Toughening The High Temperature Epoxy Resin With Epoxidized Phenoxy Resin

Epoxy resin has excellent mechanical properties,insulation properties,corrosion resistance,adhesion properties,low shrinkage properties and processing properties.It is widely used in structural adhesives,coating protection,composite resin substrates,electronic components and other applications.However,the conventional epoxy resin prepolymer generally has a low average molecular weight(<5000);due to high crosslink density after curing,its toughness,fatigue resistance and impact resistance are low,which limits its applications.Especially in the field of high heat resistance requirements,the conventional toughening method is generally difficult to achieve both toughness and heat resistance.Therefore,this paper chooses ultra-high molecular weight thermoplastic phenoxy resin(PB)as raw material and epoxidizes,the epoxidized phenoxy resin is then mixed with a common epoxy resin,the purpose to improve mechanical and thermal resistance.The main contents,results and discussion of this paper are as follows:1.In this paper,epichlorohydrin is used to epoxidize some of the hydroxyl groups of phenoxy resin under the action of catalyst,improve the compatibility with epoxy resin matrix and participate in curing crosslinking reaction.By studying the effect of performance that mixing epoxidized phenoxy resin obtained under different reaction conditions with epoxy resin,epoxidized phenoxy resin(MPB)with epoxy value of 0.092mol/100 g was selected as the research object.2.The mechanical properties,heat resistance and microscopic morphology of impact fracture surface of different content of MPB/EP were investigated,which was used to explore its toughening mechanism.Comparative analysis showed that the cured product containing 7.5wt% of epoxidized phenoxy resin had the best impact performance,and the cured product containing 5wt% of epoxidized phenoxy resin had the highest strength and modulus.Moreover,the glass transition temperature of the cured product containing different contents of epoxidized phenoxy resin is slightly higher than that of the pure epoxy resin cured product,achieving the goal of simultaneously improving the toughness and heat resistance of the epoxy resin.Compared with pure resin,epoxidized phenoxy resin exhibits better reinforcement,toughening effect and heat resistance.The bending strength,tensile strength,modulus and impact strength of MPB/EP were increased respectively by 15.99%,14.07%,24.62% and 69.14%,and thermal stability and glass transition temperature are not affected.3.The mechanical properties and heat resistance of other commercial toughening agents(including dendrimers,block copolymers,three epoxidized thermoplastic polymers)toughened modified epoxy resins were researched,and compared with the MPB/EP system.The results show that both the commercial dendrimer and the block copolymer can significantly reduce the glass transition temperature,and the mechanical property improvement effect is worse than MPB/EP.The commercial epoxidized thermoplastic polymer can significantly improve the impact properties without damaging other mechanical properties and heat resistance.It is found that MPB has better effect in improving the strength,modulus and glass transition temperature of epoxy resin,except that the toughening effect is slightly lower than that one of the commercial epoxidized thermoplastic polymers.