J.R. Araujo

Mechanical properties, morphology and thermal degradation of a biocomposite of polypropylene and curaua fibers: coupling agent effect

Biocomposites of polymers with vegetal fibers have a broad spectrum of applications due to their high specific properties in comparison to their counterparts made with fiberglass. Polypropylene, PP, composites with curaua fiber compatibilized with different concentrations of maleic anhydride grafted polypropylene, PP-g-MA, were characterized according to their mechanical properties, morphologies and thermal stabilities in oxidative and inert atmospheres. The composites were prepared by single screw extrusion and injection molded specimens were used for testing. The composite with 20 wt % of curaua fiber with and without compatibilizer presented improved mechanical properties compared to pure PP. The use of PP-g-MA as a compatibilizer significantly increased fiber/matrix adhesion, however, the mechanical properties were only slightly improved in comparison with composites without compatibilizer. We observed an improvement in thermal stability of the composites, compared to that expected from the weighted average of the individual components, both under inert and oxidative atmospheres. Furthermore, the thermal stability improved under inert atmosphere as a function of the concentration of compatibilizer. In this situation, indeed, there was a different shift of the weight loss processes owing to the presence of the compatibilizer.

Polyaniline coated curauá fibres in polyamide-6 composites: the effect of fibre surface modification on the crystallographic properties

Composites have the ability to combine the individual properties of constitutive components, generating a unique material with properties suitable for a particular purpose. This study aims to develop a polymeric reinforced composite material, which is antistatic and light. Polyaniline (PAni) is one of the most studied conductive polymers due to its ability to exist in a large number of intrinsic redox states. The possibility of carrying out PAni synthesis on vegetable fibres and incorporating this in polymeric matrices, such as polyamide-6, enables the production of antistatic reinforced materials. In this work, curaua fibres were chemically treated with polyaniline doped with p-toluene sulfonic acid and processed with polyamide-6 in a twin-screw co-rotating and interpenetrating extruder. The microstructures of the neat curaua fibres and polyaniline coated curaua fibres were characterized by X-ray diffraction (XRD) measurements. Scanning electron microscopy was employed to observe the distribution and morphology of the PAni nanoparticles. The oxidation states of PAni were evaluated by X-ray photoelectron spectroscopy. X-ray diffraction combined with microscopy analyses of PAni synthesized without a substrate, showed crystalline components embedded into amorphous regions in the sample, while the PAni synthesized on the fibres showed a lower degree of crystallinity. The XPS