Preparation And Characterization Of UV-curable Waterborne Polyurethane Acrylate

UV-curable waterborne coating is a novel type of environmental friendly coatings.It caters to the need of environmental protection,and responds to people's demand for high quality living,which has been greatly researched and developed in recent years.UV-curable waterborne polyurethane acrylate(UV-WPUA)combines the advantages of both polyurethane and polyacrylate.It is a prime material with good heat resistance,water resistance,abrasion resistance,flexibility and adhesion.In this article,UV-curable waterborne polyurethane acrylate emulsions were prepared by step polymerization.Polyethylene glycol(PEG)and isophorone diisocyanate(IPDI)respectively act as the soft segments and hard segments,dimethylolpropionic acid(DMPA)act as hydrophilic chain extending agent to introduce carboxyl groups,2-hydroxyethyl methylacrylate(HEMA)act as capping agent to introduce carbon-carbon double bonds.The optimum technology were analyzed and discussed by the result of test and characterizition.The structure of WPUA was characterized by FTIR.Other way,the properties of the emulsions and films were tested by Malvern particle size analyzer,viscometer,etc.The optimum technologies were described as follows: the initial R value(n-NCO /n-OH)was 2,the molecular weight of PEG was 600,the addition amount of DBTDL was 0.025%,the prepolymerization temperature was 65 ?,the prepolymerization time was 170 min,the amount of DMPA was 5%,the chain extension temperature was 85 ?,the end capping temperature was 75 ?,the neutralization degree was 100%.The emulsion was stable with transparent appearance,the particle sizes was small with narrow distribution,the hardness of the film reached 2H,the impact strength was up to standard and the flexibility is excellent.In order to improve the hydrophobicity and thermal performance of the films,and reduce the cost of the resin,castor oil was added to the resin.Castor oil based waterborne polyurethane acrylate(CO-WPUA)was prepared and characterized by FTIR,Malvern particle size analyzer,viscometer,etc..The results showed that the appearance of CO modified polyurethane acrylate emulsion was opaque,while the particle size ofCO-WPUA was increased,and the particle size distribution of CO-WPUA was discrete,the stability of emulsion was decreased.However,both the hydrophobic property and heat resistance of the films were improved after modification.