The effects of glass beads and silane treatments on the curing behavior of a brominated epoxy resin: DSC analyses

The curing characteristics of a brominated epoxy resin/dicyandiamide (DICY) system filled with silane-treated glass beads are studied using isothermal differential scanning calorimetry (DSC). Three different silane coupling agents, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-[2-(vinylbenzylamino)-ethyl]-3-aminopropyl-trimethoxysilane, and 3-glycidoxypropyl-trimethoxysilane, are applied. It is found that the reaction heats of the epoxy system are little affected by the curing temperature and the untreated glass fillers, but changed with the addition of silane-coated glass beads. The effect of glass beads on the curing reaction is more significant at the low curing temperature and conversion. The silane treatment results in changes in T_g, activation energy, reaction heat, reaction rate, and reaction order. Three silanes respond differently because of their differences in the activated reaction with the matrix system. Regardless of the various curing mechanisms involved, a simple kinetic expression can describe the curing extent at 170 and 180°C with a good accuracy for all systems studied. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2063–2071, 1997     

A convenient semicarbazide resin for the solid-phase synthesis of peptide ketones and aldehydes

Use of a semicarbazide resin for the solid-phase preparation of peptide ketones and aldehyde led to optimal results in terms of both purity of the final product and overall yield. This resin was prepared without complication by activation of the commercial available aminomethyl polystyrene with CDI at room temperature, followed by treatment with tert-butyl carbazate. Furthermore, the TNBSA colorimetric assay has been adapted for checking the incorporation of the carbonyl moiety onto hydrazine-based resins.     

The effect of monolithic zirconia thickness on the degree of conversion of dental resin cements: ATR-FTIR spectroscopic analysis

The purpose of this study was to evaluate the effect of monolithic zirconia thickness on degree of conversion (DC) of different resin cements. Five groups (1 mm, 1.5 mm, 2 mm monolithic zirconia, veneered zirconia substructure, and lithium disilicate) of disk-shaped ceramic specimens (14 mm in diameter) were prepared (n = 6). Three dental resin cements (Variolink II light-cured, Variolink II dual-cured and Zirconite dual-cured) were tested to evaluate their DC under each ceramic group. FTIR spectra were recorded using Attenuated Total Reflectance-Fourier Transform Infrared Spectrometer (ATR-FTIR). The DC% was calculated by ratio of infrared absorbance values of aliphatic and aromatic peaks for uncured and cured states. Data were statistically analyzed by Analysis of Variance (ANOVA) and post hoc Tukey tests (a = 0.05). DC of dental resin cement specimens under monolithic zirconia decreased with increasing thickness. For Variolink II light-cured cement, the highest DC found under lithium disilicate and the lowest DC observed under veneered zirconia specimens. Zirconite which is recommended for cementation of zirconia revealed the highest DC when polymerized under monolithic or veneered zirconia. Under lithium disilicate specimens, DC of Zirconite was similar with light-cured resin cement.