Dynamic Mechanical Properties of Cross-Linked Rubbers. VII. Butyl Rubber Networks
Dynamic Mechanical Properties of Cross-Linked Rubbers. VII. Butyl Rubber Networks
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DOI：
10.1021/ma60041a025
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发表时间：
1974-09
期刊：
影响因子：
5.5
通讯作者：
J. F. Sanders;J. Ferry
中科院分区：
文献类型：
--
作者：
J. F. Sanders;J. Ferry
通过动态剪切和蠕变测量，研究了七个不同程度的硫交联的丁基橡胶样品的线性粘弹性能。频率和温度范围为 0.1 至 600 Hz 以及 25 至 55，蠕变时间延长至 105 秒。蠕变数据被转换为相应的非常低频率的动态粘弹性函数。所有数据均通过根据方程 log=—9.03 (T-To)/(201.6+ T-To) 计算的位移因子减少到 To= 298 K。所有粘弹性函数都显示出频率依赖性的两个主要区域。对于所有交联度和化学性质几乎相同的未交联聚合物聚异丁烯，过渡区（较高频率）的行为非常相似。随着交联的增加，时间略有延长。平台柔量 JeN 是通过损失柔量 J" 或延迟光谱 L 的适当积分获得的。其倒数 Gen 随交联程度的增加而有所增加；将其外推至 2.9 X 106 dyn/cm2 至零交联，再次与聚异丁烯合理一致，并且对应于 8500 的缠结之间的平均分子量。次，发现慢机制对 L 的贡献随着交联的减少而迅速增加，与其他橡胶状聚合物的交联间距与缠结间距之比相当的轻度交联聚合物的数据相比，通过单体摩擦系数测量的分子迁移率的相应状态减少了，L 的广泛第二最大值出现在减少的时间尺度上的大约相同的点（十年内），这表明长程运动负责所有聚合物中的缓慢机制都是相似的。在本系列的前几篇文章中，描述了各种交联橡胶的粘弹性，包括天然橡胶、2 1, 4-聚丁二烯、3 苯乙烯-丁二烯橡胶、4 和聚（二甲基硅氧烷）5。特别关注在低交联度网络中观察到的松弛时间，该松弛时间主要归因于未捕获的运动。 5· 6 在本研究中，丁基橡胶的类似数据特别令人感兴趣，因为它的分子迁移率比之前研究的任何聚合物都要低；7 这种行为归因于与甲基的强位阻有关的局部运动差异。
The linear viscoelastic properties of seven samples of butyl rubber, cross-linked by sulfur to different extents, have been studied in shear by dynamic and creep measurements. The frequency and temperature ranges were 0.1 to 600 Hz and—25 to 55, and creep times extended to 105 sec. The creep data were converted to the corre-sponding dynamic viscoelastic functions at very low frequencies. All data were reduced to To= 298 K by shift factors calculatedfrom the equation log=—9.03 (T-To)/(201.6+ T— To). All the viscoelastic functions displayed two principal regions of frequency dependence. The behavior in thetransition zone (higher frequencies) was closely similar for all degrees of cross-linking and for the nearly chemicallyidentical uncross-linked polymer polyisobutylene. There was a slight shift to longer times with increasing cross-linking. The plateau compliance JeN was obtained by suitable integrations of the loss compliance J" or the retardation spectrum L. Its reciprocal, Gen, in-creased somewhat with the degree of cross-linking; it was extrapolated to 2.9 X 106 dyn/cm2 to zero cross-linking, again in reasonable agreement with that of polyisobutylene and correspondingto an average molecular weight be-tween entanglements of 8500. From measurements at low frequencies or long times, the contributions of slow mechanisms to L are found to increase rapidly with diminishing cross-linking as found for other rubberlike polymers. Data for several lightly cross-linked polymers with comparable ratios of cross-link spacing to entanglement spacing were compared with the time scale reduced tocorresponding states of molecular mobility as gauged by the mono-meric friction coefficient. The broad secondary maximum in L occurs at approximately the same point on the re-duced time scale (within a decade), indicating that the long-range motions responsible for theslow mechanisms are similar in all the polymers.In previous papers of this series, viscoelastic properties of various cross-linked rubbers were described, including natural rubber, 2 1, 4-polybutadiene, 3 styrene-butadiene rubber, 4 and poly (dimethylsiloxane). 5 Particular attention was devoted to relaxation times which are observed in net-works with low degrees of cross-linking and have been at-tributed primarily to motion of untrapped entangle-ments. 5· 6 In the present study, similar data are reported for butyl rubber. This polymer is of particular interest because it has a far lower molecular mobility than any of those previously investigated; 7 this behavior has been attributed to differences in local motions, associated with the strong ste-ric hindrance of the methyl groups. 8