Cork–polymer biocomposites: Mechanical, structural and thermal properties Emanuel M. Fernandes ⇑ , Vitor M. Correlo, João F. Mano, Rui L. Reis 3B’s Research Group – Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, 4806-909 Taipas, Guimarães, Portugal ICVS/3B’s – PT Government Associate Laboratory, Braga/Guimarães, Portugal article info Article history: Received 24 February 2015 Revised 7 May 2015 Accepted 18 May 2015 Available online 21 May 2015 Keywords: Cork Sustainable composites Biocomposites Eco-friendly Mechanical properties Thermal properties abstract This work addresses to the preparation of biocomposites resulting from the combination of different biodegradable aliphatic polyesters with cork (30 wt.%). The lignocellulosic biomass with closed cellular structure was compounded with poly(L-lactic acid) (PLLA), polyhydroxybutyrate-co-hydroxyvalerate (PHBV), poly-e-caprolactone (PCL) and starch-poly-e-caprolactone (SPCL) blend using a twin-screw extruder prior to injection moulding into tensile samples. The physico-mechanical and thermal proper- ties of the matrices and the bio-based cork composites were investigated. This study shows that the addi- tion of cork contributes to produce lightweight materials using PLLA and PHBV matrices and promotes an increase on the stiffness of PCL. The fracture morphology observations showed good physical cork–matrix bonding with absence of voids or cavities between cork and the bio-based polyesters. Cork increases the crystallinity degree of the biocomposites. These findings suggest that the cork–polymer biocomposites are a viable alternative to develop more sustainable composite materials, such as automotive interior parts and bio-based caps for wine bottles as it has been shown as proof-of-concept. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Lignocellulosic biomass represents a renewable, biodegradable, lightweight, abundant and cheap source of raw materials, making them attractive for the development of sustainable products [1– 4]. Cork is the outer bark of an oak tree known botanically as Quercus suber L.; being the major chemical constituents suberin (33–50%); lignin (13–29%); polysaccharides, (6–25%); and extrac- tives (8.5–24%) [5,6]. Cork reveals an anisotropic closed cellular structure as shown in Fig. 1. It is composed of an aggregate of cells, about 42 million per cubic centimetre [7]. Cork is a lightweight material, viscoelastic and impermeable to liquids or gases, good thermal, acoustic and electrical insulator, sound and vibration insulator and exhibits a near-zero Poisson coefficient, which found applications from the stoppers, agglomerates to aeronautics [5,8–12]. Furthermore, cork composites are one of the most promising fields of cork technology [8]. The combination of cork with polymers trough melt based technologies brought added-value to cork based materials that can promote the development of a wide range of innovative appli- cations. Studies can be found on the combination of cork and cork by-products with polyolefins such as polyethylene (PE) and polypropylene (PP) and the effect of adding coupling agent in the mechanical properties [13–15], chemical surface modification to improve cork–polymer compatibility [16,17]; cork in sandwich composite structures [18–20] and hybrid cork composite rein- forced with natural fibres [21,22]. Recently, the combination of the unique properties of cork with biodegradable matrices [23,24] was also studied aiming the production of more sustain- able materials. A sustainable product is a product which will gives as little impact on the environment as possible during its life cycle [25]. Nevertheless, one of the main drawbacks pointed to compos- ites is the low sustainability due to the separation problems of the mixed materials [25]. One interesting approach is to consider the re-manufacturing of old products or the use of biodegradable poly- mers, as matrices, combined usually with biofibres as the reinforc- ing element, to produce fully biodegradable materials, the so called biocomposites or green composites [1,26]. Biodegradable polymers and bio-based plastic products from renewal resources can form sustainable and eco-friendly products than can compete in the current market [2,27,28]. According to the market data compiled by European Bioplastics, the global produc- tion capacity of bio-based plastics is predicted to quadruple from http://dx.doi.org/10.1016/j.matdes.2015.05.040 0261-3069/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: 3B’s Research Group – Biomaterials, Biodegradables and Biomimetics, University of Minho, AvePark, Zona Industrial da Gandra, 4806- 909 Caldas das Taipas, Portugal. E-mail address: efernandes@dep.uminho.pt (E.M. Fernandes). Materials and Design 82 (2015) 282–289 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes