高分子专业英语课文翻译(5)

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。

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,