The determination of the surface free energy of the chain-folding faces of crystals of ethylene-butene random copolymer is performed by fitting the most probable value of the crystal thickness distribution with the average crystal thickness assessed from small-angle X-ray scattering. The surface free energy is the adjustable parameter in the equation of the crystal thickness distribution derived from the Thomson-Gibbs relation for the melting of lamellar crystals of finite thickness. On the one hand, the steady increase of the surface free energy of bulk-crystallized copolymers with increasing co-unit concentration is relevant to a growing disorder in the amorphous overlayer of the lamellar crystals. On the other hand, the decrease of the surface free energy with increasing dilution for a given copolymer crystallized from decalin solutions is an indication of an improved regular chain folding. Both conclusions support previous studies dealing with the mechanical behaviour ofethylene-butene copolymers in relation to co-unit concentration and crystallization conditions.
Посилання на статтю:
Surface free energy of the chain-folding crystal faces of ethylene-butene random copolymers / O. Darras and R. Seguela* // Polymer. – 1993. – Vol 34. – P. 2946-2950.