Synthesis of Polypropylene/Organoclay Nanocomposites via In Situ Polymerization with Improved Thermal and Dynamic-Mechanical Properties.

Preparation of polypropylene/clay nanocomposites via in situ polymerization is investigated. MgCl2/organophilic clay bi-supported Ziegler-Natta catalysts were used to prepare these nanocomposites. Three organophilic clays (Cloisite 30B, Cloisite 15A, and Claytone HY) were used as support and reinforcement agents. The nanostructure of the composites was characterized by X-ray diffraction. The results showed that the most active catalyst was that with clay having high inter-layer spacing without functional OH groups. Moreover, the silica layers of the clays (Cloisite 15A and Claytone HY) in these polypropylene/clay nanocomposites were exfoliated and well dispersed in the polypropylene matrix. Differential scanning calorimetric was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. These results showed that Cloisite 15A and Claytone HY acted as nucleating agents in the process of crystallization of polypropylene. Thermogravimetric analysis showed that Cloisite 15A and Claytone HY promoted an increase in resistance to thermal degradation. Dynamic-mechanical analysis showed that nanocomposites presented an increase in the storage modulus. Furthermore, Cloisite 15A and Claytone HY promoted an increase in glass transition temperature. Small-angle X-ray scattering analysis was used to determine how clay and its concentration influence the size of the polymer nanocrystals.