Zhu Feichao, Yasin Sohail, Hussain Munir
Department of Textile Engineering, College of Textile Science and Engineering, Zhejiang Sci-Tech University, Hangzhou 310027, China.
Zhejiang Provincial Key Laboratory of Industrial Textile Materials and Manufacturing Technology, Zhejiang Sci-Tech University, Hangzhou 310027, China.
Polymers (Basel). 2021 Oct 11;13(20):3485. doi: 10.3390/polym13203485.
Dynamic oscillatory shear testing is used to investigate polymeric viscoelastic behaviors. Small and large amplitude oscillatory shear tests are the canonical method for characterizing the linear and nonlinear viscoelastic behaviors of any polymeric material. With prominent and abundant work on linear viscoelastic studies, the nonlinear behavior is evasive in terms of generating infinite higher harmonics in the nonlinear regime. For this reason, intrinsic nonlinearities from large amplitude oscillatory shear (LAOS) studies have recently been used for insights on microstructural behaviors. This study is carried out for linear and nonlinear viscoelastic behavior with a main focus on LAOS of isostatic polypropylene (iPP) and relatively new low molecular weight and low modulus polypropylene-based polyolefin (LMPP) blends. The morphological results showed reduced spherulitic crystal nucleus size and increased distribution in blends with increasing LMPP. The blends showed subtle linear viscoelastic responses with strong nonlinear mechanical responses to variant strain and stress compared to pure iPP. The intracycle strain thickening and intracycle strain stiffening of high-content LMPP blends were comparatively dominant at medium strain amplitudes.
动态振荡剪切测试用于研究聚合物的粘弹性行为。小振幅和大振幅振荡剪切测试是表征任何聚合物材料线性和非线性粘弹性行为的标准方法。在线性粘弹性研究方面有大量突出的工作，而非线性行为在非线性区域会产生无穷高次谐波，因此难以捉摸。出于这个原因，大振幅振荡剪切（LAOS）研究中的固有非线性最近被用于洞察微观结构行为。本研究针对线性和非线性粘弹性行为展开，主要聚焦于等规聚丙烯（iPP）以及相对较新的低分子量和低模量聚丙烯基聚烯烃（LMPP）共混物的LAOS。形态学结果表明，随着LMPP含量增加，共混物中的球晶晶核尺寸减小且分布增加。与纯iPP相比，共混物表现出微妙的线性粘弹性响应以及对变化的应变和应力的强烈非线性力学响应。高含量LMPP共混物的周期内应变增稠和周期内应变硬化在中等应变幅度下相对占主导地位。
