Preparation Of Heat-resistant Silicone Rubber And Study On Its Adhesive Properties

As a special rubber,silicone rubber has green environmental protection and good high and low temperature resistance.This topic takes the hot vulcanized silicone rubber as the research object,mainly to improve the heat resistance of silicone rubber and the adhesion with metal.Firstly,the thermal vulcanized silicone rubber was prepared by two-stage vulcanization process with methyl vinyl silicone rubber as raw rubber,2,5-dimethyl-2,5-bis(tert butyl peroxy)ethane as vulcanizing agent,silica and structural control agent added.The effects of the compounding ratio of three structural control agents(hydroxy terminated methyl phenyl silicone oil(PMPS-OH),hexamethyldisilazane(HMDS)and hydroxy silicone oil(PDMS-OH))on the mechanical properties and heat resistance of the thermal vulcanized silicone rubber were studied.The results showed that the addition of PMPS-OH greatly improved the hardness,tear strength,resilience and heat resistance of silicone rubber,but the tensile strength of silicone rubber decreased to less than 6MPa when the content of PMPS-OH exceeded 4 phr.The addition of HMDS and PDMS-OH can improve the tensile strength and elongation at break,respectively.When the dosage of HMDS was 4 phr and the dosage of PDMS-OH and PMPS-OH were both 2phr,the effect of improving the comprehensive properties of silicone rubber was the best.Secondly,in order to further improve the heat resistance of silicone rubber,four kinds of metal oxides were selected as heat-resistant additives to silicone rubber,and the effects of four metal oxides(iron oxide(Fe₂O₃),cerium oxide(Ce O₂),tin oxide(Sn O₂)and chromium oxide(Cr₂O₃))on the mechanical properties and heat resistance of silicone rubber were studied.The results showed that the addition of Fe₂O₃ and Ce O₂helped to improve the tensile strength of silicone rubber.In terms of heat resistance,compared with Sn O₂ and Cr₂O₃,Fe₂O₃ and Ce O₂ were more helpful to enhance the heat resistance of silicone rubber.When the dosage of Fe₂O₃ was 2 phr and Ce O₂ was 6 phr,the tensile strength of silicone rubber decreased the least after aging at 250?,there was still a high maintenance rate,and the heat resistance was the best.Finally,three metal surface treatment processes were selected,and the effect of metal surface treatment process on the adhesion between silicone rubber and metal was studied by 180°peel test.The results showed that after mechanical grinding,solvent cleaning and phosphating treatment,the 180°peel strength of silicone rubber and metal was the largest and the bonding strength was the best.On this basis,four silane coupling agents were added to silicone rubber,and the properties were tested and analyzed through 180°peel test,mechanical property test,compression set test and heat and oxygen aging test.The results showed that added??(2,3-epoxy propoxy)propyltrimethoxysilane(KH-560)had the highest peel strength between silicone rubber and metal,and the failure types also occurred in the interior of silicone rubber,with the smallest decline in mechanical properties,the lowest compression set rate and the smallest impact on heat resistance.Through the thermal durability analysis,it was found that the mass loss of the prepared silicone rubber at 350?would take about a week.With the decrease of temperature,the time would be longer and longer,indicating that the prepared silicone rubber material had strong thermal stability and excellent heat resistance.