BIOPRODUCTS FROM AGRICULTURAL FEEDSTOCKS
Location: Bioproduct Chemistry and Engineering Research
Title: Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone
reinforced with sisal fibers
Submitted to: Journal of Reinforced Plastics and Composites
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 2012
Publication Date: May 9, 2012
Citation: Campos, A., Marconcini, J., Imam, S.H., Klamczynski, A., Orts, W.J., Wood, D.F., Williams, T.G., Martins-Franchetti, S., Mattoso, L. 2012. Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone reinforced with sisal fibers. Journal of Reinforced Plastics and Composites. 31 (8): 573-581.
Interpretive Summary: Growing environmental concerns have led to an increased interest in biocomposite plastics (bioplastics) as replacements for plastics made from petro-chemicals. Bioplastics are natural, renewable, compostable and eco-friendly. The use of natural fibers as reinforcements to improve the mechanical properties also offers the advantages of low cost, high specific modulus, high impact strength, good corrosion resistance, heat insulation and biodegradability. Sisal is one of the natural fibers most widely used worldwide and Brazil is one of the world’s largest producers of this material. The exceptional mechanical characteristics of sisal are already making its application in the automotive industry and civil construction possible. This study evaluated the mechanical properties of composites made using extrusion technology of polycaprolactone (a biodegradable polyester), thermoplastic starch (starch heated with a plasticizer) and sisal fiber. We then studied the biodegradation of the composites in composted soil. Biocomposite blends containing 5% and 10% sisal fibers were prepared by extrusion and characterized by scanning electron microscopy (SEM), tensile tests, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray spectroscopy, and Fourier transform infrared (FT-IR) measurements and biodegradability. The shear strength of the biocomposites were improved by chemically modifying the fiber prior to its incorporation into the bioplastic polymer.
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