Blends of poly(vinylidene fluoride) with polyamide 6: interfacial adhesion, morphology and mechanical properties

The poly(vinylidene fluoride) (PVDF)/polyamide 6 (PA6) interfacial adhesion has been measured, and morphology and mechanical properties of the binary blends have been investigated. The lap shear strength of the PVDF/PA6 pair indicates a high interfacial adhesion, which is evidence for specific intermolecular interactions between the two polymers. Immiscibility of PVDF and PA6 has clearly been observed by transmission electron microscopy (TEM). It reflects the high propensity of each polymer to crystallize on its own and the strong hydrogen bonding that prevails in PA6. This interfacial adhesion can account for the fine phase morphology of the binary blends. Dependence of Young's modulus and yield stress on the blend composition shows a slightly negative deviation with respect to the additivity law, in contrast to elongation at break, ultimate tensile strength and impact toughness that display a positive deviation. These experimental observations have been discussed in reference to the interfacial adhesion and the change in crystallinity of the continuous phase. An optimum interfacial adhesion seems to be required for promoting a synergism in the impact resistance of these polyblends. (C) 1978 Elsevier Science Ltd. All rights reserved.