Cinética de cura dos compostos Epóxi/PLA.

Abstract

The commercial and scientific applications of epoxy resins depend on the combination and reaction characters among resin/hardener/catalyst, forming a very complex reactive system. In this work, the epoxy compound based on diglycidyl ether of bisphenol A (DGEBA), methyl tetrahydrophthalic anhydride (MTHPA) as hardener and 2,4,6-tris (dimethylaminomethyl) phenol (DEH 35) as catalyst, at fixed concentration 100 / 87/5 was initially processed. In order to develop a workable epoxy system, poly (lactic acid) (PLA) was added at contents of 10, 20, 30 and 90

phr to the epoxy compound. Analysis of hydrogen nuclear magnetic resonance (H- NMR), Fourier transform infrared spectroscopy (FTIR) and differential scanning

calorimetry (DSC), were performed in order to obtain evidence of chemical interactions and curing kinetics of investigated compositions. From the H-NMR and FTIR spectra, partial miscibility between epoxy and PLA can be considered, mainly due to the hydrogen bonds between the PLA carbonyl and epoxy hydroxyls. The curing kinetics followed by the released heat during DSC scans indicated decrease in the crosslink density after PLA addition, as well as lower Tg related to neat epoxy. The epoxy network forbidden PLA crystallization, whereas neither exotherms nor endotherms were displayed in DSC scans, regarding its crystallization and melting, respectively. Partial solubility between the thermoplastic-thermosetting phases is also suggested as driving force for the complex PLA structural organization/reorganization. Increased curing temperatures, decreased conversion rate and decreased curing enthalpy were obtained in epoxy/PLA compounds. By defining the guidelines for chemical reactions and kinetics parameters of curing, the great control is achieved, which allows manipulation of the operating system and definition of properties, expanding the field of final products application.