Design And Preparation Of Foaming Materials With Thermoplastic Polyamide Elastomers And Study On Their Properties

Polymer foam materials are widely used in the fields of sound insulation,heat insulation and adsorption due to their light weight,high specific strength,good sound insulation and heat insulation performance and good impact load absorption performance.Thermoplastic polyamide elastomer(TPAE)as a typical thermoplastic elastomer(TPE),the hard segment is made of polyamide(PA),and the soft segment is made of polyether or polyester.The hard segment of PA endows TPAE with good mechanical properties,while the polyether or polyester soft segment endows TPAE with good elasticity,so TPAE possesses both good mechanical and elastic properties.TPAE foam materials has the characteristics of low foaming density,good resilience,high and low temperature resistance,etc.,and has been rapidly developed in recent years.However,the molecular chains of TPAE are mostly linear,with low branching degree and good flexibility,and the melt strength varies greatly near the melting temperature.Especially when the temperature is higher than the melting temperature of TPAE,the melt strength of TPAE will decrease rapidly,resulting in difficult to control the growth and stability of the cells during the foaming process.This is also the difficulty of TPAE foaming materials development.To solve the problem that TPAE is prone to collapse and mold sticking in the process of chemical foaming,this thesis starts from two routes.Firstly,traditional foaming material ethylene-vinyl acetate copolymer(EVA)is used as foam matrix,and TPAE is mixed with it through physical blending to develop high-performance EVA/TPAE composite foaming material.Secondly,by developing and optimizing the chemical foaming process,TPAE foaming materials with stable cells and excellent comprehensive properties were prepared.Specific research contents are as follows:(1)EVA was used as the foam matrix,TPAE with similar hardness to EVA was added,and it was mixed through physical blending.By the method of molded chemical foaming,high-performance EVA/TPAE composite foam materials were successfully developed,and the preliminary study showed that TPAE had the potential of molded chemical foaming.The influences of different dosage of foaming agent and TPAE on the properties of EVA/TPAE composite foaming materials were studied.The prepared EVA/TPAE composite foam material has the advantages of high foaming ratio,low density,good resilience,high elongation at break and high trousers tearing strength,which has a good application prospect in shoe soles.When the dosage of foaming agent is 3 phr,compared with pure EVA foaming material,adding 5 phr of TPAE can significantly improve the cellular structure,density,mechanical properties and elastic properties of EVA/TPAE composite foam material.The prepared EVA/TPAE composite foam material has uniform cellular distribution,average cellular size of 55.2μm,light weight,high foaming ratio,density of 0.16 g/cm~3,foaming ratio of 5.8,excellent elastic and mechanical properties,hardness of 44C,resilience of 53.8%,compression recovery rate of 63%.Tensile strength is 1.6 MPa,elongation at break is 284%,trousers tearing strength is 2.5 N/mm.(2)In order to further explore the potential of TPAE molding chemical foaming and the structure and properties of foaming materials,TPAE foam materials with stable cells and excellent comprehensive properties were prepared by using TPAE as the foam matrix through the development and optimization of chemical foaming process.The properties of TPAE foams varied with different molding pressure,molding temperature and molding time,optimized the best process parameters,and obtained the TPAE foams with low hardness,high tensile strength,trousers tearing strength and high compression recovery rate.When the foaming pressure was 5 MPa,the foaming temperature was 145℃and the foaming time was 30 min,the comprehensive properties of TPAE foaming material was best.The cellular distribution of TPAE foaming materials was uniform,the average cellular diameter was 156.7μm,and the cellular density was 6.75×10~5 cells/cm~3.The density of the foam material is 0.47 g/cm~3,the foaming ratio is 2.1,the hardness is 63C,the tensile strength is 3.8 MPa,the elongation at break is150%,the trousers tearing strength is 13.8 N/mm,the resilience is 45%,the compression recovery rate is 85.8%.