Synthesis And Modification Of Waterborne Polyurethane Plastic Coatings Based On Polypropylene Carbonate Diol

CO₂copolymer polyol(PPC)is a new material for synthesis of polyurethane.Compared to the traditional polyether and polyester polyurethane,PPC polyurethane has the advantages of hydrolysis resistance and high mechanical strength.Our research group has been engaged in the synthesis and application of PPC for many years,and has developed a PPC waterborne polyurethane material with excellent performance.In this paper,a series of PPC based waterborne polyurethane acrylate(PUA)emulsion were synthesized used PPC,IPDI,DMPA,hydroxyl ethyl methacrylate(HEMA)and styrene(St)as the main raw materials for the purpose of the plastic paint.The synthesis process,emulsifier,initiator,PU/PA,the hard and soft segment content of PU and PA,the content of HEMA,and the ammount of the curing agent were discussed in order to optimize the plastic coating performance.Diacetone acrylamide(DAAM),dionyl hydrazine adipate(ADH)and glycidyl methacrylate(GMA)were also used to modify PUA.Based on the crosslinked PUA,kh-550 was further used to obtain silane coupling agent and crosslinked double modified PUA emulsion.The corresponding double modified plastic coating was prepared,and the influence of kh-550 on the properties of the modified PUA was investigated.In addition,PUA polyols with-OH group at the end of the PA and PU chains were synthesized,which reacted with isocyanate curing agent to obtain the two-component plastic paint.,The influence of the hydroxyl content,PU/PA ratio,n-NCO/n-OH on the properties of the two-component plastic paint.The results are as follows:(1)the synthesis process,external emulsifier and initiator have great influence on the properties of the single-component PUA emulsion and plastic coating.The optimum synthesis process was that styrene(St)and other vinyl monomers were introduced to reduce the viscosity before neutralization followed by the addition of the external emulsifier in water,and then the mixture monomers were emulsifid and initiated to prepare single-component PUA emulsion.The emulsifier was SDS/op-10(1 or 1.5),and the initiator was ammonium persulfate(APS).The plastic coating prepared by this process exhibitted good adhesion to PS.(2)PU/PA ratio,soft and hard sections of PU and PA components,and HEMA content have great influence on the performance of PUA emulsion and plastic coating.With the decrease of the PU/PA ratio,the adhesion,pencil hardness and ethanol resistance of the film were improved.However,the water resistance of the films had no significant variation,and the centrifugal stability of the emulsion decreased.The film adhesion increased with increasing the content of styrene in PA.With the increase of the amount of HEMA,the film adhesion,pencil hardness and the water resistance improved.The alcohol resistance showed no obvious variation.The centrifugal stability decreased with the ending proportion of HEMA increasing.Moreover,an appropriate amount of curing agent could improve the film hardness and resistance of the single-component plastic coating films companied by the decreasing of the adhesion.(3)Excellent storage stability and adhesion(level 0)to the PS substrate of the single-component plastic coating were reached when the PU/PA ratio was 4:6,m(St)/m(PA)was higher than 70%,the end sealing proportion of HEMA was between20%and 30%,the PUA emulsion was prepared by the optimum synthetic process mentioned above.However,the pencil hardness and alcohol-resistance needed to be further improved.(4)though the crosslinking of the plastic coating,the pencil hardness and alcohol-resistance was improved.The alcohol-resistance of the plastic coating has reached the application requirements by further modifing by kh-550.However,the pencil hardness of PS plate was still grade B.(5)the-OH content in PU and PA component,PU/PA ratio and n-nco/n-oh of PUA polyols have extremely influence on the performance of the two-component plastic coating.When m(HEMA)/m(PA)was 25%,Rt was 0.8,PU/PA ratio was 4:6,and n-nco/n-oh was1.5 in PU,the two-component plastic coating was used as a surface coating with excellent adhesion(level 0)and pencil hardness(grade H)on PS substrate.The coating film has good resistance,which meets the application requirements of water-based coating and has a broad application prospect.