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Purpose: In industrial applications, formaldehyde-based wood adhesives have been used extensively because of their low costs and high reactivity. However, their real-world applications are hindered by some main bottlenecks, especially the formaldehyde emission and usage of nonrenewable raw materials. The purpose of this study is the development of sustainable and formaldehyde-free wood adhesive formulation. Design/methodology/approach: In this study, starch and tannin-based wood adhesive were synthesized. Chemical structures and thermal properties of the prepared bio-based resin formulations were elucidated by using Fourier transform infrared and differential scanning calorimetry analysis, respectively. Laboratory scale particleboard production was carried out to determine the performance of the developed resin formulations. Obtained results were evaluated in dry medium (P2) according to European norms EN 312 (2010). Furthermore, the board formaldehyde content was determined by using the perforator method according to the European Norm EN 12460-5. Findings: The results show that the improved starch and tannin-based wood adhesives were successful in their adhesive capacity, and the formaldehyde content of the final product was obtained as low as 0.75 mg/100 g. This paper highlights that the presented adhesive formulations could be a potential eco-friendly and cost-effective alternative to the formaldehyde-based wood adhesives for interior particleboard production. Research limitations/implications: Starch-based resins in the liquid form needed to be continuously mixed throughout their shelf life to prevent the starch from settling because it was not possible to dissolve the precipitated starch again after a while. For this reason, starch was given to the chips in powder form while preparing the particleboard. Practical implications: In conclusion, this study shows that the developed bio-based resin formulations have a high potential to be used for producing interior-grade particleboards instead of commercial formaldehyde-based wood adhesives because the obtained results generally satisfied the interior grade particleboard requirements according to European norms EN 312, P2 class (2010). In addition, it was determined that the produced boards had significantly low formaldehyde content. The low formaldehyde content of the final boards was not because of the resin but because of the natural structure of the wood raw material, press parameters and environmental factors. Social implications: The developed bio-based resin system made it possible to obtain boards with significantly low formaldehyde content compared to commercial resins. Originality/value: The developed bio-based resin formulation made it possible to produce laboratory-scale board prototypes at lower press factors and board densities compared to their counterparts. [ABSTRACT FROM AUTHOR]

The wood-based panel industry provides industrial-scale production of engineered wood products for our daily life. In the production of wood-based panels, the most important input other than wood raw material is the adhesive. Formaldehyde-based resins are used as binders in the production of wood-based panels thanks to their cost and reactivity advantages. However, their fossil origin and formaldehyde content have increased the interest in resin synthesis studies with the use of biobased materials. Tannin is one of the most studied raw materials both in academia and industry to synthesize bio-based wood adhesives due to the suitability of its chemical structure and availability. In this review, the developed tannin-based wood resin formulations that have been developed were examined in two main sections. These are crosslinked tannin-based resins developed using crosslinkers such as hexamine, furfural, etc. And hybrid tannin-based resins prepared using other biobased resources such as starch, lignin, etc. The performance of the developed resin formulations was evaluated on the mechanical and physical properties of the final product such as particleboard and plywood. The pros and cons of each resin formulation were examined in detail regarding the final product performances. All of the obtained results showed that bio-based resin formulations synthesized with tannin and without formaldehyde have the potential to compete with formaldehyde-based resins. [Display omitted] [ABSTRACT FROM AUTHOR]