英语翻译This review attempts to highlight the most significant aspects of PVC stabilisation by organotin compounds and to present a critical view of some of the work already published in this area.The review largely,but not exclusively,covcrs the

英语翻译This review attempts to highlight the most significant aspects of PVC stabilisation by organotin compounds and to present a critical view of some of the work already published in this area.The review largely,but not exclusively,covcrs the
英语翻译
This review attempts to highlight the most significant aspects of PVC stabilisation by organotin compounds and to present a critical view of some of the work already published in this area.The review largely,but not exclusively,covcrs the period from approximately 1980 onwards.
MECHANISMS OF PVC DECOMPOSITION
Unquestionably PVC decomposes by the elimination of HCl to give conjugated polyene sequences.These give rise to the characteristic discoloration and the loss of physical properties which is largely associated with cross-linking (Scheme I).Different groups of workers,however,appear to attach varying degrees of significance to the two main decomposition mechanisms.This is the‘ionic’ versus ‘free radical’ controversy which has now persisted for some time.Essentially the ionic mechanism for dehydrochlorination is based on the presence of unstable entities within the polymer characterised by an active chlorine group.There is even argument as to the nature of the major decomposition centre.The majority of opinion,however,favours the allylic chlorine entity (1) (Scheme 2) The C-CI bond in this group is susccptible to ionisation and,therefore,to the elimination of HCl.Ionisation of the so-formed allylic species (2) will then be even more facile due to enhanced resonance stabilisation of the resultant positive ion.The review by Minsker et al.suggests that the keto-chloroallylic group (3) may be even more susceptible to dehydrochlorination with the rate constant for this reaction being a factor of 102-103 greater than the same process with the simple chloroallylic group (1).Hjertberg and Sorvik have,however,concluded that there is little evidence for the existence of (3) in commercially produced PVC.

英语翻译This review attempts to highlight the most significant aspects of PVC stabilisation by organotin compounds and to present a critical view of some of the work already published in this area.The review largely,but not exclusively,covcrs the
译：本次审查试图突出的最重要方面的聚氯乙烯稳定的有机锡化合物,提出一个重要观点的一些工作已发表在这一领域.审查主要是,但不完全,covcrs期间大约从1980开始.聚氯乙烯分解机制毫无疑问,聚氯乙烯分解的消除盐酸给共轭多烯序列.这些导致特征变色和损失的物理性能,主要是与交联（计划）.不同的工人群体,然而,似乎附加意义的不同程度的2个主要分解机制.这是the'ionic '与'自由基'的争论,已经持续了一段时间.本质上的离子机制,脱氯化氢的基础是存在的不稳定的实体内的聚合物的特点是活性氯的组.甚至有论点的性质的主要分解中心.大多数的意见,然而,有利于烯丙基氯实体（1）（方案2）的c-ci债券是这一组中susccptible到电离和,因此,为了消除盐酸.电离的烯丙基物种形成（2）将更加简便而增强的共振稳定产生的正离子.审查的minsker等人.表明,keto-chloroallylic集团（3）可能更容易脱氯化氢的速率常数的这种反应是一个因素大于同一过程与仪器简单chloroallylic集团（1）.hjertberg和sorvik,然而,很少有证据表明存在（3）在商业生产的聚氯乙烯