| As society continues to focus on environmental issues, producing less environmental pollution, save energy product becomes a trend. Therefore, the study of uv curable materials obtained fast development, compared with the traditional curing material, uv curable materials greatly reduces the emissions of volatile organic compounds. This paper studies the "thiol-ene" system in the uv curing system, based on thiol compounds generally has very bad smell, and synthesizing large monomers can eliminate unpleasant smells, so we first obtain hyperbranched thiol compounds. With the addition of thiol monomers, the system convert chain polymerization into step-growth polymerization reaction, eliminating the oxygen inhibition and gelation inhibition, and double bond conversion rate were improved significantly. In addition, this system is not only with no needs for photo-initiator, which is often expensive, and greatly reduces the cost; But also eliminates the initiator to absorbs ultraviolet light, saving the energy, and provides the condition for producing the thicker specimen and small specimen.The research conten is as follows:2-methyl-1,3-Propanediol di(3-mercaptopropionic) ester (PD3ME),1,1,1-Tris(hydroxymethyl) propane tri(3-mercaptopropionic) ester (HPT3ME), Pentaerythritol tetra(3-mercaptopropionic) ester (PT3ME) were obtained through esterification reaction by2-methyl-1,3-Propanediol,1,1,1-Tris(hydroxymethyl)propane, pentaerythritol and3-mercaptopropionic, respectively. P-toluene sulfonic acid was used as a catalyst. The compounds were determined by FTIR,1H NMR. The influences of the acid alcohol ratios, reaction time, reaction temperature, dosages of catalyst and water-carrying agent on the yield were investigated. The optimum reaction conditions of a series of epoxy methacrylate-thiol compounds were obtained by orthogonal experiment.The optimum reaction conditions are as follows:(1) PD3ME:n(acid):n(alcohol)=2.4:1,11h reaction time, reaction temperature120℃, catalyst dosage of3%(by alcohol meter), dosage of dehydrant is16times (by alcohol meter), the production rate is96.4%;(2) HPT3ME:n(acid):n(alcohol)=3.6:1,12h reaction time, reaction temperature120℃, catalyst dosage of9%(by alcohol meter), dosage of dehydrant is10times (by alcohol meter), the yield is91.8%;(3) PT3ME:n(acid):n(alcohol)=5.5:1,13h reaction time, reaction temperature130℃, catalyst dosage of5%(by alcohol meter), dosage of dehydrant10times (by alcohol meter), the yield of86.3%.Hyperbranched polymer were synthesized by combined thiol terminal functionalization and "thiol-ene" addition reaction. PTE-Ai and B1were synthesized by "thiol-ene" between two mufti-functional thiol monomers and a new vinyl benzyl ester (BMPVB), respectively. Furthermore, PTE-A2, B2, A3, and B3, were synthesized by successive reactions of thiol glycolic acetate esterification and "thiol-ene" photo addition. The products were characterized with1H NMR, FTIR and GPC methods. And the analysis results reflected that obtained hyperbranched polymer owned high degree of branching.(1) PTE-A1/B1:molecular weight1200g·mol-1and1500g·mol-1,the functionality is6and8respectively;(2) PTE-A2/B2:molecular weight3694g·mol-1and4774g·mol-1, the functionality is about14and17, respectively;(3) PTE-A3/B3:molecular weight is8714g·mol-1and11274g·mol-1, the functionality is about28and36respectively;PTE-A3, PTE-B3hyperbranched polymer were modified by3-mercaptopropionic, and got hyperbranched thiol polyester PTE (SH)-A3, PTE (SH)-B3. Then obtained poly-thiol were used in photoinitiator-free "thiol-acrylate" systems with different mufti-functional acrylate monomers (HDDA, TPGTA, TMPTA, TMP(EO)3TA and DPHA). The UV induced photo-polymerization of "thiol-acrylate" systems and evaluated by DSC method. The results are as follows:(1)"thiol-acrylate" system performed very high photosensitivity and cured very fast under UV irradiation without addition of photo-initiator in air atmosphere.(2) the concentration of thiol functional group is higher, the uv polymerization reaction rate is larger.(3) the concentration of ene functional group is higher, the uv polymerization reaction rate is larger.(4) the lower the viscosity, the higher the conversion of ene. |
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