Novel sustainable composites prepared from cork residues and biopolymers Carla Vilela, Andreia F. Sousa, Carmen S.R. Freire*, Armando J.D. Silvestre, Carlos Pascoal Neto CICECO and Chemistry Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal article info Article history: Received 4 June 2012 Received in revised form 16 December 2012 Accepted 27 January 2013 Available online 7 March 2013 Keywords: Cork biomass residues Polymer-matrix composites Mechanical properties Density Renewable resources Sustainable composites abstract Novel low-density biocomposites based on cork and two biodegradable matrices, poly(lactic acid) and poly(caprolactone), were prepared by simple melting-mixing. The surface acyla- tion of cork was studied as a strategy to increase the compatibility with the matrices. The obtained composites were characterized in terms of thermal and mechanical properties, morphology, density and water absorption behavior. All composites showed a good dis- persion of cork and a strong interfacial adhesion between the cork particles and the poly- meric matrices as evidenced by SEM. The Young’s modulus values of the composites were little affected for cork loads up to 10%; but for higher loadings, a considerable decrease on this parameter was observed resulting in more flexible materials. These sustainable cork based materials could find applications in several domains such as in flooring and structural applications, depending on the amount of cork and the polymeric matrix used. ª 2013 Elsevier Ltd. All rights reserved. 1. Introduction Growing interest has been devoted in recent years to materials derived from renewable resources mainly due to the increasing concerns associated with environment, waste accumulation and disposal and the inevitable depletion of fossil resources [1]. Cork, the outer bark of Quercus suber L., is a plant tissue composed of suberin (30e60%), lignin (19e22%), poly- saccharides (12e20%) and extractives (9e20%) and with a very peculiar morphology consisting of tiny hollow hexagonal pris- matic cells stacked in base-to-base rows [2]; features that impart cork with unique properties such as very low density, hydrophobic character, resilience, low thermal conductivity, fire resistance, good insulation properties, elastic behavior, among others [2e4]. Industrially, cork is mainly processed for the production of stoppers and acoustic and thermal insulation materials; however, in recent years the development of other applications has been reinforced as a response to the decline in the traditional wine cork stoppers market, as well as to the increasing innovation requirements in such traditional indus- tries. Another important issue, that has also strongly stimulate this trend is associated with the valorization of huge amounts of industrial residues produced during cork processing, and particularly the so called “cork powder”, a residue that repre- sents about 20% of the total cork production and which, due to the low granulometry is not suitable for conventional cork applications and is simply burned to produce energy [5,6]. Cork-based thermoplastic composites are one of the most promising fields of novel high-tech applications of cork [7], which * Corresponding author. Tel.: þ351 234 370 604; fax: þ351 234 370 084. E-mail address: cfreire@ua.pt (C.S.R. Freire). Available online at www.sciencedirect.com http://www.elsevier.com/locate/biombioe biomass and bioenergy 55 (2013) 148 e155 0961-9534/$ e see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biombioe.2013.01.029