Studies on heterogeneous polymeric systems. II. Polyblends containing saturated rubbers

Saturated rubbers composed of ethylene–propylene or ethylene–vinyl acetate copolymers and terpolymers were used in the mass polymerization of high-impact styrene or styrene–acrylonitrile polyblends. Conventional polymerization procedures lead to blends of inferior mechanical properties. The cause for the poor performance was traced to the inability of the rubber-phase particles to preserve the desired size and particularity during processing. Polymeric blends of saturated rubbers having mechanical properties comparable to those obtainable with polybutadiene rubbers are prepared by (1) controlling the rubber-particle size during prepolymerization and (2) preserving such size by crosslinking and grafting of the rubber following phase inversion. Extensive crosslinking of the rubber in the final blend must take place prior to processing to resist rubber particle deformation and disintegration during mechanical working. Rubber vulcanization is realized by the presence of peroxides in the final stages of polymerization; pendant unsaturation in the rubber is also needed or helpful. The reactivity and number of unsaturated groups in the rubber must be controlled to avoid excessive grafting prior to phase inversion and to permit efficient crosslinking following phase inversion.     

Conductive rubbers made by adding conductive carbon black to EVA,EPDM, and EVA–EPDM blends

Abstract

Electrically conductive rubbers have been prepared by the incorporation of conductive carbon black into ethylene/vinyl acetate (EVA) copolymers, ethylene/propylene/diene monomer (EPDM) terpolymers, and a 50 : 50 EVA–EPDM blend. The electrical and mechanical properties of these composites have been studied. The percolation limit for high conductivity in the filled rubbers depends on their compatibility as well as the viscosity and polarity of the rubbers. The electrical resistivity decreases with increasing temperature and the activation energy for conduction decreases with increasing filler loading. The temperature dependence of resistivity can be correlated with data from DSC, XRD, and DMTA measurements. Electrical set and electrical hysteresis have been observed during heating–cooling cycles. The change in resistivity with applied pressure is also reported.     

Toughening of epoxy resin by modification with 2‐ethylhexyl acrylate–acrylic acid copolymers

2‐Ethylhexyl acrylate–acrylic acid copolymers, ie carboxyl randomized poly(2‐ethylhexyl acrylate) (CRPEHA) (LR‐1 to LR‐6), with different molecular weights and functionality were synthesized. The liquid rubbers were characterized by FTIR spectroscopic analysis, non‐aqueous titration, vapour pressure osmometry (VPO) and viscosity measurements. All the liquid rubbers were reacted with the epoxy resin in 10:100 weight ratio using triphenyl phosphine as a catalyst. The modified epoxy networks were made by reacting the homogeneous prereacted resin with an ambient temperature hardener, triethylene tetramine (HY 951). The effect of the molecular weight and functionality of the liquid rubbers on the thermal and impact properties of the modified networks was investigated. © 2000 Society of Chemical Industry     

Block copolymers of polycarbonates with several hydroxy-terminated elastomers to yield thermoplastic elastomers for higher service temperature

The synthesis of block copolymers and the study of their morphology were undertaken to find improved thermoplastic rubbers for service at elevated temperatures. The basis was the extraordinary properties possessed by ABA-type block copolymers in which the terminal blocks are polystyrene and the central block is either polyisoprene or polybutadiene. In these systems it has been well established that the unusual properties are a result of domain formation in which the hard and the soft blocks aggregate separately into distinct phases. The hard segment is thought to act both as a crosslink and as a filler. Block copolymers were synthesized with different soft and hard segments. The effects of these segments and of their properties on the morphology and the stress-strain properties of the block copolymers were measured and evaluated. Electron microscopy and birefringence were used to determine the morphology. It was found that the glass transition temperatures of the segments, the bulk of the monomer unit in the glassy segment, and the morphology determined the strength of the material. Some of the materials prepared have tensile strengths of 0.1 kg/cm² or more at temperatures in excess of 180°C and therefore appear promising as elastomers for service at elevated temperatures.     

Solution-polymerized rubbers with superior breakdown properties

Natural rubber breaks down readily during mechanical mixing, and rubber processors have traditionally made good use of this property. Emulsion SBR rubber breaks down with greater difficulty and some polybutadiene rubbers, not at all. This paper describes a new class of solution elastomers, both polybutadiene and butadiene–styrene copolymers, designed to undergo controlled breakdown during processing. They can be made by reacting active polymer lithium molecules with tin compounds to produce star-shaped molecules containing a central tin atom connected by tin–carbon bonds. When such a product is mixed with an organic (stearic) acid, some of the tin bonds are ruptured and the desired breakdown occurs. The extent of breakdown can be controlled by the mixing conditions and the amount of organic acid employed. There are numerous applications in which these rubbers process more easily and display better properties than conventional rubbers. Data on breakdown under various conditions and physical properties of the compounds are presented in this paper. In addition to the superior processing characteristics, these products introduce a new concept of elastomer breakdown. The breaking of a polymer chain at a carbon–tin bond by a chemical agent eliminates the need for breaking carbon–carbon bonds by mechanical energy or oxidative degradation. Accomplishing polymer breakdown by a controlled reaction, rather than by conventional means, has long been an unsolved problem of the rubber industry.     

Molecular packing of poly(azomethine)s having flexible (n-alkyloxy)methyl side chains in films

A new process for the sequential copolymerization of olefins has been devised (Multicatalysts Reactor Granule Technology); it allows the synthesis of thermoplastic polyolefin elastomers having polypropylene from Ti-based catalysts and ethylene-propylene rubbers from metallocenes. Such new materials have been cured with peroxides and the relevant mechanical properties measured in comparison with those of heterophasic copolymers synthesized with traditional catalysts. It resulted that the new materials present an improved balance between strength and elasticity, especially at high temperature. Received: 28 February 1997/Revised: 11 April 1997/Accepted: 14 April 1997     

橡胶改性道路沥青及其微观结构

介绍了橡胶改性道路沥青以达到高性能的改性技术，主要有废橡胶粉改性技术、丁苯橡胶乳液改性技术、ＳＢＳ改性技术等，各类技术都能有效的提高沥青的路用性能。改性沥表的微观结构研究表明，改性机理是相容性改性、溶胀网络改性、胶体结构变化改性和增强改性等。     

On the synthesis of poly(ε-caprolactam)—poly(butadiene-co-acrylonitrile) block copolymers for the reaction injection molding process

The liquid rubbers Hycar ATBN and HTBN were used in the preparation of poly(ε-caprolactam)—poly(butadiene-co-acrylonitrile) block copolymers intended for reaction injection molding by the anionic polymerization of ε-caprolactam. The conversion of Hycar end groups to polymerization growth centers and the conditions of polymerization influence the crystallization, morphology, and mechanical properties of the product through its molecular structure. The contribution of individual reactions to this molecular structure is discussed.     

国产顺丁橡胶BR 9000 性能对比测试

对国内8 家合成橡胶厂生产的顺丁橡胶BR 9000 进行了相对分子质量及其分布、微观结构、生胶性能、硫化特性和硫化胶性能的对比测试。结果表明,国产BR 9000 与国外同类产品相比其数均分子量偏低,重均分子量偏高,分子量分布较宽。国产BR 9000 在微观结构、灰分、挥发分及凝胶含量等方面相当,但A 厂的挥发分含量偏高,H 厂的凝胶含量较大; 硫化速率基本相同,硫化胶的定伸应力、拉伸强度和扯断伸长率处于同一水平; 国产BR 9000 的性能指标均能满足优等品的要求。     

Transport properties of silmethylene homo-polymers and random copolymers: experimental measurements and molecular simulation

A novel class of silicon-containing rubbers is proposed as membrane materials for separation of hydrocarbons of natural and associated petroleum gas. Homo-polymers of general formulas -Si(CH₃)₂CH₂- (PDMSM) and -Si(CH₃)₂CH₂CH₂CH₂- (PDMSTM) and the copolymers with the same randomly alternating repeat units were prepared by thermal initiated polymerization of strained silicon-containing four-member cycles. These polymers have low glass transition temperatures and reveal solubility controlled gas permeation properties. The highest permeability is characteristic for PDMSM, however, it has poor film forming properties. On the other hand, amorphous copolymers exhibit combination of good film forming properties and relatively high permeability. Transport properties of PDMSM were successfully simulated by molecular dynamics using a very efficient united-atom force field.     

Effect of rubber types on synthesis,morphology, and properties of ABS resins

A series of acrylonitrile–butadiene–styrene (ABS) copolymers were prepared using lithium‐catalyzed low‐cis rubber (PB700A), nickel‐catalyzed high‐cis rubber (BR9004), and their compounded rubber (PB700A/BR9004 = 50:50) as toughening agents through bulk polymerization. The effects of molecular structures of rubbers on the dissolving and grafting process of them were investigated. The structure and properties of ABS resins were characterized with FTIR, TEM, and performance measurements. It is shown that the characteristics of rubbers affect their dissolving state and grafting reaction and consequently influence the morphology and properties of ABS materials. BR9004 promotes the formation of irregular microsized rubber particles with special “salami”‐like structure and, therefore, presents better mechanical properties. PB700A has much higher 1,2‐isomers, which benefits its dispersion and grafting reaction; its toughening effect, however, is unsatisfactory and can be improved by the incorporation of BR9004. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Design and in vivo assessment of polyester copolymers based on trimethylene carbonate and ε‐caprolactone

Poly(trimethylene carbonate‐co‐caprolactone) (PTCL) copolymers with various trimethylene carbonate ratios were synthesized by ring‐opening polymerization and were used to prepare implants for an in vivo experiment. Medical silicone rubber was used as the control. Implants were prepared by compression molding with a laboratory instrument. The properties of these copolymer implants were investigated. PTCL implants and silicone rubbers were implanted subcutaneously in the dorsal region of New Zealand white rabbits. The assessment was performed 1, 2, 3, 4, 5, 6, 7, and 8 months postoperatively by the determination of the weight loss, water uptake, thermal behavior, molecular weight of the explanted implants, and histological examination. During the 8‐month implantation, the value of maximum weight loss was found to be 25%. A continuous decrease in the molecular weight occurred. No remarkable tissue reactions were observed during degradation, and foreign‐body reactions were similar to those of silicone rubbers, which are commercially available materials. In this study, we aimed to indicate the likely clinical behavior but good biodegradable properties of PTCL copolymers compared to those of silicone rubber. This may open a new avenue of application for them in the drug industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41815.     

Propriétés de copolymères triséquencés poly(isoprène-seq. méthacrylate d'alcoyle)

Block copolymers with a central sequence of polyisoprene (12% of 1–4 structure) and poly(alkyl-methacrylates) have been studied. The viscoelastic properties of these compounds are those of thermoplastic rubbers of the SBS type. The loss factor (tgδ) of the rubbery phase changes with the ratio of plastic compound and with the processing of the films. We studied the influence of the ester sequences (methyl, ethyl, propyl, butyl, isobutyl and diphenyl methacrylates). We correlated the viscoelastic behaviour and relaxation processes of the materials with the nature of the sequence together with the morphology observed by electron microscopy.     

Rubber toughening of poly(lactide) by blending and block copolymerization

Copolymers of L-lactide with 15 or more mole % D-lactide are amorphous, noncrystallizable hydrolytically degradable materials. These glassy materials are brittle in tension and bending. To make these materials suitable for use as load-bearing devices in biomedical applications, toughness has to be enhanced. This is effectively accomplished by introducing a separate degradable rubber phase in the amorphous matrix. Several approaches have been explored: solution blending and coprecipitation of trimethylene carbonate and ?-caprolactone rubbers and poly(lactide), preparation of ABA triblock copolymers and blending of ABA block copolymers with the amorphous poly(lactide) matrix. In all cases very tough materials could be prepared. These materials are easily processable by compression molding at relatively low temperatures.     

Grafting of natural rubber for preparation of natural rubber/unsaturated polyester resin miscible blends

Graft copolymers of natural rubber and polystyrene were synthesized by free‐radical grafting of styrene monomer onto natural rubber in latex form. The obtained graft copolymers and unsaturated polyester (UPE) resin were mixed and cast at room temperature using methyl ethyl ketone peroxide as an initiator and Co‐octoate as an accelerator. The samples prepared from ungrafted natural rubbers exhibited the aggregation of the rubber component, whereas the samples prepared from grafted natural rubbers showed good dispersion of the rubber component in a glassy matrix of UPE resin. It was found that the amount of polystyrene grafted onto natural rubber and the graft copolymer content in polymer blend significantly affect the mechanical properties of the blend samples. An increase in the amount of hard and brittle polystyrene in glassy matrix of UPE resin overshadowed the impact‐absorbing ability of the rubber component, causing the impact strength of the blend samples to be lower than that of pure UPE resin. On the other hand, an increase in easily elongated uncrosslinked rubber molecules, as the graft copolymer content in blend samples increased, resulted in a decrease in their flexural strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1496–1503, 2004     

增韧增强改性尼龙的研究及应用

综述聚烯烃弹性体、橡胶、苯乙烯系共聚物等增韧尼龙和玻璃纤维、碳纤维和芳纶纤维等增强尼龙及增韧增强相结合改性尼龙的研究进展。介绍了增韧增强尼龙的应用情况。     

Blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with polystyrene-based thermoplastic rubbers: A comparative study

This work presents the first part of our study on the modification of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with styrenic thermoplastic rubbers. Polystyrene-b-polyisobutylene-b-polystyrene (SIBS), polystyrene-b-polybutadiene-b-polystyrene (SBS) and polystyrene-b-poly(ethylene/butylene)-b-polystyrene (SEBS) triblock copolymers were melt blended with PPO and the blends were characterized. Differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and transmission electron microscopic (TEM) studies revealed that PPO/SEBS blends displayed the most pronounced phase-separated morphology with largest rubbery domains. SBS showed the most miscibility, and the least detrimental effect on dynamic mechanical properties and tensile strength. The results of this comparative study guided us to develop optimum conditions for the impact modification of PPO by SIBS thermoplastic rubbers.     

Rubber-modified epoxies: IV. Role of chain ends on the morphologies and properties

Four reactive liquid rubbers with different end-groups but the same main chain (carboxyl-, epoxy-, amino-terminated and non-functional butadiene–acrylonitrile random copolymers) were employed in the same epoxy system, the diglycidyl ether of bisphenol A and 4,4′-diamino-3,3′-dimethyldicyclohexyl methane cured at 50°C. The effects of the end-groups of the liquid rubber on the morphology, phase compositions, sub-structure inside the particles, interface between the phases and the mechanical properties were determined. The effects were related to the reactivity and the miscibility of the additive.     

新型苯乙烯树脂——SMA

介绍了橡胶改性的苯乙烯-马来酸酐无规共聚物SMA的国内外发展现状,以及SMA的优良特性、应用领域。     

高抗冲聚苯乙烯专用橡胶的研究进展

介绍了接枝聚合法生产高抗冲聚苯乙烯所使用的聚丁二烯橡胶及丁苯橡胶的研究进展，评述了橡胶的微观结构，相对分子质量及相对分子质量分布，支化度对高抗冲聚苯乙烯性能的影响，列举了高抗冲聚苯乙烯专用橡胶的牌号及性能指标。