Ultrasonic characterization performed during chemical foaming of cross-linked polyolefins

摘要

Injection molding of cross-linked low density foams made from poly(ethylene-co-octene) resins results from simultaneous reactions occurring during the process. The ultrasonic quasi-static characterization technique (no flow) can mimic adequately the conditions prevailing during the molding process (pressure, temperature, time) and monitor the blowing process through sound velocity, attenuation and specific volume measurements. In this work, compounds prepared from resins with different melt flow indices are investigated, showing the influence of the degree of cross-linking on the chemical blowing agent (CBA) decomposition, as well as the effect of viscosity on the degassing conditions. Experiments demonstrate the complexity of CBA decomposition and of gas molecule diffusion in the polymer matrix. Published by Elsevier Ltd.