Effects of crystalline forms on the deformation behaviour of nylon-6

Solid-state coextrusion draw was carried out for films of aggregates of solution- and melt-grown crystals of nylon-6 with alpha- and gamma-forms. Under ordinal crystallization conditions, the crystal form was primarily a monoclinic alpha-form. Thus, alpha-crystals were converted to the gamma-form by iodine treatment, followed by treatment with aqueous solution of sodium thiosulfate. The maximum extrusion draw ratio achieved (EDRmax) at temperatures in the range of 100-180 degrees C was greatly affected by both the crystal forms and the initial morphologies. At a given crystal morphology, the EDRmax for the gamma-crystals was higher than the alpha-crystals. Further, the efficiency of draw evaluated from the crystalline chain orientation was higher for gamma-crystals than alpha-crystals. For him with alpha-cry6 the intercrystalline network has an important role in transmitting the stress on draw. On the other hand, for films with gamma-crystals, the effect of intercrystalline network on the efficiency of draw was less prominent. These results were almost independent of the extrusion temperature studied. The effect of crystal form on the ductility is explained based on the difference in the interchain interactions due to hydrogen bonding in the crystalline regions. (C) 1998 Elsevier Science Ltd. All rights reserved.