高分子材料工程专业英语课文翻译(曹同玉,冯连芳)主编

高分子材料工程专业英语课文翻译(曹同玉,冯连芳)主编 高分子专业英语选讲课文翻译资料 A 高分子化学和高分子物理 UNIT 1 What are Polymer? 第一单元 什么是高聚物, What are polymers? For one thing, they are complex and giant molecules and are different from low molecular weight compounds like, say, common salt. To contrast the difference, the molecular weight of common salt is only 58.5, while that of a polymer can be as high as several hundred thousand, even more than thousand thousands. These big molecules or ‘macro-molecules’ are made up of much smaller molecules, can be of one or more chemical compounds. To illustrate, imagine that a set of rings has the same size and is made of the same material. When these things are interlinked, the chain formed can be considered as representing a polymer from molecules of the same compound. Alternatively, individual rings could be of different sizes and materials, and interlinked to represent a polymer from molecules of different compounds. 什么是高聚物,首先,他们是合成物和大分子,而且不同于低分子化合物,譬如说普通的盐。与低 56分子化合物不同的是,普通盐的分子量仅仅是58.5,而高聚物的分子量高于10,甚至大于10。这些大 分子或“高分子”由许多小分子组成。小分子相互结合形成大分子,大分子能够是一种或多种化合物。举例 说明,想象一组大小相同并由相同的材料制成的环。当这些环相互连接起来,可以把形成的链看成是具 有同种分子量化合物组成的高聚物。另一方面,独特的环可以大小不同、材料不同,相连接后形成具有 不同分子量化合物组成的聚合物。 This interlinking of many units has given the polymer its name, poly meaning ‘many’ and mer meaning ‘part’ (in Greek). As an example, a gaseous compound called butadiene, with a molecular 0 高分子专业英语选讲课文翻译资料 weight of 54, combines nearly 4000 times and gives a polymer known as polybutadiene (a synthetic rubber) with about 200 000molecular weight. The low molecular weight compounds from which the polymers form are known as monomers. The picture is simply as follows: 许多单元相连接给予了聚合物一个名称,poly意味着“多、聚、重复”,mer意味着“链节、基体”,希腊 语中,。例如,称为丁二烯的气态化合物,分子量为54,化合将近4000次,得到分子量大约为200000 被称作聚丁二烯,合成橡胶,的高聚物。形成高聚物的低分子化合物称为单体。下面简单地描述一下形 成过程, butadiene + butadiene + ??? + butadiene--?polybutadiene (4 000 time) 丁二烯 ，丁二烯，…，丁二烯——?聚丁二烯 ,4000次, One can thus see how a substance (monomer) with as small a molecule weight as 54 grow to become a giant molecule (polymer) of (54×4 000?)200 000 molecular weight. It is essentially the ‘giantness’,巨大的, of the size of the polymer molecule that makes its behavior different from that of a commonly known chemical compound such as benzene. Solid benzene, for instance, melts to become liquid benzene at 5.5? and , on further heating, boils into gaseous benzene. As against this well-defined behavior of a simple chemical compound, a polymer like polyethylene does not melt sharply at one particular temperature into clean liquid. Instead, it becomes increasingly softer and, 1 高分子专业英语选讲课文翻译资料 ultimately, turns into a very viscous, tacky molten mass. Further heating of this hot, viscous, molten polymer does convert it into various gases but it is no longer polyethylene. (Fig. 1.1) . 因而能够看到分子量仅为54的小分子物质,单体,如何逐渐形成分子量为200000的大分子,高聚 物,。实质上,正是由于聚合物的巨大的分子尺寸才使其性能不同于象苯这样的一般化合物。例如,固态 苯,在5.5?熔融成液态苯,进一步加热,煮沸成气态苯。与这类简单化合物明确的行为相比,像聚乙烯 这样的聚合物不能在某一特定的温度快速地熔融成纯净的液体。而聚合物变得越来越软,最终,变成十 分粘稠的聚合物熔融体。将这种热而粘稠的聚合物熔融体进一步加热,不会转变成各种气体,但它不再 是聚乙烯,如图1.1,。 固态苯——?液态苯——?气态苯 加热,5.5? 加热,80? 固体聚乙烯——?熔化的聚乙烯——?各种分解产物-但不是聚乙烯 加热 加热 图1.1 低分子量化合物,苯,和聚合物,聚乙烯,受热后的不同行为 Another striking difference with respect to the behavior of a polymer and that of a low molecular weight compound concerns the dissolution process. Let us take, for example, sodium chloride and add it slowly to s fixed quantity of water. The salt, which represents a low molecular weight compound, dissolves in water up to s point (called saturation point) but, thereafter, any further quantity added does not go into solution but settles at the bottom and just remains there as solid. The viscosity of the saturated salt solution is not very much different from that of water. But if we take a polymer instead, 2 高分子专业英语选讲课文翻译资料 say, polyvinyl alcohol, and add it to a fixed quantity of water, the polymer does not go into solution immediately. The globules of polyvinyl alcohol first absorb water, swell and get distorted in shape and after a long time go into solution. Also, we can add a very large quantity of the polymer to the same quantity of water without the saturation point ever being reached. As more and more quantity of polymer is added to water, the time taken for the dissolution of the polymer obviously increases and the mix ultimately assumes a soft, dough-like consistency. Another peculiarity is that, in water, polyvinyl alcohol never retains its original powdery nature as the excess sodium chloride does in a saturated salt solution. In conclusion, we can say that (1) the long time taken by polyvinyl alcohol for dissolution, (2) the absence of a saturation point, and (3) the increase in the viscosity are all characteristics of a typical polymer being dissolved in a solvent and these characteristics are attributed mainly to the large molecular size of the polymer. The behavior of a low molecular weight compound and that of a polymer on dissolution are illustrated in Fig.1.2. 发现另一种不同的聚合物行为和低分子量化合物行为是关于溶解过程。例如,让我们研究一下,将 氯化钠慢慢地添加到固定量的水中。盐,代表一种低分子量化合物,在水中达到点,叫饱和点,溶解, 但,此后,进一步添加盐不进入溶液中却沉到底部而保持原有的固体状态。饱和盐溶液的粘度与水的粘 度不是十分不同,但是,如果我们用聚合物替代,譬如说,将聚乙烯醇添加到固定量的水中,聚合物不 是马上进入到溶液中。聚乙烯醇颗粒首先吸水溶胀,发生形变,经过很长的时间以后进入到溶液中。同 样地,我们可以将大量的聚合物加入到同样量的水中,不存在饱和点。将越来越多的聚合物加入水中, 认为聚合物溶解的时间明显地增加,最终呈现柔软像面团一样粘稠的混合物。另一个特点是,在水中聚 乙烯醇不会像过量的氯化钠在饱和盐溶液中那样能保持其初始的粉末状态。总之,我们可以讲,1,聚乙 3 高分子专业英语选讲课文翻译资料 烯醇的溶解需要很长时间,,2,不存在饱和点,,3,粘度的增加是典型聚合物溶于溶液中的特性,这些 特性主要归因于聚合物大分子的尺寸。如图1.2说明了低分子量化合物和聚合物的溶解行为。 氯化钠晶体加入到水中——?晶体进入到溶液中.溶液的粘度不是十分不同于 充分搅拌 水的粘度——?形成饱和溶液.剩余的晶体维持不溶解状态. 加入更多的晶体并搅拌 氯化钠的溶解 聚乙烯醇碎片加入到水中——?碎片开始溶胀——?碎片慢慢地进入到溶液中 允许维持现状 充分搅拌 ——?形成粘稠的聚合物溶液.溶液粘度十分高于水的粘度 继续搅拌 聚合物的溶解 图1.2 低分子量化合物,氯化钠,和聚合物,聚乙烯醇,不同的溶解行为 ——Gowariker VR, Viswanathan N V, Sreedhar J. Polymer Science. New York: John Wiley & Sons, 1986.6 UNIT 2 Chain Polymerization 第二单元 链式聚合反应 Many olefinic and vinyl unsaturated compounds are able to form chain-0like macromolecules through elimination of the double bond, a phenomenon first recognized by Staudinger. Diolefins 4 高分子专业英语选讲课文翻译资料 polymerize in the same manner, however, only one of the two double bonds is eliminated. Such reactions occur through the initial addition of a monomer molecule to an initiator radical or an initiator ion, by which the active state is transferred from the initiator to the added monomer. In the same way by means of a chain reaction, one monomer molecule after the other is added (2000~20000 monomers per second) until the active state is terminated through a different type of reaction. The polymerization is a chain reaction in two ways: because of the reaction kinetic and because as a reaction product one obtains a chain molecule. The length of the chain molecule is proportional to the kinetic chain length. Staudinger第一个发现一例现象,许多烯烃和不饱和烯烃通过打开双键可以形成链式大分子。二 烯烃以同样的方式聚合,然而,仅限于两个双键中的一个。这类反应是通过单体分子首先加成到引发剂 自由基或引发剂离子上而进行的,靠这些反应活性中心由引发剂转移到被加成的单体上。以同样的方式, 借助于链式反应,单体分子一个接一个地被加成,每秒2000,20000个单体,直到活性中心通过不同的 反应类型而终止。聚合反应是链式反应的原因有两种,因为反应动力学和因为作为反应产物它是一种链 式分子。链分子的长度与动力学链长成正比。 One can summarize the process as follow (R. is equal to the initiator radical): 链式反应可以概括为以下过程,R?相当与引发剂自由基,,略 One thus obtains polyvinylchloride from vinylchloride, or polystyrene from styrene, or polyethylene from ethylene, etc. 因而通过上述过程由氯乙烯得到聚氯乙烯,或由苯乙烯获得聚苯乙烯,或乙烯获得聚乙烯,等等。 5 高分子专业英语选讲课文翻译资料 The length of the chain molecules, measured by means of the degree of polymerization, can be varied over a large range through selection of suitable reaction conditions. Usually, with commercially prepared and utilized polymers, the degree of polymerization lies in the range of 1000 to 5000, but in many cases it can be below 500 and over 10000. This should not be interpreted to mean that all molecules of a certain polymeric material consist of 500, or 1000, or 5000 monomer units. In almost all cases, the polymeric material consists of a mixture of polymer molecules of different degrees of polymerization. 借助于聚合度估算的分子链长,在一个大范围内可以通过选择适宜的反应条件被改变。通常,通过 大量地制备和利用聚合物,聚合度在1000,5000范围内,但在许多情况下可低于500、高于10000。 这不应该把所有聚合物材料的分子量理解为由500,或1000,或5000个单体单元组成。在几乎所有的 事例中,聚合物材料由不同聚合度的聚合物分子的混合物组成。 Polymerization, a chain reaction, occurs according to the same mechanism as the well-known chlorine-hydrogen reaction and the decomposition of phosegene. 聚合反应,链式反应,依照与众所周知的氯,气,-氢,气,反应和光气的分解机理进行。 The initiation reaction, which is the activation process of the double bond, can be brought about by heating, irradiation, ultrasonics, or initiators. The initiation of the chain reaction can be observed most clearly with radical or ionic initiators. These are energy-rich compounds which can add suitable unsaturated compounds (monomers) and maintain the activated radical, or ionic, state so that further monomer molecules can be added in the same manner. For the individual steps of the growth reaction one needs only a relatively small activation energy and therefore through a single activation step (the 6 高分子专业英语选讲课文翻译资料 actual initiation reaction) a large number of olefin molecules are converted, as is implied by the term “chain reaction”. Because very small amounts of the initiator bring about the formation of a large amount of polymeric material (1:1000 to 1:1000), it is possible to regard polymerization from a superficial point of view as a catalytic reaction. For this reason, the initiators used in polymerization reactions are often designated as polymerization catalysts, even though, in the strictest sense, they are not true catalysts because the polymerization initiator enters into the reaction as a real partner and can be found chemically bound in the reaction product ,i.e. ,the polymer, In addition to the ionic and radical initiators there are now metal complex initiators (which can be obtained, for example, by the reaction of titanium tetrachloride or titanium trichloride with aluminum alkyls), which play an important role in polymerization reactions (Ziegler catalysts) ,The mechanism of their catalytic action is not yet completely clear. 双键活化过程的引发剂反应,可以通过热、辐射、超声波或引发剂产生。用自由基型或离子型引发 剂引发链式反应可以很清楚地进行观察。这些是高能态的化合物,它们能够加成不饱和化合物,单体, 并保持自由基或离子活性中心 以致单体可以以同样的方式进一步加成。对于增长反应的各个步骤,每一 步仅需要相当少的活化能,因此通过一步简单的活化反应,即引发反应,即可将许多烯类单体分子转化 成聚合物,这正如连锁反应这个术语的内涵那样。因为少量的引发剂引发形成大量的聚合物原料,1, 1000,1,10000,,从表面上看聚合反应很可能是催化反应。由于这个原因,通常把聚合反应的引发剂 看作是聚合反应的引发剂,但是,严格地讲它们不是真正意义上的催化剂,因为聚合反应的催化剂进入 到反应内部而成为一部分,同时可以在反应产物,既聚合物的末端发现。此外离子引发剂和自由基引发 剂有的是金属络合物引发剂,例如,通过四氯化钛或三氯化钛与烷基铝的反应可以得到,,Z引发剂在聚 7 高分子专业英语选讲课文翻译资料 合反应中起到了重要作用,它们催化活动的机理还不是十分清楚。 UNIT 3 Step-Growth Polymerization 第三单元 逐步聚合 Many different chemical reactions may be used to synthesize polymeric materials by step-growth polymerization. These include esterification, amidation, the formation of urethanes, aromatic substitution, etc. Polymerization proceeds by the reactions between two different functional groups, e.g., hydroxyl and carboxyl groups, or isocyanate and hydroxyl groups. 许多不同的化学反应通过逐步聚合可用于合成聚合材料。这些反应包括酯化、酰胺化、氨基甲酸酯、 芳香族取代物的形成等。通过反应聚合反应在两种不同的官能团,如,羟基和羧基,或异氰酸酯和羟基 之间。 All step-growth polymerization fall into two groups depending on the type of monomer(s) employed. The first involves two different polyfunctional monomers in which each monomer possesses only one type of functional group. A polyfunctional monomer is one with two or more functional groups per molecule. The second involves a single monomer containing both types of functional groups. The synthesis of polyamides illustrates both groups of polymerization reactions. Thus, polyamides can be obtained from the reaction of diamines with diacids 所有的逐步聚合反应根据所使用单体的类型可分为两类。第一类涉及两种不同的官能团单体,每一 种单体仅具有一种官能团。一种多官能团单体每个分子有两个或多个官能团。第二类涉及含有两类官能 团的单种单体。聚酰胺的合成说明了聚合反应的两个官能团。因此聚酰胺可以由二元胺和二元酸的反应 或氨基酸之间的反应得到。 8 高分子专业英语选讲课文翻译资料 nH2N-R-NH2+nHO2C-R’-CO2H? H-(-NH-R-NHCO-R’-CO-)n-OH+(2n-1)H2O (3.1) or from the reaction of amino acids with themselves nH2R-CO2H? H-(-NH-R-CO-)n-OH+(n-1)H20 (3.2) The two groups of reactions can be represented in a general manner by the equations as follows A+B-B ?–[-A-A-B-B-]-A-B?–[-A-B-]- 两种官能团之间的反应一般来说可以通过下列反应式表示 反应式略 Reaction (3.1) illustrates the former, while (3.2) is of the latter type. 反应,3.1,说明前一种形式,而反应,3.2,具有后一种形式。 图3.1 逐步聚合的示意图 ,a, 未反应单体,,b,50%已反应,,c,83.3%已反应,(d) 100%已反应,虚线表示反应种类, Polyesterification, whether between diol and dibasic acid or intermolecularly between hydroxy acid molecules, is an example of a step-growth polymerization process. The esterification reaction occurs anywhere in the monomer matrix where two monomer molecules collide, and once the ester has formed, it, too, can react further by virtue of its still-reactive hydroxyl or carboxyl groups. The net effect of this is that monomer molecules are consumed rapidly without any large increase in molecular weight. Fig. 3.1 illustrates this phenomenon. Assume, for example, that each square in Fig. 3.a represents a molecule of hydroxy acid. After the initial dimmer molecules from (b), half the monomer molecules have 9 高分子专业英语选讲课文翻译资料 been consumed and the average degree of polymerization (DP) of polymeric species is 2. As trimer and more dimer molecules form (c), more than 80% of the monomer molecules have reacted (d), DP is 4. But each polymer molecule that forms still has reactive end groups; hence the polymerization reaction will continue in a stepwise fashion, with each esterification of monomers. Thus, molecular weight increases slowly even at high levels of monomer conversion, and it will continue to increase until the viscosity build-up makes it mechanically too difficult to remove water of esterification or for reactive end groups to find each other. 聚酯化,是否在二元酸和二元醇或羟基酸分子间进行,是逐步聚合反应过程的一个例子。酯化反 应出现在单体本体中两个单体分子相碰撞的位置,且酯一旦形成,依靠酯上仍有活性的羟基或羧基还可 以进一步进行反应。酯化的结果是单体分子很快地被消耗掉,而分子量却没有多少增加。图3.1说明了 这个现象。例如,假定图3.1中的每一个方格代表一个羟基酸分子。,b,中的二聚体分子,消耗二分之 一的单体分子聚合物种类的聚合度,DP,是2。,c,中当三聚体和更多的二聚体形成,大于80%的单体 分子已反应,但DP仅仅还是2.5。,d,中当所有的单体反应完,DP是4。但形成的每一种聚合物分子 还有反应活性的端基,因此,聚合反应将以逐步的方式继续进行,其每一步酯化反应的反应速率和反应 机理均与初始单体的酯化作用相同。因此,分子量缓慢增加直至高水平的单体转化率,而且分子量将继 续增加直到粘度的增加使其难以除去酯化反应的水或难以找到相互反应的端基。 It can also be shown that in the A-A+B-B type of polymerization, an exact stoichiometric balance is necessary to achieve high molecular weights. If some monofunctional impurity is present, its reaction will limit the molecular weight by rendering a chain end inactive. Similarly, high-purity monomers are necessary in the A-B type of polycondensation and it follows that high-yield reactions are the only 10 高分子专业英语选讲课文翻译资料 practical ones for polymer formation, since side reactions will upset the stoichiometric balance. 在A-A+B-B的聚合反应中也可以看到,精确的当量平衡是获得高分子量所必需的。假如存在一些 但官能团杂质,由于链的端基失活,反应将使分子量减少。同样,在A-B类的缩聚反应中高纯度的单体 是必要的,而且可以归结高收率的反应仅是形成聚合物的实际反应,因为副反应会破坏当量平衡。 -------Stevens M P. Polymer Chemistry. London: Addison-Wesley Publishing Company, 1975. 13 UNIT 4 Ionic Polymerization 第四单元 离子聚合反应 Ionic polymerization, similar to radial polymerization, also has the mechanism of a chain reaction. The kinetics of ionic polymerization are, however, considerably different from that of radical polymerization. 离子聚合反应,与自由基聚合反应相似,也有链反应的机理。但是,离子聚合的动力学明显地不同 于自由基聚合反应。 (1) The initiation reaction of ionic polymerization needs only a small activation energy. Therefore, the rate of polymerization depends only slightly on the temperature. Ionic polymerizations occur in many cases with explosive violence even at temperature. below 50?(for example, the anionic polymerization of styrene at –70? in tetrahydrofuran, or the cationic polymerization of isobutylene at –100? in liquid ethylene ). (1)离子聚合的引发反应仅需要很小的活化能。因此,聚合反应的速率仅对温度有较少的依赖性。在 许多情况下离子聚合猛烈地发生甚至低于50?,例如,苯乙烯的阴离子聚合反应在-70?在四氢呋喃中, 或异丁烯的阳离子聚合在-100?在液态乙烯中,。 11 高分子专业英语选讲课文翻译资料 (2) With ionic polymerization there is no compulsory chain termination through recombination, because the growing chains can not react with each other. Chain termination takes place only through impurities, or through the addition of certain compounds such as water, alcohols, acids, amines, or oxygen, and in general through compounds which can react with polymerization ions under the formation of neutral compounds or inactive ionic species. If the initiators are only partly dissociated, the initiation reaction is an equilibrium reaction, where reaction in one direction gives rise to chain initiation and in the other direction to chain termination. ,2,对于离子聚合来说,不存在通过再结合反应而进行的强迫链终止,因为生长链之间不能发生链 终止。链终止反应仅仅通过杂质而发生,或者说通过和某些像水、醇、酸、胺或氧这样的化合物进行加 成而发生,且一般来说,链终止反应,可通过这样的化合物来进行,这种化合物在中性聚合物或没有聚 合活性的离子型聚合物生成的过程中可以和活性聚合物离子进行反应。如果引发剂仅仅部分地离解,引 发反应即为一个平衡反应,在出现平衡反应的场合,在一个方向上进行链引发反应,而在另一个方向上 则发生链终止反应。 In general ionic polymerization polymerization can be initiated through acidic or basic compounds. For cationic polymerization, complexes of BF3, AlCl, TiCl, and SnCl with water, or alcohols, or 344 tertiary oxonium salts have shown themselves to be particularly active. The positive ions are the ones that cause chain initiation. For example: 通常离子聚合反应能通过酸性或碱性化合物被引发。对于阳离子聚合反应来说,BF,AlCl,TiCl和334 SnCl与水、或乙醇,或叔烊盐的络合物提供了部分活性。正离子是产生链引发的化合物。例如,(反应4 略) 12 高分子专业英语选讲课文翻译资料 三乙基硼氟酸烊 However, also with HCl, HSO, and KHSO, one can initiate cationic polymerization. Initiators for 244 anionic polymerization are alkali metals and their organic compounds, such as phenyllithium, butyllithium, phenyl sodium, and triphenylmethyl potassium, which are more or less strongly dissociated in different solvents. To this group belong also the so called Alfin catalysts, which are a mixture of sodium isopropylate, allyl sodium, and sodium chloride. 然而,BF也可以与HCl、HSO和KHSO引发阳离子聚合反应。阴离子聚合反应的引发剂是碱3244 金属和它们的有机金属化合物,例如苯基锂、丁基锂和三苯甲基锂,它们在不同的溶剂中或多或少地强 烈分解。所谓的Alfin催化剂就是属于这一类,这类催化剂是异丙醇钠、烯丙基钠和氯化钠的混合物。 With BF (and isobutylene as the monomer), it was demonstrated that the polymerization is 3 possible only in the presence of traces of traces of water or alcohol. If one eliminates the trace of water, BF alone does not give rise to polymerization. Water or alcohols are necessary in order to allow the 3 formation of the BF-complex and the initiator cation according to the above reactions. However, one 3 should not describe the water or the alcohol as a “cocatalyst”. BF为引发剂,异丁烯为单体,,证明仅在痕量水或乙醇的存在下聚合反应是可以进行的。如果消3 除痕量的水,单纯的BF不会引发聚合反应。按照上述反应为了能形成BF-络合物和引发剂离子水或乙33 醇是必需的。但是不应将水或乙醇描述成“助催化剂”。 Just as by radical polymerization, one can also prepare copolymers by ionic polymerization, for example, anionic copolymers of styrene and butadiene, or cationic copolymers of isobutylene and 13 高分子专业英语选讲课文翻译资料 styrene, or isobutylene and viny ethers, etc. As has been described in detail with radical polymerization, one can characterize each monomer pair by so-called reactivity ratios r and r. The actual values of 12 these two parameters are, however, different from those used for radical copolymerization. 正与自由基聚合反应一样,通过离子聚合反应也能制备共聚物,例如,苯乙烯-丁二烯阴离子共聚 物,或异丁烯-苯乙烯阳离子共聚物,或异丁烯-乙烯基醚共聚物,等等。正如对自由基型聚合已经详细描 述过那样,人们可以用所谓的竞聚率r和r来表征每单体对。然而,这两个参数的实际意义不同于那些12 用于自由基共聚合反应的参数。 ---Vollmert B. Polymer Chemistry. Berlin: Sping-Verlag, 1973.163 PART B 聚合反应工程 UNIT 11 Reactor types 第十一单元 反应器类型 Reactors may be categorized in a variety of ways, each appropriate to a particular perspective. For example, Henglein (1969) chooses a breakdown based on the source of energy used to initiate the reaction (i.e., thermal, electrochemical, photochemical, nuclear). More common breakdowns are according to the types of vessels and flows that exist. 反应器可以用许多方法分类,各自适用于特定的目的。例如,Henglein,1969,基于用于产生反应 的能量来源,即,热量,电化学,光化学,原子核,选择了一种细目分类。更多普通的细目分类是按照 所存在的容器和流量的类型。 1. Batch Reactors 14 高分子专业英语选讲课文翻译资料 1. 间歇反应器 The batch reactor (BR) is the almost universal choice in the chemist’s laboratory where most chemical processes originate. The reason is the simplicity and versatility of the batch reactor, whether it be a test tube, a three-neck flask, an autoclave, or a cell in a spectroscopic instrument. Regardless of the rate of the reaction, these are clearly low production rate devices. As scale up is desired, the most straightforward approach is to move to a larger batch reactor such as a large vat or tank. 间歇反应器在化学实验室几乎是一般的选择,大多数的化学过程在那里产生。间歇反应器的原理具 简单性和通用性,不管它是一支试管,一个三颈瓶,一个高压釜,还是一个光谱仪器的比色皿。不管反 应比例,很清楚这些是低产率设备。当要求放大反应器时,大多直截了当的途径是移至一个较大的间歇 反应器如一个较大的大桶或罐。 Commercial batch reactors can be huge, 100 000 gal or more. The cycle time, often a day or more, typically becomes longer as reactor volume increases in order to achieve a substantial production rate with an inherently slow reaction. Fabrication, shipping, or other factors place a limit the size of a batch reactor. For example, transportation capacity can limit the size of a batch reactor for which shop, as opposed to on-site, fabrication of the heat exchange surface is required. This limits the production rates for which batch reactors may be economically utilized. Also, batch reactors must be filled, emptied, and cleaned. For fast reactions these unproductive operations consume far more time than the reaction itself and continuous processes can become more attractive. 商业化的间歇反应器是庞大的,10万加仑或更大。对于慢化学反应,为提高生产率必须增加反应 器体积,而这往往导致反应器的循环周期变长,常常以天计算。制造、运输以及其他因素限制了反应器 15 高分子专业英语选讲课文翻译资料 的规模,如热传递能力会限制间歇反应器的尺寸,热交换器必须在制造厂而不是在现场加工。这限制了 产率由于这间歇反应器可以被经济地利用。间歇反应器也必须装料、卸料和清洗。为了加快反应这些非 生产性的操作消耗了多于反应本身的时间,连续化过程可能更有吸引力。 2. Semibatch Reactors (SBR) 2.半间歇反应器 Some reactions may yield a product in a different phase from the reaction mixture. Examples would be liberation of a gas from a liquid-phase reaction or the formation of a precipitate in a fluid-phase reaction. To drive the reaction to completion, it may be desirable to continuously separate the raw product phase. A semibatch operation may result as well from differing modes of feeding the individual reactants. For reasons we will discuss later, it may be desirable to charge one reactant to the reactor at the outset and bleed a second reactant in continuously over time. Such reactors have both a batch and a flow character and, like batch reactors, are useful for slow reactions and low production rates. 一些反应器可以从反应混合物的不同相态中生产出某种产品。例如液相反应中气体的释放,或流动 相反应中沉淀的生成。为了驱使反应完全,希望继续分离粗产物相。个别反应物的不同加入方式也导致 半连续操作。原因我们以后讨论,可希望一开始加入一种反应物以后连续加入第二种反应物。这类反应 器同时具有一个间歇和一个流动的特征,像间歇反应器,适用于慢反应和低产率。 3. Continuous Stirred Tank Reactors (CSTR) 3. 连续流动搅拌反应器 It is a small step from the batch reactor to the CSTR. The same stirred vessel may be used with 16 高分子专业英语选讲课文翻译资料 only the addition of piping and storage tanks to provide for the continuous in-and outflow. Faster reactions can be accommodated and larger production rates can be achieved because of the uninterrupted operation. CSTRs are most often used for liquid-phase reactions, such as nitration and hydrolysis, and multiphase reactions involving liquid with gases and/or solids. Examples would be chlorination and hydrogenation. 从间歇反应器到连续流动搅拌反应器是小小的一步。同样的搅拌式容器的使用可仅仅添加管道和储 罐以提供连续进料和出料。因为连续操作可加快反应并提高产率。通常大多数连续流动搅拌反应器用于 液相反应,例如硝化和水解,多相反应器涉及液-气和/或液-固。例如氯化和加氢。 4. CSTR in Series 4.多级串联连续流动搅拌反应器 It was shown that considerable gains in production rate and economics can be achieved by passing the reacting mixture through a series of CSTRs. Again, we see how easy it is to achieve a gradual scale up, say for a specialty chemical for which is increasing. CSTRs in series are usually used for liquid-phase reactions. 事实证明通过一系列多级串联连续流动搅拌反应器的混合能够获得高产率和重大的经济效益。再者, 这种反应器容易放大,例如某种化学品的需求逐步增加时常这样做。多级串联连续流动搅拌反应器通常 用于液相反应。 5.Tubular Reactors 5.管式反应器 As the production rate requirement increases, batteries of CSTRs become increasingly complex 17 高分子专业英语选讲课文翻译资料 and tubular reactors become attractive. With the transition to tubular reactors, some versatility is lost and more process integration is required. Nevertheless, tubular reactors find extensive application in liquid-phase reactions, for example, polymerization, and are almost always the continuous reactor of choice for gas-phase reactions, for example, pyrolysis. Exceedingly high production rates can be achieved with tubular reactors either by increasing the diameter of the tube or more commonly by using a sufficient number of tubes in parallel. 当产率需要增加时,增加许多套连续搅拌式反应器变得复杂,而管式反应器变得诱人。转化成管式 反应器失去了一些通用性并要求综合许多操作。尽管如此,管式反应器在液相反应中起着广泛作用,例 如,聚合反应,气-液反应几乎总是选择连续反应器,例如,高温裂解。采用管式反应器能够获得非常高 的产率,要么增加管的直径要么通过使用充足数量的并列管提高更大的通用性。 6. Recycle reactors 6. 循环反应器 Recycle reactor can be batch, CSTR, tubular, and so on in nature with the purpose of the recycle varying from one case to the next. Many large-scale commercial processes incorporate the recycle of one or more streams back to an earlier point in the process to conserve raw materials. This practice often results in the accumulation of impurities, which in turn requires separation. Usually it is not simply the reactor outlet stream that is recycled back to the reactor inlet, but it can be. For example in a batch reactor the reacting mixture can be recycled, or pumped around, through a heat exchanger to provide thermal control. 循环反应器出于从一种情况到下一种情况循环变化的目的,在种类上可以是间歇反应器、连续流动 18 高分子专业英语选讲课文翻译资料 搅拌反应器、管式反应器等等。回到较早的观点,在节省粗原料的过程中,许多大规模的商业操作合并 了一个或多个循环。这一实践通常导致了杂质的累积,它们依次需要分离。通常不是简单地将反应器的 出料返回到入口,当然也可以这样做。例如,在间歇反应器中反应混合物可以回收,或用泵打循环,通 过热交换器控制热。 Recycle reactor have also found valuable application in the laboratory and pilot plant because of their special characteristics. At one extreme, in which all of the product is recycled (no net flow), the reactor is the exact equivalent of the well-stirred batch reactor. At the other extreme of no recycle, the reactor is simply the tubular variety. If there is some net flow but the recycle rate is high, the overall reactor performs like a CSTR. Yet the reaction tube itself behaves like differential tubular reactor. This versatility of the recycle reactor can be exploited to great advantage in research and development. 循环反应器由于其特殊的特性在实验室和中试车间也发现了应用价值。一个极端是将所有的产物循 环,没有净的流出,,此时循环反应器严格等效于全混间歇反应器。另一个极端是没有循环,反应器是简 单的管式类。假如有一些净的流出但循环率很高,所有的反应器运行类似于连续流动搅拌反应器。然而 反应器本身的 类似于不同的管式反应器。在研究和发展中循环反应器的通用性能够开发出更大的优点 ,势,。 ——Bisio A. , Kabel R L. Scaleup of Chemical Processes. New York: John Wiley & Sons Inc. , 1985. 255~257 T 14 Styrene-Butadiene Copolymer 第十四单元 丁二烯-苯乙烯共聚物 The synthetic rubber industry, based on the free-radical emulsion process, was created almost 19 高分子专业英语选讲课文翻译资料 overnight during World War II. Styrene-butadiene (GR-S) rubber crated at that time gives such good tire treads that natural rubber has never regained this market. 合成橡胶工业,以自由基乳液过程为基础,在第二次世界大战期间几乎很快地形成。那时,丁苯橡 胶制造的轮胎性能相当优越,使天然橡胶在市场黯然失色。 The GR-S standard recipe is 丁苯橡胶的标准制法是 组分 重量分数 组分 重量分数 丁二烯 72 过硫酸钾 0.3 苯乙烯 25 肥皂片 5.0 十二烷基硫醇 0.5 水 180 This mixture is heated with stirring and at 50? gives conversions of 5%~6% per hour. Polymerization is terminated at 70%~75% conversion by addition of a “short-stop”, such as hydroquinone (approximately 0.1 part), to quench radicals and prevent excessive branching and microgel formation. Unreacted butadiene is removed by flash distillation, and syrene by steam-stripping in a column. After addition of an antioxidant, such as N-phenyl-β-naphthylamine (PBNA) (1.25 parts), the latex is coagulated by the addition of brine, followed by dilute sulfuric acid or aluminum sulfate. The 20 高分子专业英语选讲课文翻译资料 coagulated crumb is washed, dried, and baled for shipment. 混合物在搅拌下50?加热,每小时转化5%,6%,在转化率达70%,75%时通过加入“终止剂” 聚 合反应终止,例如对苯二酚,大约0.1的重量百分含量,,抑制自由基并避免过量支化和微凝胶形成。未 反应的丁二烯通过闪蒸去除,苯乙烯在萃取塔中通过蒸汽萃取,剥离,。在加入抗氧剂后,例如N-甲基- β-萘胺,1.25的重量百分含量,,加入盐水,其次加入稀释的硫酸或硫酸铝后乳液凝胶。凝胶碎片被洗涤、 干燥并包装装运。 Fig.14.1 SBR plant flow diagram Courtesy of Hydrocarbon Processing and Petroleum Refiner. 图14.1 丁苯橡胶厂 流程图 破产流程图 免费下载数据库流程图下载数据库流程图下载研究框架流程图下载流程图下载word 取自烃类加工和石油产品精制 This procedure is still the basis for emulsion polymerization today. An important improvement is continuous processing illustrated in Fig. 14.1; computer modeling has also been described. 今天这种生产过程仍是胶体聚合反应的基础。如图14.1所示一个重要的进步是连续操作,也采用计 算机模型描述。 In the continuous process, styrene, butadiene, soap, initiator, and activator (an auxiliary initiating agent) are pumped continuously form storage tanks through a series of agitated reactors at such a rate 21 高分子专业英语选讲课文翻译资料 that the desired degree of conversion is reached at the last reactor. Shortstop is added, the latex warmed with steam, and the unreacted butadiene flashed off. Excess styrene is steam-stripped, and the latex finished as shown in Fig. 14.1. 在连续操作中,苯乙烯、丁二烯、肥皂、引发剂和活化剂,一种助引发剂,用泵从储罐通过一系列的混合反应器,泵送流率根据末釜的转化率控制。加入终止剂,乳液用蒸气加热,未反应的丁二烯被闪蒸。剩余的苯乙烯被蒸气剥离,如图14.1表示乳液完成。 表14.1 冷丁苯胶的典型配方 组分 配方1 配方2 丁二烯 72 71 苯乙烯 28 29 特十二烷基硫醇 0.2 0.18 过氧化二异丙苯 0.08 22 高分子专业英语选讲课文翻译资料 过氧化薄荷烷 0.08 硫酸亚铁七水合物 0.14 0.03 焦磷酸钾 0.18 磷酸钠十水合物 0.5 乙二胺四乙酸钠 0.035 甲醛次硫酸钠 0.08 松香酸 4.0 4.5 水 180 200 SBR prepared from the original GR-S recipe is often called hot rubber; cold rubber is made at 5? by using a more active initiator system. Typical recipes are given in Table 14.1 At 5? ,60% conversion to polymer occurs in 12~15h. 由常规丁苯制法制备的丁苯胶常称作热胶,冷胶通过使用一种更高活性的引发体系在5?制成。典 型的配方在表14.1中给出。5?、60%转化率、12,15 h聚合物形成。 Cold SBR tire treads are superior to those of hot SBR. Polymers with abnormally high molecular weight (and consequently too tough to process by ordinary factory equipment) can be processed after the addition of up to 50 parts of petroleum-base oils per hundred parts of rubber (phr). These oil extenders make the rubbers more processible at lower cost and with little sacrifice in properties; they are usually emulsified and blended with the latex before coagulation. 23 高分子专业英语选讲课文翻译资料 冷丁苯橡胶轮胎优于那些热丁苯胶。具有异常高的分子量的聚合物,因此采用常规的工厂设备由于 太粘稠而难以加工,在每一百份的橡胶中加入大于50份的石油基础油后能够加工。这些油添加剂使橡胶 更易加工体现在低成本和性能方面低损耗,他们在凝胶之前通常乳化并与胶乳混合。 Recent trends have been toward products designed for specific uses. The color of SBR, which is important in many nontire uses, has been improved by the use of lighter-colored soaps, shortstops, antioxidants, and extending oils. For example, dithiocarbamates are substituted for hydroquinone as shortstop; the latter is used on hot SBR where dark color is not objectionable. A shortstop such as sodium dimethyldithiocarbamate is more effective in terminating radicals and destroying peroxides at the lower temperatures employed for the cold rubbers. 最近倾向于 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 特殊用途的产品。丁苯橡胶的颜色,在许多非轮胎使用中十分重要,通过使用浅 色的肥皂、终止剂、抗氧剂和扩展油加以改进。例如,二硫化氨基甲酸盐替代对苯二酚作为终止剂,后 者适用于不被人反对的黑色丁苯橡胶。在冷胶的制备中如二硫化氨基甲酸钠的终止剂在低温情况下对终 止自由基和消灭过氧化物更有效。 Free-radical dissociative initiators that function by dissociation of a molecule or ion into two radical species are normally limited to inorganic persulfates in the case of butadiene polymerization. 在丁二烯聚合反应过程中自由基分解的引发剂即一分子分解或离子成两个自由基物种的引发剂通 常限制于过硫酸盐。 The other important class of free-radical initiators, redox systems, contain two or more components that react to produce free radicals. Dodecyl mercaptan added to control molecular weight also appears to aid free-radical formation by reaction with persulfate. The commercial importance of 24 高分子专业英语选讲课文翻译资料 such chain-transfer agents or modifiers cannot be overemphasized. Without molecular weight control the rubbers would be too tough to process. 其他重要的自由基引发剂类别,氧化还原体系,包含反应产生自由基的两种或多种组分。加入控 制分子量的十二烷基硫醇与过硫酸盐反应也出现了助自由基的形成。这种链转移剂或调节剂具有极其重 要的商业价值。不控制分子量橡胶将过于粘稠难以加工。 --------Tate D p , Bechea T W. Encyclopedia of Polymer Science and Engineering, 2nd ed. Vol. 2. Editor-in-chilf Kroschwitz JI. New York: John wiley & Sons, 1985. 553~555 C 聚合物材料的加工、性能和应用 UNIT 21 Polymer Processing 第二十一单元 聚合物加工 Polymer processing , in its most general context , involves the transformation of a solid ( sometimes liquid ) polymeric resin , which is in a random form (e. g. powder, pellets , beads ), to a solid plastics product of specified shape , dimensions , and properties. This is achieved by means of a transformation process: extrusion, molding, calendering , coating , thermoforming , etc. The process, in order to achieve the above objective, usually involves the following operations: solid transport , compression, heating, melting, mixing, shaping, cooling, solidification, and finishing . Obviously, these operations do not necessarily occur in sequence, and many of them take place simultaneously. 在其最一般的情况下,聚合物加工涉及固体,有时侯是液体,聚合物树脂以一种不规则的形式,例 如粉末、颗粒、珠子,转化成一种具有特殊形状、尺寸和性能的固体塑料产品。这借助于转换加工,挤 25 高分子专业英语选讲课文翻译资料 出、模塑、压延、涂敷、热成型等。为了获得上述目的,加工通常涉及下述操作,固体输送、压缩、加 热、混合、成型、冷却、固化并完成。显然,这些操作不必按序发生,而许多可以同时发生。 Shaping is required in order to impart to the material the desired geometry and dimensions. It involves combinations of viscoelastic deformations and heat transfer, which are generally associated with solidification of the product from the melt. 成型是为了给予材料所需要的几何形状和尺寸。它涉 及粘弹形变和热传递,这种粘弹形变和热传递是和产品从熔体的固化,或冷却,相联系的。 Shaping includes : (1) two-dimensional operations , e.g. dieforming, calendering and coating , and (2) three-dimensional molding and forming operations. Two-dimensional processes are either of the continuous , steady state type )e.g. film and sheet extrusion , wire coating , paper and sheet coating ,calendering ,fiber spinning , pipe and profile extrusion , etc. ) or intermittent as in the case of extrusions associated with intermittent extrusion blow moulding. Generally, moulding operations are intermittent, and, thus, they tend to involve unsteady state conditions. Thermoforming, vacuum forming, and similar processes may be considered as secondary shaping operations, since they usually involve the reshaping of an already shaped form. In some cases, like blow molding, the process involve primary shaping (parison formation) and secondary shaping (parison inflation ). 成型包括,,1,二元操作,例如,口模成型、压延和涂敷,,2,三元的模型和成型操作。二元的操 作要么是连续的,固定形状,例如薄膜和板材,电线涂布,纸和平面涂布,压延,纤维拉伸,管材和型 材挤出等等。, 要么是间歇式的,在挤出的情况下伴有间歇挤出吹膜。通常,模塑操作是间歇的,然而 同时倾向于非固定条件。热成型,真空成型,和相似的加工可以认为是二次成型操作,因为它们通常包 26 高分子专业英语选讲课文翻译资料 括已成型形状的再次成型。在某些情况下像吹模,加工包括首次成型,型胚成型,和二次成型,型胚膨 胀,。 Shaping operations involve simultaneous or staggered fluid flow and heat transfer. In two-dimensional processes, solidification usually follows the shaping process, whereas solidification and shaping tend to take place simultaneously inside the mold in three dimensional processes. Flow regimes, depending on the nature of the material, the equipment, and the processing conditions, usually involve combinations of shear, extensional, and squeezing flows in conjunction with enclosed (contained) or free surface flows. 成型操作包括同时或交叉的液体流动和热传递。在二元加工中,固化,或冷却,伴随着成型加工, 反之在三元加工的模塑中固化 ,或冷却,和成型倾向于同时发生。根据材料的性质、设备和加工条件, 流动状态以及根据流动面的自由与否,通常包括剪切、延伸和挤压流动。 The thermo-mechanical history experienced by the polymer during flow and solidification results in the development of microstructure (morphology, crystallinity, and orientation distributions) in the manufactured article. The ultimate properties of the article are closely related to the microstructure. Therefore, the control of the process and product quality must be based on an understanding of the interactions between resin properties, equipment design, operating conditions, thermo-mechanical history, microstructure, and ultimate product properties. Mathematical modeling and computer simulation have been employed to obtain an understanding of these interactions. Such an approach has gained more importance in view of the expanding utilization of computer aided design/computer assisted manufacturing/computer aided engineering (CAD/CAM/CAE) systems in conjunction with 27 高分子专业英语选讲课文翻译资料 plastics processing. 经历了流动和固化,或冷却,的聚合物热机械过程导致了制造业微结构的变革,形态学、结晶学和 取向分布,。最终产品的性能与微结构紧密相关。因此,加工和产品质量的控制必须基于树脂性能、设备 设计、操作条件、热机械过程、微结构和最终产品性能之间相互作用的理解。数学模型和计算机被同时 用于获得这些相互作用的理解。鉴于进一步利用计算机辅助设计/计算机辅助制造/计算机辅助工程 ,CD/CAM/CAE,系统协同塑料加工诸如这一趋近获得了更多的重要性。 The following discussion will highlight some of the basic concepts involved in plastics shaping operations. It will emphasize recent developments relating to the analysis and simulation of some important commercial processes, with due consideration to elucidation of both thermo-mechanical history and microstructure development. More extensive reviews of the subject can be found in standard references on the topic (1~6). 下面的讨论将重点放在包括塑料成型操作一些基本概念上。适当考虑说明热机械过程和微结构发 展,将强调最近关于分析和一些重要商品加工模型的进展。在上端,1,6,的标准参考中能够找到本主 题更广泛的综述。 As mentioned above, shaping operations involve combinations of fluid flow and heat transfer, with phase change, of a visco-elastic polymer melt. Both steady and unsteady state processes are encountered. A scientific analysis of operations of this type requires solving the relevant equations of continuity, motion, and energy (i.e. conservation equations). 如上面提到的,成型操作包括液体流动和热传递,对于相态变化,还包括粘弹性聚合物的熔融。稳 定和非稳定状态加工是相冲突的。这种典型操作的科学分析需要解决相关连续、运转和能量平衡,如守 28 高分子专业英语选讲课文翻译资料 恒方程,。 —— Austarita G , Nicolas L. Polymer prscessing and properties New York: Plenum press 1984, 1~3 UNIT 29 Synthetic Plastics 第二十九单元 合成塑料 It would be difficult to visualise our modern world without plastics. Today they are an integral part of everyones lifestyle with applications varying from commonplace articles to sophisticated scientific and medical instruments. Nowadays designers and engineers readily turn to plastics because they offer combinations of properties not available in any other materials. Plastics offer advantages such as lightness , resilience , resistance to corrosion , colour fastness , transparency , ease of processing , etc. , and although they also have their limitations , their exploitation is limited only by the ingenuity of the designer. 现代社会没有塑料真是难以想象。今天它们是组成每个人生活的必备部分,从不断变化的平凡物品 到尖端科技的医学仪器。当今的设计师和工程师已开始着手塑料的研究,因为它们提供了不能应用于任 何其它材料的综合性能。塑料所呈现的优点诸如质轻、弹性、防腐、不易褪色、透明性、易于加工等等, 尽管也有它们的制约,它们的开发仅因设计师的创造力受到限制。 It is usual to think that plastics are a relatively recent development but in fact, as part of the larger family called “polymers”, they are a basic ingredient of plant and animal life. Polymers are materials 29 高分子专业英语选讲课文翻译资料 which consist of very long chain-like molecules. Natural materials such as silk, shellac, bitumen, rubber thand cellulose have this type of structure. However, it was not until the 19 century that attempts were made to develop a synthetic polymeric material and the first success was based on cellulose. This was a material called “Parkesine”, after its inventor Alexander Parkes, and although it was not a commercial success it was a start and eventually led to the development of “Celluoid”. This material was an important break-through because it became established as a good replacement of natural materials which were in short supply . 通常认为塑料是一种相对新的发展,但事实上作为 “聚合物”大家族的成员,它们是动植物生活的一 个基本组成部分。聚合物是由象链一样非常长的分子组成的材料。象丝、虫胶、沥青、橡胶和纤维素之 类的天然材料有这种类型的结构。然而,直到19世纪才尝试开发了一种合成聚合物材料,首次成功基于 赛璐珞。这是一种叫做“硝化纤维素塑料”的材料,它的发明者是Alexander Parkes ,尽管不是一种开始的 商业成功,最终导致了“赛璐珞”的发展。这种材料是一个重要的突破因为它成为了供应短缺的天然材料的 良好替代品。 During the early twentieth century there was considerable interest in these new synthetic materials. Phenol-formaldehyde (“bakelite”) was introduced in 1905 and about the time of the second World War materials such as nylon, polyethylene and acrylic (“Perspex”) appeared on the scene. Unfortunately many of the early applications for plastics earned them a reputation as being cheap substitutes. It has taken them a long time to overcome this image but nowadays the special properties of plastics are being appreciated which is establishing them as important materials in their own right. The ever increasing use of plastics in all kinds of applications means that it is essential for designers and 30 高分子专业英语选讲课文翻译资料 engineers to become familiar with the range of plastics available and the types of performance characteristics to be expected so that they can be used to the best advantage. 二十世纪初,人们十分关注这些新合成材料。酚醛树脂,“电木粉”,于1905年问世,大约在第二次 世界大战期间象尼龙、聚乙烯和丙烯酸类,“有机玻璃”,的材料相继出现。可惜塑料的许多早期应用带来 的是廉价代用品的名声。这种印象花费了长久的时间才被消除,但如今,塑料的特性正在被人们认识到, 而塑料也正在确立它们作为重要材料的地位。塑料在各种应用中的用途不断增加,这意味着对于设计师 和工程师来说,通晓塑料应用的范围和预期的性能特征是十分必要的,以致能以最好的方式利用它们。 The words “polymers” and “plastics” are often taken as synonymous but in fact there is a distinction. The polymer is the pure material which results form the process of polymerisation and is usually taken as the family name for materials which have long chain-like molecules and this includes rubber. Pure polymers are seldom used on their own and it is when additives are present that the term plastic is applied. Polymers contain additives for a number of reasons. In some cases impurities are present as a result of the polymerisation additives such as stabilisers, lubricants, fillers, pigments, etc., are added to enhance the properties of the material. 单词“聚合物”和“塑料”通常被看作是同义的,但事实上是有区别的。聚合物是缘于聚合反应过程的 纯物质,常常被看作具有长链分子材料的系列名称,这也包括橡胶。纯的聚合物很少独自使用,当存在 添加剂时它适用于专有名词塑料。由许多原因聚合物含有添加剂。在某些情况下作为聚合反应的结果存 在杂质,去除这些杂质以获得纯的聚合物可能是不经济的。在其它情况下,添加象稳定剂、润滑剂、填 充剂、颜料等之类的添加剂,以增强材料的性能。 There are two important classes of plastics: 31 高分子专业英语选讲课文翻译资料 有两种重要类别的塑料, (1) Thermoplastic materials. In a thermoplastic material the long chain-like molecules are held together by relatively weak Van der Waals forces. A useful image of the structure is a mass of randomly distributed long strands of sticky wool. When the material is heated the intermolecular forces are weakened so that is becomes soft and flexible and eventually, at high temperatures, it is a viscous melt. When the material is allowed to cool it solidifies again. This cycle of softening by heat and solidifying when cooled can be repeated more or less indefinitely and is a definite advantage in that it is the basis of most processing methods for these materials. It does have its drawbacks, however, because it means that the properties of thermoplastics are heat sensitive. A useful analogy which is often used to describe these materials is that like candle wax they can be repeatedly softened by heat and will solidify when cooled. ,1, 热塑性材料。在热塑性材料中象长链一样的分子间力是相对较弱的范德华力。对于结构 一个有效的比喻是一大团自由分布的粘性纤维长线。当材料被加热时,内部的分子作用力变弱,以致变 得柔软和柔韧,最终在高温下,成为粘性熔融体。当材料被冷却时再次固化。加热软化、冷却固化大体 上能反复多次地循环,对于材料这是一个明显的优点,也是许多加工方法的基础。然而,热塑性材料的 确有其缺点,因为这意味着热塑性塑料的特性是热敏的。常常用于描述这些材料的有效比拟是象烛蜡加 热能够反复软化而当冷却时又将固化。 Examples of thermoplastics are polyethylene, polyvinyl chloride, polystyrene, nylon, cellulose acetate, acetal, polycarbonate, polymethyl methacrylate and polypropylene. 热塑性塑料的例子是聚乙烯、聚氯乙烯、聚苯乙烯、尼龙、醋酸纤维素、聚甲醛、聚碳酸酯、聚甲 32 高分子专业英语选讲课文翻译资料 基丙烯酸甲酯和聚丙烯。 (2) Thermosetting materials. A thermosetting material is produced by a chemical reaction which has two stages. The first stage results in the formation of long chain-like molecules similar to those present in thermoplastics, but still capable of further reaction. The second stage of the reaction takes place during moulding, usually under the application of heat and pressure. The resultant moulding will be rigid when cooled but a close network structure has been set up within the material. During the second stage the long molecular chains have been interlinked by strong bonds so that the material cannot be softened again by the application of heat. If excess heat is applied to these materials they will char and degrade. This type of behaviour is analogous to boiling an egg. Once the egg has cooled and is hard, it cannot be softened again by the application of heat. ,2, 热固性材料。热固性材料是通过两步化学反应生产而来的。第一步形成类似于存在于热 塑性塑料中象长链一样的分子形式,但还能够进一步反应。第二步反应在模塑时发生,通常在加热加压 条件下进行。当冷却时最终的模塑将是刚硬的,但在材料中建立了封闭的网状结构。在第二步反应中长 分子链通过强键相互连接,所以材料加热不再软化。如果将这些材料超高温加热将炭化并分解。这种行 为类似于煮熟的鸡蛋。一旦鸡蛋冷却则变硬,加热不能再次软化。 Since the cross-linking of the molecules is by strong chemical bonds thermosetting materials are characteristically quite rigid materials and their mechanical properties are not heat sensitive. Examples of thermosets are phenol formaldehyed, melamine formaldehyde, urea formaldehyde, epoxies and some polyesters. 因为由强化学键交链的热固性塑料十分刚硬,它们的机理性能不是热敏的。热固性塑料的例子是 33 高分子专业英语选讲课文翻译资料 酚醛树脂、胺醛树脂、脲醛树脂、环氧树脂和一些聚酯。 34