J Polym Eng 2015; aop *Corresponding author: Pavel Kucharczyk, Centre of Polymer Systems, University Institute, Tomas Bata University in Zlín, tr. T. Bati 5678, 760 01 Zlín, Czech Republic, e-mail: p_kucharczyk@ft.utb.cz Gabriela Jandikova, Alena Pavelkova and Vladimir Sedlarik: Centre of Polymer Systems, University Institute, Tomas Bata University in Zlín, tr. T. Bati 5678, 760 01 Zlín, Czech Republic Norbert Miskolczi: Institute of Chemical Engineering and Process Engineering, Faculty of Engineering, MOL Department of Hydrocarbon and Coal Processing, University of Pannonia, H-8200, Veszprém, Egyetem u. 10, Hungary Adriana Kovalcik: Institute of Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria Gabriela Jandikova, Pavel Kucharczyk*, Norbert Miskolczi, Alena Pavelkova, Adriana Kovalcik and Vladimir Sedlarik Copolymer of natural fibre reinforced polyester urethane: effect on physico-chemical properties through modification to interfacial adhesion DOI 10.1515/polyeng-2015-0077 Received March 2, 2015; accepted May 31, 2015 Abstract: This work is dedicated to polyester urethane (PEU)-based biocomposites, with special focus placed on techniques for compatibilisation to heighten interfacial adhesion between the PEU matrix and flax fibres. Tests were conducted on the effects of modification so as to increase interfacial adhesion between the flax fibres and the polyester matrix. These tests involved a commercial silane-based compatibilising additive, two experimen- tally synthesised agents, oleic acid (OA) and di-tert-butyl peroxide (DTBP). Furthermore, the flax fibres underwent acid or alkali treatment. The biocomposites were char- acterised by gel permeation chromatography, infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties were investi- gated through tensile testing. Biocomposites with a com- mercial silane-based additive and synthesised agent, based on maleic-anhydride, were assessed as the best solution. Nevertheless, all modifications, excluding alkali treatment of fibres, significantly increased the perfor- mance of the material. Keywords: adhesion; biocomposite; compatibilisation; flax; polyester urethane. 1 Introduction Polymer composites have been used heavily in various business sectors over the past few decades, such as civil engineering, the construction industry, transportation, aerospace, electronics and the biomedical field [1–3]. The most beneficial properties of this type of polymeric mate- rial [4] include their low weight, excellent mechanical behaviour and ability to tailor properties to meet wide- ranging performance requirements, along with the possi- bility to considerably decrease costs. Owing to the current recycling problem concerning petroleum-based polymers, great effort has been made to replace them with biodegradable polymers, which exhibit a so-called sustainable life cycle. As regards polymer com- posites consisting of at least two different materials – a polymer matrix (continuous phase) and a reinforcing agent (dispersed phase) – it is supposed that both phases of the composites would turn out to be biodegradable within a reasonable time [4, 5]. The favoured polymer matrix [6, 7] is polylactide (PLA), as a biodegradable aliphatic linear thermoplastic polyester. Its properties of biocompatibility, biodegradability and reasonable mechanical behaviour mark it out as a disposable and biodegradable plastic sub- stituent. Consequently, it has been applied in tissue engi- neering, drug delivery and food packaging [8–11]. Natural fibres are commonly used as a biodegrad- able reinforcing phase due to their combination of good mechanical properties, low weight and price. However, their relatively high hydrophilicity makes them poorly compatible with hydrophobic polymer matrices and pretreatment is necessary [12, 13]. The most common methods known for hydrophobisation of flax fibres are alkali etching [14, 15], acetylation [14, 16], silanisation [14, 17] and peroxide treatment [14]. Maleic-anhydride- based compatibilising agents have also been launched Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 2/12/16 3:20 PM