Development of PUF Resin Adhesive for E0 Grade Class I Bamboo Plywood

Research progress on bio-based wood adhesives

Authors: Pang Yanfang, Xu Weitao, Li Qi, et al.

With the increasing public awareness of environmental protection in home life and the ever-increasing environmental protection requirements for engineered wood products, environmentally friendly adhesives prepared primarily from biomass materials, such as low-formaldehyde/formaldehyde-free adhesives, have become a research hotspot in recent years. This article reviews the characteristics, preparation processes, modification methods, and current research progress of several bio-based adhesives using tannins, lignin, starch, and soybean protein as main raw materials. It discusses their current application status in the engineered wood product industry and summarizes and forecasts existing research problems and future development directions.

Development of PUF Resin Adhesive for E0 Grade Class I Bamboo Plywood

Authors: Wang Lijun, Gao Shishuai, Zhao Linwu, et al.

Based on the PUF adhesive used in E0-grade outdoor plywood, a urea-modified phenolic (PF) resin adhesive with a U/(P+U) mass ratio of 30% and an F/(P+U) molar ratio of 1.40 was prepared under alkaline conditions using NaOH as the catalyst and following the preparation process of phenolic (PF) resin adhesive. This adhesive was then used in the production of Class I bamboo plywood. The physical and mechanical properties of the produced bamboo plywood met the requirements for outdoor bamboo plywood, with a formaldehyde release of 0.1 mg/L. The preparation process of this adhesive is simple, the reaction is stable, the operation is easy to control, it has good reproducibility, and the cost is low.

Comparative Study on Lateral Tensile Mechanical Properties of Nail Connections Between Douglas Fir and Spruce Wood

Authors: Yao Lihong, Xu Weitao, Fei Benhua, et al.

Nail connections are a common connection method in timber structures, playing a crucial load-bearing role in shear walls. This article focuses on key connection nodes in shear walls of lightweight timber structures, comparing the lateral tensile mechanical properties and failure displacement of 30 connection nodes using different structural single nails to connect Douglas fir and spruce with structural plywood and oriented strand board (OSB) of varying thicknesses. The results show that nail size and veneer type significantly affect the lateral tensile mechanical properties and failure displacement of connection nodes formed with Douglas fir and spruce. With 6D nails, the lateral tensile force of Douglas fir is greater than that of spruce; with 8D nails, the lateral tensile force of spruce is greater than that of Douglas fir; with 10D nails, the force values ​​of the two timber types show a consistent trend. The failure displacement trends of Douglas fir and spruce connection nodes with different nail sizes are similar, but the difference in failure displacement becomes significant with increasing nail size; with 10D nails, the failure displacement trends of the two timber types are consistent, with the largest failure displacement observed when spruce is connected to 22mm thick OSB using 10D nails.

Comparison of shear properties of commercially available adhesives for timber structures

Authors: Xie Lisheng, Wu Jiahua, Qiao Luting, et al.

Four representative room-temperature curing adhesives for wood structures were selected from the market. Tensile shear strength tests were conducted along the grain of the glue joints according to Appendix A of GB/T 50708-2012 "Technical Specification for Glued Laminated Timber Structures" to test their shear strength, and the results were compared with those of thermosetting phenolic resin adhesives. The results showed that the average values ​​of the normal shear strength and wet shear strength of the glue joints of the three commercially available wood structure adhesives-one-component polyurethane, resorcinol-formaldehyde resin, and polyvinyl acetate-isocyanate-all met the national standard requirements and were basically equivalent to those of thermosetting phenolic resin adhesives, with resorcinol-formaldehyde resin adhesive showing the highest strength value. The normal shear strength of the glue joints of the commercially available two-component polyurethane adhesive for wood structures met the national standard requirements, but its wet shear strength did not. There was a significant positive correlation between the glue joint shear strength and the wood breakage rate at the glue joint; that is, the higher the wood breakage rate, the higher the glue joint shear strength value. These findings provide a certain reference for the selection of adhesives for wood structures.