Abstract
Polymerization characteristics of 4 types of ethyl methacrylate (EMA)-based resin, composed of EMA and EMA/methyl methacrylate (MMA) copolymers and initiated by tributylborane (TBB), were studied from the aspects of long term changes of residual monomer (RM) and molecular weight (Mw). The resins were polymerized at room temperature for 30min, stored at 37°C for 24hr, 1 and 4 weeks and then analyzed by high performance liquid chromatography and size exclusion chromatography to determine RM and Mw. RM decreased significantly from 4.47-1161% after 30min to 0.94-7.73%, 0.81-7.81%, and 0.78-7.10% after 24hr, 1 and 4 weeks, respectively, demonstrating a tendency to decrease with time for each resin. Mw showed a tendency to decrease from 427×103-551×103 after 30min to 354×10 3-530×103 after 4 weeks. TBB-initiated EMA resin had polymerization characteristics similar to those for TBB-initiated MMA resin in the temporal changes in RM and Mw during postpolymerization.
