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Study On The Formation And Properties Of Polyethylene Composites Under Tensile Flow Field Enhanced By Ultrasonic

Posted on:2018-11-05Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhangFull Text:PDF
GTID:2311330515975660Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
High density polyethylene(HDPE)has been widely used in production and life because of its excellent heat resistance,chemical corrosion resistance and mechanical properties.However,it still has some disadvantages such as insufficient toughness and poor wear resistance.Since the development and application of ultra high molecular weight polyethylene(UHMWPE),it has attracted much attention from industry and academia because of its excellent wear resistance,impact strength and toughness.Compared compared with other polymers,molecular composition and structure of UHMWPE are similar with HDPE's,so they have good compatibility and HDPE modified by UHMWPE is one of the hot topic.Crystallization kinetics of polymers could be acclerated by the elongational field and the polymers can be induced to form highly oriented structure.Then the polymer could have higher higher density,modulus,hardness and low permeability and coefficient of thermal expansion.Therefore,we designed that molecular weight ratio of HDPE and UHMWPE was 5.6:1,12.5:1,25:1 and 50:1.Firstly HDPE and UHMWPE were disolved in the solution to get well dispersed mixture and then were processed by ultrasonic assisted extrusion equipment,at last the samples were prepared by injection molding.The paper futhur study effect of the content and molecular weight of UHMWPE on the rheological properties,the crystallization behavior and morphology evolution,shish-kebab structure formation and mechanical properties of the composite which were treated by ultrasound enhanced tensile flow.Firstly,the HDPE/UHMWPE composites were prepared by solution blending,and then treated by ultrasonic assisted twin screw extrusion.The effects of UHMWPE content and molecular weight on the rheological behavior of the composites were investigated by means of high temperature rheometer.The results showed that the phase of HDPE/UHMWPE did not seperated and storage modulus,loss modulus and viscosity were greatly affected by the UHMWPE mass fraction and molecular weight.Secondly,the paper studied the effects of UHMWPE content and molecular weight on the non isothermal crystallization kinetics,isothermal crystallization kinetics,and the lamellae thickness and distribution of the matix.Finally,this paper investigated the effect of UHMWPE content and molecular weight on shish-kebab structures formed in the process of injection molding,evolution of crystal structure morphology during tensile process.Then finally its influence on the mechanical properties of the composites was analyzed.
Keywords/Search Tags:PE composites, rheology, crystallization kinetics, extensional flow, Shish-Kebab
PDF Full Text Request
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