Reduction of Viscosity of Polymer Melt by Shear-Thinning and Disentanglement: Rheological Criteria and Commercial Perspectives

摘要

Mechanical performance of polymers improves with molecular weight (MW). Unfortunately, melt viscosity and thus lack of processability also increases with MW. Recently, a method to temporarily reduce the melt viscosity without changing MW has been proposed. The method uses processing windows such that shear oscillation superposed on extensional flow at gradually increasing shear thinning amplitude are created by imposing conditions of strain, frequency and temperature that bring the melt (G'/G~*) close to 0.75-0.85. The purpose of the present communication is to report results of a two-year research and development effort aimed at reducing the viscosity of several commercial resins using a pilot stage disentanglement machinery. The paper explores the commercial implications and answers the following questions: is it possible to shear-disentangle a large quantity of commercial resin at fast throughput, is it possible to process the disentangled melt before it regains its normal entanglement, and is it possible to speed-up the re-entanglement process after forming to regain mechanical benefits? From a laboratory and low throughput extrusion scale, the answer to all these questions is positive. The technology is presently being tested at a pilot pre-production scale to quantify the answers from a commercial perspective.