塑料的性能外文文献翻译、中英文翻译

外文资料翻译
资料来源：书籍
文章名：Chapter 2 The Properties of Plastics 书刊名：《English for Die & Mould Design and Manufacturing》
作者：刘建雄王家惠廖丕博主编
出版社：北京大学出版社，2002
章节：2.2 The Properties of Plastics
页码：P24~P31
文章译名：塑料的性能
The Properties of Plastics
Plastics are organic materials made from large molecules that are constructed by a chain-like attachment of certain building-block molecules. The properties of the plastic depend heavily on the size of the molecule and on the arrangement of the atoms within the molecule. For example, polyethylene is made from the ethylene building block that is initially a gas.Through a process called polymerization, a chain of ethylene molecules is formed by valence bonding of the carbon atoms within the ethyle ne molecule. The high molecular weight product which results iscal led a polymer. Hence, the designation polyethylene is used todisti nguish the high- molecular-weight plastic from its gaseous counterp art, ethylene, which is the monomer that becomes polymerized.The “poly”refers to the “many”ethylene building block molecules
or monomers, which join to form the polyethylene plastic molecule. Frequently, the term “resin”is used, interchangeably with “poly
mer”to describe the backbone molecule of a plastic material. Ho wever, “resin”is sometimes used to describe a syrupy liquid of both natural and synthetic resin.
Plastics, in the finished product form, are seldom comprised e xclusively of polymer but also include other ingredients such as fillers, pigments, stabilizers, and processing aids. However, design ation of the plastic material or molding compound is always taken from the polymer designation.
Broadly speaking plastics may be divided into two categories: thermoplastics and thermoset plastics. The classes of materials are so named because of the effect of temperature on their properties .
2.2.1Thermosets
Thermoset plastics are polymers which are relatively useless in their raw states. Upon heating to a certain temperatureaa chemical reaction takes place which causes the molecules to bond together or cross-link. After vulcanization and polymerization, or curing,the thermoset material remains stable and cannot return to its origi nal state. Thus, ├thermo-set┠identifies those materials that become set in their useable state resulting from the addition o f heat. Normally, a thermoset polymer is mixed with fillers and reinforcing agents to obtain the properties of a molding compound. Thermosets are the hardest and stiffest of all plastics, are chem ically insoluble after curing, and their properties are less affec ted by changes in temperature than are the heat-sensitive thermopl astics. The closest non-plastic counterparts to thermosets in prope rties are ceramics. Common examples of thermoset plastics are: phe nolics, melamine, urea, alkyds, and epoxies. Molding compounds made from these polymeric resins always contain additional fillers and reinforcing agents to obtain optimum properties.
2.2.2Thermoplastics
Thermoplastic polymers are heat-sensitive materials which are solids at room temperature,like most metals. Upon heating, the thermopla stics begin to soften and eventually reach a melting point and b ecome liquid. Allowing a thermoplastic to cool below its melting
point causes resolidification or freezing of the plastic. Successiv e heating and cooling cycles cause repetition of the melting-freez ing cycle just as it does for metals.
The fact that thermoplastics melt is the basis for their proc essing into finished parts. Thermoplastics may be processed by any method which causes softening or melting of the material. Exampl es of thermoplastic fabrication techniques using melting are: injec tion molding, extrusion, rotational casting, and calendering. Fabric ation methods which take advantage of softening below the melting point are: thermoforming (vacuum or pressure), blow molding, and forging. Of course, normal metal-cutting techniques can also be applied to thermoplastics in the solid state. Common examples of thermoplastics are: polyethylene, polystyrene, polyvinyl chloride (PV
C), and nylon (polyamide).
2.2.3Fillers
Plastics often contain other added materials called fillers. Fi llers are employed to increase bulk and to help impart desired p roperties. Plastics containing fillers will cure faster and hold c loser to established finished dimensions, since the plastic shrinka ge will be reduced. Wood flour is the general-purpose and most c ommonly used filler. Cotton frock, produced from cotton linters, i ncreases mechanical strength. For higher strength and resistance to impact, cotton cloth chopped into sections about 1/2-inch square c an be processed with the plastic. Asbestos fiber may be used as a filler for increased heat and fire resistance, and mica is u sed for molding plastic parts with superior dielectric characterist ics. Glass fibers, silicon, cellulose, clay, or nutshell flour may also be used. Nutshell flour is used instead of wood flour where a better finish is desired. Plastic parts using short fiber fil lers will result in lower costs, while those with long fiber fil lers having greater impact strengths are more expensive. Other m aterials, not defined as fillers, such as dyes, pigments, lubrican ts, accelerators, and plasticizers may also be added. Plasticizers are added to soften and improve the moldability of plastics. Fi ller and modifying agents are added and mixed with the raw plast ic before it is molded or formed.
2.2.4Properties of Plastics
1.General Properties
The problem of selecting plastic materials is that of finding the material with suitable properties from the standpoint of inten ded service, methods of forming and fabricating, and cost.
New and improved plastic materials possessing almost any desired c haracteristic are being introduced continually. There are plastics that do not require plasticizers that have greater flexibility und er lower temperatures, and are stable under higher temperatures. S ome resist water, acids, oils, and other destructive matter. The wide use of plastics testifies to their value; however, fundamenta l limitations should be considered when applying a new material o r adapting an old material to new applications.
2.Effects of Temperature
Plastics are inclined toward rigidity and brittleness at low t emperatures, and softness and flexibility at high temperatures. The y are fundamentally unstable dimensionally with respect to temperat ure, and are susceptible to distortion and flow when subjected to elevated temperatures. The thermoplastics are particularly suscepti ble, while the thermosetting plastics are much more resistant, dif fering, however, only in degree. The distinction between the therm al stability of the thermosetting and thermoplastic resins is not well defined. A true distinction can be drawn only between indi vidual plastics, rather than between classes of plastics. High tem peratures not only seriously reduce the mechanical properties of p lastics, but also accelerate the destructive action of external ag ents to which they are sensitive. Continuous heating also may ind uce brittleness and shrinkage in heavily plasticized materials by volatilization of plasticizers. The use of one plastic in contact with a dissimilar plastic in a proposed application should be c hecked first in the light of possible ├migration of plasticizer â”
, sometimes resulting in discoloration or hardening of one of the plastics.
In general, moderate temperatures are required for storage of plas
tics over long periods; low temperatures are to be avoided becaus e of the low-temperature brittleness of most of the plastics, and high temperatures should be avoided because of the rapid loss o f mechanical properties, volatilization of plasticizers, and the su sceptibility of a large number to distortion.
Plastics, with only a few exceptions, are extremely sensitive to the effects of water. High- humidity atmospheres induce water absorption and varied resulting effects, depending upon the composi tion and formulation of the plastics. Increased water content plas ticizes some materials, and there is a general lowering of the m echanical properties. Water absorption is responsible for swelling in certain plastics and the ultimate decomposition of a few. Mois t or wet atmospheres may extract plasticizers from heavily plastic ized materials and also provide conditions favorable to fungal gro wth. In recent years, however, new plastics have come into use t hat have first-class moisture resistance and may contain water ind efinitely while resisting other influences at the same time.
Extremely dry environments may cause brittleness in certain pla stics as a result of loss of water that normally contributes to their plasticity. Cyclic wet and dry atmospheres are more destruct ive to plastics than continuous exposure at constant humidity beca use of the mechanical stresses induced in the plastics by swellin g and shrinking with moisture absorption and moisture emission. Re latively constant, moderate to low humidities are preferred for pl astic storage because of the adverse effects of water on the str ucture and properties of these materials, and the possibility of plasticizer loss by extraction and fungal attack in moist atmosphe res
3.Effects of Light
Prolonged exposure to sunlight will affect adversely all plastics with exception of tetrafluoroethylene (Teflon). The change induced by the ultraviolet components may vary in kind and severity from slight yellowing to complete disintegration as a result of the chemical degradation of the polymeric compound or plasticizers. Los s of strength, reduced ductility, and increased fragility usually accompany such action. Many plastics are offered in special formul
ations containing “ultraviolet inhibitors”which should be utilize d when this influence is present. Exposure of plastics to sunligh t during storage should be avoided, especially when the transparen cy of clear materials is to be preserved.
4.Weight
As a family, plastics are light when compared to metals. Most plastics have a specific gravity between 1.35 and 1.45, which is less than that of magnesium.
5.Electrical Resistivity
Plastics have excellent electrical resistivity making them have wide application as an insulating material. In the high-frequency applications, plastics are particularly advantageous and, consequentl y, are being used to a large extent in the fields of radar and television.
6.Heat Insulation
Plastics have low heat conduction and, consequently, have appli cation as an insulating material. In particular, they are used as handles for appliances and tools subjected to heat.
Fabrication
The principal characteristic of plastics from fabrication standp oint is case of molding. Both thermosetting and thermoplastic mate rials lend themselves to molding irregular and complex shapes with relatively short curing cycles.
Plastics may be joined by using various cements, chemical solv ents, and mechanical fasteners. Heat-sealing, which parallels somewh at the welding process of metals, is used extensively in joining light thermoplastic films. In such cases, dielectric heating is th e technique usually used. Friction adhesion has had moderate app lication also in the joining of small thermoplastic parts.
Plastics can be machined with conventional machine tools. Howev er, certain cautions should be exercised. In order to maintain a good finish, a heavy flow of coolant should be used so as to a void temperatures that will distort the work. In some thermosettin
g laminates (glass, for example), the customary high-speed steel t ool will not stand up in view of the abrasive action of the la minating material. Here, either tungsten carbide or ceramic cutting tools must be used.
7.Effects of Oxygen
Organic plastics are nearly all subject to oxidation when expo sed to the atmosphere. The process is accelerated by high tempera tures and light; but, over long periods of time, oxidative deteri oration may take place at room temperature. Oxidation susceptibilit y depends largely upon the chemical nature of the plastic and it s compounding. Materials with the greatest number of double bonds in their molecular structure will generally be the most sensitive to oxidation. Yellowing and a gradual loss of strength and ductil ity are the principal results of oxidative processes.
Oxidation is not a problem of great magnitude in storage, sin ce the rigid plastics are rather resistant to oxidative deteriorat ion under moderate conditions.
8.Effects of Loading
Under moderate conditions the common thermoplastic materials are subject to distortion and flow when significantly loaded. Such pla stics cannot be expected to maintain a high degree of mechanical stability over extended periods when subjected to stress; especiall y is this true when they are also exposed to relatively high te mperatures. The thermoplastics should, however, ma- intain themselve s fairly well when not subject to load or when subjected to onl y moderate load. Recently, fillers, such as glass wool, have been added to thermoplastics to further improve this property.
The thermosetting plastics are much more load-stable than the thermoplastics because of their structure and the inclusion of fil lers in their formulation. In the laminated form they provide a rather high order of distortion and creep resistance. When not su bjected to mechanical stress they may be considered to be highlys table. These materials, however, may suffer creep over long period s, especially when maintained at elevated temperatures.
The thermoplastic types should not be subjected to load when stored; and, whenever possible, the loading of stress-bearing therm osetting moldings or laminates should be removed or reduced.
10.Chemical Stability
Plastics, in general, possess a high degree of inherent stabil ity with respect to chemical deterioration. In many instances, thi s stability may be fortified by the addition of the proper stabi lizers during compounding. While there is vast difference from one plastic to another, the general statement may be made that there is a plastic available to resist virtually any commercial chemical ..
塑料的性能
热塑性塑料熔体是热塑性塑料加工成品的基础。

热塑性塑料可以用任何方法加工，导致材料软化或熔化。

t的例子采用熔融的气塑制造技术有：注射成型、挤压、旋转铸造和压延。

利用熔点以下软化的制造方法有：热成型(真空或压力)，吹塑，锻造。

当然，普通的金属切削技术也可以应用于固态热塑性塑料.热塑性塑料的常见例子CS为：聚乙烯、聚苯乙烯、聚氯乙烯(PVC)和尼龙(聚酰胺)。

2.2.3填料
塑料是由大分子制成的有机材料，由某些积木分子组成的链状附着体构成。

塑料的性能在很大程度上取决于o的大小。

f分子和原子在分子内的排列。

例如，聚乙烯是由最初是气体的乙烯构件制成的。

通过聚合法乙烯分子中的碳原子价键形成了一条乙烯分子链。

高分子量的产物被称为聚合物。

因此，聚乙烯是用来区分高分子量塑料与其气态对应物乙烯，乙烯是聚合的单体。

“poly”指的是“多”et。

聚烯类物质的组成分子或单体，它们连接在一起形成聚乙烯塑料分子。

经常使用“树脂”一词，并与“聚合物”互换来形容背板。

塑料的分子。

然而，“树脂”有时被用来描述天然和合成树脂的糖浆液体。

塑料，以成品的形式，很少被包括在内。

广泛的聚合物，但也包括其他成分，如填料，颜料，稳定剂，和加工助剂。

然而，塑料材料或模塑化合物的名称总是从聚合物称广义地说，塑料可分为两类：热塑性塑料和热固性塑料。

由于温度的影响，
2.2.1热固性材料
热固性塑料是一种聚合物，在其原始状态下是相对无用的。

在加热到一定温度时，会发生化学反应，使分子结合在一起，或交叉链接。

经过硫化、聚合或固化后，热固性材料保持稳定，不能恢复到原来的状态。

因此，“热集”识别了那些成为由于加温而处于可用状态。

通常，热固性聚合物与填料和增强剂混合，以获得模塑化合物的性能。

热固性塑料是所有塑料中最坚硬、最坚硬的，固化后不溶于化学，其性能受温度变化的影响小于热敏热塑性塑料。

抽搐。

与热固性材料最接近的非塑性材料是陶瓷。

热固性塑料的常见例子有：酚醛、三聚氰胺、尿素、醇酸和环氧。

成型化合物f这些树脂总是含有额外的填料和增强剂，以获得最佳的性能。

2.2.2 热塑性塑料
热塑性聚合物是一种热敏材料，在室温下是固体，就像大多数金属一样。

加热后，热塑性塑料开始软化，最终达到熔点，变成液体。

允许热塑性塑料冷却到其熔点以下会导致溶解。

塑料的冻结或冻结。

连续的加热和冷却循环会导致熔化-冻结循环的重复，塑料通常含有其它被称为填料的附加材料。

使用填料来增加体积并帮助赋予所需的性能。

含有填料的塑料将更快地固化并保持更紧密以确定成品尺寸，由于塑料收缩将减少。

木粉是一种通用的，也是最常用的填充剂.棉质长袍，由棉短绒制成，增加。

机械强度。

为了更高的强度和抗冲击能力，将棉布切成约1/2英寸的方形，可以用塑料加工。

石棉纤维可用作填充剂提高了耐热性和耐火性，云母用于成型具有优良介电特性的塑料零件。

玻璃纤维、硅、纤维素、粘土或壳面也可以使用。

n在需要更好的光洁度的地方，
用utshell面粉代替木粉。

使用短纤维填料的塑料零件会降低成本，而长纤维填料的成本会更高。

行动能力更昂贵。

其他未定义为填料的材料，如染料、颜料、润滑剂、促进剂和增塑剂也可加入。

增塑剂被添加到软化和IM中。

证明塑料的可模塑性。

填充剂和改性剂在成型或成型之前，先加入原塑料，然后与其混合。

2.2.4塑料性能
1.一般特性
塑料材料的选择问题是从服务目的、成型方法、制造方法、成本等方面寻找性能合适的材料。

新的和改进的塑料材料具有几乎任何所需的特性正在不断引入。

有些塑料不需要具有更大柔韧性的增塑剂。

呃温度低，在高温下是稳定的。

有些能抵抗水、酸、油和其他破坏性物质。

塑料的广泛使用证明了它们的价值；然而，基本的l在应用新材料或使旧材料适应新应用时，应考虑模仿。

2.温度效应
塑料在低温下倾向于刚性和脆性，在高温下倾向于柔软和灵活。

就温度而言，它们在尺寸上基本上是不稳定的。

，并且在高温下易受变形和流动的影响。

热塑性塑料特别敏感，而热固性塑料则更耐高温，差别很大。

然而，吴只在学位方面。

热固性树脂和热塑性树脂的热稳定性之间的区别还没有很好地界定。

只有在单个pl之间才能进行真正的区分。

不是在塑料类之间。

高温不仅严重降低了塑料的力学性能，而且加速了外界因素对Wi的破坏作用。

它们很敏感。

连续加热也可通过增塑剂的挥发而在严重增塑材料中引起脆性和收缩。

一种塑料与迪西米的接触在提议的应用中，LAR塑料应首先根据可能的“增塑剂迁移”进行检查，有时会导致其中一种塑料变色或硬化。

一般来说，塑料的长期储存需要适度的温度；由于大部分塑料的低温脆性，所以必须避免低温。

由于力学性能的迅速丧失、增塑剂的挥发和大量变形的敏感性，应避免Gh 温度的升高。

塑料，除了少数例外，对水的影响极为敏感。

高湿度的大气会引起不同的吸水率，并会产生不同的影响，这取决于成分。

塑料的配方。

水分含量的增加使一些材料的力学性能普遍下降。

吸水是导致宫颈肿胀的原因。

在塑料和最终分解的几个。

潮湿或潮湿的大气可以从高度塑化的材料中提取增塑剂，也可以为真菌的生长提供有利条件。

参考文献然而，在过去的几年里，新塑料已经投入使用，它们具有一流的防潮性能，并且在抵抗其他影响的同时，也可能无限期地含有水。

极度干燥的环境可能会导致某些塑料材料的脆性，这是由于水分的流失，而水的流失通常会导致塑料的可塑性。

循环潮湿和干燥的大气对塑料比连续暴露在恒定湿度下，由于机械应力在塑料中引起的溶胀和收缩与吸湿和水分排放有关。

相对由于水对这些材料的结构和性能的不利影响，以及增塑剂lo的可能性，所以在塑料储存中首选恒定、中、低湿度。

潮湿大气中的SS提取与真菌攻击
3.光的影响
长时间暴露在阳光下会对所有塑料产生不利影响，但四氟乙烯除外（特氟隆）。

紫外线成分引起的变化可能与S的种类和严重程度不同由于聚合物或增塑剂的化学降解
而完全崩解。

失去强度，降低延性，增加脆性通常是accom。

有这样的行动。

许多塑料是以含有“紫外线抑制剂”的特殊配方提供的，当这种影响存在时，应加以利用。

期间塑料暴露于阳光下应避免储存，特别是在要保持透明材料的透明度时。

4.韦特
作为一个家庭，塑料与金属相比是轻的。

大多数塑料的比重在1.35到1.45之间，比镁的比重小。

5.电阻率
塑料具有优异的电阻率，因而作为一种绝缘材料有着广泛的应用。

在高频应用中，塑料特别有利，因此Y，在很大程度上被用于雷达和电视领域。

6.绝热
塑料具有低导热性，因此作为绝缘材料有着广泛的应用。

特别是，它们被用作受热的电器和工具的把手。

7.制造
从制造角度看，塑料的主要特点是成型。

热固性材料和热塑性材料都适合于用Re 成型不规则和复杂的形状。

固化周期短。

塑料可以使用各种水泥、化学溶剂和机械紧固件连接。

热密封与金属的焊接过程平行，在连接热密封中得到了广泛的应用。

热塑性薄膜。

在这种情况下，电介质加热是通常使用的技术。

摩擦粘着在小型热塑性零件的连接中也有一定的应用。

塑料可以用传统的机床加工。

但是，应采取某些警告措施。

为了保持良好的光洁度，应使用大量的冷却剂，以避免温度升高。

会扭曲作品的模型。

在一些热固性层压板(例如玻璃)中，由于层压材料的磨料作用，传统的高速钢工具将不会起立。

艾尔。

在这里，必须使用碳化钨或陶瓷刀具。

8.氧效应
有机塑料在暴露于大气中时几乎都会受到氧化。

这一过程是由高温和光加速的，但在很长一段时间内，氧化恶化。

可能在室温下发生。

氧化敏感性在很大程度上取决于塑料的化学性质及其复配。

m中双键数最大的材料分子结构通常对氧化最敏感。

变黄和逐渐失去强度和延展性是氧化过程的主要结果。

氧化不是一个很大的储存问题，因为硬质塑料在中等条件下是相当抵抗氧化劣化的。

9.加载效应
在适当的条件下，普通热塑性材料在显著加载时会发生变形和流动。

这种塑料不可能维持高度的机械稳定。

当他们承受压力时，会长时间处于状态；尤其是当他们也暴露在相对较高的温度下时。

然而，热塑性塑料应该是属于自己的。

当不受负荷或只承受中等负荷时，良好。

最近，在热塑性塑料中加入了玻璃棉等填料，以进一步改善这一性能。

热固性塑料由于其结构和填料的存在，比热塑性塑料具有更高的负载稳定性。

在层叠形式中，它们提供了一个相当不错的高次变形和抗蠕变性能。

当没有受到机械应力时，它们可以被认为是高度稳定的。

然而，这些材料可能会长期蠕变，特别是在高温下保持。

热塑性材料储存时不应承受载荷；凡有可能，应移除或减少承受应力的热固性模塑或层压板的负荷。

10.化学稳定性
一般来说，塑料在化学退化方面具有高度的内在稳定性。

在许多情况下，加入适当的稳定剂可以加强这种稳定性。

在复合过程中。

虽然一种塑料和另一种塑料有很大的不同，但一般的说法是，有一种塑料可以抵抗几乎任何商业化学品。