Physical structure
Fig. 3 shows SEM images after cryogenic fractures of 30 wt.% alfa/PP composite, 30 wt.% coir/PP composite and 30 wt.% bagasse/PP composite. The good dispersion of fibers in the polymer matrix is well exposed (Fig. 3a–c), and the surface morphology of the alfa, coir and bagasse fibers are clear. Alfa, coir and bagasse fibers are tubular with circular section. And an enlargement of single fiber shows that each fiber was composed of microfibers (Fig. 3a0–c0). The surface morphology of the three composites presents a reduced number of pulled-out fibers which indicates a better affinity at fiber/polymer interface. Also, the fibers surface was fractured which supported the previous explication. So, the polymer wets perfectly the surface of fibers. This is a result of the alkali treatment on the surface composition of the used fibers.