with the increase of GNPs content. The effect of water absorbed on the dynamic-mechanical properties and on the electrical conductivity of the nanocomposites was analyzed. Whatever the temperature the storage modulus shows a continuous increase with the increase of the nanoparticles content, the effect of hydrothermal ageing is to decrease the modulus only in the glassy state (T < Tg). Water aged specimens show broadening of the tanδ peak related to the plasticization of the matrix. Tg of aged specimens coincides with the one of the unaged matrix, indicating that hydrothermal ageing does not produce noticeable matrix damage even after two years. Water aged specimens show similar electrical conductivity than unaged ones, which is another indication of no degradation of samples by water.

  • Studying chemical reaction rate using a difference algebraic converging method— A study on the thermal decomposition of poly-α-methyl styrene
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-22
    Weiguo Sun, Yi Zhang, Jia Fu, Zhanwen Zhang, Weidong Wu, Yongjian Tang

    A difference algebraic converging method for rate problem (DACMr) is proposed to study the rate function of a simple chemical reaction that is the function of activation energy and rate constant. The applications of this method to the thermal decomposition reactions of solid poly-α-methyl styrene (PαMS) indicate that: 1) All experimental thermal decomposition reaction rate functions W(T) are excellently reproduced using converged DACMr rate constant a(Np) and activation energy Ea. 2) The DACMr results can correctly generate the physical data of this thermal decomposition reaction in the reaction boundary region where experiments have difficulties. 3) The DACMr results correctly describe the observed data crossing between the rate functions of a greater PαMS molecule and that of a smaller one. 4) The DACMr method might be extended to study the rate problem of other simple chemical reactions.

  • Hydrolytic kinetic model predicting embrittlement in thermoplastic elastomers
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-18
    A. Bardin, P.Y. Le Gac, Stéphane Cérantola, Gaëlle Simon, Hervé Bindi, B. Fayolle

    A hydrolytic kinetic model predicting chains scissions of a polyurethane elastomer (TPU) containing an anti-hydrolysis agent (stabilization via carbodiimide) was developed. This model is based on four components: uncatalysed hydrolysis, acid-catalysed hydrolysis, carboxylic acid dissociation and competitive carbodiimide-based deactivation of acid. Protons were considered as the key catalyst responsible for the hydrolysis. Model parameters were determined by fitting experimental data measured on unstabilized and stabilized TPUs, aged in immersion from 40 to 90 °C. Scission kinetics were predicted for immersion and 50% relative humidity conditions, from 10 to 100 °C. Structure-failure property relationships were also investigated, between molar mass and elongation at break. A master curve was established for elongation at break with molar mass, including both TPUs at four ageing temperatures. By combining predictions for scission kinetics with the molar mass-elongation at break master curve and an embrittlement molar mass as the end-of-life criterion, non-Arrhenian lifetime predictions are proposed for all exposure conditions considered.

  • Nanobiocatalyst from lipase non-covalently immobilized on multiwalled carbon nanotubes for copolymerization of ε-caprolactone and trimethylene carbonate
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-17
    Marta Socka, Magdalena Sitko, Sławomir Boncel, Bartłomiej Kost, Anna Chrobok, Marek Brzeziński
  • Effect of radiation-induced oxidative degradation on the non-isothermal crystallization of ethylene-butene copolymer
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-15
    V.A. Alvarez, M.D. Failla, C.J. Pérez

    A random ethylene–butene copolymer was irradiated with high ionizing energy in environments with different oxygen concentration. The non-isothermal crystallization process of the materials was studied by differential scanning calorimetry. When the polymer was exposed to radiation under free oxygen ambient, the temperature and the crystallinity degree decreased almost linearly with dose because chain-linking reaction prevails. On the contrary, those thermal parameters increased in the material obtained by irradiating the copolymer in environments with oxygen availability where chain scission reactions dominate. It was also found that, at equivalent irradiation dose, the crystallization rates decreased with the dose at a given cooling rate and with the reduction in oxygen content. The parameters obtained from different applied models also confirm the tendencies observed for the experimental variables.

  • A synthesized multifunctional rubber additive and its improvements on the curing and antioxidative properties of styrene-butadiene rubber/silica composites
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-14
    Yangkun Sun, Jingwei He, Bangchao Zhong, Lixin Zhu, Fang Liu

    A multifunctional additive (1-allyl-3-(4-(phenylamino)phenyl)thiourea, APPT) with amine, thiourea and allyl groups was synthesized by reacting N-phenyl-p-phenylenediamine (PPD) with allyl isothiocyanate (AITC). The chemical structure of APPT was confirmed by FTIR, UV–Vis, 1H NMR, 13C NMR and elemental analysis. When employed in styrene-butadiene rubber (SBR)/silica composites, APPT endowed the composites with much better antioxidative properties than the commercial antioxidant N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD), oxidation induction time (OIT) of composites containing APPT (126.61 min) was almost twice as long as that with IPPD (63.87 min). Meanwhile, APPT could accelerate the vulcanization effectively resulting from the synergistic effect among amine, thiourea and allyl groups. Moreover, APPT could help silica disperse much homogeneously in the rubber matrix than did IPPD. Besides, although as an amine derivative like IPPD, APPT showed much slighter effect on the discoloration of SBR/silica composites. Taken together, this study might provide an option for the preparation of multifunctional amine rubber additive with high-efficiency yet slight discoloration.

  • Flame retardant polyester fabric from nitrogen-rich low molecular weight additives within intumescent nanocoating
    Polym. Degrad. Stabil. (IF 3.780) Pub Date : 2019-10-14
    Igor Jordanov, Eva Magovac, Abbas Fahami, Simone Lazar, Thomas Kolibaba, Ryan J. Smith, Sandra Bischof, Jaime C. Grunlan

    An intumescent nanocoating composed of chitosan (CH) and ammonium polyphosphate (APP), with and without low-molecular weight nitrogen and nitrogen/sulphur based derivatives, was deposited on polyester fabric using the layer-by-layer technique. Guanidine sulfamate (GSM), urea and thiourea were added to the aqueous chitosan deposition solution in an effort to improve flame retardancy. Exceptional self-extinguishing behavior is observed with a 10 bilayer (BL) CH:GSM/APP coated fabric. This water-based coating added 19.6 wt% to the polyester and reduced peak heat release rate by 61.7%, relative to uncoated fabric. Furthermore, the polyester is not fully ignitable because of earlier decomposition of GSM that helps to generate a thicker sponge-like char that acts as a physical barrier. This unique addition of low-molecular weight molecules in traditional intumescent polyelectrolyte pairs is a new opportunity for imparting flame retardancy to highly flammable synthetic fibers used in clothing and home furnishing.

  • 更新日期:2019-10-10
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