Inverse Temperature Dependence of Strain Hardening in Ultrahigh Molecular Weight Polyethylene: Role of Lamellar Coupling and Entanglement Density

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• 作者：Bing Na ; Ruihua Lv ; Wenfei Xu ; Pingsheng Yu ; Ke Wang ; Qiang Fu
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：November 22, 2007
• 年：2007
• 卷：111
• 期：46
• 页码：13206 - 13210
• 全文大小：84K
• 年卷期：v.111,no.46(November 22, 2007)
• ISSN：1520-5207

文摘

Irradiation of ultrahigh molecular weight polyethylene (UHMWPE) with a dose of 150 kGy by an electronbeam can effectively increase the entanglement density in the amorphous phase and has little influence onthe properties of the crystalline phase, which provides examples to comparatively investigate the role oflamellar coupling and entanglement density in determining the strain-hardening effect in semicrystallinepolymers. The strain-hardening modulus, deduced from the Haward plots of true stress-strain curves, isinversely temperature-dependent and has a sharp transition around 65 C that corresponds to the mechanical_I-process of the crystalline phase for both nonirradiated and irradiated samples, irrespective of the entanglementdensity in the amorphous phase. Lamellar coupling takes more effect in determining the strain-hardeningbehavior before the mechanical _I-process is activated. With further increasing temperature, lamellar couplingbecomes weaker and the role of the entangled amorphous phase is gradually presented. However, the sametemperature dependence of the strain-hardening modulus in both nonirradiated and irradiated samples indicatesthat the strain-hardening behavior in semicrystalline polymer is mostly determined by lamellar coupling ratherthan by entanglement density.