Preparation And Properties Of Acrylate-modified Waterborne Polyurethane With Interpenetrating Networks

Today,with the increasingly serious global environmental problems,waterborne polyurethane(WPU)as a safe,non-toxic and excellent green environmental protection material has attracted more attention.However,a single WPU is limited by its own molecular structure characteristics,which has the problems of poor water resistance,weather resistance and low mechanical properties.Therefore,using acrylate(PA)as a modified component to making up for the performance defects of WPU by its own characteristics has become one of the important directions of WPU high-performance research.In this study,a series of waterborne polyurethane acrylate polymers(WPUA)were prepared by interpenetrating polymer network(IPN)method with polytetrahydrofuran glycol(PTMG),isophorone diisocyanate(IPDI),methyl methacrylate(MMA),butyl acrylate(BA),styrene(St)and isooctyl acrylate(EHA)as main raw materials and trimethylolpropane(TMP)and divinylbenzene(DVB)as crosslinking agents.The effects of interpenetrating polymer network structure type(IPN,Semi-IPN),PU/PA value,second crosslinking network density,different types of acrylate monomers and the ratio of soft and hard monomers on the properties of WPUA composite emulsion and its film were discussed.The results show that:(1)Compared with the two kinds of interpenetrating network structure WPUA film,the film with IPN structure has lower water absorption,better dynamic mechanical properties and thermal stability,while the film with Semi-IPN structure has better hydrophobicity;At the same time,with the decrease of PU/ PA value in the system,the emulsion particle size gradually increases,the tensile strength of the film decreases,the water absorption decreases gradually,and the dynamic mechanical properties and thermal stability of the film become better.(2)The density of the second crosslinking network is changed by controlling the amount of PA component crosslinking agent DVB.When the content of DVB reaches 0.75 %,WPUA film shows better dynamic mechanical properties and thermal stability.With the increase of DVB content,the water resistance and mechanical properties of the film improved continuously.When the DVB content reaches1.25%,the water absorption of the film decreases to the lowest,reaching 7.13 %,the water contact angle increases from 97.2 ° to 106.5 °,and the tensile strength also increases by129.2 %.(3)By comparing the two kinds of WPUA with acrylate monomer composition of MMA/EHA and St/BA respectively,it was found that the particle size of the emulsion decreased with the increase of the content of hard monomer MMA and St.At the same time,the increase of PA hard monomer content also leads to the enhancement of hydrogen bond interaction between WPUA and PU,which makes the tensile strength and elongation at break increase obviously.In addition,the non-polar segments in hard monomers also had an effect on the water resistance of WPUA films.When the content of hard monomers accounted for 40 % of the total PA,the water absorption of WPUA films in MMA/EHA group and St/BA group decreased by 4.11 % and 3.85 %,respectively.