Preparation And Properties Of Soybean Oil Based Nano-compsite Coating Via Thiol-ene/radical Hybrid Photopolymerization

In this article, a series of UV curable epoxidized soybean modified resins/SiOx hybrid coatings were prepared via thiol-ene/radical photopolymerization and the inorganic phase were introduced through blending with polyhedral oligomericsilsequioxane(POSS), sol-gel method or blending with SiO2 nano particles. Photopolymerization process and properties of the coatings with different x(x was 1.5、1.6、1.75、1.85、1.95、2) were measured and the details of the dissertation are as follows:Epoxidized soybean oil was modified to prepare acrylated epoxidized soybean oil(AESO) and vinyl/acrylate ended soybean oil(VASO), which were blended with mercaptopropyl polyhedral oligomericsilsequioxane(POSS-SH),nano-SiOx-SH(x=1.6,1.75,1.85,1.95) sol and modified SiO2 nanoparticles to prepare UV curable thiol-acrylate and thiol-ene-acrylate hybrid coatings. All synthesized resins were characterized by Fourier transform infrared spectrometer(FTIR) and 1H Nuclear Magnetic Resonance(1H-NMR).Real-time Infrared spectroscopy(FTIR) was conducted to monitor photopolymerization process of the coatings and the results showed that there were two competitive reactions in thiol-acrylate system: homopolymerization and transfer to thiol. As a result, addition of POSS-SH obviously increased the conversion of double bond especially for thiol-ene-acrylate system. The physical and mechanical properties of all cured samples were investigated, which indicated that the pencil hardness, tensile strength and fracture toughness were significantly improved by POSS-SH. The roughness of thiol-acrylate and thiol-ene-acrylate hybrid coatings was increasing with the addition of nano particles which were explored with atomic force microscope(AFM). Moreover, with increasing POSS-SH content, the water contact angles of cured samples were increased and the medium resistance was also improved. The abrasion resistance of hybrid coatings was also improved with nanoparticles addition. The abrasion loss weight of thiol-acrylate decreased from 32.8 mg with 250 laps without POSS-SH addition to 11.7 mg, whereas thiol-ene-acrylate decreased from 20.6 mg without POSS-SH addition to 4.6 mg with 5.64% POSS-SH addition and increased to 10.3 mg with 8.23% POSS-SH addition while the abrasion resistance of hybrid coatings decreased.Photopolymerization process of the coatings was measured by FTIR and the results showed that addition of mercaptopropyl sol(x=1.75) obviously improved the double bond conversion of thiol-acrylate compared to POSS-SH hybrid coating at the same content of sol. The addition of sol showed more efficiency to improve the hybrid coatings’ pencil hardness, which was increased from H to 4H. However, for thiol-ene-acrylate hybrid coatings, with increasing sol content, the flexibilities and the adhesion of cured samples were decreased. The roughness of thiol-acrylate hybrid coatings increased with the addition of mercaptopropyl sol(x=1.75). The medium resistance was greatly improved of cured samples with increasing sol content and the water contact angles of AESO-15.18%SiO1.75-SH was 102°. However, the water resistance would be worsen with excessive sol addition. The abrasion resistance of the hybrid coating was improved with increasing x value in SiOx sol.Meanwhile, photopolymerization process of the ESO/nano-SiO2(size: about 25 nm) hybrid coating was studied and the results indicated that the double bond conversion of thiol-acrylate increased from 60.47% without KH-590 modified SiO2 nanoparticles addition to 87.79% with 4wt% modified SiO2 nanoparticles addition while the double bond conversion for thiol-ene-acrylate systems increased slowly. The physical properties of sol hybrid coatings samples were studied, which showed that the hybrid coating had high pencil hardness 4H with suitable flexibilities and adhesion.The roughness of thiol-acrylate hybrid coatings increased with the addition of modified SiO2 nanoparticles, which were explored with AFM. The water resistance was greatly improved with increasing nanoparticles content. The abrasion resistance of hybrid coatings was also improved with nanoparticles addition. The abrasion loss weight of thiol-acrylate decreased from 32.8 mg without nanoparticles addition decreased to 12 mg with 250 laps whereas thiol-ene-acrylate decreased from 20.6 mg without nanoparticles addition to to 5.9 mg with only 5wt% modified SiO2 nanoparticles addition.