A new approach to increase weld line strength of incompatible polymer blend composites: selective filler addition

A ternary blend composite composed of two immiscible organic phases, polypropylene (PP) and polyamide-6 (PA), and talc as inorganic filler is studied in terms of weld line properties and morphology. Effects of different filler levels as well as compatibilizer on weld line strength under tensile loading condition of each polymeric phase are investigated. Special attention is paid to relate the nature of dispersed domains especially in weld line regions with final performance. It is observed from scanning electron microscopy (SEM) studies that addition of talc filler which is selectively wetted by dispersed PA phase dramatically reduces the elongated domain size in the weld line region and causes to much more homogeneous microstructure. The selective wetting of talc particles by PA phase, therefore, seems to be beneficial in increasing weld line strength via increasing the viscosity of the PA dispersed phase and consequently decreasing the elongated domains at weld line region. Compared to uncompatibilized blend composites, compatibilized ones represent much higher weld line strength for all levels of talc loading.