Reinforcement of polybenzoxazine matrix with organically modified mica

Novel polybenzoxazine-clay hybrids were prepared by the in situ polymerization of the typical benzoxazine monomer, bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (B-a) in the presence of aminolauric acid-modified mica (ALA-mica). Various ratios of ALA-mica were dispersed into solutions of B-a in N,N-dimethylacetamide, followed by casting into film form. The hybrids were thermally cured up to 230 degrees C, affording transparent nanocomposite films up to 10 wt% of mica loadings. The cure behavior was monitored by both IR and differential scanning calorimetry, indicating the catalytic effect of the modified mica. The morphology of the nanocomposites was studied by XRD, showing a featureless pattern, which suggests the disordered dispersion of mica into polybenzoxazine matrix. The dynamic mechanical properties of some hybrids show that the nanocomposites have higher storage modulus over the whole temperature range than the neat polybenzoxazine. Thermogravimetric analysis results confirmed that the thermal stability and char yield of polybenzoxazine resin increased apparently by hybridization with mica corresponding to the mica content.