Processing and Characterization of Policaprolactone/Clay Nanocomposites

LEANDRO LUDUEÑA; ANALÍA VÁZQUEZ; VERA ALVAREZ

Rio de Janeiro, Brasil

Congreso; COMAT 2007; 2007

Nanocomposite films of PCL/clay were prepared by two techniques: casting and intensive mixing. In the last case, films were performed by compression molding, being this combination useful for industrial purposes.In both cases, a mixed clay structure, intercalated and exfoliated, coexisted in nanocomposites. Dichloromethane produced holes in the films evaporation surface whereas clay was acting as nucleation points of these holes decreasing mechanical properties. An appropriate solvent is critical for this technique.The dispersion degree estimated from mechanical properties modelling was higher for intensive mixing and no evidence of particles agglomeration was founded while for casting the agglomeration began at 7.5 wt. % of clay. Therefore, shear forces during processing are critical to obtain well-dispersed PCL/C30B nanocomposites and to achieve, consequently, a good mechanical performance.By studying the cristallyzation process it was demonstrated that the presence of the clay affected not only the bulk crystallization but also the spherulitic growth. The induction time was lowered by the clay incorporation and as a function of clay content. The global crystallization rate was faster with the presence of the clay.  The amount, shape and size of the spherulities were changed as clay was incorporated compared with the neat matrix at the same time and undercooling degree. These changes were dependent on the compatibility between the matrix and the clay: the nanocomposite with the less dispersed clay produced the lowest induction time, the highest global crystallization rate and the highest spherulitic growth rate.It was established that the clay acted as reinforcement enhancing the creep resistance of PCL. The nanocomposites prepared with the modified clay displayed the higher effect. Higher clay content produced the same effect. These results were in accordance with static tensile tests. Burgers and Findley power law models were used to correlate the experimental data. The parameters obtained from the models were in accordance with temperature, nanocomposites structure and clay content.