HYDROSTATICALLY EXTRUDED GLASS-FIBER-REINFORCED POLYOXYMETHYLENE .1. THE DEVELOPMENT OF FIBER AND MATRIX ORIENTATION

This paper describes the determination of fiber and matrix orientation in oriented short-glass-fiber-reinforced polyoxymethylene (POM) compo sites produced by hydrostatic extrusion, The starting material was ran dom glass fibers (25 wt% and average length 150 mu m) in an isotropic POM matrix, and the oriented composites were produced by extrusion thr ough a reducing conical die at 15 degrees C below the polymer melting point: after extrusion the average Fiber length was reduced slightly t o 133 mu m. Fiber orientations were measured using an image analysis m ethod developed at Leeds University, and the matrix orientation was de termined using wide angle X-ray diffraction. The development of fiber orientation with extrusion ratio was found to be close to that predict ed by the pseudo-affine deformation scheme although the fiber orientat ion was greater than that predicted by the model at low draw ratios an d slightly less at the highest draw ratio. The development of the orie ntation of the crystalline portion of the matrix was found to be alway s significantly greater than that predicted by the pseudo-affine schem e.