Mechanical reinforcement of unsaturated polyester by Al2O3 nanoparticles

Nanometer-sized Al2O3 particles (15 run average diameter) were used as reinforcements to enhance the fracture toughness of a highly crosslinked, nominally brittle, thermosetting-unsaturated polyester resin. It was observed that the addition of untreated, as-received Al2O3 particles does not result in enhanced fracture toughness. Instead, the fracture toughness decreases by 15% as the volume fraction of the particles is increased from 0% to 4.5%. Similar degradation in fracture toughness was observed for reinforcement by 1 - and 35-mum Al2O3 Particles. The lack of reinforcement was attributed to poor particle-matrix bonding, as observed from scanning electron micrographs of the fracture surfaces. However, considerable reinforcement was observed when the nanocomposites were fabricated using an organofunctional silane to enhance particle-matrix interface strength. For the case of a 4.5% volume fraction of well-bonded Al2O3 particles added to the unsaturated polyester, the fracture toughness was increased by almost 100%. (C) 2003 Published by Elsevier B.V.