Study On Oscillating Flow And Strain-Harding Of PE And PP Melt

This project studied the behaviors of oscillating flow and tensile hardening and explored its viscoelastic mechanism systematically. The strain hardening rheological response and oscillating flow, which usually refers to the whole capillary pressure oscillation under constant piston speed, has been widely studied as an important instability phenomenon in capillary flow. Constant pressure capillary rheometer and constant rate double-capillary rheometer were used in this study to research the melt elastcity effect of LLDPE, HDPE, MLLDPE, PPR.There were three aspects which we focused on as follows. (1) Established the multi-size blob chain model, discussed the relaxation mechanism of the multi-hardening from the view of long range entanglement. (2) Associated tensile hardening and the elastic behavior on both the entrance and exit of the capillary rheometer, characterized the elasticity uniformly, to study the viscoelastic tensile rheological mechanism deeply. (3) Created the phenomenological theory of the relationship between the molecular structure, the related functions and the elasticity behavior through the principle study on the tensile hardening and the structure of polymer bulk.The research results of this study contribute to the perfection and development of scientific theories of polymer melt elasticity effect and extrudate distortion, and play an important role on the high-speed and stable high quality processing of the polymer materials.