Siliconas de reação por condensação: caracterização físico-química e avaliação daestabilidade dimensional.

Abstract

It can be concluded that condensation silicones have a low dimensional stability. High stability condensation silicones are currently under development; however, no physico-chemical evidence to support this affirmation has been reported in the literature. The aim of the present study was to evaluate the dimensional stability and to formulate a physico-chemical characterization of conventional and high dimensional stability condensation silicones, so as to detect composition differenceswhich may in fact influence dimensional properties as well as to monitor composition changes during material storage. For the dimensional stability evaluation, the molds gotten with the materials had been taken directly to a microscope MITUTOYO, where the measures were made at the following time periods: T0 (immediate), T1 (30 min.), T2 (2 hours), T3 (24 hours), T4 (72 hours), and T5 (7 days) after the setting time. Forphysico-chemical characterization, putty, light and catalyst materials of conventional silicone (Coltex/Coltoflax®- Coltène), and high stability silicones (Speedex®- Coltène and Optosil Comfort/Xantopren VL Plus®-Kulzer) were analyzed using Infra-Red Spectroscopy (HATR), Thermogravimetry (TG/DTG), Differential Scanning Calorimetry (DSC) and Nuclear Magnetic Ressonance Spectroscopy (NMR1H, 13C).The polymerized materials were analyzed at the time periods: T0 to T5, applying the HATR and Gas Cromatography (GC) techniques. In addition, at T0, T3, T4, and T5 the DSC, TG/DTG were used. Residues from polymerized materials produced by Thermogravimetry at T0 were submitted for analysis by X-ray diffraction X Ray Diffraction (DRX). The dimensional analysis showed that the materials do not presentthe stability praised for the manufacturers, being that for the materials Coltex® fine/Coltoflax®- Col tène e Optosil® Comfort / Xantopren® VL Plus Kulzer to obtain a more accurate model, it would be necessary to fill the mold with plaster within the first 30 minutes after impression, while for the material Speedex®- Coltène, this time can be extended for two hours. Spectra HATR, and NMR1H, 13C as wel as TG/DTG andDSC curves, showed different compositions among putty and light materials and for light conventional materials and modified materials. Similar composition was noted among putty materials. The DRX analysis detected an amorphous filler in modified light materials and a crystalline filler in conventional materials. Spectra HATR of the polymerized materials revealed a hydroxyl band suppression at T3 in the light materials. The GC experiment confirmed the release of ethanol from all materials after polymerization.