PVC抗冲改性剂的发展

综述了我国PVC抗冲改性剂的发展状况,主要介绍了ACR、CPE、MBS、ABS、EVA及EPR的生产、市场需求及研究进展。     

核壳结构丙烯酸酯类聚合物的合成及性能研究

采用乳液聚合技术合成了硬聚氯乙烯（R－PVC）抗冲击改性剂丙烯酸酯类聚合物（ACR）。研究了ACR用量及合成参数对R－PVC冲击性能的影响。     

Functional MBS impact modifiers for PC/PBT alloy

Functional group containing MBS impact modifiers for the poly carbonate/poly(butylene terephthalate (PC/PBT) alloy were synthesized and characterized in this study. The novel MBS consisted of three layers, in which the inner, middle, and outer layers were styrene butadiene rubber (SBR) latex, polystyrene, and a copolymer of the methacrylic acid (MMA) and the functional group containing vinyl monomer, respectively. Three different kinds of the functional monomers were used in this study, glycidyl methacrylate (GMA), acrylamide (AAM), and MAA. The functional group was used to improve the adhesion between the MBS and the PC/PBT alloy. Our results showed that the layer composition of the MBS exhibited a significant effect on the impact strength. A large variation of the impact strength from 14.1 to 23.6 ft‐lb/in. was observed when the SBR content increased from 30 to 70%. An optimum amount (4–6%) of the functional monomer enhanced the adhesion between the MBS and the PC/PBT alloy and thus improved the impact strength. Furthermore, a much smaller amount of the functional group containing MBS in the PC/PBT alloy than the conventional MBS could obtain an impact strength as high as 25.2 ft‐lb/in. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1280–1284, 2000     

EPDM based weatherable PVC impact modifiers

Graft polyblends of styrene, acrylonitrile or methyl methacrylate with EPDM rubbers are PVC impact modifiers. Specific compositions in PVC composites have unaged impact strengths similar to PVC composites with commercial ABS, polyacrylate, and chlorinated polyethylene modifiers at equivalent concentrations. Modifier efficiency and weatherability of the EPDM based modifiers are compared to ABS, polyacrylate, and chlorinated polyethylene.     

A new method for judging efficiency of PVC impact modifiers

To determine the efficiency difference between impact modifiers, S-shaped polyvinyl chloride impact curves are compared. But in highly variable scatter regions, the position of the curves is uncertain. A new method focuses on the scatter region by statistically comparing percent ductility for different impact modifiers. If a sufficient number of samples are tested, percent ductility is a sensitive and reproducible function of impact modifier concentration and testing temperatures.     

Siloxane modification of polycarbonate for superior flow and impact toughness

Reactive modification of polycarbonate (PC) with a small amount of ultra-high molecular weight polydimethylsiloxane (PDMS) provides an effective route to a novel blend polymer with superior flow and excellent impact toughness. Low temperature impact toughness for such a blend was found to be comparable to polycarbonate copolymers made by interfacial copolymerization of bisphenol A and specialty silicones with phosgene. Interestingly, the blend also showed strong shear thinning behavior and a viscosity that is almost an order of magnitude lower than the starting PC resin. Analysis of the blend composition and blend morphology revealed the presence of both PC-PDMS copolymer and un-grafted siloxane as a dispersed phase in the polycarbonate matrix. The PC-PDMS copolymer provides a compatibilization effect for the stable sub-micron blend morphology in an otherwise immiscible PC-PDMS blend system. Improvement of low temperature ductility (e.g., at −40 °C) by PDMS was thus made possible. The lubricating effect from siloxane and the possibility of fibrillation flow at high shear stress are suspected to be the main reasons for high flow characteristics of these blends.     

我国PVC抗冲击改性剂的生产及市场概况

叙述了目前国内PVC抗冲击改性剂的生产与需求现状，并对CPE、MBS、ACR、ABS、EVA等常用改性剂的性能、生产现状、发展前景等进行了分析，指出了CPE改性剂在国内仍占主导地位，MBS在未来的生产装置及生产能力都较有较大发展，而ACR在国外的前景看好。     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005     

Toughening of nylon 6 with grafted rubber impact modifiers

Recent work has shown that nylon 6/acrylonitrile–butadiene–styrene (ABS) blends can be made tough by the addition of some polymer additives that are chemically reactive with nylon 6 and physically compatible with the styrene-acrylonitrile copolymer (SAN) phase of ABS. Imidized acrylic polymers (IA) represent a successful example of such additives that improve the dispersion of ABS in the nylon 6 matrix and render the blends tough. This article examines the possibility of toughening nylon 6 with ethylene/propylene/diene elastomer grafted with SAN copolymer (EPDM-g-SAN). This EPDM-g-SAN consists of 50% rubber and 50% SAN by weight. However, it was found that the same IA that works well to disperse ABS materials of similar rubber content is not as effective for EPDM-g-SAN, primarily because the EPDM forms the continuous phase, not SAN, and, thus, interfaces with nylon 6 during melt blending. Maleated elastomers like maleic anhydride grafted ethylene–propylene copolymer (EPR-g-MA) and styrene–(ethylene-co-butylene)–styrene triblock copolymer (SEBS-g-MA) were more effective for dispersing EPDM-g-SAN in the nylon 6 matrix than IA. Various mechanisms that improve the dispersion are discussed. © 1995 John Wiley & Sons, Inc.     

Ethylene copolymers as sintering enhancers and impact modifiers for rotational molding of polyethylene

The objective of this work was to evaluate the effect of blending minor amounts of ethylene styrene Interpolymer or ethylene vinyl acetate (EVA) with polyethylene on cycle times and impact strength in rotational molding. The blends sintered significantly faster than polyethylene. The sintering rates were primarily influenced by the melting points of the minor blend components, and not by differences in melt viscosity and/or elasticity at low shear rate. Blending Interpolymer or EVA with polyethylene resulted in improved environmental stress crack resistance and decreased flexural modulus. In rotational molding, blending Interpolymer or EVA with polyethylene generally resulted in faster bubble removal, more uniform thickness and shorter cycle times. Ductile failure was generally observed at the peak mean failure energy (MFE). The blend containing Interpolymer yielded significantly increased MFE, possibly because the Interpolymer was compatible with polyethylene and was very well dispersed.     

Impact modifiers: Providing a boost to impact performance

Some of the additives used in plastics formulations, such as flame retardants, fillers, heat distortion temperature modifiers, and pigments, can have a detrimental effect on the impact resistance of the material. Impact modifiers can sometimes be used to “correct” for the detrimental effects of these additives by boosting the impact performance of the material. The functions of core/shell impact modifiers in improving impact resistance are described. Some general guidelines for selecting impact modifier products are discussed.     

用新型结构调节剂合成溶聚丁苯橡胶

以正丁基锂为引发剂、环己烷为溶剂,考察了不同调节剂在不同温度下的苯乙烯与丁二烯的负离子共聚合.结果表明,通过改变引发温度可以使共聚产物中聚丁二烯链段部分的乙烯基结构摩尔分数在30%～70%间灵活调节,所得溶聚丁苯橡胶具有较好的物理机械性能和抗湿滑性能.     

PVC抗冲改性机理和新型PVC冲击改性剂的设计

对PVC冲击改性剂——MBS、CPE和ACR的分子组成和分子结构进行了分析,研究了其抗冲改性机理及对PVC制品低温冲击强度、耐候性、维卡软化点、韧性的影响。从高分子热力学的角度分析了CPE和ACR在PVC中分散所形成的制品结构。指明了传统ACR和CPE在PVC改性中所存在的优缺点。在此基础上分析了理想冲击改性剂ACR应具有的结构特点,并设计和开发了新型冲击改性剂ACRHL-56和HL-58,通过试验对其性能与传统冲击改性剂ACR和CPE进行了比较,发现其性能远优于后者。