THERMAL AND MECHANICAL-PROPERTIES OF POLY(METHYL METHACRYLATE) USED AS DENTAL BASE MATERIAL

The thermal and mechanical properties of poly( methyl methacrylate) pr epared at different curing times were studied using DSC, TGA, tensile, and three-point bending test methods. The molecular weights of the po lymer samples were determined from the viscosity measurements. The cur ing time applied for two different commercial materials, manufactured for dental use, ranged from 15 to 180 min. The samples cured for 15 an d 20 min were soluble in chloroform completely, but the others were pa rtially soluble. The insoluble fraction increased with curing time but the molecular weight of the soluble fraction remained constant. DSC t hermograms showed further curing of the samples cured for 15 and 20 mi n. After curing for 180 min and/or annealing at room temperature for a bout 13 months, the samples were completely crosslinked. The character istic values obtained from the tensile and the three-point bending tes ts were similar for samples cured at different times. (C) 1998 John Wi ley & Sons, Inc.