Desenvolvimento, caracterização e envelhecimento térmico de compósitos híbridos PP/sisal-organobentonita.

Abstract

The present work is concerned with the effect of the chemical treatment of the fibers, loading level of sisal fiber and organoclay, compounding equipment, and thermal aging time on the mechanical and thermo-mechanical properties of polypropylene/sisal composites and polypropylene/sisal/organoclay hybrids. Short sisal fibers natural or chemically treated with aqueous solutions of sodium hydroxide were characterized by FTIR, TGA and SEM. PP/sisal composites with 10 and 20% natural or modified fiber content were compounded in single and twin-screw extruders (co- and counter-rotating). Hybrid composites with 20% sisal fibers and 1, 3, and 5% organoclay were prepared in the corotating twin-screw extruder. Composites were characterized by TGA and DSC. The quality of dispersion was estimated from optical and electron microscopy. Mechanical properties in tension, impact strength, and hardness, heat deflection temperature, water absorption capacity were measured, and performance was studied after thermal aging for up to 15 days. Sisal fiber addition resulted in stiffer and tougher materials, but the type of processing equipment don’t significantly affect the properties; chemical treatment of the fibers didn’t affected properties either. Clay was found to be well dispersed in the hybrids. Clay addition lowered the elastic modulus and resulted in a moderate decrease in tensile strength and an equally moderate increase in impact strength. Thermal aging affected the performance in proportion to exposure time; the presence of organoclay resulted in the near complete breakdown of the PP matrix after 15 day aging.