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  • An efficient flame retardant for epoxy resin: Preparation and pyrolytic behaviour
    High Perform. Polym. (IF 1.584) Pub Date : 2018-12-10
    Baoping Yang; Xiang Li; Lurong Wang; Yabin Zhang; Jinfeng Cui; Junhong Guo; Li Tian

    Using 4,4-diaminodiphenyl methane as a curing agent, three kinds of monomers, 4,4′-dihydroxybenzophenone, diphenyl chlorophosphite and 1,4-phenylene diisocyanate (NCO), were introduced into a thermosetting resin (DGEBA). The flame retardancy properties of the composites were studied, and the results were compared with those of 5 wt% bis(bis(4-((diphenoxyphosphoryl)oxy)phenyl)methyl) 1,4-phenylenedicarbamate (DHPP-OH-NCO), 10 wt% DHPP-OH-NCO and 15 wt% DHPP-OH-NCO curing agents. The results showed that 15 wt% DHPP-OH-NCO had an improved flame retardancy, the limited oxygen index reached 33.5% and the vertical burning test (UL94) achieved a V-0 level. A cone calorimeter experiment showed that the addition of the flame retardant significantly reduced the amount of generated smoke and heat. Macroscopic digital images, scanning electron microscopy images and thermogravimetric analysis results further revealed that the epoxy resin (EP) with DHPP-OH-NCO exhibited greater char yields. The flame retardancy mechanism of the flame retardant was preliminarily shown by pyrolysis–gas chromatography–mass spectrometry analysis. The combined test results demonstrate that a high-efficiency phosphorous-containing flame retardant for EPs was successfully developed.

    更新日期:2019-10-25
  • Moisture absorption and hydrothermal aging of phenylethynyl-terminated pyromellitic dianhydride-type asymmetric polyimide and composites
    High Perform. Polym. (IF 1.584) Pub Date : 2018-12-10
    Yixiang Zhang; Masahiko Miyauchi; Steven Nutt

    The effects of moisture on a polymerized monomeric reactant (PMR)-type polyimide (TriA X) and associated composites were investigated. Water uptake tests were performed on the polyimide at various temperatures and relative humidity levels to investigate moisture absorption behavior. Two-stage moisture absorption was observed, in which the first stage was diffusion controlled, whereas the second stage was moisture plasticization controlled. As exposure temperature increased, the equilibrium moisture content of the polyimide decreased, indicating an exothermic absorption process. The Arrhenius temperature dependence and moisture saturation as functions of temperature and humidity in the neat polymer were determined using curve fitting based on the published mathematical models. Long-term hydrothermal aging at 95°C was conducted on the neat polyimide and associated carbon fiber composites. Reversible hydrolytic reactions and a trace of irreversible hydrolysis were observed in the long-term exposure. The tensile ductility of the neat polyimide and the short-beam shear strength of the composites decreased with increasing aging time, while the tensile strength and modulus and thermal properties of the polyimide exhibited little change after 2000-h aging, demonstrating hydrothermal stability. The decrease in the ductility of the neat polymer after long-term moisture exposure was attributed to the network structure change, driven by hydrolysis and moisture plasticization.

    更新日期:2019-10-25
  • Preparation of reversible photoresponsive N-hydroxyethyl spiropyran/polyacrylonitrile fiber materials with mechanical stability by electrospinning for regulating wettability and humidity automatically
    High Perform. Polym. (IF 1.584) Pub Date : 2018-12-23
    Caifeng Wang; Zhenfu Liu; Chunhao Li; Yun Wu; Shuai Wang

    Novel photoresponsive N-hydroxyethyl spiropyran (SP-OH)/polyacrylonitrile (PAN) fiber materials with reversible changes in wettability and humidity were prepared by electrospinning in this work. SP-OH and PAN were mixed through a physical doping method. The wettability and humidity regulation of the electrospun films can be reversibly manipulated by the simple change of ultraviolet (UV)-visible (UV-Vis) light irradiation due to the photoisomerization mechanism of the spiropyran chromophore. Under UV light irradiation, SP-OH molecules exhibit a colored polar open-ring status, resulting in electrostatic attraction with water. However, under visible light irradiation, they are colorless and nonpolar and lose the attraction effect. Wettability and ambient humidity were regulated by this repeated transformation between polar surface and nonpolar surface. The tensile strength and the reversible change ranges of wettability and humidity under UV-Vis irradiation are all closely related to the doping amount of SP-OH. Electrospinning is a promising method to achieve large-scale production that can put such a material into practical application.

    更新日期:2019-10-25
  • Studies on naphthalene and 1,2,3-triazole ring containing polyimides/zinc oxide nanocomposites
    High Perform. Polym. (IF 1.584) Pub Date : 2018-12-23
    Rukmanikrishnan Balasubramanian; Sam Soo Kim; Jaewoong Lee

    A novel diamine containing naphthalene and 1,2,3-triazole was synthesized by click reaction in the presence of Cu (I) catalyst. The synthesized diamine reacts with commercially available dianhydride and zinc oxide (ZnO) to form polyimide (PI) nanocomposites by a conventional two-step method. The structure of the monomers and polymers was characterized by Fourier transform infrared and proton nuclear magnetic resonance spectra. The morphology of the PI and PI/ZnO nanocomposite films was investigated by scanning electron microscopy and X-ray diffraction analysis. Meanwhile, due to the presence of a naphthalene side group, PI and PI/ZnO nanocomposite films possess high thermal stability, with a glass transition temperature over 259°C and a decomposition temperature with 5% weight loss over 501°C under nitrogen atmosphere. Also, low moisture absorption (0.28%) and good optical transparency were evident. The hybrid films possessed good mechanical properties, with a tensile strength of 112–127 MPa, an elongation at break of 10–15%, and a tensile modulus of 2.8–3.2 GPa.

    更新日期:2019-10-25
  • Cu (II) coordination modification of aramid fiber and effect on interfacial adhesion of composites
    High Perform. Polym. (IF 1.584) Pub Date : 2018-12-26
    Ting Li; Zengxiao Wang; Junrong Yu; Yan Wang; Jing Zhu; Zuming Hu

    In this article, active groups were introduced to the surface of aramid fiber by building a Cu2+ bridge between the aramid fiber and polyethyleneimine (PEI) to improve adhesion in composites between the aramid fiber and the matrix such as epoxy resin. The changes in the structure and properties of the aramid fiber were verified with Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and the single-fiber pull-out test. The FTIR and XPS results show a significant change in the structure and morphology of the aramid fiber after modification. The results of the single-fiber pull-out test show that the interfacial shear strength (IFSS) of epoxy composites reinforced with PEI-grafted aramid fiber increases by 48.8% compared with the IFSS of epoxy composites reinforced with untreated fiber. Thus, the proposed method can improve the interfacial bonding of composites by creating a copper ion bridge between the aramid fiber and PEI.

    更新日期:2019-10-25
  • Synthesis and properties of benzocyclobutene-terminated imide-containing cyano group
    High Perform. Polym. (IF 1.584) Pub Date : 2019-01-06
    Xianfeng Que; Zhiming Qiu; Yurong Yan

    Benzocyclobutene (BCB) resins have aroused much interest because of their excellent physical and chemical properties. Unfortunately the temperature required to induce cross-linking in typical BCBs is higher than 250°C, which restricts their applications. In this study, a novel cyano-containing BCB-terminated imide monomer was synthesized through the reaction of 1-cyano-5-amino-benzocyclobutene with 4,4′-oxydiphthalic anhydride. This monomer allows a 50–100°C lower curing temperature in comparison with typical BCBs, and it is highly soluble in various solvents and can easily convert to cured film at 150–200°C. Because of the presence of rigid imide group and strong polar cyano group, the cured film exhibits excellent mechanical strength with tensile strength up to 87.8 MPa, high glass transition temperature up to 350°C, low coefficient of thermal expansion (36.9 ppm K−1), and outstanding planarity with the average surface roughness as low as 0.26 nm.

    更新日期:2019-10-25
  • Synthesis and properties of pyrazine-based oligomeric phthalonitrile resins
    High Perform. Polym. (IF 1.584) Pub Date : 2019-01-07
    Yao Liu; Puguang Ji; Zhenjiang Zhang; Xiaoyan Yu; Kimiyoshi Naito; Qingxin Zhang

    The pyrazine-based oligomeric phthalonitrile (PN) monomer, 2,6-bis[3-(3,4-dicyanophenoxy)phenoxy]pyrazine (BCPP), was synthesized from the reaction of an excess amount of resorcinol with 2,6-dichloropyrazine in the presence of potassium carbonate, followed by end-capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. 4-(Aminophenoxy)phthalonitrile was applied to promote the curing reaction. The curing behavior was investigated by differential scanning calorimetry and rheological behavior, showing a wide processing window of 94°C, a complex viscosity of less than 1.5 Pa·s and a lower reaction activation energy of 32.57 kJ mol−1. The structure of the BCPP monomer was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The unit cell was determined to be tetragonal system by wide-angle X-ray diffraction. The monomer was cured to yield cross-linked polymers, which exhibited a high initial storage modulus, excellent glass transition temperature, outstanding thermal stability, and low water uptake.

    更新日期:2019-10-25
  • Synthesis, pyrolysis of a novel carborane ceramic precursor, and coating on carbon fiber
    High Perform. Polym. (IF 1.584) Pub Date : 2019-01-08
    Yakun Zong; Dejin Tong; Zhanxiong Li

    A novel carborane–carbosilane–(cyclo-silazane) polymer has been synthesized as precursor of ceramic and applied to the surface treatment of carbon fiber (Cf) by precursor infiltration and pyrolysis method. The preparation of carborane precursor was carried out by hydrosilylation of trivinyltrimethylcyclosilazane with dimethylchlorosilane firstly, and then by polycondensation reaction with hydroxylated 1,1′-hydroxysilylene-2,2′-bis(hydroxydimethylsilyl)biscarborane whose −OH was formed by transferring the newly introduced C–H bond via hydroxylation. Chemical structure of the polymer was studied by liquid-nuclear magnetic resonance while evolution of various ceramic phases was studied by Fourier transform infrared spectroscopy and the thermal curing process was studied by thermogravimetric/differential thermal analysis and pyrolysis-gas chromatography/mass spectrometry. The cross-linked polyborosilazane precursor exhibited higher ceramic yield of 65.6% at 1000°C. The coating on the Cf was identified to be uniform, relatively smooth, and continuous with a thickness ranged from 0.1 to 0.5 μm through scanning electron microscope and energy dispersive spectroscopy. Thermogravimetric analysis revealed high temperature stability of the coated Cf in flowing air up to 600°C.

    更新日期:2019-10-25
  • Optical, thermal and gas separation properties of acetate-containing copoly(ether-imide)s based on 6FDA and fluorenyl diamines
    High Perform. Polym. (IF 1.584) Pub Date : 2019-01-09
    Yunhua Lu; Jican Hao; Guoyong Xiao; Lin Li; Zhizhi Hu; Tonghua Wang

    The diamine, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl]fluorene (BAHPPF) was synthesized by the modified two-step method. Then, a series of acetate-containing copoly(ether-imide)s were prepared by the copolymerization of BAHPPF, 9,9-bis(4-aminophenyl)fluorene (BAF) and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) followed by chemical imidization. The structures and properties of the BAHPPF and copoly(ether-imide)s were characterized by nuclear magnetic resonance spectrometer (NMR), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), ultraviolet-visible spectrophotometer (UV-VIS), and tensile testing. Single gas permeation performances of these copoly(ether-imide)s were also studied for five representative gases of interest including H2, O2, N2, CO2, and CH4. The experimental results showed that the copoly(ether-imide)s showed excellent optical properties with high light transmittance above 80.2% at 450 nm. The glass transition temperature of these copolymers were higher than 333°C. Their tensile strength and Young’s module also increased, and the elongation decreased with the decrease of BAHPPF. High gas permeabilities of copoly(ether-imide)s were obtained, and the ideal selectivity of CO2/CH4 was improved due to the introduction of acetate group and flexible ether linkage. These copoly(ether-imide)s could be applied to the field of optics and gas separation.

    更新日期:2019-10-25
  • EPDM-based heat-shielding materials modified by hybrid elastomers of silicone or polyphosphazene
    High Perform. Polym. (IF 1.584) Pub Date : 2019-01-24
    Shaojun Wu; Shuangkun Zhang; Raheel Akram; Abbas Yasir; Bowen Wang; Zhongqiang Han; Zhanpeng Wu; Dezhen Wu

    The erosion resistances of ethylene propylene diene monomer (EPDM) insulations are often inadequate for advanced solid rocket motor (SRM) applications. EPDM modification by blending secondary matrixes is a feasible approach to improve the ablative properties of EPDM insulations. The addition of flexible inorganic hybrid rubbers as a secondary matrix, such as silicones and polyphosphazenes, may impart EPDM insulations with better ablative performance. The blends of EPDM/hybrid rubbers represent the state-of-the-art heat-shielding materials for SRM. In the present work, methyl-phenyl silicone/EPDM and poly(diaryloxyphosphazene)/EPDM insulation systems with various blending ratios of secondary matrixes have been prepared. The ablative properties of the insulations were examined by oxy-acetylene ablation tests, and the results showed that these properties could be enhanced accordingly by blending with hybrid rubbers under appropriate proportions. The unique charred layers resulting from the hybrid rubbers contributed to their excellent ablation properties. For example, the silicone/EPDM insulations exhibited a more significant improvement of ablation resistance properties. With a 1:1 blending ratio of silicone/EPDM, the linear ablation rate was 0.06 mm s−1 after 20 s of oxy-acetylene ablation. The enhancement in the ablative resistance was attributed to the charred layers with bunches of embedded compact microtubes with a length of 2–3 mm, which consisted of silicon carbide, silicon dioxide, and Si–O–C ceramics.

    更新日期:2019-10-25
  • Remarkable enhancement of mechanical and tribological properties of polyamide 46/polyphenylene oxide alloy by polyurethane-coated carbon fiber
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-03
    Jincheng Ran; Xuejun Lai; Hongqiang Li; Xingrong Zeng

    How to significantly improve the mechanical and tribological properties of polyamide 46/polyphenylene oxide (PA46/PPO) alloy is an urgent but challenging issue. The PA46/PPO alloy reinforced with polyurethane-coated carbon fiber (PCF) was prepared and characterized. It was found that the mechanical properties, heat resistance, and tribological properties of PA46/PPO were greatly enhanced by incorporating PCF. When the composite containing 40 wt% of PCF, the tensile strength of the composite increased from 82 MPa to 282 MPa; meanwhile, volumetric wear was 0.56 mm3, which decreased by 95% in comparison with PA46/PPO. Scanning electron microscopy results showed that PCF had a good compatibility with the polymer matrix, due to good interfacial interaction between the PCF and the PA46/PPO. X-Ray photoelectron spectroscopy and laser Raman spectroscopy results further revealed that more graphitic carbon was microcracked to form a lubricating layer during friction process, thus remarkably improving the wear resistance of PA46/PPO.

    更新日期:2019-10-25
  • Asymmetric bismaleimide-based high-performance resins with improved processability and high Tg over 400 °C
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-03
    Zhidong Ren; Sijia Hao; Yue Xing; Cheng Yang; Shenglong Dai

    Asymmetric 2-(4′-maleimido)phenyl-2-(4′-maleimidophenoxyl)phenylbutane (EBA-BMI) was successfully mixed with N,N′-(4,4′-diphenylmethane)bismaleimide (DDM-BMI) to prepare the matrix resins for high-temperature fiber-reinforced polymeric composites (glass transition temperature (Tg) > 400°C). Experimental results imply that DDM-BMI/EBA-BMI (DE-BMIs) show excellent melting performance with wide processing temperature window and low molten viscosity, suggesting excellent compatibility between DDM-BMI and EBA-BMI. For example, the viscosity of DE-BMI41 (DDM-BMI/EBA-BMI, 4/1) is about 474–51 mPa·s in the temperature range of 148–180 °C. In addition, cured DE-BMIs represent remarkable thermal properties with Tg over 400°C, under which the storage modulus could still reach as high as 3.2 GPa. Meanwhile, the coefficient of thermal expansion of these cured resins is about 36–40 ppm °C−1 at 50–250°C, and the 5% weight loss temperature is about 470°C.

    更新日期:2019-10-25
  • Fast pyrolysis bio-oil from lignocellulosic biomass for the development of bio-based cyanate esters and cross-linked networks
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-10
    Mehul Barde; Charles Warren Edmunds; Nicole Labbé; Maria Lujan Auad

    Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear magnetic resonance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. It was further used as a raw material for producing a mixture of biphenolic compounds (ORG-biphenol). ORG-bio-oil, ORG-biphenol, and bisphenol-A were reacted with cyanogen bromide to yield cyanate ester monomers. Cyanate esters were characterized using FTIR spectroscopy and were thermally cross-linked to develop thermoset materials. Thermomechanical properties of cross-linked cyanate esters were assessed using dynamic mechanical analysis and compared with those of cross-linked bisphenol-A-based cyanate ester. ORG-biphenol cyanate ester was observed to have a superior glass transition temperature (350–380°C) as compared to bisphenol-A cyanate ester (190–220°C). Cyanate esters derived from bio-oil have the potential to be a sustainable alternative to the bisphenol-A-derived analog.

    更新日期:2019-10-25
  • Highly conductive and stretchable film fabricated by efficient transfer of silver nanowires
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-19
    Xiaoheng Ding; Hailin Cao; Siyu Sun; Mingyu Li; Haitao Liu

    Wearable devices have become an important development direction for future consumer electronics, and films with conductivity, stretchability, and transparency are crucial for achieving wearability. In this article, silver nanowires (AgNWs) with a certain aspect ratio and Al2O3-polyethylene terephthalate films with specific size pit structures were prepared. Uniform coating of the AgNW layer and polydimethylsiloxane transfer were successfully realized. The surface resistance of the final obtained film was 14 Ω/sq with a light transmittance of 50.57%. During repeated deformations, the film conductivity was not significantly reduced, and excellent electrical conductivity was maintained. A relatively complicated flexible AgNW circuit was prepared by adding a patterned mask in the scrape-coating step. This is a low-cost method and can be used to form large films. The final product has excellent conductivity and some transparency and can provide new research directions for flexible electronic devices.

    更新日期:2019-10-25
  • Influence of HTPB prepolymer on achieved properties of composite solid propellant
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-26
    I Kingstone Lesley Jabez; Urmila Das; R Manivannan; Sarat Babu Anne

    Changes/variations during manufacturing and storage of free radical-polymerized hydroxyl-terminated polybutadiene resin/prepolymer (widely used binder for the composite solid propellants) are not reflected in terms of appreciable change in the hydroxyl value. As a result, cured properties of the propellant mixed using the given formulation finalized by keeping R ratio (NCO/OH ratio) within 0.7–0.9 did not yield predicted mechanical properties. Investigations carried out subsequently, by the authors, identified the root cause to be variations in molecular weight and its distribution, which were not indicated in terms of change in hydroxyl value. Authors confirmed their findings by 1H1NMR studies whereby the variation in molecular weight distribution could be explained in terms of variation in spin–spin relaxation time (T 2) values.

    更新日期:2019-10-25
  • Synthesis and gas transport properties of novel poly(ether ether ketone)s containing fluorene group
    High Perform. Polym. (IF 1.584) Pub Date : 2019-02-28
    Yayun Zheng; Xing Yang; Meng Yuan; Jujie Luo

    Two novel gas separation membranes (Phenyl(Ph)-poly(ether ether ketone)s (PEEKs) and PEEKs) based on PEEKs with a high fractional free volume were designed and synthesized. The structure and thermodynamic stability of the membranes were investigated using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The two membranes, which were determined to be high-molecular weight polymers by gel permeation chromatography, showed good solubility in a weakly polar solvent. The gas transport properties of the Ph-PEEK membranes were investigated for different gases (CO2, O2, CH4, and N2) at 25°C and 1 atm. The Ph-PEEK-3 membrane with the largest free volume had the largest gas permeability coefficient and maintained good selectivity. The effect of operating temperature on the gas permeation of the Ph-PEEK-3 membrane was also investigated, and the maximum permeability of the four single gases was reached at 55°C and 1 atm.

    更新日期:2019-10-25
  • Surface modification of GO by PDA for dielectric material with well-suppressed dielectric loss:
    High Perform. Polym. (IF 1.584) Pub Date : 2019-03-17
    Yujia Kou; Wenying Zhou; Li Xu; Huiwu Cai; Guangheng Wang; Xiangrong Liu; Qingguo Chen; Zhi-Min Dang

    To suppress the high dielectric loss of graphene oxide (GO)/poly(vinylidene fluoride) (PVDF) while maintaining high dielectric constant (high-k) near the percolation threshold, in this study, GO nanosheets coated with polydopamine (PDA) were integrated into PVDF to investigate the effects of the PDA shell and its concentrations on the dielectric properties of the nanocomposites. The results indicate that the dissipation factor and conductivity of the GO@PDA/PVDF are significantly suppressed to very low values compared with the pristine GO/PVDF composites, attributable to the PDA interlayer between the GO nanosheets which prevents them from direct contact with each other and remarkably reduces the leakage loss. Furthermore, activation energies of the GO/PVDF and GO@PDA/PVDF composites were calculated as 1.247 and 0.884 eV, respectively, indicating that the presence of PDA interlayer reduces the relaxation activation energy and makes the relaxation occur at low temperature for the GO@PDA/PVDF. The prepared GO@PDA/PVDF nanocomposites with high-k but low loss have potential applications in microelectronic engineering.

    更新日期:2019-10-25
  • Enhancing mode I and II interlaminar fracture toughness of carbon fiber-filled epoxy-based composites using both rice husk silica and silk fibroin electrospun nanofibers
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-03
    Quang-Vu Bach; Cuong Manh Vu; Huong Thi Vu; Dinh Duc Nguyen

    In this study, we used both silk fibroin nanofibers (nSFs) and rice husk silica nanoparticles as epoxy (EP) resin reinforcement materials to improve the modes I and II interlaminar fracture toughness of EP-filled carbon fiber-based (CF/EP) composites. The nSFs were obtained by electrospinning, while the rice husk silica nanoparticles were obtained via acidic and thermal treatments. The results showed that the interfacial shear strength, GIC, and GIIC of the CF/EP composites improved by 25, 36, and 30%, respectively, by adding 0.2 wt% nSF and 20 wt% silica nanoparticles.

    更新日期:2019-10-25
  • Study on the modification of hexamethylenediamine-phenol-based polybenzoxazine resins by halloysite nanotubes
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-03
    Jing Li; Zhiqiang Shen; Li Xu; Huaijun Song; Gang Guan; Guoji Liu

    In this study, hexamethylenediamine-phenol-based benzoxazine monomer (Ba-h) was synthesized using 1,6-hexamethylenediamine, phenol, and paraformaldehyde. Halloysite nanotubes (HNTs) were treated with silane coupling agent and succinic anhydride, respectively. Then the pristine and grafted HNTs were used as nano-fillers to modify Ba-h at different mass ratios ranging between 0 and 2.5 wt% via solution processing. Nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy confirmed the molecular structure of the monomer. The curing behaviors of the nanocomposites were examined by differential scanning calorimetry (DSC). The results of DSC, thermogravimetric analysis, and dynamic mechanical analysis displayed the obvious improvement in the thermal stability of the nanocomposites modified by the grafted HNTs. The results of impact and flexural tests revealed the improvement in the mechanical property of the nanocomposites modified by the pristine HNTs. These enhancements are related to the homogeneous dispersion of HNTs based on the scanning electron microscopy and transmission electron microscopy results.

    更新日期:2019-10-25
  • Thermal stability and flame retardancy of an epoxy resin modified with phosphoric triamide and glycidyl POSS
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-21
    Jialiang Li; Hongyu Wang; Shichao Li

    Phosphoric triamide (PTA) and glycidyl polyhedral oligomeric silsesquioxane (POSS) were simultaneously incorporated into the cured network of a bisphenol F epoxy resin and 4,4′-diaminodiphenyl methane (DDM) to improve the thermal stability and flame retardancy. PTA was synthesized by triethyl phosphate and DDM, and its chemical structure was confirmed by 1H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR). The differential scanning calorimetric (DSC) results showed that the introduction of PTA and POSS slightly increased the glass transition temperature of the epoxy resin. The thermogravimetric analysis results indicated that compared with the pure, phosphoric, and silicic epoxy resins, the modified epoxy resin possessed the lowest weight loss rate and highest char residue. Its limiting oxygen index value was as high as 30.5, and the UL-94 grade reached V-1. A decomposition test was carried out to obtain sufficient char residue and investigate the condensed mechanism. The scanning electron microscopic images demonstrated that the char residue of the modified epoxy resin had a compact structure. The energy dispersive X-ray and FTIR analyses verified the synergistic effect of the phosphorus and silicon in the PTA and POSS, respectively, on the epoxy resin.

    更新日期:2019-10-25
  • Preparation of graphene/polyaniline nanocomposite by in situ intercalation polymerization and their application in anti-corrosion coatings
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-23
    Yiyi Li; Yiting Xu; Shicheng Wang; Hongchao Wang; Meng Li; Lizong Dai

    This study reports a strategy for further simplifying the synthesis process of polyaniline-modified graphene (An/G) nanocomposite. For this purpose, the An/G nanocomposite was prepared by expanded graphite (EG) and aniline (An) via in situ polymerization. The structures and morphologies of the An/G nanocomposite were examined by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, ultraviolet–visible spectroscopy and atomic force microscopy. The results show that the An/G nanocomposite was synthesized successfully. The coatings were prepared using polyaniline (PANI) and An/G as the fillers and epoxy resin as the matrix. The anti-corrosion performance was evaluated by electrochemical impedance spectroscopy, Tafel polarization curve and salt immersion test. When An/G100 nanocomposite with a mass ratio of An to EG of 100:1 as a filler is used, the coating on the steel exhibited superior anti-corrosion effect. In particular, the impedance at 0.01 Hz of the coating with the An/G100 nanocomposite at a low loading of 2 wt% (An/G100-2) remained constant above 1 × 1010 Ω·cm2 for up to 35 days in 3.5 wt% sodium chloride solution. The Tafel plots reveal that the undamaged zone of the An/G100-2 coating possessed a high corrosion potential of −0.16 V, and the corrosion current density was only 1.5 × 10−11 A cm−2. The protective mechanism of graphene and PANI is discussed.

    更新日期:2019-10-25
  • One-pot hydrothermal synthesis of polyaniline nanofibers/reduced graphene oxide nanocomposites and their supercapacitive properties
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-24
    Shanxin Xiong; Yuancheng Wang; Jia Chu; Xiaoqin Wang; Runlan Zhang; Ming Gong; Bohua Wu; Zhen Li

    In this article, polyaniline nanofibers/reduced graphene oxide (PANI-NFs/rGO) nanocomposites were prepared by a one-pot hydrothermal method. Under the condition of high temperature and high pressure, graphene oxide (GO) was reduced to rGO and aniline was in-situ polymerized to form PANI-NFs using ammonium persulfate as oxidant. The morphologies and structures of PANI-NFs/rGO nanocomposites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and Raman analysis. The results show that PANI-NFs uniformly grow on the surfaces of rGO sheets, which can act as spacers to prevent the aggregation of rGO. Combining with FTIR and Raman analysis, it can be concluded that PANI-NFs/rGO nanocomposites are successfully prepared. The electrochemical performances of PANI-NFs/rGO nanocomposites were tested by cyclic voltammetry and galvanostatic charge–discharge. The PANI-NFs/rGO nanocomposites exhibit superior electrochemical performances compared to the PANI-NFs. With 10 wt% of GO loaded, the PANI-NFs/rGO nanocomposite exhibits highest specific capacitance of 942 F g−1 at a current density of 1 A g−1. The PANI-NFs/rGO nanocomposites also demonstrate good rate capacity and high cycling stability under the high discharging current density (10 A g−1), the specific capacitance can still reach to 680 F g−1. After 1000 charge–discharge cycling at a current density of 5 A g−1, 78% of specific capacitance can be retained. The enhanced capacitive performances can be attributed to the facile electron conduction pathway brought by the even distribution of highly conductive rGO nanosheets.

    更新日期:2019-10-25
  • Investigations of the humidity sensing properties of side-chain-type sulfonated poly (arylene ether ketone)s
    High Perform. Polym. (IF 1.584) Pub Date : 2019-04-29
    Fanting Meng; Zhuang Zhuang; Yurong Zhang; Hui Na

    Side-chain-type sulfonated poly (arylene ether ketone)s containing naphthalene moieties with a degree of sulfonation (Ds) from 0.2 to 1.9 were synthesized. Humidity sensors were fabricated by cast coating on silver–palladium interdigital microelectrodes. The properties of this series of materials in terms of water absorption, glass transition temperature, and humidity sensing were characterized in detail. The investigations on the humidity sensing performance showed that with the increase in the Ds, the hysteresis of our materials exhibits an increasing trend first, followed by a decrease. This special phenomenon has not been reported before and caught our attention. From the results of humidity sensing properties, among the materials, the one with 0.2 Ds is promising for applications in humidity sensing due to its small hysteresis and fast response to varied relative humidity (RH). For a better understanding of the humidity sensing behavior of the sensor, complex impedance spectra were also measured. In the long-term stability measurement, the deviation of the measured impedance of the sensor at 97% RH is not obvious, proving good stability in a humid environment.

    更新日期:2019-10-25
  • Synthesis and thermal stability of a novel acetylene end-capped silicon-containing polyimide coupling agent with a silane pendant group
    High Perform. Polym. (IF 1.584) Pub Date : 2019-05-02
    Teng Yang; Yanhong Hu; Shifeng Deng; Lei Du; Jiali Zhou; Junjie Hu; Xue Jian

    In this study, a novel heat-resistant polyimide macromolecular coupling agent (PSI-C) was designed and synthesized. Silicon-containing diamine was one of the monomers used to increase the solubility of the polyimide, and m-aminophenylacetylene was the end-capping reagent that copolymerized with the resin matrix. A silane coupling group was introduced into the side chain to match the reinforced fiber. Thermogravimetric analysis revealed that the 5% thermal decomposition temperature (T d5) of the cured PSI-C could reach 454°C and the residual rate at 800°C was 53%. Thermal pyrolysis of the vaporized resin showed that the heat-resistant functional group was still detectable at 550°C. The thermal stability of the alkynyl-terminated silicon-containing polyimide silane coupling agent was higher than those of conventional silane coupling agents. The curing process of the composite system was not affected when adding the coupling agent PSI-C to the quartz fiber/alkynyl resin composite. The interlaminar shear strength and bending strength of the composite were increased by 55% and 61%, respectively, at room temperature. The high-temperature retention rate at 500°C reached 58% and 63%.

    更新日期:2019-10-25
  • Thermoplastic and soluble co-polyimide resins fabricated via the incorporation of 2,3,3′,4′-biphenyltetracarboxylic dianhydride
    High Perform. Polym. (IF 1.584) Pub Date : 2019-05-05
    Jinfeng Hu; Jianhua Wang; Shengli Qi; Guofeng Tian; Dezhen Wu

    A series of co-polyimide (co-PI) resins with distorted noncoplanar structure were carefully designed and successfully fabricated by copolycondensation of 2,3,3′,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydianiline (ODA), and 4,4′-(1,3-phenylenedioxy)dianiline (TPER). As-introduced asymmetric structure endowed these co-PI resins with excellent solubility and relatively low melt viscosity. Molecular simulation and dielectric analysis confirmed that the distorted noncoplanar structure induced a large amount of free volume. The minimum melt viscosity of co-PI resins decreased with increasing TPER content and reached 520 Pa·s at 400°C, indicative of good processability. Besides, the co-PI resins displayed outstanding thermal performance with glass transition temperature ranging from 256°C to 330°C and 5% weight loss temperature higher than 550°C in nitrogen atmosphere. Moreover, the co-PI sheets prepared by compression molding possessed tensile strength of 79.5–91.7 MPa and bending strength of 71.0–81.2 MPa when tuning the TPER/ODA ratio, with lower strengths observed at higher TPER content.

    更新日期:2019-10-25
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