Empirical Analysis of the Effect of Compatibilisation Strategies on Mechanical Properties and Morphology of Polypropylene/Polyamide Polymer Blends

Polymer blending of polypropylene and polyamide offers the potential to combine the processing ease and low cost of polypropylene with the toughness and barrier properties of polyamide, but the thermodynamic immiscibility of this pair necessitates compatibilisation to achieve useful properties. This study empirically analyses the effect of four compatibilisation strategies, maleic anhydride-grafted polypropylene, epoxy-functional copolymer, reactive extrusion without grafting, and block copolymer addition, on the mechanical properties and morphological characteristics of 70:30 and 60:40 polypropylene-to-polyamide blends. Blends were prepared by twin-screw extrusion at a compounding facility in Lagos State, South West Nigeria. Notched and unnotched impact strength, tensile modulus, elongation at break, and flexural strength were determined. Phase morphology was characterised by scanning electron microscopy of cryogenic fracture surfaces, and dispersed polyamide domain size was measured by image analysis. Interfacial adhesion quality was assessed through analysis of fracture surface features. Results demonstrate that maleic anhydride-grafted polypropylene compatibiliser produced the most significant impact strength improvement at 70:30 blend ratio, increasing notched Izod impact from 32 to 118 J/m, a 269 percent improvement. Dispersed polyamide domain size was reduced from 4.8 micrometres in uncompatibilised blends to 0.6 micrometres with maleic anhydride-grafted polypropylene addition, confirming substantially improved interfacial interaction. Epoxy-functional copolymer produced comparable morphological refinement with superior elongation at break. The study provides a comparative evaluation of compatibilisation effectiveness for polypropylene/polyamide blends, supporting formulation decisions for Nigerian plastics compounders developing engineering blend grades. Keywords: polymer blend, polypropylene, polyamide, compatibilisation, mechanical properties