Comportamento cinético e de tensão de contração de elastômeros submetidos com diferentes sistemas de iniciação

Abstract

The aim of this study was to characterize the reactivity of new light-curing elastomers, also the shrinkage stress. Thus, the present study used a new class of methacrylates containing urethane groups. 18 dimethacrylates elastomeric resinous blend containing (commercially called ExothanesTM 8, 9, 10, 24 and 32) and urethane dimethacrylate (UDMA) were formulated as control. For each blend system photoinitiater was added, and the unitary system, with only camphorquinone (CQ); the binary system with CQ and ethyl 4-dimethyl (EDAB) as co-initiator, and ternary with CQ, and EDAB diphenyliodonium hexafluorophosphate (DPI). After formulation, each resin was evaluated as to the kinetics, rate and degree of polymerization using an infrared spectrophotometer model Fourier transform (FTIR) and light cured for 60 seconds by a curing unit model XL - Curing Light 3000 (3M ESPE, St. Paul, MN, USA). Shrinkage stress analyzes was performed using a universal testing machine ( E3000 Electro Puls, Instron, Norwood, MA, USA) and glass rods (5 mm diameter) as substrates bonding. These rods were obtained in two different lengths (13 and 28 mm), the biggest one was coupled to an upper claw, while the smaller, the lower jaw of the Instron. Quantitative data were analyzed by analysis of variance and Tukey post hoc test ( P < 0.05). It can be concluded that Exothanes evaluated demonstrated satisfactory degree of conversion kinetics and good rate of polymerization, with some of them reaching the conversion significantly higher when compared to the control group UDMA. Furthermore, it can be concluded that the low shrinkage stress Exothanes evaluated demonstrated the polymerization. These characteristics may make them suitable for some biomedical applications. Through this study, we analyze characteristics of new elastomers such as degree of conversion and polymerization stress. It was also possible to determine the influence of the initiators in the characteristics analyzed.