Variables that Determine the Fiber‐Matrix Bond Strength in Ethylene‐Type Ionomer Composites

The effects of some variables, namely, ion concentration, matrix tensile strength, matrix yield strength and the matrix tensile modulus on the fiber‐matrix bonding strength were determined for six ionomers (coded PEA‐1 to PEA‐6) bonded to surface‐modified poly(p‐phenylene terephthalamide) (PPTA) fibers. The results obtained show that the mean bonding shear strength of the ionomers correlates well with both their ultimate tensile strengths and their tensile yield stresses. However, correlation of the bonding shear strengths with the matrix yield stresses reveals that the bonding shear strength was about 1.1 times that of the matrix tensile stress. Failure criteria for all the materials predict maximum shear stress to be either 0.5 or 0.577 of the tensile yield stress, hence a value greater than unity cannot be interpreted nor theoretically justified. It was found that the bonding shear strength of the ethylene‐type ionomer PEA‐6 compared to carboxymethyl surface‐modified PPTA is about 20% lower than the bonding shear strength of this resin against sized PPTA fibers. The reduction of entanglements and/or ionic crosslinking across the bound polymer/bulk polymer interface leads to a weak interface with a subsequent decrease in the measured shear strength.     

Development of Ethylene‐Vinyl Acetate Composites Reinforced with Graphene Platelets

Composites of ethylene‐vinyl acetate (EVA) reinforced with graphene platelets are fabricated. Morphological, thermal, mechanical, electrical properties as well as moisture absorption of the composites are characterized. Transmission electron microscopy shows a good dispersion of graphene platelets in the matrix. The unidirectional orientation of graphene platelets parallel to the surface of the composites is revealed by field emission scanning electron microscopy and is validated using the Halpin–Tsai model. Tensile strength and elongation of the composites are respectively improved by 109 and 83%, after the addition of 3 wt% graphene platelets. The incorporation of 5 wt% graphene platelets enhances the char residue of the composites from 0.544% for pure EVA to 6.63% for the composites. The electrical conductivity of the composite with 3 wt% graphene platelets is two orders of magnitude higher than that of pure EVA with 10⁻¹³ S cm^–1 electrical conductivity.

     

硅酸铝纤维/石英复合隔热材料的研制

本文研制了一种纤维布/纤维毡叠层、层间穿刺纤维加强的纤维增强石英基复合材料,该材料体积密度小、导热率低、可耐受1200℃高温,有希望成为我国航天运载器的新一代复合隔热材料.     

短纤维／橡胶复合材料中的短纤维预处理

论述了短纤维橡胶复合材料中短纤维预处理的必要性,并详细的介绍了短纤维的各种预处理方法     

Mechanical Performance of Soy‐Hull‐Reinforced Bioplastic Green Composites: A Comparison with Polypropylene Composites

A blend composition of poly(3‐hydroxybutyrate‐co‐valerate) and polylactide is used as a bioplastic matrix and reinforced with soy hull to engineer novel green composites. A comparative study with soy‐hull‐reinforced polypropylene composite system is performed. A compatibilizer is used to engineer the novel class of green composites with a balanced stiffness and toughness performance with the target to substitute PP‐based composites. The flexural and impact strength along with hydrophobicity of compatibilized composites are improved significantly over the noncompatibilized counterpart. The fiber/matrix interaction is investigated by SEM. These green composites have the potential to substitute PP‐based composites in some applications.

     

Properties Enhancement of Mengkuang Leaf Fiber/Ethylene‐Vinyl Acetate/Natural Rubber Thermoplastic Elastomer Composites by Alkaline Peroxide Bleaching Treatment

In this article, the effect of alkaline peroxide bleaching treatment using hydrogen peroxide on mengkuang leaf fiber (MLF) to the tensile, thermal properties and water absorption of thermoplastic elastomer composites based on ethylene‐vinyl acetate/natural rubber and MLF was investigated. Fiber morphology and the fiber‐matrix interface were further characterized by scanning electron microscopy (SEM). Treated composites showed better tensile properties than untreated fiber composites. SEM of the fractured surfaces of the composite specimens indicates that the bleaching treatment improved the interfacial interaction between the fiber and the matrix. The results of thermogravimetric analysis showed a higher thermal stability for treated composites than untreated composites. Furthermore, alkaline bleaching treatment has resulted in reduction of water absorption from 31% to 26% as compared with untreated composites. J. VINYL ADDIT. TECHNOL., 26:127–134, 2020. © 2019 Society of Plastics Engineers     

IPMC的制备及其电极结构的表征

由聚乙烯-乙烯醇(EVOH)和1,3-丙烷磺酸内酯合成了EVOH磺酸钾离子聚合物(EVOH-SO3K),并用2,4-甲苯二异氰酸酯(TDI)对其进行了交联改性,得到TDI改性EVOH磺酸钾离子聚合物(EVOH-TSO3K),通过EVOH-TSO3K溶液的铸膜和化学沉积制得离子聚合物膜金属复合材料(IPMC).采用傅立叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)分别对EVOH-TSO3K及其IPMC进行了结构表征.结果表明,EVOH-TSO3K形成了交联结构,银金属电极均匀沉积在聚合物膜表面.通过三次化学沉积,IPMC表面电阻可达到8×10-1Ω/mm2,从而在外加负载电压下(3V)实现了电形变,电形变角度达到36°.     

PPTA树脂在甲磺酸中的溶解及其溶液性质初探

实验首次用甲磺酸(MSA)对聚对苯二甲酰对苯二胺(PPTA)树脂进行溶解制备PPTA/MSA溶液,并对所形成溶液性质进行研究并制备PPTA浆粕。通过偏光显微镜观察了PPTA树脂在MSA中的溶解规律,用树脂比浓对数粘度随时间的变化研究了树脂在MSA中的稳定性。并通过比表面积(BET)分析、X射线衍射(XRD)分析和热失重分析(TGA)研究了PPTA浆粕的比表面积、结晶度和热性能。结果表明:在低浓度下,PPTA树脂能与MSA混合均匀得到均一稳定的溶液,由所得溶液制备的PPTA浆粕性能优于同条件下用PPTA/硫酸溶液制备的浆粕性能。     

Preparation and Performance of the Room‐Temperature‐Cured Heat‐Resistant Phosphate Adhesive for C/C Composites Bonding

Carbon/carbon(C/C) composites were bonded with a phosphate adhesive prepared from H₃PO₄ (orthophosphoric acid) and Al(OH)₃ as the matrix and Si and CuO as the inorganic fillers. The mechanical properties were tested at room temperature after the bonded specimens were treated from RT to 1500°C. The results showed that the addition of CuO could greatly improve the adhesive's mechanical properties due to the formation of Cu_nSi (copper silicides). The shear strength of bonded specimens could be up to 8.2 MPa without heat treatment and remain above 2 MPa within the whole heat‐treatment temperature range.     

Preparation and Properties Study of Core‐Shell CL‐20/TATB Composites

The insensitive high explosive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) was selected for coating and desensitization of hexanitrohexaazaisowurtzitane (CL‐20), another high explosive, after surface modification. About 2 wt‐% polymer binder was adopted in the preparation process to further maintain the coating strength and fill the voids among energetic particles. The structure, sensitivity, polymorph properties, and thermal behavior of CL‐20/TATB by coating and physical mixing were studied. Scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) results indicate that submicrometer‐sized TATB was compactly coated onto the CL‐20 surface with coverage close to 100 %. The core‐shell structure of CL‐20/TATB was confirmed by observation of hollow TATB shell from the CL‐20 core dissolved sample. X‐ray diffraction (XRD) analysis revealed that the polymorph of CL‐20 maintained ε form during the whole preparing process. Thermal properties were studied by thermogravimetry (TG) and differential scanning calorimeter (DSC), showing effects of TATB coating on the polymorph thermal stability and exothermic decomposition of CL‐20. Both the impact and friction sensitivities were markedly reduced due to the cushioning and lubricating effects of TATB shell. The preparation of explosive composites with core‐shell structure provides an efficient route for the desensitization of high explosives, such as CL‐20 in this study.     

Compatibilization of Polyamide‐6/Polyarylate Blends by Means of an Ionomer

Summary: Polyamide‐6 (PA6)/polyarylate of bisphenol A (PAr) blends rich in PA6 and modified with an additional 15% poly[ethylene‐co‐(methacrylic acid)] partially neutralized with zinc (PEMA‐Zn) as a compatibilizer were obtained by melt mixing. Their phase structure, morphology, and mechanical performance were compared with those of the corresponding binary blends. The ternary blends were composed of a PA6 amorphous matrix and a dispersed PAr‐rich phase in which reacted PA6 and PEMA‐Zn were present. Additionally, minor amounts of a crystalline PA6 phase, and a PEMA‐Zn phase were also present. The chemical reactions observed led to a clear decrease in the dispersed particle size when PEMA‐Zn was added, indicating compatibilization. Consequently, the mechanical behavior of the blends with PEMA‐Zn improved, leading, mainly in the case of the blend with 10% PAr, to significant increases in both ductility and impact strength with respect to those of the binary blends. These increases were more remarkable than the slight decrease in stiffness as a consequence of the rubbery nature of the compatibilizer.

Cryogenically fractured surface of the PA6/PAr‐PEMA‐Zn 70/30‐15 ternary blend.     

ABS/石墨/NBR导热复合材料性能的研究

采用熔融共混法制备丙烯腈-丁二烯-苯乙烯共聚物(ABS)/石墨/丁腈橡胶(NBR)导热复合材料,通过热常数分析仪、同步热分析仪、扫描电子显微镜、力学性能测试等手段研究了NBR、ABS高胶粉及石墨(G)的添加量对ABS复合材料导热性能及力学性能的影响。结果表明,ABS高胶粉和NBR均能明显提高ABS的热导率和缺口冲击强度,但是丁腈胶粉的改性效果优于高胶粉。以NBR作为ABS复合材料的增韧剂,随着石墨含量的增大,增韧效果下降,ABS复合材料的热导率提高到纯ABS的5倍,热分解温度提高40℃左右,热膨胀系数下降。当ABS/G/NBR复合材料的质量比为60/15/25时,其热导率为纯ABS的2倍,缺口冲击强度达21.8 kJ/m2,明显高于纯ABS(2.6kJ/m2)。     

UHMWPE纤维/LDPE复合材料防弹性能及机理研究

本文探讨了用超高分子量聚乙烯（UHMWPE）纤维增强低密度聚乙烯（LDPE）复合材料的防弹性能，研究了不同基体含量对复合材料防弹性能的影响。实验证明，UHMWPE纤维／LDPE复合材料具有较好的防弹性能，其最佳的基体含量在26％左右。同时，本文还通过分析防弹片材的断裂区域及复合材料的防弹机理确定了弹丸的变形情况和靶片“背凸”在防弹作用中的贡献。     

High‐Performance Pristine Graphene/Epoxy Composites With Enhanced Mechanical and Electrical Properties

High‐strength conductive pristine graphene/epoxy composites are prepared by two simple processing methods – freeze dry/mixing and solution processing. PVP‐stabilized graphene is aggregation‐resistant and allows for excellent dispersion in both the resin and final composite, as confirmed by optical microscopy and SEM images. The superior dispersion quality results in excellent nanofiller/matrix load transfer, with a 38% increase in strength and a 37% improvement in modulus for 0.46 vol% graphene loading. The composites have a very low electrical percolation threshold of 0.088 vol%. Despite the effectiveness of both methods, the freeze‐drying method is more promising and versatile enough to be used for graphene dispersion in a wide range of other composite precursors.

     

Effect of Maleated Compatibilizer on Performance of PLA/Wheat Straw‐Based Green Composites

In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.

     

Preparation and characterization of composites: Ethylene–propylene–diene terpolymer‐graft‐maleic anhydride/CaCO3

In this paper, a new method was applied to form crosslinking networks in the ethylene–propylene–diene terpolymer (EPDM) matrix with calcium carbonate(CaCO₃) particles, which were chemically treated by maleic anhydride (MAH). The tensile test showed that the tensile strength and the elongation at break of the composites were improved significantly, and when the content of CaCO₃ was about 20 wt % in the composites, the maximum tensile properties were achieved. The results of swell and solution text showed that the composites had evident crosslinking structure. The results of attenuated transmission reflectance‐Fourier transform infrared (ATR‐FTIR) spectrum proved that the Acid‐Base reaction between CaCO₃ and MAH had happened. SEM micrographs showed that the interfacial adhesion between CaCO₃ and copolymer was well. The thermogravimetric analysis curves showed that the composites had a new change in mass between 655 and 700°C, which might be the decomposition temperature of calcium maleicate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1810–1815, 2006     

超支化聚磷酸酯/聚苯乙烯复合材料的性能研究

以密炼、模压等工艺制备了超支化聚磷酸酯(HPPE)/聚苯乙烯(PS)复合材料,研究了HPPE的代数和用量对HPPE/PS复合材料性能的影响及其规律性,研究的性能包括拉伸强度、弯曲强度、冲击强度、维卡软化点温度以及熔体质量流动速率,并通过SEM观察其冲击断面的微观形态和研究其增韧机理.结果表明:HPPE/PS复合材料的拉伸强度、冲击强度和熔体质量流动速率随HPPE用量的增加先增加后降低,随HPPE摩尔质量的变化影响较小.在HPPE-2用量为6 phr左右,复合材料的综合性能较佳,对比纯PS,拉伸强度可提高124%,冲击强度可提高56%,熔体质量流动速率可提高84%,但弯曲强度和维卡软化点温度有微弱下降.     

T-ZnOw/TLCP抗静电复合材料的制备与性能研究

以热致液晶高分子(TLCP)为基体,四针状氧化锌晶须(T-ZnOw)为导电填料,用单螺杆挤出机制备抗静电性T-ZnOw/TLCP复合材料,分别探讨了偶联剂对T-ZnOw的影响;T-ZnOw用量对T-ZnOw/TLCP复合材料表面电阻率、热变形温度、力学性能的影响。结果表明,T-ZnOw经过偶联剂改性后,随着其用量的增加,复合材料表面电阻率显著下降,热变形温度、拉伸强度、冲击强度均呈现先增大后减小的趋势。     

Piezoelectric Properties of a Pioneering 3‐1 Type PZT/Epoxy Composites Based on Freeze‐Casting Processing

Lead zirconate titanate (PbZr_1 ? xTi_xO₃, PZT)/epoxy composites with one‐ dimensional epoxy in PZT matrix (called 3‐1 type piezocomposites) have been fabricated by tert‐butyl alcohol (TBA)‐based directional freeze casting of PZT matrix and afterward infiltration of epoxy. The composites with PZT volume fraction ranging from 0.36 to 0.69 were obtained by adjusting initial solid loading in freeze‐casting slurry. The effect of poling voltage on piezoelectric properties of the composites was studied for various volume fraction of PZT phase. With the increasing of PZT volume fraction, relative permittivity (ε_r) increased linearly and piezoelectric coefficient (d₃₃ and d₃₁) increased step by step. The resultant composites with 0.57 PZT volume fraction possessed the highest hydrostatic piezoelectric strain coefficient (d_h) value (184 pC/N), voltage coefficient (g_h) value (13.6 × 10^?3 V/m Pa), and hydrostatic figure of merit (HFOM) value (2168 × 10^?15 Pa^?1).     

Properties of Poly(3‐hydroxybutyric acid) Composites with Flax Fibres Modified by Plasticiser Absorption

Natural fibre‐biopolymer composites have been prepared from flax and polyhydroxybutyrate (PHB). The flax was modified by drying, followed by plasticiser absorption to replace the water lost to prevent embrittlement. This protects the fibres from problems associated with their water content and changes in water content due to equilibration with the environment. Flax and PHB showed good interfacial adhesion, which was decreased when plasticisers were present. Some plasticiser migrated from the flax to PHB and caused complex changes in the glass transition, crystallisation and crystallinity of the PHB. Morphology of the composites was examined by scanning electron microscopy (SEM) and optical microscopy (OM), SEM provided information on the interfacial adhesion through fractography. OM showed extensive transcrystallinity along the fibre surfaces. Dynamic mechanical analysis was used to measure elastic and damping characteristics and their relation to composition and morphology.

SEM micrograph of the PHB‐plasticiser‐flax system PHB‐PEG‐flax.