Microstructure of Thermoplastic Composites Reinforced with Wool and Wood

Acknowledgements: The authors are grateful to FEDER – Fundo Europeu de Desenvolvimento Regional, in the aim of COMPETE 2020 with the copromotional project WOWW - World of Outstanding Wool and Wood and to Portuguese Foundation for Science and Technology (FCT) through the Project reference UID/Multi/04044/2013 and PAMI – ROTEIRO/0328/2013 (Nº 022158). The authors gratefully acknowledge the contribution to language revision of Dr Sonia Fiuza. The Coimbra Chemistry Centre, CQC, supported by FCT, through the project PEstOE/QUI/UI0313/2013 is also acknowledged In the last decades the studies on thermoplastic composites reinforced with natural fibres have been mostly focused on vegetable lignocellulosic or cellulosic fibres. These materials provide eco-sustainable solutions for a large range of applications and have been actually adopted by multiple industries. The interest on fibres of animal origin is more recent and research on composites reinforced with these fibres predominantly composed of keratin, such as wool, feathers or silk, is increasing in virtue of some advantageous properties that may overcome some of the intrinsic limitations from vegetable fibres. The combined use of vegetable and animal fibres in composites appropriate for melt blending processing is at early stages of research. After chemical treatments, the fibres of animal origin have been mostly applied as binders between vegetable fibres and polymers, but not as main constituents of these composites. The use of both types of fibres simultaneously in composites of thermoplastic matrices is the subject of the present study where the fibres of animal origin (wool) are sourced from different kinds of residues from a textile industry and the fibres of vegetable origin (wood) are the residues from carpentry activities. The chemical composition, the macro and microstructure of the fibres is analyzed, as well as that of the composites that combine non-biodegradable and biodegradable polymers with diverse ratios of the fibres in different conditions (wool as cards, yarns and felt cloths; wood as sawdust). The addition of coupling agents to enhance the compatibility between wool, wood and different polymers is also analysed.