Abstract
Resorcinol-formaldehyde (RF) resin is a kind of excellent exterior-grade wood structural adhesive, which can be conveniently cold-set for various applications. In order to decrease the production cost, pyrolysis bio-oil from renewable bioresources was used to replace resorcinol to synthesize the bio-oil-resorcinol-aldehyde (BRF) resin. The effect of replacing resorcinol with bio-oil on the properties, bonding performance, and characterization of resorcinol-aldehyde resin was comparatively investigated. A higher solid content and viscosity, albeit a lower shear strength, was found when the replacement ratio of bio-oil increased. The bonding performance of BRF with 10 and 20 wt % bio-oil was close to that of the pure RF resin. However, the trends of being less cross-linked, more easily decomposed, but more porous were found when the substitution ratio of bio-oil was higher than 20 wt %. Interestingly, it was found that the wood failure values of the BRF resins with bio-oil of no more than 20 wt % were slightly higher than that of the pure RF resin. On the whole, BRF resins with 20 wt % bio-oil is recommended as a wood structural adhesive, comprehensively considering the bio-oil substitution ratio and resin properties. The results obtained here showed that pyrolysis bio-oil is a promising green raw material for the production of RF resin with lower cost.
Highlights
Wood construction, which has many advantages, such as providing natural, environmental protection and saving energy, has long been considered favorable
The results showed that the RF adhesive exhibited the best flexural and tensile strength in the three kinds of adhesive systems evaluated
The aim of this study was to investigate the effect of replacing resorcinol with bio-oil on the properties of resorcinol-aldehyde resin, which was expected to be used as a cold-set adhesive for wood construction
Summary
Wood construction, which has many advantages, such as providing natural, environmental protection and saving energy, has long been considered favorable. The contemporary construction of tall buildings from wood timber, the only significant building material that is grown, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable [1]. Given the rapid development of wood construction, the requirement of cold-set structural adhesive for on-site bonding is growing quickly. Polyurethanes, and resorcinol-formaldehyde are common types of adhesive used for on-site bonding, and their characteristics and prospects were previously reviewed by Pizzo et al [2]. Resorcinol-formaldehyde (RF) resin is one of the mostly used thermosetting adhesives in the production of exterior-grade wood structural materials. Due to the presence of the very reactive resorcinol moiety, RF resin is able to set at ambient temperature. A study on the effects of Polymers 2017, 9, 232; doi:10.3390/polym9060232 www.mdpi.com/journal/polymers
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