Fundamental Studies of Maxillofacial Materials: Part 1. Differential Scanning Calorimetric Analyses of a Heat-Polymerized Silicone

Differential scanning calorimetry was used to evaluate the efffects of polymerizing conditions and the addition of pigments for a heat-activated maxillofacial silicone (MDX 4-4515). Unpigmented specimens were examined in the starting condition and after polymerizing at 100 degrees C for 1 hour, 4 hours and 20 hours, and specimens of four different pigmented silicones processed 1 hour at 100 degrees C were also included. The DSC scanning was performed from -150 degrees C to 200 degrees C at 10 degrees C per minute, and a strong melting-recrystallization peak at approximately -40 degrees celcius was found for all eight specimen groups (N=5). Modulated differential scanning calorimetry resolved this peak into separate melting and recrystallization peaks, and confirmed the existence of a very weak glass transition peak in this silicone at approximately -125 degrees celcius. The mechanical properties of the MDX 4-4515 silicone appear to be dominated by melting and recrystallization, rather than the glass transition, and differences may exist in the viscoelastic and creep behaviour for the unpigmented and pigmented materials.