화학공학소재연구정보센터
Journal of Polymer Science Part A: Polymer Chemistry, Vol.42, No.5, 1227-1238, 2004
Fluorescent probes for monitoring the pulsed-laser-induced photocuring of poly(urethane acrylate)-based adhesives
Fluorescence spectroscopy was used to study the kinetics of polymerization of acrylic adhesive formulations exposed to a 355-nm pulsed emission from an Nd-YAG laser. Nine fluorescent probes were used for monitoring the laser curing, showing different sensitivities. In general, the fluorescence intensity emission increased as crosslinking occurred. In addition, solvatochromic fluorescent probes showed a blue-shift in their emission. A relative method was applied for the evaluation of the polymerization rates in three different acrylic systems. Special features of pulsed-laser-induced polymerization were treated in detail, such as the influence of the laser pulse frequency and the incident laser beam intensity. The polymerization rate slowed down as the pulse repetition rate decreased. An inhibition period due to oxygen quenching was observed, and it was highly dependent on the laser repetition rate and the nature of the photoinitiator. The effect of the laser beam intensity on the kinetics of such fast reactions was studied. In general, increasing the laser energy improved the rate of polymerization. The degree of cure improved as the polymerization rate increased as a result of faster crosslinking, rather than relaxation volume kinetics. Moreover, a saturation rate effect occurred that depended on the photoinitiator. The different behaviors of the two photoinitiators in the curing of the same acrylic formulation was explained on the basis of primary radical termination. (C) 2004 Wiley Periodicals, Inc.