Síntese, caracterização e cinética de polimerização de novas benzoxazinas a partir do Cardanol

Abstract

Benzoxazines are a class of monomers which have aroused great interest in the scientific scenario, due regarding its excellent chemical, thermal and mechanical properties, characterizing itself as a great alternative for the development of new polymeric materials. This work aims to obtain two novel 2-substituted benzoxazines through a procedure carried out in three steps: (1) Functionalization of the cardanol, a monophenol present in the Cashew Nut Shell Liquid (CNSL), to obtain an ortho-formylated product; (2) Functionalized cardanol was combined with furfurylamine, an amine derived from furfural, obtained from lignocellulosic waste, to obtain an ortho-aminomethylphenol compound; (3) This product combined with different aldehydes (valeraldehyde and benzaldehyde), gives rise to novel monomers through a solvent-free procedure under microwave irradiation. The synthetic pathway was efficient to obtain the products, which had their chemical structures confirmed by Nuclear Magnetic Resonance Spectroscopy (1H-NMR and 13CNMR) and Fourier Transform Infrared Spectroscopy (FT-IR), with good yields and high purity. The thermal stability of the monomers was evaluated by Thermogravimetric Analysis (TGA) and kinetic polymerization behavior was studied by Differential Scanning Calorimetry (DSC), by applying Kissinger, Flynn-Wall-Ozawa and Crane methods to determine the activation energy (Ea) of the studied system. DSC thermograms showed that the synthesized monomers presented lower values of Ea and polymerization temperatures compared to the corresponding unsubstituted benzoxazine, in addition to a wide processing-window. The use of different aldehydes allowed to obtain monomers with high polymerization potential, which allows the addition of new functions to the resulting polymers, according to the applications perspectives.