Fortified mangrove tannin-based plywood adhesive

Abstract

SYNOPSISMangrove bark tannin adhesives are based on a renewable resource. They are potential substitutes or supplements for phenol-formaldehyde (PF) wood-bonding adhesives which are derived from petroleum, a finite natural resource. However, mangrove tannin adhesives exhibit poor adhesive properties including poor wet strength, brittleness, and poor wood penetration. These problems were addressed by treating tannin extract with acetic anhydride and then sodium hydroxide followed by modification with 20% resole-type P F resin. Significant structural changes occurred after the chemical treatment. Heat of reaction of tannin with formaldehyde was increased while the activation energy was drastically reduced. Premature cure was also reduced. The fortified formulations had good plywood adhesive properties.

Bio‐oil from whole‐tree feedstock in resol‐type phenolic resins

“…Lignocellulosic biomass can be converted into organic compounds, including phenolic compounds, by thermochemical technologies, such as pyrolysis and liquefaction . In the last decade, researchers have made much effort to partially replace petrochemical phenol by phenolics from renewable resource such as lignins, tannins, cardanol, bio‐oil, and biocrude …”

Термопластичні Полімери У Виробництві Фанерної Продукції: Переваги, Можливості Та Перспективи Застосування

“…Впродовж останніх років були запропоновані клеї для склеювання деревини, які не містять формальдегіду (Huang & Li, 2008, Kishi et al, 2006, Mittal & Sharma, 1992, Sowunmi et al, 1996, Tohmura et al, 2005, Umemura et al, 1999, Hu et al, 2005, Liu & Li, 2007. Для одержання клеїв без формальдегіду використовують промислові ізоціанатні смоли (Tohmura et al, 2005, Umemura et al, 1999, епоксидні смоли (Kishi et al, 2006) та інші, а також деякі натуральні продукти, такі як танін (Sowunmi et al, 1996), лігнін (Mittal & Sharma, 1992) та соєвий білок (Liu & Li, 2007). Здійснюється низка досліджень у напрямку пошуку нових і нетоксичних смол, які не містять формальдегіду і можуть застосовуватися в процесі виробницт ва фанери без зниження її міцності.…”

Effect of natural rubber on wood‐reinforced tannin composites

“…1) are reactive sites in crosslinking with hardeners, such as formaldehyde and hexamethylenetetramine (HEXA) 5–7. Many scientific studies and technological reports on the applications of tannin extracts are related to their use in particleboard, plywood, and laminated woods 6–8…”

“…Besides, it must be taken into account that tannin molecules are big and rigid and cannot rotate freely. All these effects are responsible for the residual active centers in the network becoming too far apart for hardener molecules to react and increase the extent of crosslinking 8, 10. The resulting incomplete curing and the high number of inert hydroxyls and polar ammonia groups from the HEXA decomposition in the final material cause poor resistance to adverse humid environments.…”