专业英语复习2012.docVIP

Adventitious(偶然) branching sometimes occurs as a result of an atom being abstracted(被夺取) from the original linear molecule, with chain growth occurring from the resulting active site.Molecules with this kind of accidental(偶然) branching are generally still called linear, although the presence of significant branching(支化) has profound effects on some properties of the polymer, most notably the tendency(趋向) to undergo crystallization. 有时，当线性分子的某个原子被夺取时就会生成反应活性点，同时发生链增长，这就导致了偶然支化反应。尽管这种发生偶然支化的分子带有对聚合物性能（特别是结晶性）有巨大影响的支链，但它依然是线性的 The moment we admit the possibility of having more than one kind of repeat unit,we require additional(额外的) variables to describe the polymer.First,we must know how many kinds of repeat units are present and what they are.This is analogous(类似的) to knowing what components are present in a solution,although the similarity ends there,since the repeat units in a polymer are bonded together and not merely(仅仅) mixed. 考虑到可能不止一种重复单元，我们需要额外的变量来描述聚合物。首先,我们必须知道多少种重复单元存在以及它们分别是什么。这和我们要去了解溶剂中的化合物的种类和数量是相似的，尽管有着一定的相似性，但是不同的是，聚合物的重复单元不仅仅是简单的混合，还有键合作用。Chain termination takes place only through impurities, or through the addition of certain compounds(化合物) such as water, alcohols, acids, amines, or oxygen, and in general through compounds(化合物) which can react(反应) with polymerization ions under the formation(形式) of neutral compounds or inactive ionic species. 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。 Different average molecular weights are obtained because the properties being measured are biased(偏差) differently toward the different sized polymer molecules in a polymer sample. （对同意聚合物）得到了不同的平均分子量，因为所测得的性质对试样中不同尺寸的聚合物分子有不同的偏差。 The folded-chain lamella(片晶) theory arose in the late 1950s when polymer single crystals in the form of thin platelets termed lamella were grown from polymer solutions. 1950年以来，从聚合物溶液中得到了以片状晶体形式生成的单晶（即片晶），折叠链片晶理论诞生。 The extent and type of crystallinity in a polymer