Preparation And Properties Of Polyethylene/Polypropylene Double Layers Microporous Membrane By Melt-stretching Method

Melt-stretching method is an important method to manufacture Polyolefin microporous membrane.The double-layers PP/PE microporous membrane is also prepared by this method.During the producing process,there have several steps including:preparing double-layers cast film by melt-stretching,annealing the cast film,cold stretching,hot-stretching and heat-setting.The annealing condition,cold and hot stretching condition have a strong impact on the pore-forming of the microporous membrane.In this paper,the influence of annealing,cold stretching and hot stretching condition on the microstructure and property of microporous membrane were studied.The best annealing time of double-layers PP/PE microporous membrane was measured.The influence of cold-stretching rate and ratio on the microstructure of double-layers PP/PE microporous membrane were studied.The best value of cold-stretching was measured.The influence of hot-stretching rate and ratio on the microstructure of double-layers PP/PE microporous membrane were studied.The best value of hot-stretching was measured.The results of experiment were as follows:1.With the annealing time increasing,the orientation value of PP layer and PE layer was increasing,the regularity of lamella was also improved.With annealing the 4 hour,the property of double-layers PP/PE annealing film and microporous membrane were best.The best annealing time of double-layers PP/PE microporous membrane was 4 hour.2.During the cold-stretching,both the stretching ratio and stretching rate should be considered at the same time.The different stretching condition can get microporous membrane with different properties.By considering all the properties,the cold stretching rate set at 150-200mm/min and the cold stretching ratio set at 40-60%,which can prepared the double-layers PP/PE microporous membrane with the best overall performance3.When the hot stretching temperature of double-layers PP/PE microporous membrane set at 100-130?,the lamellar cluster could separate effectively and the pores were found.With the hot stretching temperature increasing,the size of the pores and lamellar cluster were increasing,the puncture resistance and the thermal dimensional stability turned better,the porosity and the air permeability increased at 80?-126?and then decreased after 126?.The hot stretching temperature set at 126? can prepare the double-layers PP/PE microporous membrane with the best performance.The hot stretching rate was also considered.With the hot stretching rate increasing,the size of pores was increasing,the puncture resistance and the thermal dimensional stability turned better,the porosity and the air permeability increased form 80%to 126%and then decreased after 160%.The hot stretching rate set at 160%can prepared the double-layers PP/PE microporous membrane with the best performance.