Polymer fiber composite with mechanical properties enhanced by particle

Abstract

The invention relates to a composition comprising a polymer, a short and a long fiber composite that can be used in the form of a linear extrudate or thermoplastic pellet to manufacture structural members. The linear extrudate or pellet can have a cross-section of any arbitrary shape, or can be a regular geometric. The polymer and short/long fiber composite containing structural members can be manufactured from the composite or pellet in an extrusion process or an injection molding process. The pellet can have a cross-section shape having a volume of at least about 12 mm.sup.3. Preferably the pellet is a right cylindrical pellet having a minimum radius of about 1.5 mm and a minimum length of 1 mm weighing at least 14 mg. The initial mixing step before extrusion of the composite material insures substantial mixing and melt contact between molten polymer and wood fiber. The extruded pellet comprises a consistent proportion of polymer, short and long fiber and water. During the extrusion, water is removed intentionally to dry the material to a maximum water content of less than about 10 wt-% based on the pellet weight. To make a structural unit, the pellet is introduced into an extruder or injection molding apparatus wherein, under conditions of temperature and pressure, the composite pellet material is shaped into a useful cross-section.