Mechanical properties of injection-moulded styrene maleic anhydride (SMA): Part I: Influence of weldline and reprocessing

This paper presents the results from the first part of a study on the influence of reprocessing and weldlines on the properties of styrene maleic anhydride (SMA) polymer. Specimens for this study were injection moulded and reprocessed up to five times. It was found that while mechanical properties such as strength and modulus in both tension and flexure tests were virtually independent of the number of reprocessing cycles, the energy to fracture decreased as a result of reprocessing. Fracture parameters such as fracture toughness and strain energy release rate also showed little variation with reprocessing; although at times a reduction in these parameters was obtained for the fifth cycle. We found that tensile strength, fracture energy and fracture toughness were all reduced substantially in the presence of the weldline. However, none of these properties showed any significant variation with the number of reprocessing cycles. © 1998 Chapman & Hall     

Influence of weldlines on tensile properties of hybrid acrylonitrile butadiene styrene (ABS) composites filled with short glass fibres (GF) and glass beads (GB)

The present study investigated the effect of weldlines on tensile strength and modulus of injection moulded ABS polymer reinforced with both short fibres (GF) and spherical glass beads (GB). It was observed that tensile strength and modulus of ABS/GF/GB hybrids increased with increasing the concentration total of glass in the hybrid as well as the concentration of glass fibres in the hybrid (χ _GF ). Results indicated that tensile strength and modulus of ABS/GF/GB hybrids obey the rule-of-mixtures. The presence of weldlines had a negative effect on tensile properties of ABS/GF/GB hybrids. Although tensile strength and modulus of ABS/GF/GB hybrids were reduced in the presence of weldlines, nonetheless both increased with increasing the total concentration of the glass particles and χ _GF . The observed linearity of weldline strength and modulus with χ _GF indicated that these properties like their unweld counterparts can be expressed by simple rule-of-mixtures. It was noted also that weldline integrity factor for tensile modulus and strength decreased with increasing χ _GF and the total concentration of the glass particles in the hybrids. Weldline integrity values indicated that hybrid tensile strength was more affected by the weldlines than hybrid modulus.     

Hybridisation effect on flexural properties of single- and double-gated injection moulded acrylonitrile butadiene styrene (ABS) filled with short glass fibres and glass beads particles

The present study investigated the effect of hybridisation on flexural strength and modulus of single-gated (SG) and double-gated (DG) injection moulded acrylonitrile butadiene styrene (ABS) polymer reinforced with both short glass fibres (GF) and spherical glass beads (GB). It was observed that flexural strength and modulus of SG and DG ABS/GF/GB hybrids increased with increasing the total concentration of the glass in the hybrid as well as the concentration of glass fibres in the hybrid (χ _f). Results indicated that hybrid flexural properties for both SG and DG mouldings obey the simple rule of mixtures. The presence of weldlines in DG mouldings had a negative effect on flexural properties. It was noted that weldline integrity factor (weld to unweld property ratio) for flexural modulus and strength decreased with increasing the total concentration of the glass in the hybrid. However, whilst weldline integrity factor for flexural modulus decreased with increasing χ _f, weldline integrity factor for flexural strength showed no significant variation with respect χ _f. Weldline integrity factors indicated that the hybrid flexural strength is more affected by the presence of weldline than the hybrid flexural modulus.     

Mechanical properties of single- and double-gated injection moulded short glass fibre reinforced PBT/PC composites

Tensile and flexural properties of single-gated (SG) and double-gated (DG) injection moulded blend of polybutylene terephthalate (PBT) and polycarbonate (PC) and its composites containing 15, 20 and 30 wt.% short glass fibres were investigated. In the DG mouldings, a weldline was formed by direct impingement of two opposing melt fronts (i.e. cold weld). It was found that tensile modulus was not affected by the weldline but flexural modulus decreased in the presence of weldline. For both specimen types, modulus increased linearly with volume fraction of fibres (ϕ _f), according to the rule-of-mixtures for moduli. The weldline integrity (WIF) factor for flexural modulus decreased linearly with increasing ϕ _f. Results showed that tensile and flexural strengths for SG mouldings increase with increasing ϕ _f in a linear manner according to the “rule-of-mixtures” for strengths. The presence of weldline affected both strengths in a significant way; WIF factor decreased linearly with increasing ϕ _f and was independent of loading mode. It was noted also, that the overall fibre efficiency parameter for tensile modulus was independent of specimen type but for flexural modulus it was lower in the case of DG mouldings. In all cases, efficiency parameter for strength was considerably lower than for the modulus. Impact strength and fracture toughness of SG mouldings were significantly greater than for DG mouldings. Although these properties for SG mouldings increased with increasing ϕ _f, they decreased significantly for DG mouldings. Results showed that WIF factor for impact strength and fracture toughness decreased linearly with increasing ϕ _f.     

Temperature and weldline effects on tensile properties of injection moulded short glass fibre PC/ABS polymer composite

The effect of weldline and temperature on tensile properties of injection moulded PC/ABS blend reinforced with different concentration levels of short glass fibres was investigated between 23 and 100 °C. The weldline was formed in the moulded specimens by direct impingement of two opposing melt fronts. It was found that weldline had no significant effect on tensile modulus with weldline integrity factor in the range of 1–0.98. Tensile modulus for both weld and unweld specimens increased linearly with increasing volume fraction of fibres, ϕ_f, and decreased linearly with increasing temperature. Tensile strength of both weld and unweld tensile specimens increased non-linearly with increasing ϕ_f reaching a maximum at ϕ_f≈ 0.16 for specimens without weldline and ϕ_f≈ 0.12 for specimens with weldline. A linear dependence with respect to ϕ_f was found for both weld and unweld tensile strengths for fibre volume fractions in the range 0–0.1. It was found that below the glass transition temperature of the matrix, tensile strength of the composite with and without weldlines decreased linearly with increasing temperature. The weldline integrity factor for tensile strength decreased with increasing ϕ_f, but showed no significant variation with respect to temperature.     

Tensile and flexural properties of injection-moulded short glass fibre and glass bead ABS composites in the presence of weldlines

The effect of weldline on tensile and flexural properties of ABS reinforced with short glass fibres (ABS/GF) and spherical glass beads (ABS/GB) was investigated as a function of glass fibre and glass bead concentrations. The weldline was formed in the moulded specimens by direct impingement of two opposing melt fronts (i.e. cold weld). It was found that elastic modulus of ABS/GF composites, with or without weldlines increased linearly with increasing volume fraction of fibres (ϕ_f), according to the rule-of-mixtures for moduli. The presence of weldline reduced tensile and flexural modulus of the ABS/GF composites. Weldline integrity factor for elastic modulus of ABS/GF composites decreased linearly with increasing ϕ_f. Results showed that tensile and flexural strength of ABS/GF increased with increasing ϕ_f in a nonlinear fashion. Flexural strength was consistently greater than tensile strength for the same ϕ_f. Weldline affected both strengths in a significant way; weldline integrity factor decreased with increasing ϕ_f and was independent of loading mode. Tensile and flexural modulus of ABS/GB composites increased linearly with increasing volume fraction of glass beads (ϕ_b), showing no loading mode dependency. Although modulus of the ABS/GB system was not affected significantly by the weldline, its strength was affected, and more so in flexure than in tension. Weld and unweld strengths decreased with increasing ϕ_b in both tension and flexure according to Piggott and Leidner relationship; for the same ϕ_b, flexural strength was always greater than tensile strength. Weldline integrity factor for tensile strength of ABS/GF system was considerably lower than that for ABS/GB system but weldline integrity factor for flexural strength was almost the same for the two composite systems.     

Mechanical properties of glass fibres containing aluminium dispersoids

Glass fibres containing metallic aluminium dispersoids up to 7.5 at% AI have been made using ceramic bushings. The metallic granules have diameters ranging from 5 to 40 nm. A new technique based on strength-strain regression analysis has been used to determine the Young's moduli of the glass fibres. The Weibull parameters have been evaluated by both the graphical regression (GRE) and maximum likelihood (MLE) techniques. Fracture studies have also been carried out. The presence of aluminium particles increases the Young's modulus of the fibres but reduces the strength. The latter arises due to the metallic particles acting as stress concentrators within the glass matrix.     

马来酸酐封端聚丙撑碳酸酯及其性能研究

以马来酸酐(MA)为封端剂对聚丙撑碳酸酯(PPC)进行了封端,采用红外光谱、凝胶渗透色谱、热失重分析和差示扫描量热分析等对封端前后样品的性能进行了表征.红外光谱分析确认了马来酸酐参与了封端反应,聚合物分子量的测试表明,封端过程中有扩链反应的发生,热失重分析结果表明,马来酸酐封端能较大地提高聚丙撑碳酸酯的热分解温度.     

Mechanical properties of injection moulded blends of polypropylene with thermotropic liquid crystalline polymer

Blends of a thermotropic liquid crystalline polymer (LCP) with polypropylene (PP) were injection moulded. The LCP exhibited a higher viscosity than that of PP. Static and dynamic mechanical measurements, Izod impact tests, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were performed on these blends. The static tensile tests show that the tensile modulus and strength of PP are improved with the addition of LCP. The improvement in mechanical properties is associated with the formation of LCP fibrils as evidenced by SEM observations. Dynamic studies on these blends show an increase in the storage modulus but a decrease in loss factor with the addition of LCP. Furthermore, TGA measurements show that the thermal stability of PP is improved substantially with the addition of LCP.     

Study on short ramie fiber/poly(lactic acid) composites compatibilized by maleic anhydride

Short ramie fiber reinforced poly(lactic acid) (PLA) composites without and with maleic anhydride (MA) were developed. The influence of PLA-g-MA as a compatibilizer on the properties of the composites was studied. The tensile, flexural and impact strength of the composites have improvements with the addition of PLA-g-MA. The morphology of fracture surface evaluated by SEM indicates that the composites with the addition of PLA-g-MA can get better adhesion between the fiber and the matrix. And the Vicat softening temperature and the degradation temperature of the composites are increased with the addition of PLA-g-MA. However, PLA-g-MA leads the glass transition temperature (T_g) decrease according to the DSC results.     

Influence of short dispersed and short integral glass fibres on the mechanical behaviour of textile-reinforced concrete

This article addresses the influence of the addition of short dispersed and short integral fibres made of alkali-resistant (AR) glass on the fracture behaviour of textile-reinforced concrete (TRC) subject to tensile loading. A series of uniaxial, deformation-controlled tension tests was performed to study the strength, deformation, and fracture behaviour of thin, narrow plates made of TRC, both with and without the addition of short fibres. Additionally, uniaxial tension tests on specimens reinforced with only short fibres were performed to figure out the difference in behaviour in the absence of textile reinforcement. Furthermore, multifilament-yarn and single-fibre pullout tests were carried out to gain a better understanding of bonding properties and crack-bridging behaviour. While pronounced enhancement of first-crack stress was achieved due to the addition of short dispersed fibres (the value increased by a factor of 2), a significant improvement in tensile strength was recorded for TRC specimens with the addition of integral glass fibres; the value increased by approximately 30 %. Moreover, TRC specimens reinforced with short dispersed glass fibres showed formation of more and finer cracks in comparison to the specimens with integral fibres. It was also found that short integral fibres can improve the bond between multifilament-yarns and the surrounding matrix by means of “special” cross-links. In TRC with short dispersed fibres this phenomenon was less pronounced. The investigations were accompanied by microscopical investigations which provided additional basis for an in-depth discussion of the decisive working mechanisms of hybrid reinforcement.     

苯乙烯马来酸酐共聚物的阳离子化改性及其对颜料的分散

以无水乙醇和2,3-环氧丙基三甲基氯化胺(ETA)为改性剂,对苯乙烯马来酸酐共聚物(SMA)进行阳离子化改性,制备出一种高分子阳离子表面活性剂(SMG).通过红外光谱、含氮量以及溶解性测定表明:SMG分子中的酸酐基团已全部开环,部分形成酯键,含氮量增至0.372%,在SMG上成功引入了季铵盐基团.SMG易溶于水,降低表面张力的能力比SMA钠盐差,但对颜料黄14的分散效果较好,可以使颜料的zeta电位提高至 35.4mV.     

聚乳酸接枝马来酸酐/丙烯酸丁酯共聚物的制备与性能

以马来酸酐(MAH)和丙烯酸丁酯(BA)为单体,通过溶液接枝法制备了聚乳酸(PLA)接枝MAH/BA共聚物(m PLA)。使用红外光谱(FT-IR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)、热重分析仪(TG)研究了接枝共聚物的结构和性能。结果表明,随着单体质量比BA/MAH的增加,单体在PLA上的接枝率出现先增大后减小的趋势,当m(MAH)/m(BA)=1/1,m(MAH)/m(PLA)=3/100时,制备的m PLA接枝率最高为1.96%;与纯PLA相比,m PLA的结晶度和热稳定性均比有所下降,且样品的接枝率越大其结晶度越低;随着单体中BA含量的增加,m PLA的熔融温度和玻璃化转变温度有减小的趋势。     

Preparation and properties of mid-infrared glass fibres and poly (chlorotrifluoroethylene) composites

Fluorophosphate-glass-fibre-reinforced poly(chlorotrifluoroethylene) (PCTFE) composites with a transmittance of 80% from 0.4 to 3.7 μm were prepared. The transparent PCTFE composites transmit light to longer wavelengths and have a better chemical resistance to organic solvents (60–70% transmittance after immersing in p-xylene for 24 h) than transparent poly(methyl methacrylate) composites do. The tensile strength of the PCTFE increased by about 20% when it contained 1.1 vol% of unidirectional fluorophosphate glass fibre. The method for preparing the glass fibres and the composites is also described. This revised version was published online in November 2006 with corrections to the Cover Date.     

Terpolymerization of 2-ethoxy ethylmethacrylate,styrene and maleic anhydride: determination of the reactivity ratios

Terpolymerization of 2-ethoxyethyl methacrylate (2-EOEMA), styrene (St) and maleic anhydride (Ma) initiated by benzoyl peroxide was carried out in acetone as common solvent for three monomers. The structure and composition of terpolymer were determined by FTIR spectroscopy by recording analytical absorption bands for St (3002 cm⁻¹), Ma (1781 cm⁻¹) and 2-EOEMA (1261 cm⁻¹) units, respectively. The reactivity ratios for the monomers were calculated according to the general copolymerization equations following the Finnemann-Ross and Kelen-Tudos models. The results show that terpolymerization were carried out through primary “complex” mechanism at near-binary copolymerization of [St...Ma] complex with 2-EOEMA. Structure of the resulting terpolymer illustrated by¹H-NMR and differential scanning calorimeter showed reduction inT _g value.     

Mechanical properties of alkali treated plant fibres and their potential as reinforcement materials II. Sisal fibres

The tensile strength and Young’s modulus of sisal fibre bundles were determined following alkalisation. The results were then analysed with respect to the diameter and internal structure such as cellulose content, crystallinity index and micro-fibril angle. The tensile strength and stiffness were found to vary with varying concentration of caustic soda, which also had a varying effect on the cell wall morphological structure such as the primary wall and secondary wall. The optimum tensile strength and Young’s modulus were obtained at 0.16% NaOH by weight. The stiffness of the sisal fibre bundles obtained using the cellulose content also referred to as the micro-fibril content was compared with the stiffness determined using the crystallinity index. The stiffness obtained using the crystallinity index was found to be higher than that obtained using the cellulose content however, the difference was insignificant. Alkalisation was found to change the internal structure of sisal fibres that exhibited specific stiffness that was approximately the same as that of steel. These results indicates that the structure of sisal fibre can be chemically modified to attain properties that will make the fibre useful as a replacement for synthetic fibres where high stiffness requirement is not a pre-requisite and that it can be used as a reinforcement for the manufacture of composite materials.     

Microstructure-related fracture behaviour of injection moulded short fibre reinforced polyarylamide in dry and wet states

The fracture behaviour of injection moulded polyarylamide (PAR) composites containing 30, 50 and 60 wt% glass and 30 wt% carbon fibres has been investigated in both dry and wet states. Kinetics of moisture absorption study revealed that PAR and its composites exhibit Fickian behaviour. The incorporation of short fibres into a PAR matrix has resulted in the reduction of both maximum moisture content (M _m ) and diffusion coefficient (D). The fracture mechanical characterization of the various materials was evaluated by using notched compact tension (CT) specimens. Testing was performed as a function of temperature (T = –40, 20 and 80°C) and crosshead speeds (v = 1 and 1000 mm min^–1) on as received (AR) specimens. The influence of water uptake due to the hygrothermal ageing (HA) process on residual fracture performance was also studied. The combined action of moisture-induced plasticization of the PAR matrix and interfacial degradation has been concluded to play a significant role in controlling the fracture behaviour of the (HA) composites. The residual fracture properties of both neat PAR and its composites are almost fully recovered in the case of redrying (RD). Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope (SEM) are discussed.