With the rapid growth of China’s economy and people’s high-level pursuit of life, eco-friendly materials are gradually used in home decoration, furniture and construction industries. Compared to wood, bamboo has its own advantages such as large strength, good toughness, and great abrasion resistance when it is applied as a material to structural engineering or home decor. However, bamboo also has several limitations, for example, a small diameter, a longitudinal difference in diameter, thin and hollow walls, and a disposition to corrosion and cracking. Therefore, there is an urgent need to develop a new efficient and high-value utilization technology of bamboo. “Bamboo flattening” is a kind of high-efficiency utilization technology adopted to construct flattened bamboo boards from bamboo tubes or pre-softened arc-shaped bamboo sheets. Prior to flattening, pretreatments are requested, including softening, outer layer removal, and inner layer removal. For the bamboo tubes, penetrating grooves are requested to be created which are supposed to be widened during the saturated steam heat treatment and are conducive for the tubes to enter into the flattening machine. Moreover, tapered, rectangular or “V”-shaped protrusions nails with uniform dispersions, or diamond-shaped line grooves with a width, depth and spacing of 1.5–2.0 mm, 2.0–4.0 mm and 5.0–8.0 mm are always created to release the generated internal stress during the flattening processes. For the arc-shaped bamboo slices, a non-notched flattening method is introduced with a machine equipped with the unfolding rolling component, the flattening component, and the reverse roller component. There are no grooves, nails or guide lines on the inside surface of the obtained bamboo board. It is worth mentioning that all boards obtained should be treated by cooling, shaping and drying. Bamboo flattening technology can increase the utilization rate of bamboo resource from the original 30–55 %, reduce the amount of adhesive by 30 %, and increase the added value by more than 20 %. Herein, the achievements in bamboo flattening technology based on published papers and patents are described, along with their underlying physicochemical mechanisms.

Bamboo flattening technique: a literature and patent review

Bamboo scrimber, a bio-material which is made of bamboo, has been considered as a substitute material in place of wood in China under the situation of increasing contradiction between supply and demand of wood resources. In the last decades, the fabrication technology of bamboo scrimber has been improved, which promotes the applications of this material. Especially in China where the bamboo scrimber was developed originally, blowout-like growth has emerged in related research in the recent 3–5 years. It is urgent to summarize the relevant research and present it to more people who are concerned with the aspects of bamboo scrimber as a bio-material. This paper presents a comprehensive introduction to bamboo scrimber including fabrication, properties, heat treatment, anti-mildew and anti-fungi, surface coating, machining, applications, etc. based on a review of literature from Chinese National Knowledge Infrastructure (CNKI) and Web of Science. This work not only establishes fabrication parameters, surface proof technologies and application samples for the industry practice but also summarizes detailed inspection standards, mechanical and thermal properties regarding bamboo scrimber for the reference of scientific research.

A comprehensive overview of bamboo scrimber and its new development in China

In this work, polymer chains of different molecular weights are grafted onto a zero-dimensional filler. The effects of molecular weight and filler size on the confined crystallization of grafted polymer systems are systematically studied using Monte Carlo simulations. It is found that when the molecular weight is higher, the restriction effect is weaker. The crystallization ability and the ultimate crystallinity are enhanced. The simulation results also found that as the chain length increases, the average segment density of the interface region increases and the mobility of the molecular chain is enhanced. This leads to the increase of supercooling and the decrease of critical nucleation free energy barrier. During isothermal crystallization kinetics processes, the nucleation mode is homogeneous nucleation. The effects of the filler size of grafted polymer systems were also investigated. When the number of segments was fixed, the crystallization ability can be improved by reducing the filler size. However, when the distribution of grafting points is the same, the crystallization ability becomes stronger with the increase of filler size. The simulations reproduce the experimental results and vividly present the evolution process of microstructures, which cannot be observed experimentally at present. These findings are helpful in understanding the microscopic mechanism of crystallization behavior of polymer composites and the corresponding reinforcement mechanism.

Correlation between molecular weight and confined crystallization behavior of polymers grafted onto a zero-dimensional filler

Fungal deterioration of a novel scrimber composite made from industrially heat treated African highland bamboo

Thermal insulation potential of wood-cereal straws/plaster composite

Natural wood has certain advantages such as good processability and high specific strength and thus has been used for millennium as a structural material. But the mechanical performance and water resistance, particularly for fast-growing species, are unsatisfactory for high-end applications. In this study, the “new-type” scrimber technology was introduced to radiata pine (Pinus radiata D. Don) scrimbers. The structure, mechanical properties, and dimensional stability of the scrimber panels were investigated. Results showed that OWFMs as basic units of scrimber had been very even in size and superior permeability. The scrimbers exhibited a three-dimensional porous structure, and the porosity had a decrease with increasing density. Both OWFMs and densification contributed to the high performance in terms of mechanical properties and water resistance. The flexural, compressive, and short-beam shearing strength were significantly enhanced with increasing density. As the density was 0.80 g cm−3, the flexural strength (MOR) was approximately 120 MPa, much larger than many selected wood-based panels. Moreover, the water resistance and dimensional stability also were closely related to the density. At the density of 1.39 g cm−3, the water absorption rate and thinness swelling rate of the panels in boiled water were only 19% and 5.7%, respectively.

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Structure, Mechanical Performance, and Dimensional Stability of Radiata Pine ( Pinus radiata D. Don ) Scrimbers

https://www.srs.fs.usda.gov/pubs/ja/2019/ja_2019_hse_004.pdf

Laminating wood fiber mats into a densified material with high performance

Coating quality for scrimber products against exterior conditions is largely dependent on the surface properties. The wettability, morphology, and chemical composition of pine scrimber surfaces were investigated to better understand the surface properties. The scrimber was found to be a hydrophilic material because the water contact angles were less than 90°. The panels with a density of 1.20 g/cm3 had the largest angle change rate (k = 0.212). As the panel density increased, the instantaneous contact angle of each test liquid (i.e., water, formamide, and diiodomethane) on the panels decreased, and so did surface free energy. Panels with higher density showed lower surface roughness. Surface roughness across the wood grain was greater than that along the grain. SEM observations showed the high-density panels had a smoother surface with fewer irregular grooves in comparison with the low-density panels. X-ray photoelectron spectroscopy (XPS) analysis indicated that more unoxygenated groups appeared on the surface of high-density panels.

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Surface properties of pine scrimber panels with varying density

In this study, poplar wood and a phenol-formaldehyde (PF) resin were used to produce a large-scale scrimber product by a combined cold pressing and heat curing method. The water resistance...

Jinguang Wei

Papers

Structure, Mechanical Performance, and Dimensional Stability of Radiata Pine ( Pinus radiata D. Don ) Scrimbers

Laminating wood fiber mats into a densified material with high performance

Surface properties of pine scrimber panels with varying density

Effect of Core Temperature on Some Important Properties of Poplar Scrimber Boards during the Heat Curing Process