Thermal aging of impact-modified polycarbonate

Glassy polymers undergo relatively rapid physical aging just below their glass transition temperatures that can lead to embrittlement of normally tough materials like polycarbonate (PC). One approach for solving the embrittlement problem is to incorporate an impact modifier that can cause toughening when the matrix loses its inherent ductility due to physical aging. The effects of thermal aging below the glass transition temperature of polycarbonate on selected properties of blends of PC with various core-shell impact modifiers have been studied. Observed changes in mechanical properties are related to rubber content, free volume, fracture morphology, discoloration, enthalpy relaxation, glass transition temperature, intrinsic viscosity, and dynamic mechanical behavior. Blend mechanical properties are affected by chemical changes in the impact modifier that occur simultaneous with the physical aging of the PC matrix. The degradation mechanisms involved reduce the effectiveness of the modifier for toughening and also lead to a loss of molecular weight of the PC matrix. Blends containing 10% methacrylated butadiene-styrene (MBS) core-shell impact modifiers give the maximum extension of time to embrittlement at 135°C in air. More thermally stable modifiers are required for further extending the ductile mode of failure for physically aged PC blends.     

Deformation of rubber-toughened polycarbonate: Macroscale analysis of the damage zone

Two commercial core-shell rubbers were used as impact modifiers for polycarbonate (PC). Specimens with a single semicircular edge notch were stretched uniaxially in order to study the prefracture damage evolution of blends under a triaxial tensile stress state. The irreversible deformation of modified PC included a cavitation mechanism in addition to the three shear modes of unmodified PC. At the macroscopic level, the cavitation condition could be described by a mean stress concept. The corresponding critical volume strain for cavitation in PC blends was determined to be independent of rubber content but differed for the two impact modifiers. The critical volume strain for cavitation was used as an index of cavitation resistance for the impact modifiers. The effect of rubber content and temperature on Izod impact strength of the PC blends was also reported. From the relationship between the cavitation resistance and the Izod impact strength, it was proposed that impact modifiers with a higher cavitation resistance impart better toughness to blends with PC. © 1994 John Wiley & Sons, Inc.     

三元乙丙橡胶增韧PET/PC共混物的研究

采用三元乙丙橡胶（EPDM）及甲基丙烯酸环氧丙酯接枝三元乙丙橡（EPDM-g-GMA）作为PET/PC共混物的改性剂,并对共混体系的力学性能、相容性和断裂机理进行研究。力学性能测试结果表明EPDM-g-GMA质量分数为15%～20%时,共混体系实现了脆韧转变,当加到25%时冲击强度最高可达860 J/m,实现超韧;当PET/PC组成比为48/32时,PET/PC相容性最好,共混体系力学性能最佳。EPDM-g-GMA中环氧官能团与PET的端羧基、羟基发生反应使共混体系相容性提高。SEM结果显示共混物的增韧机理是基体的剪切屈服。     

核壳结构和层状结构改性剂对聚碳酸酯阻燃性能的影响

用自制的含有蒙脱土，纳米二氧化硅，纳米碳酸钙的改性剂与聚碳酸酯混合，通过锥形量热仪测试了聚碳酸酯合金的阻燃性能。结果发现合金的热释放速率、质量损失速率、生烟速率等均显著降低．燃烧时间增加，说明改性剂对聚碳酸酯具有阻燃性。通过分析材料的燃烧性能，探讨了其可能的阻燃机理。研究表明乳液聚合法制备的含有无机粒子的复合材料对聚碳酸酯是一种阻燃效能高、环境友好且实际可行的阻燃体系。     

Comparison of some butadiene-based impact modifiers for polycarbonate

The relationship of blend morphology to deformation mechanisms and notched Izod impact strength was studied with three butadiene-based impact modifiers for polycarbonate (PC). The impact modifiers were a linear polybutadiene (PB), a styrene–butadiene–styrene block copolymer (SBS), and a structured latex particle having a PB core and methyl methacrylate/styrene shell (MBS). The particle-size distribution in the blends was determined from transmission electron micrographs (TEM). Fractographic analysis combined with TEM examination of thin sections from impacted specimens provided insight into the failure mechanisms. Good impact was achieved with PC/MBS blends when cavitation of the core–shell particles relieved triaxiality and enabled the matrix to fracture by the plane stress ductile tearing mode that is characteristic of thin PC. The best impact properties were obtained with PC/SBS blends when the modifier was dispersed as aggregates of small particles. Cavitation at the weak internal boundaries relieved triaxiality, but subsequent coalescence of cavitated particles during ductile drawing of the matrix created critical size voids and the resulting secondary cracks reduced the toughness of the blend. In general, PB did not significantly enhance the impact strength of PC. © 1994 John Wiley & Sons, Inc.     

聚碳酸酯共混物增容改性的研究

综述了近年来聚碳酸酯与丙烯腈－丁二烯－苯乙烯共聚物、聚酯、液晶高分子、聚酰胺和聚烯烃等共聚物的研究现状。采用官能团化大分子作为共混物的相容剂或者作为改性组分是聚碳酸酯共混物改性的主要发展方向，增容聚碳酸酯共混物的分散相尺寸变小、界面粘结加强，物理与力学性能改善。讨论了聚碳酸酯共混物中的增容机理。     

Effect of functionality levels and compatibility of polycarbonate blends with maleic anhydride grafted ABS

ABS was melt grafted with maleic anhydride at three different levels of 1, 2, and 3 wt %. These three different modified ABSs were melt blended with polycarbonate using a single‐screw extruder to choose a suitable maleic anhydride grafting level on ABS for better performance. For the compatibility study, binary blends of polycarbonate with ABS and maleic anhydride‐grafted ABS were prepared over the entire range of compositions. Compatibility of these blends was studied using a Dynamic Mechanical Analyzer and by Differential Scanning Calorimetry. Both techniques suggest more partial compatibility for modified blend systems. In addition to this, DSC thermograms show multiple peaks between the transition points of ABS fractions and polycarbonate fractions for the polycarbonate/maleic anhydride‐grafted ABS blends. These multiple peaks are characteristic of better partial compatibility with fine microstructure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2102–2110, 1999     

Phase stability of ternary blends

The phase behavior of ternary blends of tetramethyl polycarbonate (TMPC), polycarbonate (PC), and styrenic polymers has been examined by experiment and analyzed in terms of thermodynamic theories. The phase boundaries were predicted using both the modified Flory-Huggins theory and the lattice fluid theory. The boundaries predicted using the lattice fluid theory agree best with the experimental results. The experimental phase behavior of ternary blends was compared with binary blends having exactly the same chemical components and compositions except that the TMPC and PC units were present in the form of a copolycarbonate in the binary. The miscible region of these ternary blends is much narrower than that of the corresponding binary blends, even though the entropic and energetic terms of such ternary blends are more favorable than those of the binary blends. It is shown that a negative value of noncombinatorial free energy in multicomponent systems is not a sufficient condition for miscibility, because of asymmetries of mer-mer interactions. A comparison of the stability conditions for these binary and ternary blends shows that increasing the degrees of freedom tends to destabilize the mixture.     

聚酯共混改性聚碳酸酯研究进展

综述近年来国内外聚酯共混改性聚碳酸酯的研究进展，分类介绍聚碳酸酯／半芳香族聚酯、聚碳酸酯／脂肪族或脂环族聚酯及聚碳酸酯／液晶聚酯等各共混体系，讨论了各体系的相行为、相容性、力学性能及光学性能等。而脂肪族或脂肪族聚酯共混改性聚碳酸酯是提高其综合性能的一条好途径。     

Mechanical properties of blends of polycarbonate with unmodified and maleic anhydride grafted ABS

Blends of polycarbonate/acrylonitrile–butadiene–styrene terpolymer (PC/ABS) and polycarbonate/maleic anhydride grafted ABS (PC/MABS) were prepared over the whole range of compositions using a single-screw extruder. Tensile, flexural, notched Izod impact properties, and the heat deflection temperature of these blends were determined. Mechanical properties of PC/MABS blends are nearly equal to or higher than, those predicted by the rule of mixtures, whilst those of PC/ABS blends show nearly equal, or negative deviation, from the rule of mixtures. The notched impact strength of PC/MABS blends shows a positive blending effect and proportionate increase from 25wt% PC to 75wt% PC. Scanning electron micrographs were taken of etched surfaces of selective blends. © 1998 SCI.     

Polystyrene/Polycarbonate/Polystyrene-block-Polycaprolactone blends. Emulsification and mechanical performance

Two polystyrene–polycaprolactone diblock copolymers, of differing molecular weights, have been extrusion-blended with polystyrene and polycarbonate. The morphologies of the resultant blends were studied using differential scanning calorimetry and scanning electron microscopy. In all compositions studied, the polystyrene and polycarbonate phases exhibited discrete glass transitions indicative of the immiscibility of these components. However, addition of the copolymer increased the extent of dispersion of the homopolymer components within one another quite effectively. Blend specimens were tested with respect to tensile, flexural, impact, thermal, and flow characteristics to probe the effects of morphology and composition on these factors. In general, the blends were rigid, brittle materials with thermal characteristics in the range between those of the polystyrene and polycarbonate components. Addition of polystyrene-block-polycaprolactone polymer to the blends resulted in increased brittleness, reduced thermal performance, maintenance of rigidity, and improved flow.     

Mechanical properties of ABS/polycarbonate blends

The mechanical properties of extruder compounded blends of ABS and polycarbonate in the form of extruded-sheet and injection-molded bars are reported and compared with commercial products based on these components. The modulus and tensile yield strength exhibit a nearly additive response to blend composition while percent elongation at break shows a minimum vs. composition. Notched Izod impact strength is nearly constant at the level of pure ABS up to 50% polycarbonate and increases rapidly upon further addition of polycarbonate.     

Polyester resin as a compatibilizing agent for some polymeric blends

Dielectric and viscosity techniques were used to determine the degree of the compatibility of poly(methyl methacrylate)/polycarbonate, poly(methyl methacrylate)/ polystyrene, and polycarbonate/polystyrene blends in different ratios (25/75, 50/50, and 75/25 w/w). The effect of the addition of 5, 10, and 20% concentrations of the prepared polyester resin [poly(butylene terephthalate adipate)] on the compatibility of these blends was studied. The dielectric properties were measured over a frequency range (from 100 Hz to 100 kHz) at various temperatures covering the glass‐transition temperatures of the polymers used (from 30 to 170°C). It was found from the dielectric and viscosity measurements that the addition of 10% polyester to poly(methyl methacrylate)/polycarbonate, 20% polyester to poly(methyl methacrylate)/polystyrene, and 5% polyester to polycarbonate/polystyrene blends enhanced the degree of compatibility of such blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of polyamide 6, polycarbonate,and poly(propylene oxide). II. Reactive compatibilization–thermal degradation relationships

The thermal degradation of some blends of polyamide 6/polycarbonate (PA6/PC) and polyamide 6/polycarbonate/poly(propylene oxide) (PA6/PC/PPO) were investigated. The copolymer formed during the mixing of polyamide 6 and polycarbonate, at 240°C, for 30 min, increases the thermal stability of PA6/PC and of PA6/PC/PPO blends. This increase in the thermal stability occurs due to the plasticizing effect of PPO, which increases the mobility of the molecules of PA6 and PC, and consequently increases the probability of the reaction between the —NH₂ and —O—CO—O groups of polyamide 6 and polycarbonate, respectively. The ternary blends with PPO (5–10% w/w) have lower thermal stability than PA6/PC blends. This is due to the decrease of miscibility between these polymers and the rise of the diluting effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2556–2562, 2001     

Polycarbonate resins

An outline of the history and manufacture of polycarbonate resins is followed by a discussion about resin product types anal their processing. The key properties of flex modulus, deflection temperature, and impact are those that make polycarbonate resins premier engineering resins. Like most other engineering plastics, polycarbonate resins' early commercial history was characterized by substitutions of polycarbonate resins for traditional materials, particularly metal and glass. Examples of applications are presented, More recently application developments involve ab initio selection of polycarbonate resins and article designs based on polycarbonate resin properties. In addition, “tailored” resins such as poly (estercarbonate) resins and polycarbonate resin blends have evolved to meet specific applications. The future growth of polycarbonate resins is predicted to feature few new resins, many new blends, and application developments using computer techniques.     

聚碳酸酯无卤阻燃剂进展

综述了当前国内外聚碳酸酯(PC)及其合金的无卤阻燃体系(除无机铝-镁系外)的研究开发进展.包括硅系、芳香族磺酸盐、无卤磷酸酯、磷-氮系、硼系及聚合物／无机纳米复合等几大体系。介绍了它们的阻燃机理,评价了它们的优缺点。指出根据PC及其合金的不同用途,研究非卤阻燃元素之间相互协同作用以及开发高效、低成本的新型阻燃剂和阻燃方式,将是该领域阻燃工作者未来努力的方向。     

PC／PE共混物的流变行为研究

考察了聚碳酸酯/聚乙烯(PC/PE)共混物的流变行为。研究发现PE的加入可使共混体系的粘流活化能降低,流动性增加;在PC/PE共混物中加入乙烯-醋酸乙烯酯共聚物(EVA)可改善PC与PE的相容性,提高其力学性能。     

游离链段在环氧官能化ABS增韧PBT中的作用研究

采用种子乳液聚合方法,在聚丁二烯(PB)表面接枝苯乙烯(St)、丙烯腈(AN)和甲基丙烯酸环氧丙酯(GMA),合成了具有反应活性的ABS-g-GMA核-壳改性剂;通过超速离心方法将改性剂中的苯乙烯-丙烯腈-甲基丙烯酸环氧丙酯共聚物(SAN-co-GMA)游离链段分离出来,得到了ABS-g-GMA'核-壳改性剂;最后将分...     

Characterization of liquid crystalline polyester polycarbonate blends

Mechanical and rheological properties of blends of a thermotropic liquid crystalline polyester with a polycarbonate have been investigated. The blends are fibrillar in character and exhibit great hardness and toughness due to high degree of molecular orientation which develops during the melt blending and processing steps. Increases of the Young modulus by 100 percent are observed for blends containing only 10 percent of liquid crystalline polymer, LCP. Time-dependent behavior of the blends was investigated by performing solid state relaxation measurements and the relaxation modulus was also found to increase by the addition of LCP. The effect is relatively small in the glassy zone of viscoelastic response, but increases through the transition and viscous flow regions. The melt viscosity of the polycarbonate is slightly shear thinning whereas that of the unblended LCP increases rapidly with decreasing shear rate at low shear rate. This suggests the presence of yield stresses as confirmed by measurements on the Rheometics RSR in the stress sweep mode. The melt viscosity of the blends was found to be similar to that of the unblended polycarbonate, but more shear-thinning and less viscous. Preliminary results of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) are also presented.     

Polyester–polycarbonate blends. V. Linear aliphatic polyesters

Polycarbonate blends with the linear aliphatic polyesters poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(1,4-butylene adipate) (PBA), and poly(hexamethylene sebacate) (PHS) were prepared by solution casting. Blends containing PES, PEA, and PBA exhibited a single T_g by DSC and thus form a single, miscible amorphous phase with polycarbonate. However, blends containing PHS exhibited only partial miscibility. Crystallinity of the polyesters was reduced by mixing with polycarbonate; however, plasticization by the polyesters induced crystallization of the polycarbonate. Miscibility in these systems is the result of an exothermic heat of mixing stemming from an interaction of the carbonyl dipole of the ester group with the aromatic carbonate. The effect of polyester structure on miscibility with polycarbonate is interpreted by and correlated with heats of mixing obtained by direct calorimetry of low molecular weight liquid analogs of the polymers.