Manufacture and properties of a polyethylene homocomposite

Abstract

A conventional composite consists of a matrix and a reinforcing phase differing in chemical composition, with the latter having superior mechanical properties. This paper presents the manufacture and mechanical properties of a homocomposite consisting of an ultra-high molecular weight polyethylene matrix and an ultra-high molecular weight polyethylene reinforcing phase. While the chemical compositions of the bulk and fibers are the same, the fibers have a higher strength and a higher melting temperature due to their high degree of molecular orientation. The homocomposite was manufactured by alternatively laying up plys of an ultra-high molecular weight polyethylene fabric or randomly oriented fibers and ultra-high molecular weight resin in a mold followed by compression molding. The molding temperature was chosen to be slightly higher than the melting temperature of the matrix, but below that of the fabric or fibers. The fibers were also crosslinked using gamma irradiation so as to retain their molecular orientation during compression molding. Mechanical properties of the homocomposite such as the elastic modulus, tensile strength, and hardness are improved in a direction parallel to the fiber orientation, when compared with the properties of ultra-high molecular weight polyethylene. The homocomposite also exhibits a lower friction coefficient and higher wear resistance, which are desirable properties in bearing applications. In addition, owing to the biocompatibility of polyethylene, the homocomposite may be acceptable as a bearing material in joint prostheses.