Development of PUF resin adhesive for E0 grade Ⅰ bamboo plywood

Research progress of bio-based wood adhesives

Authors: Pang Yanfang, Xu Weitao, Li Qi, etc.

With growing public awareness of environmentally friendly living and rising environmental standards for wood-based panels, environmentally friendly adhesives, such as those made from biomass materials with low or no formaldehyde content, have become a research hotspot in recent years. This article reviews the characteristics, preparation processes, modification methods, and current research progress at home and abroad for several bio-based adhesives based on tannins, lignin, starch, and soy protein. The article also discusses the current status of their application in the wood-based panel industry, and summarizes and outlines existing research challenges and future development directions.

Development of PUF resin adhesive for E0 grade Ⅰ bamboo plywood

Authors: Wang Lijun, Gao Shishuai, Zhao Linwu, etc.

Based on PUF adhesive for E0-grade exterior plywood, a urea-modified phenolic (PF) resin adhesive with a U/(P+U) mass ratio of 30% and a F/(P+U) molar ratio of 1.40 was prepared under alkaline conditions using NaOH as a catalyst and following the preparation process for phenolic (PF) resin adhesive. This adhesive is suitable for the production of Class I bamboo strip plywood. The resulting bamboo strip plywood meets the requirements for exterior bamboo strip plywood, with a formaldehyde emission of 0.1 mg/L. This adhesive exhibits a simple preparation process, a smooth reaction, easy controllable operation, good reproducibility, and low cost.

Comparative study on lateral tensile mechanical properties of nailed joints between Douglas fir and spruce timber

Authors: Yao Lihong, Xu Weitao, Fei Benhua, etc.

Nail connections are a common connection method in timber structures and play a crucial load-bearing role in shear walls. This study compared the lateral tensile mechanical properties and failure displacements of 30 types of connections between Douglas fir and spruce timbers, using single nails of varying construction, and structurally connected plywood and oriented strand board (OSB) of varying thicknesses. The results show that nail size and sheathing type significantly influence the lateral tensile mechanical properties and failure displacements of these connections. Six-dimensional nails significantly increase the lateral tensile strength of Douglas fir and spruce timbers; 8-dimensional nails significantly increase the lateral tensile strength of spruce timbers; and 10-dimensional nails significantly increase the strength of the two timber types. The failure displacement trends of Douglas fir and spruce timbers connected with different nail sizes are similar, with significant differences in failure displacements as nail size increases. The failure displacement trends of 10-dimensional nails between the two timber types are consistent, with the maximum failure displacement observed when spruce timber is connected to 22 mm thick OSB timber using 10-dimensional nails.

Comparison of shear performance of commercially available adhesives for wood structures

Authors: Xie Lisheng, Wu Jiahua, Qiao Luting, etc.

Four representative room-temperature curing adhesives currently available on the market were selected. Joint tensile shear tests were conducted along the grain of the GB/T 50708-2012 Technical Specification for Glued Laminated Timber Structures. The shear strength of these joints was measured and compared with that of a thermosetting phenolic resin adhesive. The results showed that the average normal shear strength and wet shear strength of the joints of the three commercially available adhesives for wood structures, including one-component polyurethane, resorcinol-formaldehyde resin, and polyvinyl acetate-isocyanate, all met the national standard requirements and were comparable to those of the thermosetting phenolic resin adhesive. The resorcinol-formaldehyde resin adhesive had the highest strength. The normal shear strength of the joint of the two-component polyurethane adhesive for wood structures met the national standard requirements, but its wet shear strength did not. The joint shear strength showed a significant positive correlation with the wood failure rate during shearing, with higher wood failure rates associated with higher joint shear strength. These results provide a reference for the selection of adhesives for wood structures.