Crystallinity as a selection criterion for engineering properties of high density polyethylene
Crystallinity as a selection criterion for engineering properties of high density polyethylene
复制标题
结晶度作为高密度聚乙烯工程性能的选择标准
DOI：
10.1002/pen.760250909
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发表时间：
1985
影响因子：
3.2
通讯作者：
B. McKinley
中科院分区：
文献类型：
--
作者：
D. M. Hoffman;B. McKinley
采用差示扫描量热仪（DSC）对25种商品高密度聚乙烯（HDPE）进行了结晶度和熔融温度的鉴别。熔融吸热下的面积与蠕变和热膨胀测量值成正相关和负相关。由于高结晶度与设计所需的密度、蠕变和热膨胀性能有关，DSC研究很容易从25种聚合物中鉴定出8种更有前途的聚合物。采用Avrami方程和Fischer-Turnbull方程分析了结晶度为75%的聚乙烯的结晶动力学。结果表明小的盘状球晶（Avrami n = 2）成核控制的生长动力学。这些结论与偏光显微镜观察结果基本一致。从Hoffman-Weeks图估计平衡熔融温度在141和142/sup 0/C之间。由于在结晶时14%的体积变化，用高度结晶的聚乙烯加工厚部件是困难的。较高的结晶度与中等的分子量相关，因此这些聚乙烯的粘度范围并不特别适合通过挤出加工。这些警告需要在HDPE部件的最佳设计性能和加工要求之间进行权衡。参考文献26篇，图11幅，表2张。
The differential scanning calorimeter (DSC) was used to discriminate among 25 commercial high density polyethylenes (HDPE) on the basis of their degree of crystallinity and melting temperature. The area under the melting endotherm correlated directly and inversely with creep and thermal expansion measurements. Since high crystallinity was related to the design required properties of density, creep, and thermal expansion, DSC studies readily identified eight of the more promising polymers from the group of 25. The overall crystallization kinetics of polyethylenes with 75% crystallinity were analyzed by the Avrami and Fischer-Turnbull equations. Results indicate small disk-like spherulites (Avrami n = 2) following nucleation-controlled growth kinetics. These conclusions are in reasonable agreement with polarizing microscope observations. An equilibrium melting temperature between 141 and 142/sup 0/C was estimated from Hoffman-Weeks plots. Processing thick parts from highly crystalline polyethylene is difficult because of the 14% volume change on crystallization. Higher degrees of crystallinity are associated with moderate molecular weight, so the viscosity range of these polyethylenes is not especially suited for processing by extrusion. These caveates necessitate tradeoffs between optimal design properties and processing requirements for HDPE parts. 26 references, 11 figures, 2 tables.