| As a traditional rigid polymer material,Epoxy resin often used for water-based polyurethane modification.However,The emulsions modified by epoxy have the problems such as unstable thermal storage and insignificant modification effects.In this research,with polypropylene carbonate polyol(PPC),isophorone diisocy anate(IPDI),and bisphenol A epoxy resin E-44 as the main raw materials,the waterborne epoxymodified polyurethane was obtained.At the same time,the effects of the prepolymerization process,the addition of the chain extension process and the ring opening on the modification performance of the waterborne polyurethane were studied.It is found that although epoxy modification can improve the performance of the polyurethane film,the introduction of epoxy groups usually affects the stability of the emulsion.It hinders the practical application of epoxy modified polyurethane emulsion.Therefore,a We studied the effects of epoxy addition process and content,hydrophilic monomer type and content,post-chain extender,neutralization and curing process on the performance and storage stability of EPUD.Finally we obtained the epoxy-modified waterborne polyurethane emulsion with better comprehensive performance and stable storage.The specific research results are as follows:1.Extending the reaction time of epoxy resin in the system or increasing the reaction temperature can improve the thermal storage stability of EPUD.For example,The thermal storage stability of EPUD can be improved by addingepoxy resinin the prepolymerization stage,extending the curing time and curing temperature and other technological means2.Reducing the epoxy,carboxyl and triethylamine content of the system can significantly improve the thermal storage performance of EPUD.Such as converting the epoxy resin into epoxy polyol through ring-opening,replacing part of carboxylic acid type hydrophilic monomer with non-ionic,sulfonate type hydrophilic monomer,,reducing DMPA content and adding triethylamine can improve the heat storage stability of the modified emulsion 3.The adjustment of the post-chain extender can effectively improve the thermal storage stability of EPUD.Among them,the bifunctional alcohol chain extender has the best effect and the modified emulsion has the best performance.4.low content of epoxy can increase the degree of cross-linking between molecular chains and the tightness of emulsion particles,reduce the particle size of emulsion particles,and improve the performance of emulsion film;when too much epoxy resin is added,the performance of the emulsion decreased.,The emulsion can be further cured by means of film formation and a paint film was obtained after curing has high hardness,excellent mechanical properties and good alkali resistance.5.With the increase of epoxy content,the particle size of the modified emulsion gradually increased,reaching to 198.3nm;the hardness of the paint film gradually increased,reaching to 2H;the hydrophilic performance gradually decreased,and the water absorption rate was 5.2%;Decomposition stability is within the range of 0-20%,the initial thermal decomposition temperature of the film increased significantly,up to272?.6.The properties of modified emulsions prepared by different epoxy types are different.The modified emulsion prepared by epoxy E-44 has a maximum particle size of 157.3nm and the best mechanical properties of the film is 29 MPa;The water resistance of the film of the adhesive prepared by epoxy E-51 is the best,and the water absorption rate is only 4.5%;the emulsion prepared by E-20 has the smallest particle size,and the thermal decomposition of the film is stable. |
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