Polypropylene toughened with ethylene-n-butyl acrylate-carbon monoxide terpolymer: structure–property relationship

Phase morphology, mechanical properties, melt rheology, and failure mechanisms of polypropylene (PP) blended with 0–30% (by weight) of ethylene- n -butyl acrylate-carbon monoxide (E- n BA-CO) were studied. A typical matrix/dispersed-droplet morphology was observed for all blends together with a relatively coarse dispersion of modifier domains in the blends having more than 20% (by weight) of E- n BA-CO. Binary blends showed tremendous improvements in tensile ductility compared with neat PP. The elastic modulus, yield stress, and tensile strength decreased steadily with E- n BA-CO loading in the blend, but the degree of reductions was insignificant and the blends exhibited a good balance of tensile properties. The impact strength on notched samples increased sharply with E- n BA-CO content up to 10% (by weight) and then decreased at higher modifier contents. E- n BA-CO did not influence the crystallization and melting characteristics of PP matrix. E- n BA-CO changed the rheological behavior of PP, and melt viscosity and elasticity for the blends increased in direct proportion to the E- n BA-CO fraction. A transition from a liquid-like response to a nearly solid-like one at low-frequency regions was detected with the progressive incorporation of E- n BA-CO into the PP matrix. Fractography analysis of impact-fractured samples revealed some localized, small-scale plastic deformations along with a relatively poor interfacial adhesion across the phase boundaries between the dispersed domains and the surrounding PP matrix. Extensive interfacial debonding–cavitation and pull out of dispersed domains were responsible for the low impact toughness for the blends containing more than 15% (by weight) of E- n BA-CO. Graphical abstract