Polyphenylene Sulfide for High-Rate Composite Manufacturing: Impacts of Processing Parameters on Chain Architecture, Rheology, and Crystallinity
Polyphenylene Sulfide for High-Rate Composite Manufacturing: Impacts of Processing Parameters on Chain Architecture, Rheology, and Crystallinity
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DOI：
10.1016/j.polymdegradstab.2023.110580
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发表时间：
2023-10
影响因子：
5.9
通讯作者：
L. Ghanbari;Erin R. Crater;N. Enos;O. McNair;Robert B. Moore;J. Wiggins
中科院分区：
文献类型：
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作者：
L. Ghanbari;Erin R. Crater;N. Enos;O. McNair;Robert B. Moore;J. Wiggins
高性能半结晶热塑性塑料需要高温加工才能形成有用的结构，但反复暴露在这些极端环境中对关键聚合物性能的影响尚不清楚。本工作研究了聚苯硫醚(PPS)在富氧环境中暴露于标准熔融加工条件下引起的降解驱动的结构变化对聚苯硫醚(PPS)的流变性、结晶行为和晶体结构的影响。熔体加工温度(300°C、320°C和340°C)和保持时间(最长60分钟)变化，以探讨热暴露对聚合物性能的影响。长时间的熔融暴露会导致PPS熔体粘度的增加，这是因为形成了复杂的支化/交联结构，其中温度的升高会使这一过程发生得更快。PPS的动态等温流变学显示，在340℃下保温60分钟后，复数粘度在10rad/S时增加了70倍。频率扫描流变学实验表明，热暴露后的斜率低至0.14，与线性(终端斜率=0.2)有明显的偏离。应力恢复实验表明，热加工聚苯硫醚在施加应变的情况下需要更多的时间来松弛应力。沿着聚合物主干以支链/交联物形式存在的缺陷会降低整体结晶度并降低片层厚度，但不会改变晶胞结构。对于依赖高结晶度来提供耐溶剂性和强度的半结晶高性能热塑性树脂基复合材料，这些结果对严格控制熔融加工步骤和了解最终材料状态的需要具有严重影响。此外，回收和再利用策略应考虑后处理聚苯硫醚聚合物的粘弹性。
High performance semi-crystalline thermoplastics necessitate high temperature processing to form useful structures, but the effects of repeated exposure to these extreme environments on key polymer properties are not well understood. This work investigates the influence of degradation-driven structural changes resulting from exposure to standard melt processing conditions in oxygen rich environments on the rheological properties, crystallization behavior, and crystal structure of polyphenylene sulfide (PPS). Melt processing temperatures (300°C, 320°C, and 340°C) and hold times (up to 60 min) are varied to probe the effects of thermal exposure on polymer properties. Extended melt-state exposure causes an increase in PPS melt viscosity due to the formation of complex branched/crosslinked structures where increasing temperature causes this process to occur more rapidly. Dynamic isothermal rheology of PPS displays a 70x increase in the complex viscosity at 10 rad/s after 60 minutes at 340°C. Frequency sweep rheological experiments reveal a notable deviation from linearity (terminal slope = 2) with slopes as low as 0.14 after thermal exposure. Stress recovery experiments indicate thermally processed PPS requires more time to relax stress under an applied strain. Imperfections along the polymer backbone in the form of branches/crosslinks decrease overall crystallinity and reduce lamellar thickness, with no changes to the unit cell structure. For semi-crystalline high performance thermoplastic matrix composites relying on high degrees of crystallinity to provide solvent resistance and strength, these results have serious implications for the need to tightly control melt processing steps and understand the final material state. Furthermore, viscoelastic properties of post-processed PPS polymers should be considered for recycling and reuse strategies.