Preparation And Thermal Resistance Of Epoxy/Polyurethane Composites

As one of the six major synthetic materials,polyurethane has the properties of high strength,high modulus and excellent fatigue resistance.At the same time,polyurethane prepolymer has good fluidity and can realize rapid prototyping.It is widely used in construction,automobile,electronics,mining,new energy and other fields.However,the long-term use temperature of polyurethane is not higher than80?,the defects of poor heat resistance greatly limit its application range.In order to improve the heat resistance of polyurethane materials,polyurethane was synthesized by the reaction of polypropylene glycol oxide(PPG)and diphenylmethane diisocyanate(MDI)as the main raw materials of polyurethane,and compounded with high performance phthalic anhydride polyester polyols.After that,epoxy resin(EP)was added to make interpenetrating network structures(IPNs)with polyurethane.Finally,nano-silicon carbide/epoxy resin/polyurethane composites materials were prepared by adding nano-silicon carbide(SiC)particles into the system.The relationship between the structure and properties of polyurethane and its composites was explored by testing the mechanical properties,dynamic mechanical properties,thermal properties and chemical structure.The main experimental conclusions are as follows:1.Based on the idea of compounding polyether polyol and polyester polyol,a two-component polyol polyurethane was prepared by the prepolymer method.When the mass ratio of phthalic anhydride polyester polyol to polyether polyol is 30/70,the comprehensive performance of polyurethane is the best.The tensile strength of the sample was 71.96 MPa,the impact toughness was 84.45 KJ/m~2,and scanning electron microscopy showed that the fracture form of impact section without notch was ductile fracture.The storage modulus(E')of the sample was higher,the endogenous heat was lower,and the loss factor(tan?)was 0.70.Thermogravimetric test found that the temperature of 5%,10%and 50%mass loss of materials were 315?,330?and369?,respectively,and the final residual carbon rate was 15.67%.2.The interpenetrating network materials of epoxy resin/two-component polyol polyurethane were prepared.It was found that the heat resistance of polyurethane material modified by epoxy was improved obviously.The structure of IPNs improved the mechanical properties of composites materials to a certain extent.However,when the EP content in the system was too much,the brittleness of the material increased,the tensile strength and impact toughness decreased.When the EP content was 25wt%,the tensile strength of the sample was 61.08 MPa,the impact strength was 57.02KJ/m~2,and the impact fracture morphology had obvious ductile tearing.The results of TGA showed that when the mass loss of the composite was 5%,10%and 50%,the corresponding temperature was 315?,330?,393?respectively,and the final carbon residue rate was 17.51%.Its Tg was about 102?,tan?was 0.59.The effective damping interval is about 66.04?when tan?>0.3,which widened the temperature tolerance range and delayed the thermal degradation rate.3.Nano-SiC reinforced EP/PU IPNs composites materials were prepared by adding nano-SiC as filler into the interpenetrating network system for physical modification.When nano-SiC was added at 0.50wt%,the tensile strength and impact toughness of the composites were 71.85 MPa and 41.81 KJ/m~2,and the effective damping temperature resistance interval was about 68.66?.At 5%,10%,and 50%mass loss of the composite materials,the temperatures were 313?,330?,and 390?.SEM showed that it was well dispersed in polyurethane Under the condition of ensuring better thermal performance,nano-SiC modification effectively improved the comprehensive mechanical properties of the materials.