EFFECTS OF 2 AMINE REDUCING AGENTS ON THE DEGREE OF CONVERSION AND PHYSICAL-PROPERTIES OF AN UNFILLED LIGHT-CURED RESIN

The influence of varying concentrations of two amine reducing agents c ommonly used in commercial light-cured composites, N,N-dimethyl-p-tolu idine (DMPT) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), on the degree of conversion (DC), Knoop hardness, and compressive and tra nsverse strengths of an unfilled light-cured resin was investigated. T he DC obtained from employing two different internal standard peaks, c arbonyl (C=O) at 1730 cm(-l) and urethane (NH) at 3350 cm(-1), was com pared. The resin consisted of 50 wt% triethyleneglycol dimethacrylate (TEGDMA) and 50 wt% thacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethyl- hexane (UDMA) activated with 0.5 mol% camphorquinone (CQ) and varying concentrations of either DMPT or DMAEMA. The DC calculated by use of either C=O or N-H absorption peak as an internal reference showed simi lar values. For both amines, the physical properties were directly rel ated to DC and appeared to reach maximal values at an amine/CQ molar r atio of 4.0. The DC, however, appeared to reach a maximum at an amine/ CQ molar ratio of 3.0. Generally, for the same amine/CQ molar ratios, the polymers formulated with DMAEMA, had greater DCs and better physic al properties than those formulated with DMPT.