Abstract

The family of polyolefins are materials with a high demand, due to thermoplastics are structurally simpler and economical in their production and processing. Within the polyolefins, the commercial use of polypropylene began with the rise of the catalyzed reactions, in this way it was possible to control its specific conformation and with it, the final properties. In order to improve their properties, these materials are usually reinforced, specially with nanometric loads. So far, three methods have been developed for obtaining nanocomposites: In situ polymerization, melt intercalation and solution mixing. In order to solve the existing problems, in terms of charge dispersion, molecular weight control of the synthesized matrix and the complexity of the immobilization processes of the metallocene catalysts, this research uses In situ polymerization of polypropylene-Sepiolite, using the nanoclay as support of the catalytic system. This study proposes a method of immobilization that contemplates the use of the density of the polar groups that has the surface of Sepiolite, to fix the co-catalyst. In addition, the resulting polymerization process defines the reaction temperature as a variable which will provide a mechanism for controlling the molecular weights of the polypropylene. The proposed method has allowed the polypropylene to be added in its own synthesis process, besides controlling its structure in terms of its stereo-specificity and molecular weight, thus improving its final properties.

Abstract

By regulating cement hydration reaction and organic monomer polymerization, the strength and deformability of in-situ polymerization modified cement-based materials are greatly improved. However, the fracture processes of this type of organic-inorganic composites have not been systematically investigated. In this work, sodium acrylate (SA) monomer in-situ polymerization modified cementitious composites (iPSA) were fabricated. Three-point bending (TPB) test was conducted with digital image correlation (DIC) technique for characterizing the fracture process zone (FPZ). Microscopic test was conducted to unravel the crosslinked organic-inorganic composite structures in the iPSA matrix. Results showed that an obvious strain concentration region occurred and grew at the notch tip of the iPSA beams with load. The gradually expanding width of FPZ was normally distributed. Microscopic test suggested that the physical interlinks between the cement hydrates and sodium polyacrylate may resist again the FPZ development of iPSA. The findings of this work would deepen the understandings of fracture process of polymer modified cementitious composites with broad engineering applications.