Marius C. Costache

Resin-modified Glass-ionomer Setting Reaction Competition

Resin-modified glass ionomers (RMGI) set by at least 2 mechanisms dependent upon reactant diffusion prior to gelation. Each reaction’s kinetics and setting mechanism may rely on and/or compete with the other. In this study, we investigated RMGI setting reaction interactions using differential scanning calorimetry (DSC) by varying light-cure initiation times. A RMGI was analyzed with isothermal and dynamic temperature scan DSC with light-curing occurring immediately, or at 5 or 10 minutes after mixing as well as without light-activation. Results show that as time allowed for the acid-base reaction increased, the light-activation polymerization exotherm decreased. Conversely, analysis of DSC data suggests that earlier light-activation may limit the acid-base reaction and result in a different structured material. During early RMGI development, acid-base and light-polymerization reactions compete with and inhibit one another.

Fire Retardancy of Polyureas

In this study, a variety of additives have been evaluated as potential fire retardants for polyureas with cone calorimetry being the method of evaluation. The additives that have been evaluated include minerals (alumina trihydrate), bromine-, nitrogen-, and phosphorus-based fire retardants. The major criteria for evaluation are the reductions in the peak heat release rate and the total heat released, the evolution of smoke and dripping.