| High-density polyethylene(HDPE)is an environment-friendly and easy-molding thermoplastic resin that is widely used in construction,drainage,and packaging.However,due to its low strength,brittle fracture,cracking,and other problems tend to occur in practical applications.At present,filling inorganic particles into HDPE is a main method.However,the majority of the single-type inorganic particle has a simple effect on the performance improvement of HDPE,and it is difficult to meet the quality requirements of extrusion molding.Therefore,this article systematically studied the modification method of HDPE multiple composite system under the extrusion process conditions,based on calcium carbonate(CaCO3),talc power(Talc),linear low-density polyethylene(LLDPE)prepared different HDPE multiple composite system.Through the study of mechanical properties,interfacial properties,crystallization properties,orientation,etc.,the strengthening and toughening mechanisms of different composite systems under extrusion process conditions were explored.It is important to achieve HDPE toughening and tempering control and improve the overall performance of HDPE molded products.(1)The HDPE/inorganic particle composite system was prepared by extrusion molding.The effects of particle size and morphology on the mechanical properties of HDPE extruded products were investigated,and the influence of the surface properties of inorganic particles and the molecular chain orientation on the mechanical behavior was investigated.Morphology and crystallization performance tests were performed to analyze the enhanced modification mechanism of HDPE/inorganic particle composite system.By analyzing the crystallization performance and the true stress-strain curves of different composite systems,the relationship between the deformation and the crystallization of the extruded products during the stretching process was revealed.(2)LLDPE with short branches has a great influence on the microstructure of HDPE,which affects the mechanical properties of the composite system.Through the crystallization property test and the observation of fracture morphology,the effects of LLDPE on the nucleation mechanism and microstructure of HDPE were analyzed.The mechanical properties of samples extruded from HDPE/LLDPE composites with different ratios were analyzed,and the microstructure and mechanical properties of the composites were analyzed.The relationship between the structure and mechanical property of the composite system was analyzed.The toughening mechanism of LLDPE was studied from crystal structure.The interfacial bonding and mechanical properties of HDPE/LLDPE/inorganic particle composite system were further studied.The relationship between the toughness of the ternary composite system and the surface activity of the inorganic particles and the interfacial bonding properties of the system was analyzed.The relationship between the toughness of the ternary composite system and the surface activity of the inorganic particles and the interfacial bonding properties of the system was analyzed.Through the crystallization performance analysis,the mechanism of the toughening of composite system with different inorganic particles were revealed.(3)The effects of different coupling treatments on the interfacial bondability of the ternary composite system were compared and analyzed.Through pretreatment,composites treated with three coupling agents,CS-201,CS-101,and KH-151,respectively,were prepared.Through the micro-morphology and impact toughness test,it is determined that the best modification coupling agent is CS-201.The interface modification mechanism of the coupling system with coupling agents molecular with different chains and reactive groups was discussed.Through the mechanical property tests of the extruded samples and the analysis of the crystallization properties,the mechanism of the toughening modification of the composite system by the interface modification was explained.(4)In order to further improve the strength of HDPE composite system,extrusion samples of HDPE/LLDPE/CaCO3/Talc composite systems were prepared.Through the morphological observation and analysis of the interaction between the two inorganic particles,the crystallization performance of the composite system was explained,and the reinforcing mechanism of the extruded product was ascertained.The effect of extrusion process conditions on the microstructure,crystallization properties and mechanical behavior of the composite system were analyzed.The relationship between the crystal structure and mechanical properties of the composite system at different extrusion rates and mold temperatures was determined and provided for improving the overall performance of the HDPE molded product.In this thesis,different HDPE multiple composite systems were prepared,the changes of property factors such as strength and toughness were analyzed.The modification mechanisms of different material systems were deeply explored.The influences of parameters of the extrusion process were compared.The theoretical guidance is provided for the development of the new composite system and the wider application of production. |
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