Molecular Weight Dependence of the viscoisity of Polydimethylsiloxane under high Pressure

• Published in: Kobunshi Kagaku Vol. 28; no. 319; pp. 830 - 834,934
• Main Authors: Ogihara, Sadahide, Sasaki, Hiroshige, Takaki, Takeshi
• Format: Journal Article
• Language: Japanese
• Published: The Society of Polymer Science, Japan 1971
• Subjects: 3.4 Power Law; Critical Molecular Weight; Molecular Weight; Polydimethylsiloxane; Static Pressure; Zero Shear Viscosity
• ISSN: 0023-2556; 1884-8079
• DOI: 10.1295/koron1944.28.830

By means of a concentric cylindrical rheometer for high pressure, the viscosity was measured for polydimethylsiloxane melts with various weight average molecular weights under static pressure up to 900 kg/cm2 at 25°C. This study aimed to discuss the effect of pressure on the molecular weight dependence of zero shear viscosity and on the critical molecular weight, Mc, related to the build-up of the entanglement between polymer chains. (1)ηp, increases with static pressure in all cases. ηp/η0 is almost independent of Mw; Mw<1×104 and Mw> 8×104, where s and s are the zero shear viscosities under static pressure P and atmospheric pressure, respectively, and K, n and A are independent of P and Mw. (2) The so-called 3.4 power law is valid under each pressure. (3) Mc is slightly dependent on static pressure.