Mechanical and morphological properties of PP/XNBR blends produced with rubber latex

In this work, polypropylene (PP)/carboxylated acrylonitrile butadiene rubber (XNBR) binary blends were prepared with the elastomer component dosed in its suspension (latex) form into the polymer matrix during melt compounding. For this purpose, samples containing 0-20 wt.% rubber were prepared using two different PP grades as matrices with lower and higher viscosity. Analogous reference samples with the same composition were also fabricated using traditional melt mixing by introducing the rubber in its dry, bulk form in order to analyze the efficiency of the latex route. Mechanical, thermomechanical and morphological analyses were used to investigate the structure-property relationships of the blends. Based on the SEM images the average domain size of the dispersed XNBR domains became markedly smaller when the rubber was introduced in its suspension form into the PP. Based on the Charpy impact tests and the tensile test results, the decreased rubber domain size led to improved ductility and toughness. The improvement was more prominent when the difference between the viscosity of the PP matrix and the XNBR rubber was higher.