Pressure-induced crystallization of polymers with dispersion of nanoparticles: Structure, interfacial interaction, and micromechanism of fracture

We describe here the relationship between fracture resistance and microstructural changes that are induced when polymers containing dispersion of nanoparticles are isothermally crystallized at elevated pressures. To identify the effects of applied crystallization pressure from nanoparticle effects, a relative comparison is made between polyethylene and polyethylene containing dispersion of nanoclay under similar experimental conditions. At high crystallization pressure, besides commonly observed orthorhombic phase, monoclinic phase is also observed. The nucleation of monoclinic phase is promoted by nanoclay even at low crystallization pressure, implying that both pressure and nanoclay have an influence on phase evolution. The addition of nanoclay to polyethylene retains adequately high impact strength and the micromechanism of deformation is altered from a combination of craze and drawing of fibrils in polyethylene to microvoid coalescence-fibrillation in polyethylene with dispersion of nanoclay. The monoclinic phase has no obvious influence on fracture resistance. (C) 2010 Elsevier B.V. All rights reserved.