Polymerization characteristics of ethyl methacrylate-based resin initiated by TBB.

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 30 min, stored at 37 degrees C for 24 hr, 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 4.47-11.61% after 30 min to 0.94-7.73%, 0.81-7.81%, and 0.78-7.10% after 24 hr, 1 and 4 weeks, respectively, demonstrating a tendency to decrease with time for each resin. Mw showed a tendency to decrease from 427 x 10(3)-551 x 10(3) after 30 min to 354 x 10(3)-530 x 10(3) 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.