A STUDY ON PET/PP MICROFIBRILLAR COMPOSITES

摘要

The objective of this project is to develop a microfibrillar composite from polyethylene terephthalate (PET) and polypropylene (PP). PET/PP blends of different compositions were extruded through a capillary die using a co-rotating twin-screw extruder. The effects of composition and extrusion condition on the morphology of the extrudates were studied. The PET/PP(20/80) extrudate was found to give profuse PET fibres in the PP matrix. Some polyamide 6 (PA6), up to 10%, was introduced into the blend during the melt extrusion process to modify the PET/PP interface. PA6 micro particles were found partially embedded on the surface of the PET fibres. These tiny particles may serve as anchorage points for the PET/PP interface and help to increase the interfacial friction during fibre pull-out. Ultrathin cross-sections of the extrudates were prepared after staining with RuO4 and examined under a transmission electron microscope. Apparently, the PET/PA interface was coherent whilst the PET/PP and PA/PP interfaces were not. The PET/PP(20/80) and PET/PA6/PP(20/10/80) extrudates were solid-state drawn to enhance the molecular orientation of the PET fibres. Cold drawing was favourable for molecular orientation, however, it caused fibre breakage at high speeds. Meanwhile, drawing at 100℃ produced a high degree of molecular orientation only at high speeds.