Densification of Bamboo: State of the Art

Abstract

Densification processes are used to improve the mechanical and physical properties of lignocellulose materials by either collapsing the cell cavities or by filling up the pores, consequently reducing the void volume fraction. This paper focuses on an extensive review of bamboo densification process, which is achieved by compressing the material in the direction perpendicular to the fibers using mainly two different techniques: an open system, thermo-mechanical (TM), or a closed system, viscoelastic-thermal-compression (VTC). The main aim of bamboo densification is to decrease its heterogeneity, as well as to improve its mechanical and physical performance. In addition, densification may occur during the manufacturing of bamboo products in which hot-pressing processes are used to mold bamboo panels. There are over 1600 publications about bamboo, concentrated in the recent decade, mainly about engineered materials. Although several papers regarding bamboo and wood densification are available, very few studies have comprehensively investigated the densification process solely through compression of natural bamboo culms. According to the literature, applying a combination of compression of 6–12 MPa at temperatures between 120–170 °C for 8–20 min can produce materials with higher strength in comparison to the mechanical properties of natural bamboo. The majority of research on bamboo densification indicates that the modified material results in improved properties in terms of density, hardness, bending strength, stiffness, and durability. This paper provides a review that consolidates knowledge on the concept of bamboo culm densification, discusses the roles of parameters that control the process, ascertains the best practice, and finally determines gaps in this field of knowledge.

Bamboo-Fiber-Reinforced Thermoset and Thermoplastic Polymer Composites: A Review of Properties, Fabrication, and Potential Applications

“… Morphological characteristics of bamboo: ( a ) bamboo culm; ( b ) node diaphragm; ( c ) internode; ( d ) culm wall; and ( e ) vascular bundle [ 69 ]. …”

“…Figure 2 and Figure 3 show the bamboo anatomy and morphological structure of bamboo culm. The contents of this bamboo consist of parenchyma, fiber, vessels, and a sieve tube [ 68 , 69 ]. Each bamboo structure consists of 50% parenchyma, 40% fibers, and 10% vessels and sieve tubes [ 70 , 71 ].…”

A Review of Basic Mechanical Behavior of Laminated Bamboo Lumber

“…After treatment, the strips are glued with adhesive, and cold-or hot-pressed to obtain a dimensionally perfect LBL. It should be noted that when using hot pressing for molding bamboo panels, densification can occur, which leads to an improvement in the mechanical properties of the material due to the destruction of the cell cavities or filling the pores and therefore reducing the volume fraction of voids [86]. According to Sinha et al [87], strips are usually glued and pressed vertically, and therefore, the dimension and orientation are the same relative to the tangential and radial direction of bamboo.…”

Mathematical models for the use, processing, and optimized utilization of natural arc‐shaped bamboo laminated lumber

“…[20][21][22][23][24][25][26] The manufacturing of the main bamboo engineering materials involves dividing or disintegrating the bamboo into small units, such as bamboo strips, bamboo strands, bamboo bundles, bamboo slivers, and bamboo chips, and then, recombining them using adhesives. [24,[27][28][29][30][31] The main limitations of these materials are the high destructiveness of raw materials, low utilization, need for large amounts of adhesives, and high cost. Furthermore, these materials lose the elegant texture and good physical and mechanical properties of the original bamboo surface.…”