Synthesis And Properties Of Waterborne UV-curable Itaconic Acid-based Unsaturated Polyester

With the gradual development of polymer materials in the world,unsaturated polyester is widely used in clothing,food packaging,coating and other fields,and gradually become an important part of each emerging advanced technology.Now it can be seen everywhere in our daily life.However,most unsaturated polyester products on the market are made from petroleum resources as raw materials.Faced with the imminent shortage of petroleum resources,it urges people to seek solutions from renewable resources.Itaconic acid(IA)is biotechnologically produced by fermentation of sugar or molasses with the fungi aspergillus terreus.It is inexpensive and widely available,and has attracted extensive attention in the polyester field in recent years.However,the adhesion and flexibility of the coating system of itaconic acid unsaturated polyester are not ideal.Therefore,it is of great significance to solve the defects of adhesion and flexibility of the coating for the green and sustainable development of polymer materials.In this study,a series of water-based UV unsaturated polyester were synthesized with itaconic acid as raw material,its structure and coating properties were characterized.The main research contents are as follows:In the first part,itaconic acid,citric acid and 1,6-hexanediol were used as raw materials to synthesize a series of itaconic acid bio-unsaturated polyester(PICH)by melt polycondensation.The effects of different reaction conditions on the synthesis of PICH were researched.The chemical structure of PICH was characterized by FTIR and ¹H-NMR,and the thermal stability and mechanical properties of the coating were investigated.The results showed that with the addition of citric acid,the coating film exhibited excellent thermal stability,and its flexibility and adhesion were obviously improved.When the molar ratio of citric acid to itaconic acid in PICH was 15:85,the comprehensive properties of PICH coating was the best,and the film hardness,flexibility,adhesion,impact resistance,gel content and water absorption were 2H,3mm,grade 2,50kg.cm,82.63%and 17.57%,respectively.The second part,in determining the molar ratio of itaconic acid and citric acid,four kinds of biological biomass UV unsaturated polyester were synthesized respectively with different biological alcohols(1,3-propanediol?1,4-butanediol?1,5-glutaric and 1,6-diol),and the structure of polyesters have been confirmed by FTIR and 1H-NMR.Subsequently,based on these unsaturated polyesters,UV water-based coatings were prepared,and their thermal stability and coating properties were researched.The results showed that these water-based UV coatings had good pencil hardness,thermal stability,water resistance and solvent resistance,among which PI₈₅C₁₅Pe system had the highest Gel content of 85.44%and the lowest water absorption of 16.43%.In the third part,the bio-based unsaturated polyesters prepared above were mixed and copolymerized with acrylated epoxy soybean oil(AESO)to obtain the full bio-based UV coating.The modified emulsion was researched by particle size analysis and surface tension test.The coating properties of polymer were tested in detail.The results showed that with the increase of AESO content,the average particle size of emulsion increased and the surface energy decreased.In addition,the modified itaconic acid unsaturated polyester system had good coating properties.The coatings modified by AESO show high hardness,flexibility and solvent resistance.With the increase of AESO content,the contact angle of PICH modified coating increased from 65°to 99°,while the contact angle of other coatings increased.The addition of AESO improved the thermal stability of the coatings.The initial degradation temperature of PICH system were increased from 209.67?to 246.42?,and each modified coating showed higher gel content and lower water absorption.