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The pith ring is an important component of bamboo, which is located on the inner side of the culm wall. However, the effect of pith ring on bamboo properties is unclear. The study aimed to analyze the influence of pith ring on the hygroscopicity and dimensional stability of bamboo. The study used X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) to measure the crystallinity and chemical composition of bamboo pith ring and middle layer. The scanning electron microscopy and high-resolution computed tomography to observe the morphology of bamboo pith ring and parenchyma. The analysis showed a higher crystallinity and lignin content for the pith ring than the middle layer. In addition, the analysis revealed that the pith ring and the middle layer formed a criss-cross structure. The existence of the pith ring reduced the hygroscopicity and hygroscopicity hysteresis to a certain extent. In fact, the pith ring improved the dimensional stability of bamboo in radial and tangential directions, while it slightly reduced the dimensional stability in the longitudinal direction. These observations indicate that the pith ring was formed in bamboo during evolution to improve dimensional stability and to better adapt to complex environmental conditions. In the manufacture of bamboo products, the retention of pith ring can improve the utilization rate of bamboo and the dimensional stability of bamboo products. • The pith ring and middle layer form a criss-cross structure in bamboo. • Pith ring improves dimensional stability of bamboo in the tangential direction. • High-resolution computed tomography can effectively and non-destructively characterize the 3D bamboo structure. [ABSTRACT FROM AUTHOR]

As a natural bamboo structure, bamboo pith ring (BPR) is commonly discarded from bamboo composites because it influences the gluing process and might cause complex handling. This study founds that the cells in BPR and bamboo middle (BM) are vertically staggered, forming vertical interlacing layers at the bonding interface in Arc-shaped Bamboo Natural Laminated Lumber (ABNLL). The role of BPR in the bonding interface was analyzed from macroscopic to cell wall scale. The retention of BPR can reduce the longitudinal, radial, and tangential deformation of bamboo blocks and composites during shrinkage and swelling. This phenomenon may be since the deformation direction of the cells in BPR and BM is vertical in the process of water absorption and dehydration, and the existence of BPR inhibits the deformation of BM. The deformation of cells in different directions in BPR and BM results from microfibrils' arrangement and chemical properties. The arrangement direction of microfibrils in BPR and BM is perpendicular to each other, leading to the vertical deformation of cell deformation in water absorption and water loss. BPR has low crystallinity (24.01%), a large microfibril angle (16.22°), high hemicellulose content, and is more sensitive to water, so BPR has a faster deformation rate and larger deformation range than BM. BPR has little effect on the mechanical properties of bamboo composites. In addition, retaining BPR increased the mass and thickness of bamboo by 7.43% and 9.40%, respectively. • Retention of bamboo pith ring can improve the dimensional stability of bamboo composite. • The cells of the bamboo pith ring and bamboo middle are arranged vertically staggered. • The deformation direction of the bamboo pith ring and bamboo middle were perpendicular to each other under the action of moisture. [ABSTRACT FROM AUTHOR]

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. • Bamboo pith ring has excellent bonding ability. • Stone cells are connected to each other through pit channel. • Physical and chemical combination are formed in the gluing. [ABSTRACT FROM AUTHOR]

The environmental problems caused by disposable plastic straws have been widely concerned around the world. Developing degradable straws made of eco-friendly materials is an effective solution. Nevertheless, the popular alternatives, for example, polylactic acid (PLA) straw and paper straw are far from satisfactory because of the restrictive degradation conditions, low mechanical performance, poor water stability, and the use of chemicals. As an abundant and sustainable natural resource, bamboo has been widely used in many fields. This study developed a mechanized and industrialized process with high efficiency and automation, including the preparation of bamboo sticks, hydrothermal treatment, and drilling holes in sticks to produce bamboo drinking straws. The production avoided chemicals and bamboo drinking straws retained the natural structure and degradability of bamboo. The performance evaluation shows that bamboo straws had superior mechanical properties (highest compressive strength of 71.65 MPa, bending strength of 123.90 MPa, and ring stiffness of 0.61 MPa), good wetting stability (high appearance quality and wet strength), reusability, high recovery value, and low manufacturing cost (around 17.5–35% of commercial degradable drinking straw costs). Bamboo drinking straws enrich the types of degradable straws and contribute to reducing plastic pollution. [Display omitted] • A novel bamboo drinking straw as alternative to plastic straw is proposed. • Bamboo straws are degradable, chemical-free, high-strength, low-cost, and reusable. • An automatic and high-accuracy drilling machine for bamboo straws is invented. • The strength, wetting stability, and reusability of bamboo straws are investigated. [ABSTRACT FROM AUTHOR]

Equal-arc shaped bamboo split (EASB) is an ecological material, and the material utilization rate is as high as 85%. With EASB as the basic unit, various arc-shaped products can be manufactured widely. EASB cleverly uses the indispensable drying process in the bamboo industry to manufacture. The bamboo splits deformation mainly undergoes two processes: uniform heating to complete softening and rapid deformation. After the arc is fixed, a wider arc-shaped bamboo split is obtained, with a width up to 100 mm. The sclerenchyma fibers showed displacement along the tensile stress direction, and the distance between vascular bundles was slightly reduced. The parenchyma's cell wall-to-lumen area ratio was reduced by 19.4%, and cracks and plastic deformation appeared in the cell wall slippage, but there is no evident densification in the bamboo split. EASB overcomes the challenge of use in standard arcs due to its different shapes, while retaining the natural texture and gradient structure of bamboo. Analyzing the deformation in the EASB manufacturing process is beneficial to understanding the EASB deformation law. Moreover, it provides a basis for the later EASB manufacturing process with different radians and biomass biomimetic materials. [Display omitted] • Development and deformation analysis of novel standard bamboo units. • Ecological and high-utilizable manufacturing technology. • Various arc-shaped products can be manufactured widely. • Further processed into square lumber and structural lumber. [ABSTRACT FROM AUTHOR]