Study on gluing characteristics of bamboo pith ring

Bamboo pith ring (BPR) was removed to ensure the gluing quality in the traditional production of bamboo composites, leading to material waste and increased energy consumption. To improve the utilization of materials and reduce energy consumption in production, the bonding characteristics of BPR were investigated. In this study, BPR and bamboo middle (BM) were glued with phenolic resin (PF), their mechanical properties were characterized by the shear strength of the adhesive layer. Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) was used to observe PF penetration. Chemical reactions were monitored by Fourier transform infrared images with in situ visualization micro infrared technique. The results show that in the bamboo composite, the shear strength of the adhesive layer with and without BPR is similar. It is found that the pit channels of stone cells connect, communicating the multi-layer structure of the cell wall and the cell cavity. In gluing process, PF resin can permeate the stone cell in BPR, forming a mechanical interlocking and interpenetrating network system, and reacts with cellulose, hemicellulose, and lignin of stone cell walls forming chemical force. The study proved that BPR can be effectively combined with PF and has excellent bonding ability. In the production of bamboo composites, to ensure the bonding strength, BPR was reserved can improve the utilization of bamboo and reduce energy consumption.