Processing and Characterization of Polycaprolactone/Clay Nanocomposites

L. LUDUEÑA; A. VAZQUEZ; V. ALVAREZ

Rio de Janeiro, Brasil

Congreso; COMAT 2007; 2007

The performance of a biodegradable polymer such as Polycaprolactone (PCL) can be enhanced by the dispersion of nanometer-size particles. Morphology and mechanical properties of PCL/modified-clay nanocomposites prepared by casting and intensive mixing were studied. Casting (laboratory-scale technique), was selected because the solvent may act as exfoliation agent. Intensive mixing was chosen because of its industrial application.  X-ray diffractograms revealed an intercalated-exfoliated mixed structure for both techniques. For casting, the morphology and mechanical properties were influenced by the solvent and preparation conditions. For intensive mixing, shear forces produced higher clay dispersion and the mechanical properties were superior. In both cases, the highest modulus was achieved for 5wt.% of reinforcement. An effective-filler-parameters model was used to compare the relative dispersion of clay. Using the best technique, crystallization and creep behavior of different modified montmorillonites at several clay contents were studied. Bulk-crystallization measurements were carried out in a Perkin-Elmer 7 DSC and modeled with the Avrami´s equation, founding that the crystallization rate depends on the polymer/clay compatibility and the clay content. For low clay dispersion, platelets may act as crystals nucleation points. It was also revealed by the spherulitic growth observed by optical microscopy. The secondary nucleation theory of polymer crystal growth was used to model the spherulitic growth rate. Creep behavior of the same materials was studied with a Perkin-Elmer DMA-7. The effect of clay content on deformation along time at different temperatures was modeled using different models: power-law, Kelvin-Voigt model and time-temperature superposition.