Cinética de cura de blendas epóxi/PCL.

Abstract

In order to produce workable thermosets, Poly (ε-caprolactone) (PCL) was added at 10, 20 and 30 parts per hundred (phr) to epoxy compound based on diglycidyl ether of bisphenol A (DGEBA), methyl tetrahydrophthalic anhydride (MTHPA) and 2,4,6-tris (dimethylaminomethyl) phenol (DEH35) at 100/87/5 (phr). Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and optical microscopy (OM) experiments were performed seeking evidencing chemical interactions, cure kinetics and phase separation. From FTIR spectra, partial miscibility between epoxy and PCL can be assumed, mainly due to hydrogen bonds between PCL carbonyl (C=O) and epoxy hydroxyl (OH), nevertheless, reaching the epoxy solubility limit the PCL secretes producing separated phases, which may take place through spinodal decomposition (SD) and/or nucleation and growth (NG), which depend on the temperature and concentration, as verified in MO images. Investigations of the curing kinetics indicated decrease in the crosslink density and lower Tg in epoxy/PCL compounds. The isoconversional Ozawa, Kissinger and Friedman; autocatalytic Friedman and Málek models were used during the curing modelling. Ozawa and Kissinger showed greater deviation, probably due to the activation energy (Ea) being considered invariable, the Friedman and Málek models provided better data adjustments. Epoxy/PCL compounds are supposed to have a spaced microstructure, composed of physical (hydrogen bonding) and chemical (covalent bonding) crosslinking affording the workable character. Reported results in this work provide tools for manipulating chemical, energetic and morphological processes.