合成聚合物-烯烃,二烯弹性体和乙烯基卤化物

B. Walker, Lynette D. Stokes
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The first specialty elastomers, polysulfides and polychloroprene, were commercialized in the 1930s, natural rubber was the major industry product until World War II, when styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were established as important synthetic rubbers. \n \n \n \nFrom these early beginnings, the elastomer industry grew rapidly to a global elastomer demand of 15 million metric tons in 1990. The range and diversity of synthetic rubber becomes evident upon reviewing the Synthetic Rubber Manual that describes both thermosetting elastomers (TSE) and thermoplastic elastomers (TPE). \n \n \n \nTSE and TPE exhibit important similarities. The most useful properties are the result of their long molecular chains linking to one another to form a three-dimensional network. In TSE this network is linked together with essentially irreversible cross-links. Vulcanization is the process of forming these cross-links, most typically using sulfur as the cross-linking agent. \n \n \n \nTSE generally arrives at the rubber fabricators in bales. Ten or more ingredients might be added to the bale in heavy mixers before the compounded elastomer is shaped into a product and vulcanized. Schunk has characterized the health hazards of many of these ingredients, including carbon blacks, mineral fillers, plasticizers, protective and cross-linking agents, and accelerators. Broadly considered, these health hazards can be considered in terms of the following: \n \n \n \nmonomers, solvents, and other materials used to prepare elastomers \n \n \n \n \nstorage and handling of elastomer (bales, pellets, and powder) \n \n \n \n \nprocessing of elastomers, generally at high temperatures \n \n \n \n \nfinished rubber product \n \n \n \n \n \n \nHealth hazards in processing, and storage and handling elastomers are the dominant focus of this section; limited references will be made to the other two areas where appropriate. \n \n \n \nCertain portions of the material refer to monomer toxicology and epidemiology because some of the monomers used in manufacturing elastomers remain at low levels in the polymer. A full discussion of the toxicity of monomers is beyond the scope of this chapter. \n \n \n \nTypical basic properties of certain elastomers are latter. Properties within a given class of elastomers can vary significantly. 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Solution polymerization with stereospecific catalysts involves reacting one or more monomers in an inert solvent; system conditions can be controlled to maximize a desired isomer arrangement in the polymer. \n \n \n \nAntioxidants are generally added for shelf, processing, and in-service stability. \n \n \n \nVulcanization is usually done with sulfur, sulfur-containing compounds, or peroxides, but it may also be accomplished with other compounds that yield free radicals at curing temperature or by radiation. Various supplementary materials such as cure accelerators, cure retarders, or reinforcing agents are commonly part of the compounding recipe. Vulcanization ideally begins when the elastomer assumes its final shape in a mold. The elastomer type and its viscosity significantly affect molding behavior. \n \n \n \nDry solid polymers usually contain less residual monomer (or solvent) than latex materials. The processing necessary to produce the dry product drives the residual monomer or solvent out of the resin, usually by heat. \n \n \n \nSeveral reports address worker health problems in the rubber fabrication industry. For example, one study suggests an association between the mortality risk of lung cancer and employment in operations involving reclaim, chemicals, and special products. Another study showed that processing workers had increased mortality from leukemia, emphysema, and cancers of the stomach, large intestine, biliary passages, and liver. \n \n \n \nIndustrial dermatitis from finished rubber products due to the various chemicals added during polymerization, curing, and processing is not uncommon. \n \n \n \nElastomers degraded at high temperatures around 800°C can yield more toxic products than elastomers degraded at smoldering temperatures or gradually rising temperatures. 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引用次数: 1

摘要

弹性体,也被称为橡胶,可以承受比其他材料更大的变形,并且即使在剧烈变形后也能独特地恢复到原来的形状。一个熟悉的例子是橡皮筋松开后拉伸的行为。所有弹性体都是由长大分子链组成,在未变形时呈随机线圈形。变形使这些线圈变直。一旦被允许放松,弹性体基本上就会恢复到原来的形状,因为链恢复了它们的随机构象。发现的第一种弹性体是天然橡胶,哥伦布把它描述为一种会弹跳的球。第一批特种弹性体,聚硫化物和氯丁橡胶,在20世纪30年代商业化,天然橡胶是主要的工业产品,直到第二次世界大战,当丁苯橡胶(SBR)和丙烯腈丁二烯橡胶(NBR)被确立为重要的合成橡胶。从这些早期开始,弹性体行业迅速发展到1990年全球弹性体需求达到1500万吨。合成橡胶的范围和多样性在回顾合成橡胶手册时变得明显,该手册描述了热固性弹性体(TSE)和热塑性弹性体(TPE)。TSE和TPE表现出重要的相似性。最有用的特性是它们的长分子链相互连接形成三维网络的结果。在TSE中,这个网络以本质上不可逆的交联连接在一起。硫化是形成这些交联的过程,最典型的是使用硫作为交联剂。TSE通常成捆地到达橡胶制造商处。在复合弹性体成形成产品并硫化之前,可以将十种或更多种成分添加到重混合器中的包中。Schunk描述了许多这些成分对健康的危害,包括炭黑、矿物填料、增塑剂、保护剂和交联剂以及促进剂。从广义上考虑,这些健康危害可从以下方面考虑:单体、溶剂和用于制备弹性体的其他材料储存和处理弹性体(包、球团和粉末)加工弹性体,一般在高温下加工的成品橡胶制品中的健康危害,而储存和处理弹性体是本节的主要重点;在适当的情况下,将有限地提及其他两个领域。材料的某些部分涉及单体毒理学和流行病学,因为用于制造弹性体的一些单体在聚合物中保持低水平。对单体毒性的全面讨论超出了本章的范围。某些弹性体的典型基本性质是后者。在给定的弹性体类别内的性质可以有很大的不同。例如,增加丁腈橡胶中的丙烯腈含量可以减少某些油和溶剂引起的丁腈橡胶膨胀。大多数橡胶都是生的或未固化的固体或液体乳胶。制造某些类型的干合成橡胶的基本步骤是聚合、混凝、洗涤和干燥。生产乳胶的基本步骤是聚合、稳定,通常还有浓缩。乳胶被定义为一种稳定的水性分散体,包含直径约0.05至5mm的离散聚合物颗粒。乳液聚合系统包含水、单体、引发剂和阴离子或阳离子表面活性剂。具有立体定向催化剂的溶液聚合涉及在惰性溶剂中反应一种或多种单体;系统条件可以控制,以最大限度地提高所需的异构体在聚合物中的排列。添加抗氧化剂通常是为了货架、加工和使用中的稳定性。硫化通常用硫、含硫化合物或过氧化物来完成,但也可以用在固化温度下或通过辐射产生自由基的其他化合物来完成。各种辅助材料,如固化促进剂、固化缓凝剂或增强剂,通常是复合配方的一部分。理想情况下,当弹性体在模具中形成最终形状时,硫化就开始了。弹性体类型及其粘度对成型性能有显著影响。干固体聚合物通常比乳胶材料含有更少的残余单体(或溶剂)。生产干燥产品所需的加工通常是通过加热将残留的单体或溶剂从树脂中除去。有几份报告涉及橡胶制造行业工人的健康问题。例如,一项研究表明,在涉及回收、化学品和特殊产品的操作中,肺癌的死亡风险与就业之间存在关联。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Synthetic Polymers—Olefin, Diene Elastomers, and Vinyl Halides
Elastomers, also called rubber, can withstand considerably greater deformation than other materials and uniquely return essentially to their original shape even after substantial deformation. A familiar example is the behavior of a stretched rubber band after its release. All elastomers are composed of long macromolecular chains that assume a random coil conformation when undeformed. Deformation causes these coils to straighten out. Upon being allowed to relax, an elastomer returns essentially to its original shape because the chains reassume their random conformation. The first elastomer identified, natural rubber, was described by Columbus as a ball that bounced. The first specialty elastomers, polysulfides and polychloroprene, were commercialized in the 1930s, natural rubber was the major industry product until World War II, when styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were established as important synthetic rubbers. From these early beginnings, the elastomer industry grew rapidly to a global elastomer demand of 15 million metric tons in 1990. The range and diversity of synthetic rubber becomes evident upon reviewing the Synthetic Rubber Manual that describes both thermosetting elastomers (TSE) and thermoplastic elastomers (TPE). TSE and TPE exhibit important similarities. The most useful properties are the result of their long molecular chains linking to one another to form a three-dimensional network. In TSE this network is linked together with essentially irreversible cross-links. Vulcanization is the process of forming these cross-links, most typically using sulfur as the cross-linking agent. TSE generally arrives at the rubber fabricators in bales. Ten or more ingredients might be added to the bale in heavy mixers before the compounded elastomer is shaped into a product and vulcanized. Schunk has characterized the health hazards of many of these ingredients, including carbon blacks, mineral fillers, plasticizers, protective and cross-linking agents, and accelerators. Broadly considered, these health hazards can be considered in terms of the following: monomers, solvents, and other materials used to prepare elastomers storage and handling of elastomer (bales, pellets, and powder) processing of elastomers, generally at high temperatures finished rubber product Health hazards in processing, and storage and handling elastomers are the dominant focus of this section; limited references will be made to the other two areas where appropriate. Certain portions of the material refer to monomer toxicology and epidemiology because some of the monomers used in manufacturing elastomers remain at low levels in the polymer. A full discussion of the toxicity of monomers is beyond the scope of this chapter. Typical basic properties of certain elastomers are latter. Properties within a given class of elastomers can vary significantly. For example, increasing acrylonitrile content in NBR reduces swelling of the NBR caused by some oils and solvents. Most rubber is sold raw or uncured as a solid or liquid latex. The basic steps in the manufacture of some types of dry synthetic rubber are polymerization, coagulation, washing, and drying. The basic steps in producing a latex are polymerization, stabilization, and usually, concentration. A latex is defined as a stable aqueous dispersion that contains discrete polymer particles about 0.05 to 5 mm in diameter. Emulsion polymerization systems contain water, monomer(s), initiator, and anionic or cationic surfactants. Solution polymerization with stereospecific catalysts involves reacting one or more monomers in an inert solvent; system conditions can be controlled to maximize a desired isomer arrangement in the polymer. Antioxidants are generally added for shelf, processing, and in-service stability. Vulcanization is usually done with sulfur, sulfur-containing compounds, or peroxides, but it may also be accomplished with other compounds that yield free radicals at curing temperature or by radiation. Various supplementary materials such as cure accelerators, cure retarders, or reinforcing agents are commonly part of the compounding recipe. Vulcanization ideally begins when the elastomer assumes its final shape in a mold. The elastomer type and its viscosity significantly affect molding behavior. Dry solid polymers usually contain less residual monomer (or solvent) than latex materials. The processing necessary to produce the dry product drives the residual monomer or solvent out of the resin, usually by heat. Several reports address worker health problems in the rubber fabrication industry. For example, one study suggests an association between the mortality risk of lung cancer and employment in operations involving reclaim, chemicals, and special products. Another study showed that processing workers had increased mortality from leukemia, emphysema, and cancers of the stomach, large intestine, biliary passages, and liver. Industrial dermatitis from finished rubber products due to the various chemicals added during polymerization, curing, and processing is not uncommon. Elastomers degraded at high temperatures around 800°C can yield more toxic products than elastomers degraded at smoldering temperatures or gradually rising temperatures. This is to be especially so with nitrile-butadiene. The commercial polymers in the vinyl halides group contain chlorine atoms, fluorine atoms, or both in a few cases. In very diverse ways these halogens can be used to produce vinyl polymers that have such characteristics as increased resistance to water, oils, and solvents, plus other distinctive properties. The prototypes are polyvinyl chloride and polyvinylidene chloride. Polyvinyl chloride and its copolymers rank first in production/consumption volume among polymers in the United States and abroad. Their key attribute is low-cost versatility. Polyvinylidene chloride resins have an extremely regular, closely packed molecular structure that results in outstanding impermeability to water, oils, and gases. Keywords: Elastomers; Olefin elastomers; Diene elastomers; Vinyl halides; PVC; Vinylidene chloride copolymers; Butyl rubber; Styrene—butadiene; EPR; Acrylic elastomers; Silicone; Polyurethanes; Polytetrafluoroethylene; Acrylonitrile-butadiene; Vinylidene fluoride coplolymers; Polyisoprene; Epichlorhydrin
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