Study On The Polybenzoxazine/vermiculite Hybrid Nanocomposites

Polybenzoxazine/vermiculite hybrid nanocomposites were prepared from two kinds of polybenzoxazine precursors and two kinds of organically modified-vermiculite minerals and expanded-vermiculite which were consisted of vermiculite ,hydrobiotite and phlogopite. After treatment of vermiculite minerals by hexadecyl trimethylam monium bromide(CTAB), the d001 of vermiculite layers of vermiculite mineral increased from 1.43nm to 2.67nm and developed a d002=1.34nm. After organically modified vermiculite intercalated with a polybenzoxazine precursor ( bisphenol A type), The d001 of vermiculite layers increased from 2.67nm to 3.63nm further and developed a d002=1.82nm and a d003=0.91nm. It showed that the polybenzoxazine precursor had intercalated into vermiculite layers. Cured the composites, the diffraction peak of vermiculite d001 in XRD spectrum disappeared . According to Atomic force microscopy (AFM) images, in the cured-composites, when the content of vermiculite minerals was less of 3%, most crystals were cleaved into the "exfoliated" shape in which crystalgallery breadth was about of 113nm. As the content of vermiculite minerals increased, the content of the "intercalated" shape, in which crystal gallery breadth was about of 40nm, also increased.In the curing reaction processing of polybenzoxazine/vermiculite hybrid nanocomposites intercalated with bisphenol A type precursor. According to the content of vermiculite minerals, while different shape of crystal was forming, these crystals were retarding the heat ring-opening polymerization of bisphenol A type precursors in the nanocomposites. As the content of vermiculite minerals was about 3%. the retardance was the most. Compared with bisphenol A type precursor itself, the tgel and the activation energy(Ea) of the curing reaction increased 7min and 8KJ/mol respectively, the enthalpy(Hd) of the curing reaction decreased 14 J/g. As a result, the cure-degree of the polybenzoxazine/vermiculite hybrid nanocomposites decreased 10%. The cured products had lower cure-degree and even lower cross-linking density. The weight loss at the second peak (300C~550C) of DTGA was 64%, but the weight loss of polybenzoxazine(bisphenol A type) itself was only 8.5%.Mechanics properties and heat resistant properties of the polybenzoxazine(bisphenol A type)/ vermiculite hybrid nanocomposites were lower than those of the polybenzoxazine(bisphenol A type) but prior to those of the polybenzoxazine(bisphenol A type)/phlogopite composites. As the content of vermiculite minerals was about 3%, the impact strength (nick) , the flexural strength and the heat distortion temperature (HDT) of the nanocomposites all were the lowest and decreased 21% , 28% ,3C, respectively. Compared with those of the polybenzoxazine(bisphenol A type) , its thermal expanded coefficient (TEC) was 3.4% bigger than that of the polybenzoxazine(bisphenol A type) . when the content of vermiculite minerals was about 10%, the impact strength (nick) and theflexural strength had maximum value ,but those of the polybenzoxazine(bisphenol A type)/phlogopite composites had been going down. As the content of vermiculite minerals was over 5%. HDT of the polybenzoxazine(bisphenol A type)/ vermiculite hybrid nanocomposites was higher than that of the polybenzoxazine(bisphenol A type). HDT of the polybenzoxazine(bisphenol A type)/phlogopite composites not changed in the range of phlogopite content from 0%to 15%.Heat resistant property of the polybenzoxazine(mulitphenol type)/ vermiculite hybrid nanocomposites was prior to that of the polybenzoxazine(mulitphenol type)/phlogopite composites. As the content of the expanded vermiculite was 20%, the Tonset of the polybenzoxazine(mulitphenol type)/ vermiculite hybrid nanocomposites from its TGA cure was 35 Chigher than that of the polybenzoxazine(mulitphenol type)/phlogopite composites. High-performance train brake plate was developed with the polybenzoxazine(mulitphenol type)/ vermiculite hybrid nanocomposites. It has a narrow brand strip of friction coefficient (0.