Functionalized polypropylenes in the compatibilization and dispersion of clay nanocomposites

The preparation of polypropylene (PP) nanocomposites was studied using clay and three types of modified PP (m-PP) as compatibilizers: diethyl maleate grafted PP (PP-g-DEM), maleic anhydride grafted PP (PP-g-MA), and PP grafted with carbamyl maleamic acid (PP-g-UMA). The clay was made organophylic by an acid treatment with octadecylamine. PP functionalization and blending were carried out in an internal mixer. Blends of PP containing 20 and 40 wt% each of the modified PP and 5 wt% of organophilic clay (IMt), in each case, were prepared. Samples were characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical microscopy, and mechanical testing. The presence of tactoid, intercalated and exfoliated structures was observed by TEM in all the samples containing clay and modified PP, which also showed improved mechanical properties with tensile modulus as much as three times that of PP. Melting temperature did not vary significantly with the addition of clay. However, because of the clay's nucleating effect, an increase in the crystallization temperature was observed, accompanied by a slight decrease in the degree of crystallinity. The best results were obtained when PP-g-MA was used as the compatibilizer; intermediate results were obtained with the use of PP-g-UMA, followed by the results obtained when PP-g-DEM was used. Property enhancements were obtained when a higher percentage of modified PP was employed.