Preparation And Properties Of Glass Fiber Reinforced Heat-resistant Polyurethane Composites

Polyurethane(PU)is widely used in chemical,electronics,textile,medical,construction,aerospace and other fields due to its good mechanical properties,chemical resistance,aging resistance,and wide performance adjustment range.However,ordinary PU has the problem of insufficient heat resistance,which limits the application of polyurethane materials in high temperature environments to a certain extent.Therefore,the development of polyurethane materials with excellent heat resistance and better comprehensive mechanical strength has become one of the current important research directions.The purpose of this paper is to improve the heat resistance of polyurethane and improve the mechanical properties of polyurethane.It uses polyoxypropylene glycol(PPG),diphenylmethane diisocyanate(MDI),3,3’-dichloro-4,4’-two Amino diphenylmethane(MOCA)is used as the main raw material to synthesize polyurethane,and nano silicon carbide(Si C)particles are added to prepare PU/Si C composite materials.On this basis,glass fiber(GF)is introduced to prepare high-strength and high-heat-resistant PU/Si C/GF composite material.The main research contents and experimental conclusions are as follows:1.Polyurethane matrix was prepared by prepolymer method using PPG as soft segment,MDI and MOCA as hard segment.The effect of chain extension coefficient on mechanical properties and heat resistance of PU matrix was studied.When the chain extension coefficient is 0.04,the comprehensive properties of PU are the best,the tensile strength is 64.16 MPa,the bending strength is 84.69 MPa,the notched impact toughness is 8.88 k J/m~2;the damping factor(Tanδmax)of PU is 1.108,the corresponding glass transition temperature Tg is 91℃,and The effective damping temperature resistance interval for loss factor tanδ>0.3 is 30.26℃(77.41℃～107.67℃);Thermogravimetric analysis(TGA)showed that when the chain extension coefficient was 0.04,the PU had the best heat resistance,and its initial decomposition temperature was 315℃.2.Nano silicon carbide(Si C)was used as filler to prepare heat-resistant PU/Si C composite.The effect of nano Si C on the structure and properties of PU was investigated by changing the content of nano Si C.When the content of nano Si C is0.2 wt.%,the comprehensive properties of PU/Si C composite are excellent,the tensile strength is 69.76 MPa,the bending strength is 99.47 MPa,and the notched impact toughness is 7.08 k J/m~2.When tanδ>0.3,the effective damping temperature range of PU/Si C composite is 50.71℃(75.97℃～126.68℃),which improves the heat resistance of the material.TGA test showed that the introduction of nano Si C delayed the thermal decomposition of the second platform and effectively improved the thermal properties of the material.3.Glass fiber reinforced PU/Si C composites(PU/Si C/GF)were prepared by hot pressing mould with glass fiber(GF)as reinforcement.When the content of GF is63 wt.%,the tensile strength is 434.33 MPa,the flexural strength is 474.02 MPa,and the notchless impact toughness is 107.46 k J/m~2.TGA results showed that the introduction of GF can effectively improve the thermal properties of PU/Si C composites.The initial decomposition temperature of PU/Si C/GF composites increases with the increase of GF content,the initial decomposition temperature increased from 311℃to 320℃,and the residual carbon content increases from10.31%to 77.28%.SEM showed that there is good adhesion and wettability between glass fiber and resin matrix.