材料专业英语(一)

1.Polymers,or plastics,are organic materials that serve as our third category of structuralmaterials for engineering.These materials are composed of long-chain or network organicmolecules formed from small molecules(monomers)by polymerization reactions.This occursin one of two ways:chain growth(addition polymerization)or step growth(condensationpolymerization).Copolymers and blends are analogs of metallic alloys.Copolymers andblends are analogs of metallic alloys.Individual mers(polymer building blocks formed frommonomers)produce linear molecular structure when they are bifunctional(have two pointsof contact with adjacent mers).Network molecular structure results from polyfunctionalmers(having more than two points of contact).聚合物或塑料是一种有机材料，是第三类应用于工程上的结构材料，这类材料是由小分子通过聚合反应形成的长链或网状有机分子。有两种聚合方式：连锁聚合(加聚反应)和逐步聚合(缩聚反应)。共聚物和混合物类似于金属合金。共聚物和混合物类似于金属合金。当单个结构单元(由单体转变而成的高分子构成单元)是双官能度的(可与邻近的结构单元连接的两个点)，可生成线形分子结构。网状分子结构是由多官能度的结构单元(有超过两个的连接点)形成的。2.The number of mers attached together to form a polymeric molecule is termedthe degree of polymerization.There is a statistical distribution of both molecularweights and molecular lengths in a given polymer.Also,the length of a linearmolecule can be characterized by both coiled and extended configurations.Formany polymers rigidity and melting point increase with increasing molecularlength and complexity.Thermoplastic polymers become softer upon heating dueto thermal agitation of weak,secondary bonds between adjacent linearmolecules.An important trend in the past decade has been the increaseddevelopment of“engineering polymersv for metals substitution andthermoplastic elastomers,rubberlike materials with the processing convenienceof traditional thermoplastics.Thermosetting polymers are network structuresthat form upon heating,resulting in greater rigidity,and include the traditionalvulcanized elastomers.相互连接形成聚合物分子链的结构单元数目被称为聚合度。对于一种给定的聚合物高分子，它的分子量和分子长度都是由统计分布得出的。同样，一个线形分子的长度也可由盘绕和伸直的构象进行描述。对于许多聚合物来说，它的刚性和熔点都随着分子链长和复杂度增加。热塑性聚合物在加热时会变软，这是由于相邻线形分子间的范德华键热振动引起的。近十年来，人们着重开发替代金属的 工程高分子”和具有传统热塑性材料成型方便的，类似橡胶的材料-热塑性弹性体。3.As Figure 9.1-2 shows,this process begins with an initiator(an hydroxyl freeradical in this case).The initiation reaction converts the double bond of onemonomer into a single bond.Once completed,the one unsatisfied bondingelectron is free to react with the nearest ethylene monomer,extending themolecular chain by one unit(step 2).This chain reaction can continue in rapidsuccession limited only by the availability of unreacted ethylene monomers.Therapid progression of step 2 through n is the basis of the descriptive term“addition polymerization.Eventually,another hydroxyl radical can act as aterminator(step n),giving a stable molecule with n mer units(step n).For thespecific case of hydroxyl groups as initiators and terminators,hydrogen peroxideis the source of the radicals.如 图9.1-2所示，（聚合）过程是从引发剂（这个例子中是一个羟基自由基）开始的。引发反应将单体的双键转化为单键。一旦引发反应结束，一个不饱和价电子就可以和任何一个最接近的单体反应，分子链扩展一个单元（步 骤2）。这种链反应可很快地接连继续进行，仅受是否存在未反应的聚乙烯单体的量的限制。步 骤2至步骤n的快速系列（反应）过程是描述性术语 加聚反应”的基础（由来）。最后，在步骤n时，另一个羟基作为终止剂，得到一个具有n个结构单元的稳定分子。在这个特例中，过氧化氢产生的羟基既作为引发剂又作为终止剂。4.TablelO.1-1 lists some common glass compositions used for fiber reinforcement.Each is the result of substantial development that has led to optimal suitabilityfor specific applications.For example,the most generally used glass fibercomposition is E-glass,in which E stands for uelectrical type.The low sodiumcontent of E-glass is responsible for its especially low electrical conductivity andits attractiveness as a dielectric.表10.1-1列出许多纤维增强所用的普通玻璃的成分。每种成分都是针对某种具体应用领域最佳适用性的实质性研究成果（都是重要发展的结果，具有最适用的具体应用领域。）例如，最常使用的玻纤成分是E-玻璃，这里的E代表 电子型,E-玻璃中的低钠含量使其具有低电导率，还有引人注目的绝缘性。5.Composites bring together in a single material the benefits of various componentsdiscussed in previous chapters.Fiberglass typifies human-made fiber-reinforcedcomposites.Glass fibers provide high strength and modulus in a polymeric matrixthat provides ductility.Various fiber geometries are commonly used.In any case,properties tend to reflect the highly anisotropic geometry of the compositemicrostructure.复合材料将前面几章所讲的不同组分的优点集中到了一种材料中。玻璃钢是一种典型的人造纤维增强复合材料。在聚合物基体中的玻璃纤维提供高强度和高模量，基体则提供韧性。常用的有多种纤维几何排布方式。在任何情况下，材料的性质都会反映复合材料微观结构的高度各向异性。6.For ductile-matrix composites,the effective use of property averaging depends ongood interfacial bonding between the matrix and dispersed phase andcorresponding high interfacial strength.For brittle ceramic-matrix composites,low interfacial strength is desirable,in order to provide high fracture toughnessby a mechanism of fiber pull-out.The major mechanical properties important tostructural materials are summarized for various composites.对于韧性基体复合材料，能否性质均衡取决于基体相和分散相之间好的界面张力。对于脆性陶瓷基复合材料，需要低的界面强度，是为了通过拔出纤维机理提供高的断裂韧性。总结了不同的复合材料主要机械性能，这些性能对结构材料来说很重要。7.In solid materials,discrete energy levels give way to energy bands.It is the relativespacing of these bands（on an energy scale）that determines the magnitude ofconductivity.Metals,with large values of conductivity,are termed conductors