Rheological and mechanical properties of highly filled polyolefin based on PP/barium sulfate

In the last few years the use of polypropylene (PP) has shown the highest growth rate among all polymers due to its versatility and possibility to vary its mechanical properties by compounding and blending techniques. In this study, rheological, morphological and mechanical properties of highly filled (60Wt%) polypropylene with barium sulfate (BaSO4) were studied. Since mechanical and rheological properties of highly filled polymer composites are dominated by polymer-filler interfacial interaction, two methods were used to enhance PP/ BaSO4 interfacial interaction. a) coating the fillers with stearic acid and b) using coated fillers and maleic anhydride grafted polypropylene (MA-g-PP) at the same time. Morphological observation showed that the filler-polymer interfacial interaction was improved by either filler surface coating or using surfactant and compatibilizer together. Rheological measurements revealed that high amount of BaSO4 drastically increased the storage modulus of composites due to stiffness effect of barium sulfate. Moreover, nonterminal region for storage modulus in low frequency was detected which was attributed to formation of a three dimensional network of the filler particles in high filler concentration. Izod impact strength test stated that in highly filled PP/BaSO4, better interfacial interaction hindered polymer chains movements and decreased the impact strength.