Coconut fiber/LDPE composites: effect of surface treatment of coconut fibers to produced green composites

摘要

The development of polymer composites reinforced with natural fibers have gained attention as alternative technology for the processing of new material that provide a lower environmental impact, associated with lower density, biodegradability and interesting mechanical properties. Natural fibers that come from the green coconut have higher stiffness and mechanical resistance when compared with other natural fibers, considering its chemical composition. Although, natural fibers show a weak interaction with the polymer matrix, due to its hydrophilicity when compared to the matrix, hydrophobic. In this work, coconut fibers (CF) were chemically treated by alkalization with sodium hydroxide (NaOH) and mechanically treated by ultrasound in aqueous media. Low-density polyethylene (LDPE)/CF composites were prepared with different contents of coconut fiber (5 and 10 wt%), in the molten state using a homogenizer with high rotation (DRAIS) and stamping for the preparation of the specimens. The treated fibers were characterized by scanning electron microscopy (SEM) and the LDPE/FC composites were characterized according to the thermal properties (differential scanning calorimetry - DSC), mechanical properties (tensile tests) and morphology (SEM). From the results obtained, it can be concluded that no significant change was observed with the different treatments for composites with 5 wt% of CF compared to the neat LDPE. The best results of mechanical resistance noticed on composites with 5 wt% of CF when compared with composites with 10 wt% of CF. The ultrasound treatment demonstrated the best performance. The crystallization degree of the neat LDPE was not affected by the presence of the coconut fibers, although there was a good interaction and adhesion between the CF and the polymer matrix.