Rolltrusion: Doubly-Orientation Processing and Morphology – Property Relationships for Commercial Plastics**

Abstract

Commercial grade polyolefins were processed in a single operation named, rolltrusion, to produce highly transparent semicrystalline doubly-oriented¹) specimens. The process may be performed stepwise or continuously and the sample size produced is only limited by the practical dimensions of the roller and wind-up arrangement used to receive the processed workpiece. The Young's moduli of HDPE and iPP doubly-oriented specimens prepared by this procedure were enhanced × 25 and × 15 times respectively, over that for the original polymers received from the manufacturer. Tensile strength of these products were significantly improved at least × 8 (HDPE) and × 30 (iPP) over the original polymer. Draw ratios of × 30 for HDPE and × 60 for iPP have been obtained. Besides, extensive morphological characterization conducted using WAXS, SAXS, SEM, birefringence, etc., demonstrated that the polymer crystallites in the rolltruded HDPE and iPP sheets were oriented with the molecular c-axis along the draw direction, while a low index plane was parallel to the roll surface of the workpiece for high draw patios. This “two phase” morphology with triaxial crystal symmetry shows many potential applications industrially. From DSC traces it was established that the melting temperature, the sharpness of the melting peak, and the degree of crystallinity all increased with increasing draw ratio. GPC measurements (made before and after processing) confirmed that the commercial plastics did not undergo thermomechanical degradation during processing. The considerable advantages of the rolltrusion technique compared with other currently used solid state deformation techniques are discussed.