Study On Synthesis And Properties Of Polyurethane Based On TMXDI

Tetramethylxylene diisocyanate(TMXDI)is a new developed aliphatic isocyanate,which is widely used in water-based polyurethane(WPU),inks,sealants,adhesives,elastomers,automotive coatings and wood coatings.TMXDI can effectively improve the strength,adhesion,appearance,elasticity and durability of polyurethane products.This thesis has carried out a series of studies around TMXDI synthetic polyurethane.First,we synthesis NCO terminated precursor by using synthesized polyester as the soft segment,TMXDI as the hard segment and dimethylolpropionic acid(DMPA)for chain extension.SCA resins with anti-sagging properties was synthesized by adding benzylamine and more TMXDI into above NCO terminated precursor.Through designed experiments,it is found that the thixotropic factor of SCA resin is closely related to the NCO value of the prepolymer.The variable factor increases first and then decreases when SCS crystal content increase from 1% to 9%.Through screening,when the NCO value is 2% and the SCA crystal content is 4%,the thixotropy is the best,that is,the sag resistance is the strongest.In the application test of automotive coatings,the appearance of the coating by using lab SCA resin sample,the grid and the stone-strike adhesion can all meet the requirements,possessing potential commercialization value.Secondly,the anionic WPU Emulsion is synthesized by using polyester,TMXDI,dimethylolpropionic acid(DMPA),and dimethylethanolamine(DMEA);two different isocyanates Type of cationic WPU emulsions are synthesized by using TMXDI or isophorone diisocyanate(IPDI),N-methyldiethanolamine(N-DMEA),glacial acetic acid.FTIR,GPC,particle size analysis,Potential analysis,rheological behavior testing are performed on those emulsions.It can be found through experiments that the prepolymer synthesized by using TMXDI has a low viscosity compared with prepolymer synthesized by using IPDI,which is beneficial to synthesize a higher molecular weight WPU emulsion.As the degree of neutralization increases,the particle size of the WPU emulsion becomes smaller,the potential increases,the viscosity becomes higher,and the dispersion and stability of the emulsion are improved.In this paper,when the neutralization degree is 95%,the WPU emulsion obtained has the best dispersibility and stability.Comparing the rheology curve of cationic WPU emulsions and anionic WPU Emulsion,the viscosities of emulsions havethe same change rule.The application test of anionic WPU emulsion for automotive coatings can meet the requirements on appearance and stone adhesion.