高分子专业英语UNIT 10

1、UNIT 10 Tb脆化温度 Tg玻璃化温度Tf黏流温度 Td分解温度第一段An ordinary rubber ball if cooled below -70 becomes so hard and brittle(易碎的） that it will break into pieces like a glass ball falling on a hard surface!设想一个普通的橡胶球在零下70摄氏度冷却会变得如此硬而脆以至于像一个玻璃球摔碎在坚硬的表面成碎片。Why does a rubber ball become like glass below -70?This is be

2、cause there is a “temperature boundary（范围）” for almost all amorphous（无定形的） polymers (and many crystallinepolymers结晶聚合物) only above which the substance remains soft,flexible(柔软的） and rubbery（橡胶状的） and below which it becomes hard,brittle and glassy.这是因为对于几乎所有的无定型聚合物（和许多结晶聚合物）有一个温度范围，这个范围存在于软的，橡胶状物质之上，

3、变成硬而脆，玻璃态的物质以下。 This temperature ,below which a polymer is hard and above which it is soft,is called the “glass transition temperation” Tg.这个温度被称为“玻璃化转变温度Tg” ，低于该聚合物是硬的，高于是软的。The hard,brittle state is known as the glassy state（玻璃态 ）and the soft,flexible state as the rubbery or viscoelastic state（黏弹态

4、）.坚硬，易碎的状态被称为玻璃态和温和的，柔软的状态为橡胶或黏弹态。On further heating,the polymer(if it is uncross-linked非交联的)becomes a highly viscous（黏的） liquid and starts flowing;this state is termed viscofluid state(黏流态）,and the another transition takes place at its flow temperature Tf.再进一步加热，聚合物（如果是非交联的）成为一个高粘性液体开始流动；这种状态称为黏流态，

5、另一个转化发生在流动温度Tf。第二段Now，let us consider a polymer，say，polyethylene（聚乙烯）. At room temperature，polyethylene is solid，exhibiting all characterisitics of a low molecular weight substance. 现在,让我们考虑一种聚合物,就说聚乙烯。在室温下,聚乙烯是固态的,表现出的所有的分子量本质的特性。At high temperatures，however，the characteristic difference between hi

6、gh and low molecular weight substance can be seen. 然而,在高温下,这个特性的差异在高、低分子量本质中可以看到。Deepending on（根据）the temperature，the molectures of a low molecular weight substance either move apart（分开，分离，移开）as a whole or do not move at all，i. e. ，there is a definite temperature ( melting point Tm ) below which the

7、 molecules do not move and above which they do move.根据温度,低分子量的物质要么整个分子移开,要么根本不运动,有一个特定的温度(熔点Tm)在低于这一温度时分子不运动,而在高于这一温度时分子则运动。On the other hand，with polymers，if the temperature increases above Tg，localized units ( chain segments 链段) within the long chain molecture are first mobilized（运动，流动）before the

8、whole molecture starts moving. 在另一方面,对于聚合物如果温度高于Tg,在长分子链里的局部单元（链段）在整个分子开始运动之前先运动。In some parts within the molecule,there is aconsiderable localized motion，but not in other parts of the same molecture.在分子中的某些部分,有一个重要的局部运动,但是不同于这个分子的其他部分。Thus，within the long chain of the polymer molecule，some segments

9、 have a certain freedom of movement，whereas others do not.因此,在聚合物的长链中,一些链段有确定的有规则的运动,而其他的不会这样。The molecule as a whole（作为一个整体，整体上）does not move although some of its segments do.分子作为一个整体不动,尽管分子的一些链段可以动。第三段In the case of polymers, there is indeed an intermediate（中间的） state. If the temperature ranges be

10、tween Tg and Tf, the localized mobility（局部的流动） is activated（被激活）, correspond to（相当于） the mobility is not. 在聚合物的情况下，确实是一个中间状态。如果温度范围之间的Tg和Tf，局部流动被激活，与流动性不对应。The local segments（局部链段）, where mobility is already activated, correspond to the liquid state, while the molecule as a whole, where mobility is

11、forbidden（被禁止的）, is in the solid state. 在一条分子链上某些流动性已经被激活的局部链段相对应着流体状态，而没有被完全激活的整体分子则处于固体状态。This state,which is really a combination of liquid and solid,is called the rubbery state. 这个状态，真的是一个液体和固体的组合，称为橡胶态。Under the influence of an applied stress, it exhibits properties（属性） of a viscous fluid （粘性的流

12、体）as well as an elastic（弹性的） solid and undergoes（经历） what is called viscoelastic deformation（变形）. 在外加应力的作用下，聚合材料既显示出黏性液体的性质，也显示出弹性固体的性质，并发生所谓的黏弹形变。第四段The glass transition temperature Tg is an important parameter（参数） of a polymeric material.玻璃的转变温度Tg是聚合材料的一个重要参数。The Tg value of a polymer decides whet

13、her a polymer at the “use temperature” will behave like rubber or plastics.这个Tg表明，聚合物是否在这个“可用的温度”决定着聚合物是橡胶态或是塑料态。The Tg value along with （连同）the Tm value gives an indication of （表明）the temperature region（范围） at which a polymeric material trasforms from（由转变成） a rigid（坚硬的） solid to a soft viscous state.Tg值和Tm值表明了一个温度范围，在这个范围内聚合材料会由刚性固体变成黏流态。This helps in choosing the right processing temperature, i. e. , the temperature region in which