State of research and trends in development of wood adhesives

Abstract

We aim to present an overview of the status of adhesives in the wood industry, especially in the area of wood-based panels. The review summarizes the current state of research of two kinds of adhesives, i.e., synthetic adhesives and natural adhesives. Synthetic adhesives, consisting of urea-formaldehyde resins (UF), phenol-formaldehyde resins (PF), polyvinyl acetate emulsion (PVAc) and isocyanates, are widely used. For UF, most investigations are concerned with the reduction of free formaldehyde; for PF, most studies focus on fi nding new chemicals to replace phenol. PVAc has poor properties, but these can be improved by a blending reactions and copolymerization with other chemicals. Isocyanate is an environmentally friendly synthetic adhesive, but also suffers from inadequate properties. Natural adhesives, such as protein/starch, lignin and tannins, have poor bonding effect that limits their level of use, but their main advantages are that they are environmentally friendly and a renewable resource. Studies of modifi cation can improve the bonding performances and gradually cause natural adhesives to become applied in industrial production. Some proposals for future development and the importance of environmentally friendly adhesives are provided, which will be helpful in future theoretical and experimental research.

Development of sustainable bio-adhesives for engineered wood panels – A Review

“…1 The mechanical strength of manufactured panels and especially their moisture tolerance are additional crucial parameters the new, bio-based adhesives have yet to full satisfactorily. 2 There are two main factors driving the trend to move away from using formaldehyde-based synthetic resins for woodbased panel manufacturing: formaldehyde emissions and sustainability of raw materials and nal products. In the panel industry, sustainability and petroleum independency cannot, as of yet, justify the increase in cost due to new bio-based adhesives.…”

“…reducing formaldehyde/urea molar ratio). 2 The most typical scavenger for wood-based panels is urea, but other compounds like ammonia and ammonium salts can also be used. 6 They can be added directly to the synthetic resin or wood particles.…”

Chemical Composition and Light Extinction Contribution of PM2.5 in Urban Beijing for a 1-Year Period

“…The decline of visibility, particularly frequent hazes in megacities like Guangzhou, Chengdu and Beijing during the recent years (Tan et al, 2009;Zhao et al, 2011;Wang et al, 2013a), has become a major concern for the general public in China.…”

A Review of Isocyanate Wood Adhesive: A Case Study in Indonesia

“…To our best knowledge, isocyanate adhesive is a general term for a variety of esters, which rely mainly on phosgene synthesis in conventional synthesis industries. As of now, toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) are the most commercially important diisocyanates [24]; they are widely used and have the largest output [25]. TDI has quite a high vapor pressure; hence, increased health risks involved with the use of this isocyanate are significant [7].…”