ORIGINAL PAPER Effect of Coconut, Sisal and Jute Fibers on the Properties of Starch/Gluten/Glycerol Matrix Elisa ˆngela Corradini Æ Syed H. Imam Æ Jose ´ A. M. Agnelli Æ Luiz H. C. Mattoso Published online: 17 April 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torque rheometer (120 °C, 50 rpm) for 6 min. The mixtures obtained were molded by heat compression and further characterized. Addition of ligno- cellulosic fibers in the matrix decreased the water absorp- tion at equilibrium. The diffusion coefficient decreased sharply around 5% fiber concentration, and further fiber additions caused only small variations. The thermogravi- metric (TG) analysis revealed improved thermal stability of matrix upon addition of fibers. The Young’s modulus and ultimate tensile strength increased with fiber content in the matrix. The storage modulus increased with increasing fiber content, whereas tand curves decreased, confirm- ing the reinforcing effect of the fibers. Morphology of the composites analyzed under the scanning electron microscope (SEM) exhibited good interfacial adhesion between the matrix and the added fibers. Matrix degraded rapidly in compost, and addition of increased amounts of coconut fiber in the matrix caused a slowdown the biode- gradability of the matrix. Keywords Starch  Gluten  Coconut  Sisal  Jute  Fiber  Composite  Reinforcement  Cellulosic Introduction The use of renewable resources such as plant derived polymers and fibers in the production of biodegradable materials/products has attracted much attention lately, particularly from the standpoints of sustainability and environmental conservation [1, 2]. Natural fibers like sisal, coconut, jute, and cotton have been used as reinforcements in synthetic and natural polymer matrices [3, 4]. Compared to inorganic fillers, plant fibers offer many advantages. Besides being renew- able, they also offer low cost, low density, high specific strength and modulus, and are comparatively easier to process due to their nonabrasive nature [5]. In a biocomposite, starch in conjunction with gluten offers an interesting combination of natural polymers as matrix components. Starch and gluten are relatively inex- pensive, abundantly available, and are naturally biode- gradable. Gluten is a low cost polymer with much lower hydrophilic character than starch, but has poor process- ibility compared to other proteins, starch or synthetic polymers [6]. Starch polymer, on the other hand, can be readily processed at high temperature (90–180 °C) in the presence of plasticizer under shear conditions [7] but the resulting material is overly sensitive to moisture. Efforts Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may be suitable. E. Corradini  J. A. M. Agnelli Departamento de Engenharia de Materiais da UFSCar, CP 676, 13560-905 Sa ˜o Carlos, SP, Brazil S. H. Imam (&) Bioproduct Chemistry & Engineering Research Unit, Western Regional Research Center, ARS-USDA, Albany, CA 94710, USA e-mail: syed.imam@ars.usda.gov E. Corradini  L. H. C. Mattoso Embrapa Instrumentac ¸a ˜o Agropecua ´ria, CP 741, 13560-970 Sa ˜o Carlos, SP, Brazil 123 J Polym Environ (2009) 17:1–9 DOI 10.1007/s10924-009-0115-1