Preparation And Mechanical Properties Of Several In-situ Microfibrillar Blends

In-situ microfibrillar blends based on polyethylene (PE)/Nylon 6 (PA6), block copolymer of propylene (PP-B)/PET, HDPE/PET, mixed polyolefin (PO)/PET were prepared through melt extrusion-cold stretching-hot stretching processing. The choice of polyolefin matrix, molding process, forming position of microfibrils, draw ratio and dispersed phase content on the impact of the in-situ fiberilizing as well as mechanical properties of the product were studied in this paper. Also the micro-morphology, size, aspect ratio and distribution of microfibrils were observed by SEM.The miniature platinum resistance (Pt100) was first applied to temperature measuring elements of extruding machine in China. Practical application showed that its characteristics were as follows:sensing temperature accurately, consistent with thermometer readings, accurate and reliable under long-term use.Study on melt extruding HDPE/PET and PP-B/PET blends through single screw extruder proved that part of microfibrils were formed by simple melt extrusion, however these microfibrils got small aspect ratio, uneven thickness and less number. Microfibrils of uniform thickness and better quality could be formed through stretching treatment to extrusion die strips.The SEM results showed that micro-morphology of blends could be clearly observed through sample preparation, series of studies suggested that the diameter of PA6 microfibrils was between 5-12μm and PET between 1-3μm combined with reverse etching.In PE/PA6 in-situ microfibrillar system, the content of PA6 should be under 20%, the extrusion temperatures were 200,230,250,200℃ (the die), the melt should cool and anneal during stretehing, the temperature of cold water bathe was about 20℃, the annealing temperature was 80-90℃,the draw ratio was 3. The greater the draw ratio and content of PA6, the smaller the MFR of in-situ microfibrillar blends. The tensile strength and the elongation at break of blends increased with the improvement of draw ratio. With the increase of PA6 content, the tensile properties were not improved significantly, whereas the impact strength at yield was on the rise.In PO/PET in-situ microfibrillar system, the continuous phase for the best extrusion process was PP-B. The optimum process conditions were as follows:the barrel temperatures were 220,250,260,220℃ (the die), the screw speed was 50 rpm, and the draw ratio was 3. With the enhancement of draw ratio, MFR of PO/PET reduced significantly, the tensile stress at yield and the impact properties of the blends were improved. With the increase of PET content, MFR of blends also reduced, the tensile strength at yield and the elongation at break increased, however, the impact properties of the blends were not improved.