The curing performance of UV-curable semi-interpenetrating polymer network structured acrylic pressure-sensitive adhesives

This article reports on the curing performance of UV-curable acrylic binders prepared with trifunctional monomers and a photoinitiator. The curing reaction was achieved by direct excitation of pressure-sensitive adhesives (PSAs) by irradiation with a 100-W high-pressure mercury lamp with different UV doses. The curing performance of PSAs was studied by photo-differential scanning calorimetry (photo-DSC), gel-fraction determination and Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy. The reaction rate and extent of UV curing were found to be strongly dependent on the curing rates of the trifunctional monomers, trimethylolpropane triacrylate (TMPTA) and trimethylolpropane ethoxylated (6) triacrylate (TMPEOTA), which have different molecular weights. Exothermic areas increased with increasing acrylic acid concentration. Moreover, gel fractions sharply increased after UV irradiation and then remained constant with prolonged UV exposure. TMPTA blends had higher gel fractions than TMPEOTA blends because of TMPTA's fast curing rate. Also, the gel fractions of TMPTA blends showed no variation with acrylic acid concentration. However, the FTIR-ATR absorption peak areas representing the relative concentration of C = C bonds showed more conspicuous trends for the curing reaction. Although the gel fractions of TMPTA blends showed no differences, the relative concentrations of C = C bonds increased with increasing acrylic acid concentration. In addition, TMPTA blends showed higher relative concentrations of C = C bonds because of the faster curing rate of TMPTA.