The Study Of Room-Temperature Curing Epoxy Adhesives With High Toughness For Untreated Surface Of Nitrile Rubber

The aerospace industry has always been the main driving force for the development of modern adhesive technology.How to obtain higher bonding strength is an important content of research in this field.As for nitrile rubber used as a thermal insulation material for the inner wall of solid rocket engines,its area to be bonded is large,heat curing is hard to be achieved,and a room temperature curing adhesive is required on it.Generally,when bonding nitrile rubber,it is necessary to perform surface treatment on it to achieve a good bonding effect.However,the surface treatment on it increases the bonding process steps,takes a long time and costs a lot,and sometimes the surface treatment conditions are not available at the bonding site.For the untreated surface of nitrile rubber,adhesive properties can be improved by toughening the adhesive.Therefore,it is of great significance to develop room temperature curing hightoughness adhesives to achieve effective bonding with untreated surface of nitrile rubber.In this paper,carboxyl-terminated acrylate polymer and polysulfide rubber were used to toughen epoxy resin.Epoxy resin modified with carboxyl-terminated acrylate polymers(PAA)of different mass fractions was adopted,and the types of epoxy resin curing agents were screened to determine suitable epoxy room temperature curing agents.Polysulfide rubbers with different mass fractions were used to further toughen the modified epoxy resin to prepare a modified epoxy resin with better toughness.FR-IR and XPS analysis showed that both the-COOH group of PAA and the-SH group of polysulfide rubber reacted with epoxy groups to form a chemical bond among PAA,polysulfide rubber and epoxy resin,which was beneficial to increase adhesive properties of epoxy resin.SEM analysis showed that PAA and polysulfide rubber were uniformly dispersed in the epoxy resin,and the fracture surfaces of the epoxy resin produced silver morphology and island-like structures,respectively,increasing the toughness.By controlling the coating thickness,coating time and applied pressure on the adhesive,the bonding process and curing process of the epoxy adhesive were optimized.The results showed that,for the untreated surface of nitrile rubber,when the curing temperature is 30 ° C,the curing time is 2 d,and the additional pressure is 0.15 MPa,its peel strength and shear strength can reach 4.12 N / mm and 2.89 MPa,and the ratio of its elongation at break can reach 66.12%,As a result,a better bonding effect of the untreated surface of nitrile rubber is obtained.The modified epoxy adhesive was treated under heat aging and high and low temperature alternating environments.The results showed that its peel strength,shear strength and elongation at break all kept stable.TG analysis showed that thermal aging and high-low temperature alternation had little effect on the thermal weight loss of the modified epoxy resin.If the modified epoxy adhesive was tested at-40 and 100 ° C respectively,its peel strength and shear strength remained stable without significant changes,indicating that the material had good temperature adaptability.