Preparation And Application Of UV Curable Polyurethane Acrylate Transparent Viscoelastic Material

Curved screen has the advantages of wider vision and so on,in recent years,it has been widely used in the field of hand-held devices such as mobile phones.However,in the important step of the production process of curved screen-screen lamination,the transparent viscoelastic material?TVM?used in the bending position of the screen has poor fluidity before curing,and it is easy to generate bubbles under the actual working conditions,so the yield is low,resulting in high cost of finished products.Therefore,it is urgent to improve the performance of TVM to improve the yield and reduce the cost.At present,the commonly used polyacrylate TVM film has poor fluidity and low modulus of elasticity at room temperature,so it is difficult to process and store for a long time.Although liquid TVM can solve the bubble problem and storage processing problem,it also has the disadvantages of easy overflow and complex use process.In this study,the UV curable polyurethane acrylate transparent viscoelastic material?PUA?was prepared,then the polyacrylate?PA?was synthesized and blended with PUA to improve its adhesion properties.It had good fluidity at high temperature?i.e.lamination temperature,80?,HT?,large and stable elastic modulus at room temperature?RT?,which solved the above two problems.The specific research are as follows:?1?PUA was prepared by using polycarbonate diols?PCD,molecular weight 1000 and2000?as polydiols,isophorone diisocyanate?IPDI?,1,6-hexamethylene diisocyanate?HDI?and4,4'-dicyclohexylmethane diisocyanate?HMDI?as diisocyanate?DI?,1,4-butanediol?BD?and3-methyl-1,5-pentanediol?MPD?as chain extender?CE?,2-hydroxyethyl acrylate?HEA?as end capping agent and MEK as solvent.The optimum reaction conditions were determined as follows:after mixing the pre-dehydrated PCD and MEK evenly,added DI and catalyst at 60?,after the temperature was stable,raised the temperature to 80?for 1 h,then added CE for 1.5h,and finally added HEA for 2 h.UV-vis test showed that the transmittance of PUA in visible light range was more than 90%,FTIR analysis showed that PUA had double bond characteristic peaks before curing,and disappeared after curing,indicating that HEA was effectively involved in the curing reaction.?2?The effects of different isocyanate index R?R₁ and R₂?,different monomer types and consumption on the properties of PUA were discussed.The rheological and adhesion property test results showed that when R₁?2.5,the high temperature fluidity of PUA could be improved by increasing R₁ or increasing R₂ when R₁ was constant,increasing the amount of HDI and BD could improve the room temperature elastic modulus and stability,while increasing the amount of HMDI and MPD could improve the high temperature fluidity;The GPC,gel rate and adhesion properties analysis showed that,when M_w<200K,the higher the gel rate of the PUA was,the lower the peel strength was.Through a lot of experiments,we determined that:n_?HDI?:properties formulation,but the adhesion properties?especially at HT?of the PUA-13 series prepared from this formulation needed to be improved..?3?In order to improve the adhesion properties of the PUA-13 series,PA was prepared by using azodiisopentnitrile as chain initiator,mercaptoethanol as chain transfer agent and MEK as solvent under certain conditions,then PA modified PUA was obtained by physical blending of PUA and PA in a certain proportion.The effects of different PA formulation and blending ratio on the performance of PA modified PUA were studied.DSC and UV-vis test results showed that the prepared PA had good compatibility with the PUA;The gel rate and adhesion properties analysis showed that with the increase of PA ratio and the dosage of MMA in the PA synthesis,the gel rate of PA modified PUA decreased,RT peel strength increased first and then decreased with the increase of PA ratio,while HT peel strength increased with the increase of PA ratio.The rheological analysis shows that the elastic modulus of PUA after PA modification is higher than that before PA modification,while the fluidity at high temperature is lower.Through lots of experiments,we preliminarily determined that when PA synthesized by obtained system had better combination properties.