溶液法马来酸酐接枝EPDM的研究及对尼龙的相容,增韧效应

本文介绍采用溶液法制备马来酸酐（ＭＡＨ）接枝乙丙橡胶（ＥＰＤＭ）以及该接枝物对尼龙（ＰＡ）的相容、增韧效应。研究了引发剂ＢＰＯ和ＭＡＨ用量与接枝率、接枝效率、交量的关系，当ＭＡＨ／ＥＰＤＭ为１０／１００（质量比，下同）时，ＢＰＯ／ＥＰＤＭ的最佳值约为２．２８／１００；固定ＢＰＯ／ＥＰＤＭ为１０／１００时，ＭＡＨ／ＥＰＤＭ的最佳值约为１２．５／１００。由Ｍｏｌａｕ实验表明，ＭＡＨ接枝ＥＰＤＭ／ＰＡ比     

SMA/PVC合金

介绍了国内外苯乙烯－马来酸酐无规共聚物（SMA）、聚氯乙烯（PVC）合金的研究进展，列举了文献报道的SMA／PVC合金配方、加工方式，并以图示的方式阐述了合金的耐热性、阻燃性、加工性与SMA含量的关系。用国产SMA制备SMA／PVC合金，表明SMA不仅能起耐热作用，而且能缩短PVC塑化时间；对制样方法研究后表明：双辊开炼工艺制得的试样力学性能比注塑的好。     

Elastomeric joint performance of PVC,VC, and FRC Pipes

For rubber ring joints to resist plant root penetration in drier countries, it has been reported and promulgated into some national standards that a sufficiently high contact pressure between the rubber and the pipe must be maintained. The evaluation of the appropriate interfacial pressure to be used has been under discussion for some time and different values have been stated in different standards. This matter has been the subject of considerable controversy, and decisions on the interface pressure used will affect the performance and ease of insertion of a rubber ring joint. This paper reports and discusses previous and current research on root penetration past elastomeric joints, the existing test requirements of elastomeric pipe joints for resisting root penetration given in standards, and the inconsistencies in performance requirements across the different pipe material types. The initial interface sealing pressures for commonly used PVC. VC and FRC joints were assessed and these are discussed in light of the accelerated root intrusion tests performed in Black Hill Flora Centre in Adelaide, South Australia.     

Thermal-mechanical properties of PVC flame retarded alloys

Several segments of the plastics conversion industry are concerned with meeting critical functional and performance demands. Relevant concerns include flame spread, smoke generation, and toxicity. In recent decades, the transportation and electrical/electronics industries have consumed tremendous quantities of polymeric materials. Many of these plastics have been extensively modified to meet flammability criteria, processability demands, and other functional requirements. Aircraft and electronics applications of these materials include printed circuit boards, electrical connectors, wiring, wire harnesses, and aircraft cabin flooring, ceiling, paneling, carpeting, and cargo storage bins. The traditional mechanism for imparting flame retarding properties is to incorporate external additives, which alter burning characteristics, but at the expense of functional properties. An alternate solution to flame retarding that has gained much attention in recent years is the alloying, or blending, of flammable polymers with inherently flame retarded polymers. ASTM protocol has established dynamic mechanical testing (DMT) techniques to evaluate the rheological properties of such materials. This paper exhibits how DMT can be used to monitor the solid properties of various flame retarded alloys.     

PVC/ABS合金国内最新研究进展

综述了国内PVC/ABS合金的生产现状和最新研究进展,从PVC/ABS合金的组成、成型方法和加工影响因素3个方面描述了合金的共混改性,并对国内PVC/ABS合金的发展提出了一些建议.     

New generation of high‐performance PVC alloys

Newly developed alloys of flexible poly(vinyl chloride) (PVC) and polyolefin elastomers have been shown to exhibit improved physical properties compared to those of conventional flexible PVC control compounds. In particular, the new alloys display enhanced electrical properties, better high temperature stability, greater low temperature flexibility, and superior gas barrier properties. In addition, this study demonstrated that PVC/polyolefin rubber alloys have potential utility in many applications where conventional flexible vinyl compounds do not meet certain end‐use performance requirements.     

CPE对PVC/HDPE合金材料的增容改性

以CPE为增容剂,通过单螺杆挤出机熔融共混制备了PVC/HDPE合金材料,考察了CPE的氯含量和残余结晶度对PVC/HDPE合金材料力学性能和维卡软化温度的影响,并通过电镜观察了空白样和3#PVC/HD PE合金材料的微观形貌。结果表明:采用含氯质量分数20%、熔融焓19.5 J/g的C PE制备的3#PVC/HD PE合金材料具有较好的力学性能和较高的维卡软化温度,其具有典型的微相分离的多相凝聚态结构。     

PVC／环氧树脂E51合金性能的研究

采用模压法制备了PVC/环氧树脂E51合金,研究了环氧树脂E51用量对合金力学性能及维卡软化温度的影响.结果表明:当环氧树脂E51用量为1～5份时,随着环氧树脂E51用量的增加,试样的缺口冲击强度、拉伸强度、断裂伸长率、维卡软化温度先增加后减小.当环氧树脂E51用量为3份时,试样的缺口冲击强度、拉伸强度、维卡软化温度出现最大值;当环氧树脂E51用量为4份时,试样的断裂伸长率出现最大值;当环氧树脂E51用量为5份时,试样的缺口冲击强度、拉伸强度、维卡软化温度虽有所降低,但仍比原始PVC试样(指未添加环氧树脂E51的试样)高,而试样的断裂伸长率则骤降,比原始PVC试样还低.在试验条件下,环氧树脂E51的最佳用量为3份.试样冲击断面SEM照片的分析结果与缺口冲击强度的测试结果相符.     

Preparation and Properties of PVC Ternary Nanocomposites Containing Elastomeric Nanoscale Particles and Exfoliated Sodium‐Montmorillonite

Summary: A novel rigid PVC ternary nanocomposite containing NBR‐ENP and untreated Na‐MMT has been fabricated. X‐ray diffraction XRD, TEM and SEM observations revealed that the untreated Na‐MMT was exfoliated and most NBR‐ENPs (about 90 nm) were separately dispersed in the PVC matrix. DMTA and TGA demonstrated that the PVC ternary nanocomposites had a higher glass transition temperature and a higher decomposition temperature than neat PVC, while the toughness increased simultaneously. Combustion tests showed that the exfoliated clay in the PVC/NBR‐ENP/MMT ternary nanocomposites did not improve the flame retardancy after ignition under strong heat flux.

Schematic diagram of the fabrication procedure of PVC/NBR‐ENP/Na‐MMT ternary nanocomposites.     

不同弹性体对ABS/PVC合金性能的影响

研究了弹性体对ABS／PVC合金的各项性能的影响。研究结果表明，弹性体与ABS／PVC合金共混，能显著改变ABS／PVC合金的各项性能。     

Multiphase polymer systems: PVC/styrene copolymer alloys

The compatibility of blends of poly(vinyl chloride) (PVC) and styrene copolymers containing maleic anhydride have been investigated by thermal and dynamic and mechanical studies. Unlike homopolymer polystyrene, these styrene/maleic anhydride copolymers, when blended with PVC, provide a degree of miscibility. Complete miscibility or single phase morphology is present only at low concentrations. At higher concentrations, the alloy system separates into two altered phases—neither of which is a pure component. At intermediate alloy compositions, the phases are relatively constant in polymer composition, but the ratio of phases can vary. These altered phases are dispersed at extreme concentrations and are cocontinuous at levels approaching approximately 60 wt % PVC. The intermixed, altered phases show various degrees of miscibility and provide significant adhesion between the two phases. Physical property improvements are attributable to the partial miscibility of the phases.     

PVC/styrene copolymer alloys for a balance of properties

Styrene maleic anhydride copolymers blended with PVC result in alloys that exhibit elevated thermal properties and improved processability. These improvements will help PVC usage in electrical/electronic housings. The PVC component maintains flame retardance for the compound, without the need for further additives.     

Particle Adhesion to Elastomeric Substrates and Elastomeric Substrates with Semi-Rigid Coatings

The force needed to remove micrometer-size polystyrene particles from elastomeric substrates having Young's moduli of 3.8 and 320 MPa was measured using atomic force techniques. It was found that the removal force was approximately an order of magnitude less for the more rigid substrate than for the more compliant substrate. In both cases the removal force was independent of applied load. However, when the more compliant material was overcoated with the stiffer material, the particle removal force was found to increase with increasing pressure, with the limit at low pressure commensurate with the removal force observed for the stiffer substrate and commensurate with the more compliant material at higher pressures. The results are interpreted in terms of the penetration depth of particle asperities into the substrates.     

Multiphase PVC/styrenic copolymer alloys: Internally reinforced by partial miscibility

Although polymer/polymer miscibility is considered the exception to the general rule, in polymer thermodynamics specific interactions between active sites on two polymers can be a driving force for polymer/polymer miscibility. Both the intermolecular interactions of the alpha hydrogen of PVC with carbonyl groups in various polyesters and the polarity of the chlorine bond have been claimed to promote miscibility. Both of these interactions are potential in PVC/styrene maleic anhydride (SMAnh) polymer blends. These specific interactions promoting miscibility and the resulting mechanical properties of these systems is the subject of this report. SMAnh (12.5% MA) copolymer was melt compounded with a stabilized PVC compound using a Haake Rheocord twin screw extruder. Test data generated for these blends were analyzed for miscibility and effects of SMAnh copolymers on heat resistance, fire retardance, impact strength, and processability of PVC.     

Elastomeric matrix-short fibers adhesion

This paper analyzes the effects of the addition of a three-component dry type adhesive system on the properties of composite SBR (styrene-butadiene rubber) material containing 20 percent short polyamide (5 mm length and 60 μm diameter). The curing times are extended and green strength is doubled. The replacement of the silica component in the system by a natural silicate is not only feasible, but proves to be favorable for certain properties, such as the storage modulus E′, which becomes less sensitive towards temperature changes. Dynamic property measurements provide evidence of an additional dispersion corresponding to the matrix-fiber interface located around 40 to 50°C, which does not occur in the composites without adhesive. The activation energies of the main relaxation process of these materials are determined, amounting to 175 KJ/mol for the matrix and 250 KJ/mol for adhesive-containing composites, as a consequence of the formation of strong bonds between both phases.     

Elastomeric and mechanical properties of poly-m-carboranylenesiloxanes

A new high-temperature elastomer, SiB-2, has been investigated by stress relaxation, modulus-temperature, and volume--temperature techniques. SiB-2 was found to be more stable than a related elastomer, radiation-cured silicone rubber, having about twice as long as a chemical relaxation time at 250°C. Possible mechanisms to account for this increased stability are discussed. At low temperatures, T_g for SiB-2 was estimated at –34°C., which compares well with T_i = ?30°C. for this polymer. By comparison, SiB-3 has T_i = ?60°C., while phenyl-modified SiB-4 was found to have T_i = ?25°C. T_m for SiB-2 was estimated to be + 56°C.     

Elastomeric domain-type interpenetrating polymer networks

Elastomeric latex interpenetrating polymer networks (IPNs) can result from a two-stage emulsion polymerization procedure in which styrene is polymerized and cross-linked on a lightly cross-linked polyacrylate (PA) seed latex in a ratio of 75 : 25 PA-PS. The multiphase nature of these IPNs is indicated by two distinct T_gs and is confirmed by cold-stage transmission electron microscopy and by the unique mechanical and rheological properties that are intimately related to the material's structure. PS microdomains reinforce the elastomeric PA, yielding a significant modulus, and interparticle PS physical ties yield a significant ultimate tensile strength. The elastomeric latex IPN's dual thermoset-thermoplastic nature is revealed in a stick, slip, roll flow mechanism of the cross-linked submicrometer particles, which can be injection molded as a thermoplastic. The relationships among the polymerization procedure, the structure, and the physical properties are characterized by the examination of several different materials using a variety of analytic techniques.     

Elastomeric films from structured latexes

A model structured latex that is capable of forming a self-curable elastomeric film under mild temperature conditions was developed. In this model latex system, a small amount of dimethyl meta-isopropenyl benzyl isocyanate (TMI®) was copolymerized with n-butyl acrylate (BA) onto poly(butadiene-co-styrene) [(P(Bd-S)] seed latex particles. In the final stage of the film formation process, the latex particles coalesce with each other, and interdiffusion of PBA-based polymer chains in the shell layers of adjacent structured particles occurs. At this stage, the isocyanate groups in the P(BA-TMI) shell layer would begin to crosslink by either a moisture-cure reaction via trace amounts of water remaining in the latex film or by a post-added crosslinker that contains amine groups. Improved elastomeric properties of the latex film are expected from this kind of “interphase” crosslinking structure. However, latex films prepared from the model P(Bd-S)/P(BA-TMI) core/shell latexes were cracked and brittle, which was explained by the formation of a highly crosslinked/grafted core/shell interphase zone. Saturation of the residual double bonds in the P(Bd-S) seed latex particles by hydrogenation was found to be an effective way to reduce the development of the interphase zone and the degree of crosslinking during the second-stage polymerization. An elastomeric film with good mechanical and anti-aging properties was formed from this hydrogenated-P(Bd-S)/P(BA-TMI) structured latex. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1143–1152, 1997     

Elastomeric polyurethanes reinforced with aramid fibers

Thermolplastic polyurethane is a relatively new development in the elastomers field, combining elastomeric behavior with thermoplastic processing characteristics. Thus, high production rate and reduced scrap can be achieved but, increased versatility for the incorporation of additives is also possible. In this work, thermoplastic polyurethane matrices were prepared and Kevlar pulp was dispersed as a reinforcing agent. Since good dispersion and appropriate filler volume fraction are critical factors for a reinforcing effect, special attention was paid to the optimization of these parameters. Thermoplastic polyurethanes were prepared by mixing a low melting polyol with a low melting diisocryanate and the subsequent addition of small amounts of a chain extender, namely, a low molecular weight diol such as 1,4 butanediol. The Kevlar pulp was added under stirring either in the polyol or the diisocyanate melt. This incorporation technique allows the disperision of small fiber percentages. Thus, calendering of the materials prepared was also performed and additional fibers were incorporated. Changes in the properties of properties of the specimens prepared as a function of the filler volume fraction and the dispersion technique were determined, taking into consideration the possibilities of chemical interaction between fibers and matrix.     

Elastomeric block polymers from ethylene sulphide

Block polymers of ethylene sulphide with butadiene, isoprene and styrene have been prepared by anionic synthesis, and their properties have been examined. The ABA polymers from ethylene sulphide and isoprene are elastomers with good thermal stability but unless of low molecular weight are difficult to process except at high temperatures, when they are prone to degradation. ABC block polymers from styrene, isoprene or butadiene and ethylene sulphide are strong resilient elastomers with improved thermal stability compared with the conventional styrene/butadiene block polymers. Good properties are obtained with small amounts (2–4%) of low molecular weight (～4000), highly crystalline poly(ethylene sulphide) blocks. X-ray, differential scanning calorimetry, and gel permeation chromatography data show the ethylene sulphide blocks to be anisotropic, extended-chain crystallites which aggregate large numbers of the attached diene/styrene chains. These aggregates persist at temperatures above the softening point of the polystyrene domains, and in solution. The polymers possess unusual flow characteristics which are not well understood. Electron micrographs of stained, cast or microtomed films show the elastomers to have a two-phase morphology. It has not been possible to identify the structure of the small poly(ethylene sulphide) domains. The ABC polymers can be oil extended and compounded with carbon black. Vulcanizates using accelerated sulphur systems have good physical properties.