Study Of Preparation Of Thr Bi-oriented Ultra-high Molecular Weight Polyethylence Film

Ultra-high molecular weight polyethylene(UHMWPE)is one of the thermoplastic engineering plastics,which has quite favorable integrated performances or properties,such as self-lubrication and the high resistance of impact,abrasive and aging.The film of UHMWPE combines the appropriate physicochemical properties of UHMWPE.Besides,the mechanical strength and optical performance are of significance improved after thinning by the bio-oriented stretch,which conforms to the concept of sustainable development for plastics to replace steel.Given the special molecular chain structures of the UHMWPE,the optimization procedures of the flow modification processes were worked out on the basis of the preliminary works of our research group.The exploration of the effects of the screw combination of TE-20 and TE-35 double-screw extruders on the flow properties of modified UHMWPE materials was figured out.The conclusion was that the larger the percent of the kneading blocks in the screw extruder,the better the mixing effect,which leads to improve the utilization efficiency of the flow modifier UL.And the comprehensive performance of fluidity and tensile strength was the best for the modified resins of the UHMWPE under the prepared condition of the added one percentage of UL for the TE-35 type of double-screw extruder,which of the flow rate is 2.44g/10min,the melting point is 135.65?,and the crystallinity is 39.9%.The variation of the microstructure of the crystals was not much,illustrating that the crystalline phase was also still composed of folded chains with the exception of the crystallinity slightly improved in comparison with the unmodified raw materials.Then,the method of tubular film was adopted in this thesis,which of the operation instruction was that the raw materials of modified resins were melt-extruded by a single-screw extruder before synchronous biaxial stretching of the film achieved under the traction of the tractor following the cone-shaped mold of our own design.The optimum parameters were that the transverse and longitudinal draw ratios of the films were all 4,the temperature and rate of stretching was 138? and 7 rpm with a width and thickness of about 500 mm 0.06 mm for the films,respectively.Last but not least,the effect of temperature,ratio and rate of stretching on the mechanical properties and crystal structure of the films was also investigated by the flat film method.It was discovered that the isotropic and anisotropic biaxially oriented UHMWPE films can be prepared by controlling the conditions using the flat film method.When the stretching ratio was 2.5×2.5,the tensile strength of the film was increased by 220.57%in comparison with the unstretched one,and a lattice structure with similar horizontal and vertical orientations appeared in the microstructure;the transverse and longitudinal tensile strength of the film was increased by 206.26%and 591.8g%,respectively,and the degree of longitudinal orientation was larger than the transverse direction with a grid structure of about 5 ?m×15 ?m appeared in the microstructure for the stretching ratio 2×3.