Industrial Crops and Products 30 (2009) 235–240 Contents lists available at ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop High resin content natural matrix–natural fibre biocomposites A. Pizzi a,∗ , R. Kueny b , F. Lecoanet b , B. Massetau a , D. Carpentier a , A. Krebs a , F. Loiseau a , S. Molina c , M. Ragoubi c a ENSTIB-LERMAB, Nancy University, Epinal, France b CETELOR, Nancy University, Epinal, France c LERMAB, Faculty of Science, Nancy University, Nancy, France article info Article history: Received 2 March 2009 Received in revised form 25 March 2009 Accepted 31 March 2009 Keywords: Biocomposites Biofibres Biomatrix Environment friendly Non-toxic abstract Composites of good performance formed from non-woven mats of flax and hemp fibres and natural resin matrices have been prepared. Both higher density thin composites as well as lower density thicker composites have been prepared. Two natural matrices types were used: (i) commercial mimosa flavonoid tannin extract with 5% hexamine added as hardener and (ii) a mix of mimosa tannin + hexamine with glyoxalated organosolv lignin of low molecular weight, these two resins mixed 50/50 by solids content weight. The composites prepared were tested for MOE in bending and in tension and for maximum breaking strength in tension. Some of the mats were corona treated and the optimum length of corona treatment determined to improve the composites MOEs and breaking strength. These were related to the morphology of the treated fibre. Thermomechanical analysis (TMA), Brinell surface hardness and contact angle tests were also carried out with good results. The composites made with the mix of tannin and lignin resins as a matrix remained thermoplastic after a first pressing. The flat sheets prepared after the first pressing were then thermoformed into the shape wanted. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Biocomposites are and have been an area of growing interest and a subject of active research for quite sometime now. This is due to both environmental concerns as well as to the foreseen future scarcity of oil and oil-derived products. Biocomposites using natu- ral fibres and oil-derived polymer matrices have now existed and have been available commercially for quite sometime. Thus, com- posites from natural fibres plus polypropylene and other oil-derived thermoplastic matrices for car doors interiors and other applica- tions are well known and are used, although not as extensively as could be wished. However, for the same type of applications, composites using also natural matrices while still presenting high performance are talked about but in reality have not been devel- oped nor commercialised. This is due to the difficulty in finding matrices of natural origin capable of imparting all the required per- formance to the resulting composites. For example, starch-bonded (Theis and Grohe, 2002) biocomposites suffer of poor water and moisture resistance, etc. A class of composites in which natural origin resins have already had a commercial/industrial impact is in the field of rigid wood ∗ Corresponding author. Tel.: +33 329296117; fax: +33 329296138. E-mail address: antonio.pizzi@enstib.uhp-nancy.fr (A. Pizzi). panels, such as particleboard, where natural origin resins are already used commercially for the last 30 years, and still growing, although as yet relatively slowly (Pizzi, 2006). In such an appli- cation, although one can speak of a composite, the binder, hence the natural matrix used, is never more than 10% by weight of the whole composite panel. This is sufficient to stay in line with the performance and costs required by the wood panels industry and their respective product standards. However, some of the natural resins used as thermosetting binders for this application could def- initely be used to produce upgraded natural fibre composites in which a high content of a natural matrix is used. The main natu- ral resins used in the timber industry are vegetal tannin adhesives, lignin adhesives and more recently also soy protein adhesives (Pizzi, 2006). Of these, tannin-based adhesives have been commercial the longest, since 1971. They present the advantage over the other two types of not needing any reinforcement with an oil-derived syn- thetic resin of some kind (Pizzi, 2006), as it is still the case for the already commercial use of lignin (Lei et al., 2008; Pizzi and Stephanou, 1993a,b; El Mansouri et al., 2007a,b) and soy binders (Lorenz et al., 2006; Wescott et al., 2006; Amaral-Labat et al., 2008; Pizzi, 2006). This paper then deals with the attempts at producing natural fibres/natural matrices composites of good performance by trying as matrices tannin resins of the latest generation, lignin resins and soy resins used on non-woven flax mats. 0926-6690/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2009.03.013