Study On New UV Curing Liner In High Energy Solid Rocket Engine

The liner is an adhesive interlayer between the propellant and the thermalinsulation layer or case, and the adhesion of its interface will directly affect thestructural integrity and functional reliability of the rocket engine. Nitrate esterplasticized polyethylene (NEPE) propellants contain large numbers of nitroglycerinsand other nitrates. During the process of pouring, curing and storage of the propellant,the small molecules of nitrates can easily migrate to the surface of the propellant andbe absorbed by the liner, which results in the debond between the liner and propellantgrain, leading to the rocket failure. Therefore, developing a high-performance liningmaterial applied to NEPE propellants is a vital task for researches on the solid rocketengine. Based on the current situation of the use of liner, the study intends to applyingUV curving technique to the liner, preparing a new liner with UV curving activitythrough optimization of formulation and synthetic technique, which has a goodmechanical property while effectively reducing the migration of nitrates.The study synthetizes a kind of base resin using the polyurethane acrylate as theUV curving liner according to the requirements of the use of liner and the relationbetween structure and property of polyurethane. Through discussion of raw material,reaction time and synthetic process, synthetic technological conditions of the baseresin are obtained: the first step is to synthesize a prepolymer terminated by isocyanateat80℃constituted by hydroxyl-terminated polybutadiene (HTPB),1,4-butanediol andisocyanate； the second step is to introduce photoactive groups through addingmeasured hydroxyethyl acrylate at70℃, which is catalyzed by0.1%dibutyltindilaurate in the reaction process.The study synthesizes a series of different molecular structures of linear baseresins with different diisocyanates, discusses the effect of the isocyanate component,curing parameter as well as the hard segment content on the mechanical property andswelling property of the UV curing liner, and obtains a formulation of the base resinwith relatively optimal comprehensive property: using2,4-toluene diisocyanate as theisocyanate component with the curing parameter of1.22and the hard segment contentof30%; determining the UV curing system through investigating the UV curing time,photoinitiator and coating solvent: Using Photoinitiator1173with the dosage of3%ofthe mass of the base resin and methylbenzene as the coating solvent, UV curing time being about20s.The study explores the application property of UV curing liner with the optimalformulation, which has a good adhesion with the thermal insulation layer and HTPB. Itverifies that the liner can better inhibit the migration of nitrates through swellingproperty comparison with the conventional thermal curing liner.