UV Curing of Acrylate Monomers Activated with Resol Resin

UV Curing behavior of acrylate monomers in the presence of resol is described. A thin layer consist of resol, monofunctional acrylate (ECA), and hexafunctional acrylate (DPCA-60) gives the crosslinked polymer under UV irradiation. IR spectra of the crosslinked polymer show characteristic absorptions due to both resol and acrylate with a decrease of ν_C=C′ which indicates the additional polymerization takes place in this system. The curing is accelerated by addition of alkali, which suggests the phenol structure is active site for the polymerization. Among several kinds of alkali investigated, Ba(OH)2 is most effective for the reaction from the point of insoluble polymer yield. Consumption of acrylate double bond in the insoluble polymer ranges above 60 % which decreases slowly with an increase in the DPCA-60 content due to steric hindrance. The synergic effect of Ba(OH)₂ appears when it is added 0.1 mold for hydroxy group in the resol. UV irradiation leads to color change of the cured layer from pale yellow to reddish violet (λ_max = 570 nm) with an appearance of ESR signal at g = 2.004, which indicates the formation of phenoxy radical. The phenoxy radical formed in the resol should be an active site for UV polymerization of this system.