Rotational moulding of expanded polyethylene by pellets

An innovative method of rotational moulding expanded polyethylene by pellet s was reported. Experiments were carried out in a laboratory scale uniaxial machine, which was capable of measuring in-mould air temperature in the cy cle. The polymeric material used was linear low-density polyethylene. The f oaming material used is endo-thermal chemical blowing agent. Before mouldin g, the polyethylene material and the chemical-foaming agent were first melt blended by a single-screw extruder and were then cut into pellets of 2-3 m m in diameter. Pellets were then dry-blended with pure LLDPE powder by a mi xer for moulding. Characterization of moulded part properties was performed after moulding. An optical microscopy equipped with an image analysis syst em was also employed to determine the bubble distribution in foamed parts. The purpose of this study is to access the mouldability of rotational mould ing expanded polyethylene by pellets, and to investigate how the foaming ag ent and processing conditions can influence the moulding process and the fi nal product quality. It was found that the rotational moulding of expanded parts by pellets saves the cost of powder grinding as well as improves the impact property of moulded parts, but is counteracted by uneven inner surfa ces.