Insight into shear‐induced modification for improving processability of polymers: Effect of shear rate on the evolution of entanglement state

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2019-05, Vol.57 (10), p.598-606
• Main Authors: Fu, Jiaxin, Wang, Yingxiong, Shen, Kaizhi, Fu, Qiang, Zhang, Jie
• Format: Article
• Language: English
• Subjects: Crystallization; Dependence; disentanglement; Entanglement; Evolution; High density polyethylenes; Molecular weight; polyethylene (PE); Polymers; processability; shear; Shear rate; Viscosity
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.24816

ABSTRACT Many experimental results have revealed that the re‐entanglement kinetics of disentangled polymers is much slower than that predicted by tube theory. This retarded recovery of fully entangled state is of practical significance that shear‐induced modification may offer a way to improve processability for a polymer by reducing viscosity. This work tried to figure out the shear‐rate dependence variation of viscosity in the view of evolution of entanglement state through disentanglement and re‐entanglement, aiming to provide fundamental insights into application prospect of shear‐induced modification in preparing “in‐pellet” disentangled polymers prior to final processing. High‐density polyethylene was sheared on a parallel‐plate rotational rheometer with a linearly increased shear rate. Results showed that higher shear rate could induce further disentanglement, resulting in a lower viscosity with a reduction rate up to 93.7%, larger molecular weight between entanglements Me, and longer re‐entanglement time. Additionally, less entanglement would give a larger lamellar thickness of sheared samples after nonisothermal crystallization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 598–606 The shear‐rate dependence variation of viscosity in the view of evolution of entanglement state through disentanglement and re‐entanglement was studied. High‐density polyethylene (HDPE) was sheared on a parallel‐plate rotational rheometer with a linearly increased shear rate. Higher shear rate could induce further disentanglement, resulting in a lower viscosity with a reduction rate up to 93.7%, larger molecular weight between entanglements Me, and longer re‐entanglement time. Besides, less entanglement would also give a larger lamellar thickness of shear samples after non‐isothermal crystallization.