Supercritical CO₂ Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC.

Since the maximum foaming temperature window is only about 4 °C for supercritical CO₂ (CO₂) foaming of pristine polypropylene, it is important to raise the melt strength of polypropylene in order to more easily achieve CO₂ foaming. In this work, radiation cross-linked isotactic polypropylene, assisted by the addition of a polyfunctional monomer (triallylisocyanurate, TAIC), was employed in the CO₂ foaming process in order to understand the benefits of radiation cross-linking. Due to significantly enhanced melt strength and the decreased degree of crystallinity caused by cross-linking, the CO₂ foaming behavior of polypropylene was dramatically changed.