Thermal and mechanical properties of chemically bonded aramid–silica nano-composites

Abstract

Thermally stable aramid-silica nano-composites have been prepared via the sol-gel process. Two types of aramid matrices were used. Polyamide chains having no pendant hydroxyl groups were prepared by reacting a mixture of 1,3-and 1,4-phenylenediamine in 65:35 mole ratio with equivalent amount of terephthaloyl chloride (TPC) in dimethylacetamide (DMAc) as solvent. The silica network was developed in the matrix by hydrolysis and condensation of various proportions of tetraethoxysilane (TEOS) and this system was used as reference. The matrix having pendant hydroxyl groups was synthesized by the co-polymerization of a mixture of phenylenediamines and 2,4-diaminophenol with equivalent amount of TPC in DMAc. The hydroxyl groups on the chain were reacted with isocyanatopropyltriethoxysilane (ICTOS), which together with TEOS produced silica network structure bonded with the polymer chain. The morphology, thermal and mechanical properties of both types of composites, with and without chemical bonding with silica network have been studied. The glass transition temperature as determined from the maxima of tan d data using dynamic mechanical thermal analysis showed a large increase in case of bonded system in comparison to the unbonded system. The value of the storage modulus was also found to be considerably higher in case of bonded system. The values of thermal expansion coefficient decreased with inclusion of silica in the matrix. The thermal decomposition temperature of these hybrids in air was in the range of 480-500 8C. q

The Effect of Surface Modification of Silica Nanoparticles on the Morphological and Mechanical Properties of Bismaleimide/Diamine Matrices

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Controlled Synthesis of ZrO2 Nanoparticles with Tailored Size, Morphology and Crystal Phases via Organic/Inorganic Hybrid Films

“…Strong interfacial interactions between the matrix and dispersed metal oxide species in the hybrid have been found to be crucial in governing the distribution and size of the metal oxide NPs. Preparation of various types of polymer-metal oxide composites employing sol-gel in situ polymerization of metal alkoxides (encompassing silica 5 , zirconia 6 or alumina 7 ) has been described. In these cases, the generated metal oxide NPs were distributed uniformly in the matrix, which has been considered to improve their mechanical strength and thermal stability.…”

Correlation between interfacial interactions and mechanical properties of PA-6 doped with surface-capped nano-silica

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