Interfacial adhesion between semi-crystalline polymers (polypropylene and nylon-6): in situ compatibilized interface and fracture mechanism

Abstract

The interfacial fracture toughness between semi-crystalline polymers (polyamide/polypropylene) were studied to understand the failure mechanisms at the interface, especially when the interface was reinforced by an in situ compatibilizer. Based on the observation of the interface using scanning electron microscopy and wide angle X-ray spectroscopy, it was revealed that crystalline structure of polypropylene was not affected by the in situ compatibilizer at the interface. The reinforcing mechanism could be qualitatively identified by investigating the evolution of fracture toughness as a function of annealing time and temperature. The adhesion strength increased with the annealing time. Depending on the annealing temperature, the fracture toughness passed a peak value and then reached a plateau after some bonding time. As long as the chain length of the compatibilizer is long enough to form entanglements with the molecules at both bulk sides, the fracture at the interface is decided by the balance between adhesion strength at the interface and cohesive strength in the weak modulus side; the failure locus follows the lower one. Thus, adhesive failure occurred first when the reaction at the interface did not occur long enough to provide high adhesive strength at the interface, but the cohesive failure occurred in the crack propagation side after the adhesive strength value became higher than the cohesive strength value.

Flow accelerates adhesion between functional polyethylene and polyurethane

“…Crystallinity is known to affect interfacial adhesion, 33,34 and this could increase the adhesive force even with constant copolymer reaction rate. We compared the crystallinity of laminated and coextruded functional PE/ LLDPE-1 blends and found that crystallinity was affected little by processing: 8-9% (pellets) and $11% (coextrusion).…”

Reactive coupling between immiscible polymer chains: Acceleration by compressive flow

“…Although pressure changes the capture volume around a reactive group and accelerates reaction, the pressure dependence of the rate constant for typical liquid‐phase reactions is much too weak to alter the rate for the range of pressures encountered here . Crystallinity is known to affect interfacial adhesion, and this could increase adhesion even with constant copolymer reaction rate. We compared the crystallinity and crystal structures near the interface for coextrusion with different dies.…”

Enhancement of the Mechanical and Thermal Properties of Polypropylene and Nylon 6.6 Composite Blends

“…Moreover, nylon 6, also known as polyamide 6, has also attracted good attention in research due to its high mechanical properties and good oxygen transport resistance [1]. PP and nylon 6.6 blends have received much attention in the last decade due to their enhanced properties [2,3]. Te blend was selected to study the material contribution to the enhancement of the overall properties and alterations of the morphology of the blend.…”