This special edition of the Forest Products Journal contains invited papers selected from the International Conference on Wood Adhesives, held October 25–27, 2017, in Atlanta, Georgia.

At the meeting, the presentations were enlightening, the 241 attendees were highly engaged, and many good discussions took place during breaks. The keynote speaker, Johan Bruck from IKEA, energized the attendees by discussing IKEA's commitment to use all bio-based adhesives in their products. This was especially relevant to the many companies and academics working on bio-based adhesives. Other plenaries highlighted the myriad opportunities available from highly reactive bio-based cross-linking agents, the long

Abstract

The development of new and improved wood adhesives is hindered by an incomplete mechanistic understanding of what makes a wood–adhesive bond able to withstand changes in moisture levels. Although common methods are established to test and report the bulk-level properties of bond lines, such as bond-line shear strength and wood failure analysis, the development of experimental tools to study wood–adhesive bond lines and the effects of moisture at the nanometer to millimeter length scales remains an active area of research. Here we introduce and briefly review four recently developed tools that, when combined, we have found capable to facilitate the study of bond lines and the effects of moisture across these length scales. The tools are X-ray computed tomography, X-ray fluorescence microscopy, nanoindentation, and small-angle neutron scattering. Their combined utility has been demonstrated by studying model bond-line systems made using loblolly pine and phenol-formaldehyde adhesives. The results led to a new insight that adhesive infiltration into cellulose microfibrils at nanometer length scales likely plays an important role in the moisture durability of wood–adhesive bond lines. A new model to facilitate the discussion of potential interactions between adhesive and wood nanostructure was also developed.

Abstract

Wood-based products can be a sustainable and more environmentally friendly alternative to traditional construction materials because of their reduced contribution to air and water pollution. An integral component of these products is often an adhesive. Because wood is hygroscopic, moisture-induced swelling in the cell walls near the wood–adhesive bond lines can lead to durability and performance issues. Unfortunately, researchers working toward improving the moisture durability of forest products are hindered by an incomplete understanding of the nanoscale mechanisms that contribute to moisture-induced swelling in wood and how chemical modifications affect the swelling. Therefore, we developed small-angle neutron scattering (SANS) into a tool that can study the 1- to 100-nm structure of unmodified and chemically modified wood cell walls and can measure the effects of moisture in this structure. In this study, SANS was used to reveal the nanostructure of a deuterium-labeled phenol-formaldehyde (dPF) adhesive infiltrated into wood cell walls. The results revealed that the dPF infiltrated the water-accessible regions between the elementary fibrils inside the wood cell walls. These results provide the new insight that adhesive infiltration into the cellulose microfibril (a bundle of elementary fibrils) may be a key to designing moisture-durable wood adhesives.

Abstract

The automated bond evaluation system (ABES), which recently became ASTM D7998-15 standard test method, is an effective tool for screen testing of different water-based wood adhesive formulations. This method enables rapid evaluations of mechanical responsiveness of different adhesive formulations to various press temperatures and/or press times, providing an efficient and realistic comparison of bondability and reactivity among the adhesive formulations.

Based on extensive testing work, this article provides experimental findings and evidence for the use of this method to evaluate bonding performance of lignin as a major ingredient in the phenolic adhesive system. The relationship between bond strength development and press temperature can be established for a particular adhesive formulation using this method, which can then help the formulation and optimization of a wood adhesive containing lignin. Softwood plywood experiments demonstrated that there is a strong correlation between ABES test results and adhesive performance in the panel products.

Effect of Decoration Complexity and Age on Aesthetic Evaluation, Purchase Intention, and Visual Attention in Wood Furniture

Tao Song,

Hemin Du,

Sifan Wu,

Wang Pohsun,

Jingran Lin,

Ziying Li, and

Liying Wen