| Waterborne polyurethane(WPU)is one of the most representative water-based polymer products,which has the advantages of non-toxic,safe and environmental protection and is widely used in many fields such as water-based ink,paint,adhesive and leather finishing agent.However,WPU is limited to a wider range of practical application because of its defects such as poor water resistance,low gloss,high cost and so on.The acrylate modified waterborne polyurethane can improve water resistance and heat resistance of WPU,reduce the cost of WPU and broaden the application range of WPU.This work made waterborne acrylate modified polyurethane Emulsion(WPUA)as study object,designed and applied different cross-linking system to improve the performance of the film,especially water resistance,systematically studied the effects of formulation,reaction process and cross-linking agents on the properties of PUA emulsions and latex films.The main work of this paper is as follows.(1)A serious of waterborne acrylate modified polyurethane(WPUA)emulsions were prepared by using coupling agent trimethylolpropane monoallyl ether(TMPME)brought carbon-carbon double bond into the side chain of the polyurethane segment and the effects of prepolymerization time,acrylic ester synthesis process,the amount of hydrophilic monomer,the type and amount of viscosity reducer,solid content on preparation conditions of WPUA Emulsion were studied.When the content of hydrophilic monomer was more than 3wt%and the dosage of viscosity reducer tetrahydrofuran(THF)was 10%and the solid content of emulsion was 30%,the synthesis process of PUA emulsion had excellent stability and repeatability and the PUA emulsion had good stability.(2)A series of PUA emulsions with different coupling agent content were prepared.The microstructure of PUA emulsion was studied by TEM,it was observed that the latex particles had a core-shell structure and the particle size and distribution of latex particles in TEM photographs were similar with the data tested by DLS measurement.The effects of TMPME content on properties of WPUA emulsion and latex films were studied,The results showed that water resistance,heat resistance,crosslinking degree,solvent resistance and mechanical properties was significantly improved when appropriate amount of TMPME was introduced,the water absorption of films was reduced to 7.0%when TMPME content was 3wt%and the tensile strength of the PUA latex film can reach 8.7Mpa when the TMPME content was 2wt%.However,the water resistance,crosslinking degree and mechanical properties were weakened when TMPME content was too high.The contact angle of the latex films decreases with the introduction of TMPME.This paper also studied the grafting rate of PUA polymer,including the studies of test methods and tests of grafting rate of PUA polymer with different coupling agents and different contents of coupling agent.The results showed that the amount of TMPME has a significant effect on the grafting rate of PUA and a certain amount of TMPME endowed PUA emulsions with high graft modification rate,but the grafting rate of PUA will decrease slightly and the film forming performance will be weaken when excessive TMPME introduced.(3)The PUA emulsions were further modified by ketone hydrazine crosslinking system and organosilicon crosslinking agents respectively,the results showed that DAAM+ADH crosslinking system has little effect on the water resistance of PUA,while the organosilicon crosslinking agent A-174 was beneficial to improve the water resistance of PUA latex film,When TMPME content was 2wt%and organosilicon crosslinking agent A-174 content was 4wt%,the latex film had excellent water resistance that the water absorption of latex film was 7.8%and the film after absorbing water was transparent.A-174 can increase contact angle of PUA latex films,the maximum contact angle is 94°,however,the introduction of DAAM + ADH crosslinking systems decreased the surface tension of PUA emulsion and increased films’ contact angle. |
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