Abstract
Sustainability and ecotoxicity issues call for innovations regarding eco-friendly adhesives in the production of biocomposite wood materials, and solutions involving nano-scale and bio-based compounds represent a valid and promising target. One possible approach is to increase the performance of adhesives such as polyvinyl acetate (PVAc) or melamine-urea-formaldehyde (MUF) by means of nanoparticles in order to obtain a material with better mechanical and environmental resistance. When applying cellulose-based nanoparticles or tannin, the concept of a circular economy is successfully implemented into the forest/wood value chain, and chances are created to develop new value chains using byproducts of forestry operations. In this study, assortments coming from young sweet chestnut (Castanea sativa Mill.) coppice stands were utilized for the preparation of single lap joint assemblies using different commercial adhesives (PVAc, MUF) and cellulose nanocrystals (CNC) and tannin as additives. The results showed that addition of CNC and tannin to PVAc glue increased tensile shear strength in lap joint tests presenting a promising base for future tests regarding the addition of CNC and tannin in MUF or PVAc adhesive formulations. Unfortunately, the tested bio-based additives did not reveal the same encouraging results when tested in the wet state.
Highlights
In the last years the necessity to substitute fossil resources with renewable ones has become one of the most important issues
Lignocellulosic resources can become a pillar in developing new value chains following basic concepts of a bio-circular economy
cellulose nanocrystals (CNC)-addition to the synthetic adhesive polyvinyl acetate (PVAc) resulted in increased mechanical performance as assessed by lap joint tensile shear strength tests under dry conditions
Summary
In the last years the necessity to substitute fossil resources with renewable ones has become one of the most important issues. The market for biocomposites is expected to grow in future thanks to a combination of factors like sustainability and renewability of wood resources, the inherent mechanical resistance of wood [2,3,4]. Among the species in Italy, which are cultivated in coppice stands and of interest for the short supply chain, sweet chestnut (Castanea sativa Mill.) represents one of the most important players [3,7]. Traditional uses of chestnut wood should be reconsidered and new applications might be focused on the production of biocomposite materials where, through the utilization of wood adhesives, small logs could be processed into a final product with satisfying mechanical properties [14,15]
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