Miscibility and synergistic effect of impact strength in polycarbonate/ABS blends

Miscibility and mechanical properties of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends prepared by a continuous kneader-type extruder were investigated. It was found that the PC/ABS blend consists of the miscible PC/SAN phases and immiscible PC/PB phases, which agrees well with that predicted by the group contribution method of solubility parameters. Differences in calculated solubility parameter () are 0.20 (cal cm^–3)^1/2 for the PC/SAN pair and 1.85 (cal cm^–3)^1/2 for the PC/PB pair. Interestingly, the impact strength of the present PC/ABS blends exhibits a synergistic effect over a much wider range of polycarbonate content, i.e. 20%–80%, than that of the previously reported ones. This may be attributed to the enhanced mixing and low butadiene content. However, further work on the relationship with the rubber particle size is required to understand fully this observation.     

Herringbone fracture of a polycarbonate/ABS blend

Tensile fracture mechanisms in single edge notched injection-moulded specimens of a polycarbonate/ABS 30/70 wt% blend have been studied by fractography. When the tensile force was applied parallel to the injection direction, a herringbone pattern could be observed on the fracture surface, while for the perpendicular case, a reverse herringbone pattern was seen. At the same testing condition, the former was tougher than the latter. Fracture images and two-dimensional temperature profiles in the thickness direction were used to locate the crack initiation sites. Herringbone fracture occurred when the main crack repeatedly interacted with secondary cracks initiated along the centreline. Reverse herringbone fracture was formed in a similar mechanism but secondary cracks initiated near the edge. Anisotropy of the fracture modes was attributed to the processing-induced orientation of the polycarbonate phase near the edge.     

Blends of polycarbonate with unmodified and maleic anhydride grafted ABS: fracture mechanics

Physical blends of polycarbonate (PC) and acrylonitrile-butadiene-styrene terpolymer (ABS) at two different weight fractions were made (PC35/ABS65 and P75/ABS25). Reactive blended similar compositions of PC with maleic anhydride grafted ABS (MABS) were also made at the same compositions. The crack resistance behaviour of these two types of blends and feedstocks (PC and ABS) were studied. The generalized locus method was used to investigate the invariance of crack resistance from any set of characteristic points. PC and PC/ABS blends failed immediately after crack initiation. The modified blends (PC/MABS) exhibited failure through crack propagation after crack initiation started. The resistance to crack initiation is determined in terms of critical J-integral value (J_c). The resistance to crack propagation at maximum load point is also determined from the locus of maximum load point on the load-displacement curves. The resistance to steady state crack growth (R_p) during extensive crack propagation is determined from the total essential energy for a complete fracture. The crack resistance values for modified blends are much high compared to unmodified blends and even feedstocks.     

The yield and deformation behaviour of some polycarbonate blends

Polycarbonate and its blends with PE and MBS have been tested to investigate the impact modification mechanism. These materials have been tested in tension over the speed range 10^–2 to 10² in. sec^–1 (2.5×10^–2 to 2.5×10² cm sec^–1). The tensile deformation behaviour of these materials is similar except for the magnitude of the yield stresses. The yield stress versus log curves have identical slopes. Based on Eyring's equation for the flow of viscous materials, these materials have identical activation volumes, implying that the mechanical behaviour modification is not due to changes in molecular mechanisms. The modifier particles probably change only the stress state of the matrix material. Three-point bending tests on notched bars of these materials have also been performed over the speed range 10^–2 to 10² in. sec^–1 (2.5×10^–2 to 2.5×10² cm sec^–1). The areas under the load-deflection curves have been measured as the total energy absorbed during the deformation. It was found that both geometric constraint and rate of deformation can bring about ductile-brittle transitions. However, the thickness sensitivity of the blends is less than that of the pure material. Scanning electron micrographs show that the matrix material voids and flows extensively around the modifier particles before the ductilebrittle transition speed is reached. This voiding probably relieves plane strain. However, at higher speeds, the modifier particles cannot relax sufficiently rapidly, and they lose this plane strain relieving capability.     

Characterization of recycled polycarbonate/polybutylene terephthalate blends

Polycarbonate (PC)/polybutylene terephthalate (PBT) blends (CBs) represent a good compromise between the properties of PC and PBT and are among the most popular engineering plastics today. To evaluate the capability of recycled and reprocessed CBs, the physical and mechanical properties of 0 to 20 times reprocessed CBs were characterized, and an attempt was made to modify a 20-time reprocessed CB to reach ≥85% of the functionality of a virgin CB. Generally, the thermal weight loss (30% at 300–450°C and 40% at ~470°C) of the CBs varied little with the reprocessing cycles, reflecting their high thermal stability. The increased melting index (from 18.7 to 92.0 g (10 min)^–1) but decreased stress values (from 6.08 to 4.99 kgf mm^–2), strains (from 79.0 to 29.1%), impact strength (from 144 to 14.7 J m^–1) and torque values (from 82 to 60 N m^–1) with reprocessing cycles suggest that the CBs undergo thermal/mechanical decomposition when reprocessing and become thereafter stiffer. Satisfactory modification of the 20 times reprocessed CB succeeded simply via adding ~30% (w/w) virgin PC and PBT. Adding styrene maleic anhydride and a chain extender failed to improve the stress values of reprocessed CBs, probably due to their weak interaction with the PC and PBT molecules.     

Fracture behaviour and morphology of PC/ABS blends

The toughness behaviour of polycarbonate (PC)/acrylnitrile-butadiene-styrene (ABS) blends under dynamical loading (1 ms^–1) based on the J-integral concept was studied. For this the multiple specimen R-curve method was used. A special experimental technique of a stop block method was developed. It was shown that the materials exhibit a very different toughness behaviour depending on temperature and ABS content. The reasons for this material behaviour are discussed with the help of scanning and transmission electron microscopical (SEM and TEM) investigation methods. It can be shown that a combination of fracture mechanics and electron microscopy allows a toughness optimization to be made on the basis of quantitative morphology-toughness correlations.     

多波段吸收PC滤光镜片的制备与性能研究

使用染料-高聚物混(dye-polymer)的方法将光吸收染料UV360、VIS532、NIR1064作为功能添加剂分散在聚碳酸酯(PC)中,采用注射成型的方法制备了一种防紫外、防眩光、防980和1 064nm激光波长的多波段吸收PC滤光镜片。研究了光吸收染料在聚碳酸酯中的吸收特性,确定了光吸收染料的添加量,最终制备的PC镜片在250~400nm紫外波段的透过率为0.06%,在400~700nm可见光波段的透过率为14.43%,在980和1 064nm激光波长处的透过率为0.006%和0.003%(吸光度4)。镜片材料的冲击强度为60.4kJ/m2,弯曲强度为120 MPa,力学性能优良。在经过高温、低温和光照环境实验后,镜片的光学性能未发生明显变化,具有良好的应用性能。     

Microdeformation in partially compatible blends of poly(styrene-acrylonitrile) and polycarbonate

Dilute 3-component 1-phase solutions in methylene chloride of poly(styrene-acrylonitrile) PSAN and polycarbonate PC are used to cast phase separated thin films. Films of pure PSAN, pure PC and five intermediate compositions are examined. The films are bonded to copper grids and strained at a constant rate of 4.1 × 10^–6sec^–1. The median tensile strain _v for void formation is determined using an optical microscope and the regions surrounding the voids are examined by TEM. At room temperature and slow strain rates both PSAN and PC plastically deform by shear yielding. For pure PSAN _v was found to be 0.13 whereas for PC _v exceeds 0.23. The addition of the more ductile polymer PC to PSAN at weight fractionsx forx 0.4 decreases _v. In this case voids form in crazes at the boundaries between the PC-rich inclusion and the PSAN-rich matrix. When the PC content is increased tox = 0.8, _v approaches 0.23. The effect of physical ageing (annealing belowT _g the glass transition temperature) on the mode of plastic deformation was also examined over the same compositional range. Physical ageing was found to suppress shear deformation and favour crazing in PSAN and PSAN-rich phases. Because crazes are more susceptible to breakdown than DZ's (shear deformation zones), physical ageing results in a marked decrease in _v. The breakdown statistics of these phase separated partially compatible blends was found to follow a Weibull distribution in strain from which two parameters may be extracted: the Weibull modulus and _w the Weibull scale parameter. is a measure of the breadth of distribution of void initiation and _w is a measure of the median strain to void formation in the films. The behaviour of _w was found to approximately mirror _v. The Weibull modulus appears to be primarily controlled by the matrix phase.     

Toughened blends of poly(butylene terephthalate) and BPA polycarbonate

The morphologies of melt blends of poly(butylene terephthalate) (PBT) and bisphenol A polycarbonate (PC) toughened with a core/shell impact modifier have been characterized by transmission and scanning electron microscopy. Selective staining with ruthenium and osmium tetroxide and etching with diethylene triamine have been used to assess the distribution of the various blend components and investigate the effects of thermal history on morphology. Strong evidence for partial melt miscibility of PC and PBT and rate-dependent segregation during cooling is presented.     

Structural-mechanical relationship of epoxy compatibilized polyamide 6/polycarbonate blends

Polyamide 6 (PA6)/polycarbonate (PC) blends compatibilized with solid epoxy resin (bisphenol type-A) were prepared by extrusion followed by injection molding. The effects of epoxy resin on the microstructure, tensile, impact and compatibility of the PA6/PC blends were investigated. The results showed that both the tensile modulus and elongation at break of PA6/PC blends were inferior as compared to their parent polymers. This resulted from incompatibility between the PA6 and PC phases. SEM observation revealed that the introduction of 0.5 part per hundred (phr) epoxy resin into the PA6/PC75/25 blend yields a finer dispersion of PC phase in PA6 matrix. The boundaries between the PC domains and PA6 matrix became obscure with the incorporation of 1 phr epoxy resin. Such an improvement in compatibility was suggested to be resulted from the formation of in situ epoxy bridged PA6-PC block copolymer in the blend during compounding. Consequently, the tensile modulus, yield strength and impact strength of the PA6/PC 75/25 blend improved considerably with increasing epoxy content.     

ABS改性剂的核壳比对CPVC/ABS共混物性能的影响

采用种子乳液聚合方法在聚丁二烯(PB)上接枝苯乙烯(St)和丙烯腈(AN)单体,合成了一系列不同核壳比的ABS改性剂,将其与氯化聚氯乙烯(CPVC)熔融共混制得CPVC/ABS共混物,研究了ABS核壳比对CPVC/ABS共混物结构与性能的影响.动态力学分析结果表明:CPVC与接枝SAN不相容;扫描电子显微镜发现:ABS...     

Fracture toughness and fracture mechanisms of polybutylene-terephthalate/polycarbonate/ impact-modifier blends

A series of polybutylene-terephthalate/polycarbonate (PBT/PC) blends with different compositions were prepared using a twin-screw extruder. The morphologies of the blends were revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that a 50/50 PBT/PC blend possessed a bicontinuous structure and the other blends had a dispersed phase of either PBT or PC depending on which was the minor component. A relatively strong interface was observed in the blends with 20%, 40% and 50% PBT; but poor interfacial adhesion was found in the blends with 60% and 80% PBT. The strength of the interfacial boundary was believed to depend on the composition and blending conditions of the individual blend. Fracture experiments showed that the sharp-notch fracture toughness of PC could be significantly increased by mixing with up to 50% PBT without losing its modulus and yield stress. The toughening mechanisms involved in the fracture processes of the blends were studied using both SEM and TEM together with single-edge-double-notched-bend (SEDNB) specimens. It was found that in the toughened blends the growing crazes initiated by the triaxial stress in front of the crack tip were stabilized by the PC domains. The debonding-cavitation mechanism occurred at the PBT/PC interface, which relieved the plane-strain constraint and promoted shear deformation in both PBT and PC. This plastic deformation absorbed a tremendous amount of energy. Crack-interface bridging by the PC domains was clearly verified by the TEM study. Thus, the PC domains not only stabilized the growing crazes they also bridged crack surfaces after the crack has passed by. This effect definitely caused a large plastic-damage zone and hence a high crack resistance. Poor crack resistances of the blends rich in PBT was caused by the poor interfacial adhesion between PBT and PC. In these polymer blends, the growing crazes easily developed into cracks, which subsequently passed through the weak interface of PBT/PC and finally produced fast unstable fracture.     

Crumb rubber blends in noise absorption study

The paper presents a study of crumb rubber blends aiming at the application in noise reduction. The major issues addressed include the fabrication method in making crumb rubber blends, the tensile strength measures, measurement of the coefficient of acoustic absorption (AAC), surface textures of crumb rubber blends, the analytic analysis on AAC and noise absorption. The results obtained in this study show that crumb rubber blends may present a potentially viable alternative to current concrete highway noise barriers.     

Influence of processing conditions on rheological and mechanical properties of polycarbonate/polypropylene blends

Rheological and mechanical data on polycarbonate/polypropylene blends are reported as a function of the blend preparation. Both kinds of properties depend on the properties of the homopolymers and on the processing conditions. In the molten state the blends are compatible at low content of polypropylene and incompatible at high content. The blends with intermediate compositions can be called semicompatible. Also in the solid state the blends with low content of polypropylene are compatible, while all other blends are incompatible.     

Tuning the localization of functionalized MWCNTs in SAN/PC blends by a reactive component

The influence of the reactive component (N-phenylmaleimide styrene maleic anhydride) on the blend morphology, the localization of functionalized multiwalled carbon nanotubes (MWCNTs), and the electrical resistivity of MWCNT filled blend systems of polycarbonate (PC) and poly(styrene-co-acrylonitrile) (SAN) was investigated. SAN, PC, amino-functionalized MWCNTs (Nanocyl™ NC3152) and the reactive component (RC) were melt mixed in a DSM Xplore microcompounder using different mixing sequences. The RC containing maleic anhydride (MA) groups is miscible with SAN and is assumed to act as linking agent to the functionalized MWCNTs.The morphology of the SAN/PC blends was studied depending on the concentration of the RC. Thereby co-continuous morphologies were found for all blends with 40 wt.% SAN and 60 wt.% PC. In all nonmodified blends the MWCNTs were localized within the PC phase. After the addition of RC the MWCNTs migrated completely into the miscible SAN–RC phase. Consequently, the electrical resistivities of the blends changed in dependence on the localization. Whereas the SAN/PC/MWCNT blends showed low electrical resistivity values, much higher values were found for SAN–RC/PC/MWCNT blends. This was assigned to a coupling or strong interaction of MA groups to the nanotubes disturbing electrical contacts and percolation between them. The occurrence of the MWCNT migration from PC towards SAN was found to be dependent on the concentrations of RC and MWCNTs. By adapting that ratio and the mixing strategy, the localization of the carbon nanotubes in the blend phases can be tuned. The investigations indicated that MWCNTs once coupled with the RC remain in the SAN–RC phase. Thus, a chemical reaction or strong interactions seem to be the driving forces for localization of the MWCNTs in the SAN–RC blend phase.     

CB/ABS连续导电介质吸波性能研究

通过热压方法制备了炭黑(CB)/ 丙烯腈-丁二烯-苯乙烯共聚物(ABS)连续导电介质吸波平板,研究了炭黑含量和厚度对CB/ABS连续导电介质介电常数和吸波效能的影响.结果表明炭黑/ABS连续导电介质的介电常数和介电损耗角正切随炭黑含量的增加而增大;在炭黑含量达到20%(质量分数)时,复合平板的吸收峰值达到最佳,对应于其体积电阻率为105Ω·cm;复合平板的厚度增加有助于改善其吸波性能.修正的Rayleigh混合有效介电常数和广义反射率计算公式计算导电介质吸波性能有很好的实用性.     

Thermal properties of nylon6/ABS polymer blends: Compatibilizer effect

Nylon6/ABS binary blends are incompatible and need to be compatibilized to achieve better performance under impact tests. Poly(methyl methacrylate/maleic anhydride) (MMA-MA) is used in this work to compatibilize in situ nylon6/ABS immiscible blends. The MA functional groups, from MMA-MA copolymers, react with NH₂ groups giving as products nylon molecules grafted to MMA-MA molecules. Those molecular species locate in the nylon6/ABS blend interfacial region increasing the local adhesion. MMA-MA segments are completely miscible with the SAN rich phase from the ABS. The aim of this work is to study the effects of ABS and compatibilizing agent on the melting and crystallization of nylon6/ABS blends. This effect has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Incorporation of this compatibilizer and ABS showed little effect on the melting behavior of the PA6 crystalline phase, in general. DMTA analysis confirmed the system immiscibility and showed evidence of compatibility between the two phases, nylon6 and ABS, produced by MMA-MA copolymer presence. The nylon6/ABS blend morphology, observed by transmission electron microscopy (TEM), changes significantly by the addition of the MMA-MA compatibilizer. A better dispersion of ABS in the nylon6 phase is observed.     

有机蒙脱土调控ABS/PA6共混体系的共连续结构

采用熔融共混的方法制备了不同配比的有机蒙脱土(OMMT)填充丙烯腈-丁二烯-苯乙烯(ABS)/尼龙6(PA6)共混物。通过抽提、SEM、TEM、XRD等表征手段研究了OMMT在PA6相中的定向分散现象及共混体系相结构的演变规律。结果表明,OMMT可以定向分散在ABS/PA6共混物的PA6相中,使形成共连续结构的聚合物比例范围变宽;随着OMMT含量的增加,形成共连续结构所需的PA6的含量降低,同时相尺寸减小;OMMT的临界含量(m(OMMT))和形成共连续PA6的质量分数(m(PA6))存在近似的反比关系,其特征参数n值约为8,据此可根据共混体系中PA6的含量,推算形成相反转所需的OMMT添加量,为相关共混物的制备提供有益的借鉴。