Investigations on the laser induced polymerization of organic-inorganic hybrid oligomers for micro stereo lithography applications

Abstract

For Micro Stereolithography applications, the correlation between the curing degree and the hardness of UV curable oligomers after irradiation is investigated. Oligomer thin films are polymerized with focused laser radiation (355 nm) by using a custom made Micro Stereo Lithography apparatus. Low-viscosity hybrid oligomers containing 50 wt% of Ormocer® (with 1 wt% of Irgacure® 369 as photo initiator) and 50 wt% of a trifunctional acrylate co-polymer are used during this study. Fourier-Transformed Infrared-Spectroscopy (FTIR) is applied in order to identify the chemical structure of both liquid and laser polymerized thin films with main emphasis on the reactive side chains. The functional group conversion of polymerized samples is monitored as a function of the accumulated laser fluence. The curing degree of the oligomers is calculated by observing the degradation of the acrylate group double bonds by using both the carbonyl and aromatic double bond vibrational modes as internal reference peaks. The maximum degree of cure of the oligomers is approximately 65 % for the trifunctional acrylate and 55 % for the Ormocer®. We observe a strong correlation between the curing degree and the hardness of the cured samples by using nanoindentation measurements.For Micro Stereolithography applications, the correlation between the curing degree and the hardness of UV curable oligomers after irradiation is investigated. Oligomer thin films are polymerized with focused laser radiation (355 nm) by using a custom made Micro Stereo Lithography apparatus. Low-viscosity hybrid oligomers containing 50 wt% of Ormocer® (with 1 wt% of Irgacure® 369 as photo initiator) and 50 wt% of a trifunctional acrylate co-polymer are used during this study. Fourier-Transformed Infrared-Spectroscopy (FTIR) is applied in order to identify the chemical structure of both liquid and laser polymerized thin films with main emphasis on the reactive side chains. The functional group conversion of polymerized samples is monitored as a function of the accumulated laser fluence. The curing degree of the oligomers is calculated by observing the degradation of the acrylate group double bonds by using both the carbonyl and aromatic double bond vibrational modes as internal reference peaks. The maximum...