Synthesis And Research Of High Viscosity And Heat-Resistant Polyurethane Adhesives

Polyurethane adhesive has the characteristics of higher strength, higher wearingresistance, low temperature resistance, oil resistance, corrosion resistance to chemicals, etc.Since 1930s, it has been applied widely in various fields. At same time, its shortcoming ofpoor heat resistance has arisen. Melamine is a nitrogen heterocyclic organic compound, whichhas the stable structure of benzene rings and contains aπbond in the molecular. Melaminehas a relatively high melting point and is not easy to decompose. Polyurethane adhesives withmelamine will have the characteristics of heat resistance.In the paper, the method of prepolymerization had been adapted in the process ofsynthesis. Polytetrahydrofuran glycol (PTMEG) was the soft segment, isophoronediisocyanate (IPDI) was the hard segment, dibutyltin dilaurate (DBTL) was a catalyst, MOCA(4,4’-Methylene bis(2-chloroaniline)) and 1,4-butylene glycol (BDO) were used as the chainextension agent respectively, and melamine was added, then the ammonia methyl silicone hadbeen implanted in PTMEG polyurethane .The L9(34) orthogonal experiment method was used to decide the better processconditions and formulations in the experiments. The structure and performancecharacterizations of synthetic products were determined by using FTIR infrared spectrum, TG(differential thermal scanners) and ultraviolet spectrum. The tests of peel strength andelongation at break for the polyurethane adhesives film had been also measured. The resultsshow: when BDO was as the chain extension agent, melamine was as the modifying agent andammonia silicone fluid was as end-capping reagent, the optimum technology conditions forPTMEG polyurethane adhesive were: the reaction time was 6 hours, reaction temperature was85℃, R value was 2.7, the ratio of nBDO:nIUPACwas 1:1, the end-capping reagent was 4%, the catalyst was 0.12%, the ratio of solvent dimethyl sulfoxide(DMSO) to reactant mixture was 1to 2. Under the conditions, the polyurethane adhesives had the better heat resistance, itsthermal decomposition temperature was 265.2℃. Compared with polyurethane adhesivesthose not used melamine for modification, the synthesized polyurethane adhesive withmelamine-free, the temperature was up 46.6℃. It had better elongation and strength.