Quantitative structural characterization of the melting behavior of isotactic polypropylene
Quantitative structural characterization of the melting behavior of isotactic polypropylene
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DOI：
10.1002/pol.1975.180130713
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发表时间：
1975-07
期刊：
影响因子：
--
通讯作者：
R. Samuels
中科院分区：
文献类型：
--
作者：
R. Samuels
定量研究了受约束等规聚丙烯纤维的熔融行为，考察了聚合物的各向异性结构状态对纤维性能的影响。在一些样品中观察到两个吸热峰。多个峰的形成和位置由非晶链的取向决定，并且与用于实现该取向的制造路径无关。在非晶链的某一最小取向以上，发生多个吸热峰形成。高温吸热（T2M）外推到220°C的完全取向非晶链的最终熔点，而低温吸热（T1M）外推到185°C的最终熔点。非晶链取向通过改变其构型熵来影响吸热温度。定量地表明，非结晶聚合物必须被认为是塑性变形，因为橡胶弹性理论不遵循预测。还报道了等温结晶样品的熔融行为，以进一步阐明所观察到的吸热的性质。
The melting behavior of restrained isotactic polypropylene fibers is examined quantitatively in terms of the influence the anisotropic structural state of the polymer has on the observed properties. Two endotherm peaks are observed to occur in some of the samples. The formation and location of the multiple peaks are determined by the orientation of the noncrystalline chains, and is independent of the fabrication path used to achieve that orientation. Above a certain minimum orientation of the noncrystalline chains, multiple endotherm peak formation occurs. The high-temperature endotherm (T2M) extrapolates to an ultimate melting point for fully oriented noncrystalline chains of 220°C, while the lower-temperature endotherm (T1M) extrapolates to an ultimate melting point of 185°C. Noncrystalline chain orientation influences the endotherm temperature through its changing configurational entropy. It is shown quantitatively that the noncrystalline polymer must be considered as plastically deformed, since rubber elasticity theory is not followed as predicted. The melting behavior of isothermally crystallized samples are also reported to further elucidate the nature of the observed endotherms.