Pan-milling to prepare ultrafine high-density polyethylene powder with sodium chloride serving as grinding aid

In this article, our self-designed pan mill equipment was used to pulverize high-density polyethylene (HDPE) to prepare its powder product. This pan mill based on three-dimensional shear forces shows much better pulverization effects on ductile polymer materials when compared with conventional pulverizing equipment based on impact force, and it can mill original HDPE pellets (particle size: 3-4 mm) into fine powder (particle size: 75 mu m) at ambient temperature. To further improve the pulverization efficiency to obtain ultrafine HDPE powder, sodium chloride (NaCl), serving as a grinding aid, was comilled with HDPE. Taking the advantages of the cutting and isolating effects of NaCl crystals, HDPE can be pulverized into ultrafine powder with the particle size below 10 pm. Another advantage of NaCl as a grinding aid lies in an easy removal process through water wash, thus conveniently separating from hydrophobic HDPE powder. This technology provides a novel and efficient method to prepare the ultrafine powder of those polymers with high ductility and low melt point, and shows a promise in future commercial application. (C) 2007 Wiley Periodicals, Inc.