Rheology and adhesion performance of adhesives formulated with lignins from agricultural waste straws subjected to solid-state fermentation

8 Pág. Instituto de Ciencias Forestales (ICIFOR)
In this study, modified residual lignins from barley and wheat straws submitted to solid-state fermentation with diverse Streptomyces strains were targeted as binders in eco-friendly castor oil-based polyurethane adhesive formulations. The thermo-rheological and adhesion properties of these adhesives were examined and related to the solid-state fermentation yields. Viscoelastic properties were enhanced by lignin addition, and the Streptomyces action generally increased the values of the linear viscoelastic functions. Adhesion performance was dominated by lignin source and further Streptomyces activity and can be correlated with the resulting lignocellulosic composition. Wheat straw lignin-based polyurethane adhesives showed the best performance in metal-textile peeling tests, whereas barley straw lignin provided the best achievements in terms of shear strength in metal-metal and wood-wood joints. Overall, solid-state fermentation with Streptomyces demonstrated to be a suitable pretreatment to conveniently modify and improve residual lignin fractions for application as binders in environmental-friendly polyurethane adhesive formulations.
This work was partially funded by two coordinated research MINECO-ERDF projects (CTQ2014-56038-C3-1R and CTQ2014-56038-C3-2R) and the ERDF-Junta de Andalucía 2014-2020 Operational Programme (project UHU-1252599). A.M.B-L. has received a Ph.D. Research Grant from the Ministerio de Educación, Cultura y Deporte (FPU16/03697). The authors gratefully acknowledge the financial support.