Design of New Thermosetting Systems based on Benzoxazines modified with Maleic Anhydride

GILBERT E.A.; SPONTÓN M.E.; MORALES G.; ESTENOZ D.A.

Congreso; XXVI International Materials Research Congress; 2017

Polybenzoxazines are thermally obtained by ring-opening of the 3,4-dihydro-2H-1,3-benzoxazines1. Benzoxazines are synthesized by a reaction mechanism of Mannich type from phenols, formaldehyde and primary amines, obtaining heterocyclic compounds with typically one or two oxazine rings in their molecules. According to the literature, these monomers offer molecular design flexibility to produce ?tailor-made? polymers for a wide range of applications2-4.In this work, novel thermosetting systems based on benzoxazines modified with maleic anhydride were synthesized. The main objective is incorporate functional groups to the chemical structure of the benzoxazine in order to accelerate the curing process and to improve of the physical and thermal properties of the material. First, BzOH and BzPOH monomers by reaction between phenol or bisphenol A, paraformaldehyde, and ethanolamine, respectively were synthesized. Then, BzOH and BzPOH were functionalized with maleic anhydride using molar ratio 1:1 and oligomers with acid functionality, named BzFA and BzPFA, respectively were obtained. The products were characterized by Nuclear Magnetic Resonance (NMR), Size-exclusion chromatography (SEC), and Fourier Transform Infrared Spectroscopy (FT-IR). The BzFA and BzPFA oligomers presented a molecular weight of 5000 g/mol and 50000 g/mol respectively. Mixtures with the new precursors synthesized (BzFA and BzPFA) and the conventional benzoxazine (BzBA) (60:40 and 40:60 weigh ratios) were prepared in order to study the effect of the composition on curing temperature and properties of the material. The curing processes were studied by FTIR and Differential Scanning Calorimetry (DSC), and mechanical, thermal, and morphologic properties of the materials were also evaluated. Blends obtained exhibited good properties even with relatively low curing temperatures. Also, these blends showed improved properties with respect to the BzBA. These results are associated to the crosslinking by ester links that promotes a high rigidity. SEM measurements indicated homogeneous surfaces