Highly-filled hybrid composites prepared using centrifugal deposition

Natural composites of high filler content, such as nacre, a composite comprised of 95-99% w/w aragonite layers, have been of interest due to their hardness, strength and toughness. High filler content composites have been prepared synthetically, although due to viscosity and processing requirements, the filler content was limited compared with natural systems. In this paper we describe hybrid high filler content composites prepared to be biomimetic of nacre. Development of processing conditions increased the filler content from 50% w/w using a laboratory stirrer to obtain hybrid composites with 77-86% w/w filler content, prepared by centrifugal deposition and hot compression molding techniques. Both methods were very different from natural formation from layer-by-layer (LBL) construction, however, the composites formed were of high filler content approaching the level in nature. The composites exhibited high modulus and strength, although deformation at break was low, consistent with highly filled materials. Glass transition of the resin phase was increased slightly, while damping was decreased by filler content. Surface morphology of the fractured composite showed a layered structure of well dispersed fillers with minute voids scattered evenly, indicating that the composite was effectively compacted.