Enhanced thermomechanical properties of long and short glass fiber-reinforced polyamide 6,6/polypropylene mixtures by tuning the processing procedures

Long and short glass fibers (GF) were incorporated into the polyamide 6,6 (PA66)/polypropylene (PP) mixtures in order to enhance the thermomechanical properties. The effect of fiber length and processing procedures on tensile strength, flexural modulus, impact strength, and heat deflection temperature has been investigated. Miscibility behavior of the PA66/PP mixtures has been examined by performing differential scanning calorimetry analysis and theoretical calculation. The mixtures exhibiting broad coexistent regions such as crystal + crystal (Cr₁ + Cr₂), crystal + liquid (Cr₁ + L₂), and liquid + crystal (L₁ + Cr ₂) revealed a significant improvement in thermal and mechanical properties by the addition of GF. Especially, long fiber-reinforced thermoplastics showed better performances compared to short fiber-reinforced thermoplastics at the same filler loading. From the morphological observation of the fractured surface, it was realized that the incorporation of long GF after the melt blending of PA66 and PP was very effective to attain high thermomechanical properties due to the better homogeneity and compatibility.