The dependence of shear and elongational viscosity on the molecular weight of poly(vinylidene fluoride)

✍ Scribed by T. Koizumi; S. Usui

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 114 KB
• Volume: 71
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19990404)71:14<2381::aid-app9>3.0.co;2-6

✦ Synopsis

The dependence of shear and elongational viscosity on the molecular weight of poly(vinylidene fluoride) has been studied using a capillary rheometer. The elongational viscosity was evaluated based on Cogswell's method with two types of capillaries: capillary length (L)/capillary diameter (D) ϭ 10 mm/1 mm and L/D ϭ 0 mm/1 mm. We used the ratio P 0 /P L that indicates the contribution of elongational flow to the total flow involving both the shear and elongational flows. P L and P 0 are the pressure losses in the capillary and the converging flows, respectively. P 0 /P L increased with molecular weight and shear rate. This corresponds to decreasing the number of entanglements of molecular chain under a large displacement, especially high shear. Thus, we suggest using P 0 /P L as the parameter of the entanglement interaction on the molecular chain under a large displacement.