| This thesis focuses on the feasibility study of foaming metallocene polyethylene with chemical blowing agent (CBA) via rotational molding and compression molding processes. This thesis further proposes and verifies a new processing technology for the manufacture of over 10-fold recyclable metallocene polyethylene foams using CBA.; Incorporating the newly developed metallocene polyethylene into foaming applications is feasible but challenging. In manufacturing recyclable metallocene polyethylene foams with over 10-fold volume expansion ratio for impact application, the current rotational foam molding and compression foam molding face some fundamental obstacles. Through extensive experiments, these obstacles are identified to be inevitable entrapped air bubbles and predecomposition of the CBA. Based on an ideal model for CBA blown foam molding, a new processing technology is developed to solve these obstacles. The overall strategy of the new technology is to decouple the two stages in foaming, i.e., the preparation of foamable compositions and foaming. Practically, foamable sheets are manufactured to facilitate the foaming, while preventing the formation of entrapped air bubbles and the pre-decomposition of CBA. Through the new compression foam molding technology based on foamable sheet, over 10-fold recyclable metallocene polyethylene foams are successfully manufactured. |
