Compósitos de poli(metacrilato de metila) – PMMA com alumina e argila vermiculita piroexpandida.

Abstract

Poly (methyl methacrylate) - PMMA has been replacing glass in many applications as it is transparent and more impact resistant. Other advantages are related to its lower density, which facilitates handling and reduces transportation costs, as well as not generating shrapnel when broken, compromising safety. It is also one of the main competitors of Polycarbonate - PC, because it is an inexpensive plastic with excellent optical properties, good resistance to discoloration and loss of light transmission. However, PMMA has high flammability, low abrasion resistance, low risk and low hardness. In order to modify these properties, PMMA composite systems with three ceramic loads were developed: alumina synthesized (ALS), commercial alumina (ALC) and vermiculite pyroexpandid clay (VERM). The composites were processed in a twin-screw extruder and injected molded with 1 and 3% loading. The composites loaded with the synthesized alumina (ALS) had the highest tensile strength, higher hardness and better dispersions, however there were no improvements in impact strength and flammability. The composites loaded with commercial alumina (ALC) showed a decrease in tensile strength, impact strength, lower values for flammability and a higher number of clusters in their micrographs, however, there was an increase in hardness. On the other hand, the composites with the vermiculite clay presented the best behavior against the impact and flammability tests, with small and well distributed clusters. The results obtained for the wear index in the abrasion test and the evaluations made on the basis of the Hoffman risk test were promising. All composites outperformed the pure PMMA behavior. The composites with ALS showed a gain of 85% in abrasion resistance, composites with ALC around 81% and composites with vermiculite around 12%. According to the risk assessment proposed by Hoffman, all the compositions indicated, by the analysis of the morphology of the risks, increase of the hardness.