Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone reinforced with sisal fibers

The incorporation of fibers as reinforcements in polymer composites has increased due to their renewability, low cost and biodegradability. In this study, sisal fibers were added to a polymer matrix of thermoplastic starch and polycaprolactone, both biodegradable polymers. Sisal fibers (5% and 10%) were extruded in a twin-screw extruder with thermoplastic starch/polycaprolactone (80:20 wt). Films were produced with a single extruder and analyzed by field emission gun scanning electron microscopy, mechanical tests, thermogravimetric analysis and differential scanning calorimetry. The morphology of the composites with 10% sisal fiber content presented an interface of fibers at the surface of the matrix, indicating poor adhesion, lower initial temperatures of thermal degradation, and decreased polycaprolactone crystallinity due to the decrease in lamellar thickness and the increase in crystalline disorder. The results were affected mainly by the lack of adhesion at the interface between the matrix and fibers. The interfacial shear strength between sisal and the matrix may be improved by chemical modification of the fiber surface.