Influence of Particle Size and Phase Connectivity on the Fracture Behavior of PA6/EOR Blends.

Structure–property relations between the blend morphology and the fracture mechanical behavior of immiscible polyamide 6/ethylene‐octene copolymer (PA6/EOR) blends are investigated. The influence of a moisture uptake of the PA6 on the blend behavior is also demonstrated. Different blend formulations lead to different blend morphologies, which vary in particle sizes, interparticle spacing, and intensity of the phase connectivity between the blend partners. The intensity of the phase connectivity is described by the rheological behavior. The morphology, defined by the particle size and the calculated interparticle spacing, is analyzed optically by a scanning electron microscope. The shift of the glass transition temperature of the blends due to moisture uptake is demonstrated via dynamical mechanical analyses. All parameters are linked to the fracture mechanical properties determined by the method of the essential work of fracture. By means of the method of the essential work of fracture it is shown that the toughness increase by a given material combination and a constant soft phase amount depends only on the particle size. However, a basic requirement is always strong phase connectivity between the blend partners. Thus, by a given material combination the smaller the soft phase particles within the matrix, the higher the increase in toughness. A moisture uptake does influence the blend properties in many ways and also leads to a change in the fracture behavior. Therefore, it is not possible to predict the fracture mechanical behavior of hydrophilic blends from one condition state to another. [ABSTRACT FROM AUTHOR]