An Experimental Study of Rotational Molding of Polypropylene/Polyethylene Copolymers

Abstract The objectives of this work are to assess the rotomoldability of rubber toughened polypropylene resins and to investigate how resin properties can influence the process of rotational molding and the final part quality. Four commercially available polypropylene/polyethylene copolymers were tested. The chemical composition and the powder, rheological and thermal properties of the resins were determined. Rotational molding experiments were carried out in a laboratory scale uniaxial machine which is capable of measuring internal mold temperature and which facilitates the visual observation of various transitions in the cycle. Impact and environmental stress cracking resistance tests, as well as thickness distribution and density measurements were performed on the roto-molded parts. It was found that increasing rubber content results in an improvement of the impact properties which is counteracted by difficulties in processing, presence of bubbles and uneven surfaces.