Decomposition analysis of binary polyfunctional urethane monomer mixtures.
Thermal decomposition in three binary monomer mixture systems containing an experimentally synthesized monomer (EXP3) and a commercial polyfunctional urethane monomer (U-4TXA) was examined in terms of differential thermal analysis (DTA) and simultaneous thermogravimetry (TG) analysis when a sample was heated to 800 degrees C. The binary EXP3/U-4TXA monomer mixtures were visible light-cured (VLC) resins which included CQ (camphorquinone=0.5 wt%) and DMAEMA (dimethylaminoethyl methacrylate=0.5 wt%) as the photoinitiator. Their DTA curves showed that thermal decomposition initiated at around 300 degrees C and finished at around 500 degrees C. TG curves showed complete weight loss at 800 degrees C during thermally induced decomposition: the decomposition reaction at weight losses of 5 to 50% was calculated from the slope of the (1/T) versus log10(Hr) diagram, because the exothermic decomposition temperature shown on DTA curves increased with increasing heating rate from 2 to 20 degrees C/min. Thermal decomposition analysis showed that a decomposition with weight change had exothermic heats ranging from 0.38 to 1.07 kJ/g for the EXP U1 mixture, 1.06 to 1.76 kJ/g for EXP U2 and 1.74 to 2.02 kJ/g for EXP U3. Activation energy ranged from 1.42 to 1.89 kJ/mol at weight losses of 5 to 50% in the three binary EXP3/U-4TXA monomer mixture systems.