Real-time kinetics study on the infrared laser-induced photopolymerizationof TMPTA

The infrared laser-induced photopolymerization kinetics of TMPTA, with a no vel cationic cyanine dye-borate complex (CBC), 1, 3, 3, 1', 3', 3'-hexameth yl-11-chloro-10, 12-propyleneindo-tricarbocyanine triphenylbutyl borate as photoinitiator, was investigated by Real-Time FTIR(RTFTIR) in this paper. T he CBC adopted here has maximum absorption wavelength lambda (max) at 790 n m (in TMPTA photopolymerization sample). The photopolymerization system con sisted of equal weight of a monomer (trimethylolpropanetriacrylate, TMPTA), a binder (AA/MMA/St/BA copolymer), and different content of CBC. The doubl e-bond conversion(Y) was determined from the drop of the absorption at 1 62 0 and 1 635 cm(-1) in FTIR spectra and was continuously monitored by RTFTIR during laser irradiation. Y increased rapidly in the first 10 seconds and reached 37% for laser irradiation power of 17.0 mW/cm(2), CBC content of 2. 0% and sample thickness of 20 mum. Higher Y and polymerization rate (R-p) c ould be achieved by increasing the laser power or decreasing the sample thi ckness. Furthermore, there existed a critical content for CBC, below which the increasing of CBC concentration would improve Y and R-p. Higher CBC con tent over the critical value would lead to the "filter effect", which preve nts the laser beam from penetrating into the deep layer of the sample, and then deteriorates the photopolymerization. The quantum photopolymerization yield of this system was 41.8 mol/einstein.