Análise da eficiência de expansão e esfoliação da montmorilonita em compósito de pvc.

Abstract

This study aims to evaluate the influence of the time of agitation on the exfoliation efficiency of the montmorillonite clays in polyvinyl Chloride (PVC) composites, prepared by the "in situ" polymerization process. The work was performed in 2 steps. In 1st. Stage: Tests of expansion with 3 different types of clays in monovinyl chloride (MVC): Nanocor I-24, Cloisite 30B and sodium bentonite, which were used to assess the degree of expansion in MVC of each of them at different times of agitation: 2, 4 and 6 h. After agitation, each system was kept in observation for 3 days to evaluate the changes in the decanted volume of the clay in the reactor. 2nd. Stage: The Influence of the time of agitation for the clay exfoliation. Part 1: Nanocor I-24 and Cloisite 30B clays were use to compare the influence of the time of agitation for exfoliation and characterized by XRD, Part 2: Cloisite 30B clay used to evaluate the influence of the time of agitation in the morphology of the composites generated and characterized by TEM. We used the same experimental procedure to generate the samples of PVC-clay composites in parts 1 and 2: we added initially MVC and clay into the reactor, and then the mixture was kept in agitation with constants pressure and temperature in the pre-defined time. Then, water and other additives were added, and we kept the mixture in agitation with constant pressure and temperature in the pre-defined time. After this period, the system was heated to initiate the polymerization of the MVC. The results obtained in step 1 showed that Cloisite 30B has greater capacity to expand in the MVC, which should be linked to its organic modifier. The influence of the time of agitation for the expansion of the clays was also verified and the higher percentage of expansion was reached in 4 hours of the time of agitation. The results of step 2 indicated that the clays in study have similar influence to the morphology and exfoliation for the time of agitation; it was identified in XRD and TEM analysis. Based on the results, we conclude that the type of the clay and the time of agitation studied influence the degree of expansion of clays in MVC, and that the times of agitation in the stages of expansion of clay in MVC and dispersion of water and additives are important for the exfoliation of the clays in PVC matrix.