Multi-Crystalline polymer systemsBiodegradable triblock terpolymers and nanostructured blends. Morphology, Crystallization and properties

Resumen

In this PhD thesis, the morphology, crystallization behavior and properties of two multi-crystalline polymer systems with at least two crystallizable phases were addressed. The two systems chosen were: triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers and double crystalline PP/PA6 nanostructured blends with nanosilica and compatibilizer agents. The PEO-b-PCL-b-PLLA triblock terpolymers, with increasing PLLA content, exhibited a triple crystalline nature. The three blocks are able to crystallize separately and sequentially upon cooling from a homogeneous melt. The PLLA block templates the spherulitic morphology of the terpolymer for the subsequent crystallization of PCL and PEO blocks. Thus, three different lamellae of PLLA, PCL and PEO coexist together within the same spherulite. Complex competitive effects such as plasticizing, nucleation, anti-plasticizing and confinement occurred during the isothermal crystallization of the terpolymers. The second system, 80:20 PP/PA6 blends with a fixed amount of PPgMA and decreasing nanosilica content, was prepared by melt mixing.After optimization by varying components and composition, a PP/PA6 blend, stabilized with 1.6 % hydrophobic nanosilica and compatibilized with high grafting level PPgMA, exhibited a droplet size reduced morphology with enhanced ductility and barrier properties. The use of an optimal content of nanosilica along with a compatibilizer yields a synergistic effect on the PP/PA6 blend.