What is bamboo plywood?

Introduction

bamboo plywood is a building material that is made of moso bamboo as the main structure and filling material, and is formed into blanks by high pressure. Due to its high hardness, flexural resistance and compression resistance, bamboo plywood has replaced steel formwork in many areas of use. And because bamboo is easy to cultivate and grow into a forest quickly, it can be felled in three to five years and can replace wood. Therefore, the policy of the Ministry of Forestry of the State supports the vigorous development of wood-based panels with bamboo as the main processing material, use of wood-based panels which has been replaced in many places.


Application

Bamboo plywood has widely used, suitable for horizontal formwork, shear wall, vertical wall panel, bridge, viaduct, dam, tunnel subway and beam pile formwork in house construction, and is also widely used in various containers, packaging boxes, automobiles and train floor, household floor, interior ceiling, door panel, furniture, etc.


Advantage

In engineering construction, before pouring concrete components, it is necessary to make a model that conforms to the drawings according to the shape and size of the components specified in the design drawings. The material that surrounds the model is the template. Pour in and make components. General formwork is divided into steel formwork, wood formwork, composite wood formwork. Generally, wooden formwork is made according to the size of the components, and there is no fixed specification. Bamboo plywood is also used as a template, and the surface of the components is smooth and flat, which can save the plastering process. Steel formwork is usually fixed size.

Application range of bamboo plywood: This bamboo plywood formwork is very suitable for horizontal formwork, shear wall, vertical wall panel, viaduct, overpass, dam, tunnel and beam-column formwork, etc.


Manufacturing

It is made by gluing equal-thickness bamboo slices with grooves as its constituent units, and the bamboo slices are prepared by rolling and planing. Bamboo plywood can be used as a common structural board, and can also be used as a car floor through board extension and surface treatment.


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Crafts characteristics

1. Preparation of equal thickness bamboo slices with grooves

Cut the large-diameter moso bamboo into bamboo sections, mill out the outer knots and cut them into 2-4 pieces vertically, then mill out the inner knots for cooking and softening, and then heat and pressurize them on an upper-pressure single-layer flat press to compress the arcs. The bamboo blocks are spread out into a flat surface. Finally, it is processed into bamboo chips of equal thickness without bamboo green and bamboo yellow after double-sided planing.

2. Styling and drying

In order to prevent the flat bamboo pieces from curling and deforming under the action of the transverse elastic restoring force during the drying process, a pressure drying process and equipment must be used to heat the wet bamboo pieces under pressure. when the pressure is relieved, moisture and free shrinkage.

3. Bamboo sizing

Use a four-roller gluing machine to apply water-soluble phenolic resin glue to the bamboo sheets, and the glue amount is 300-350g/㎡ (double-sided). 1% - 3% of flour, soybean flour, etc. can be added to the adhesive as fillers. The filler can easily form an adhesive film on the surface of the bamboo sheet after gluing, and it is not easy to produce glue flow during hot pressing, and the brittleness of the adhesive layer can be improved after curing.

4. Group blanks

The blanks are assembled by hand, and the blanks are assembled in strict accordance with the principle of symmetry, the principle of odd-numbered layers, and the principle that the textures of adjacent layers of bamboo are perpendicular to each other. It is required that the panel should be made of bamboo with good material, and the bamboo with inferior material should be used as the backboard. The bamboo green faces of the front and back plates face outward, and the bamboo yellow faces face inward; when the core board is assembled, the orientation of the adjacent bamboo pieces is required to be arranged alternately in order of the bamboo green face and the bamboo yellow face.

5. Pre-pressing and hot-pressing

(1) Pre-pressing In order to prevent defects such as core stacking and separation caused by the displacement of the slab when the slab is loaded into the hot press, the slab should be pre-pressed at room temperature before hot pressing after assembling to make it stick. Synthesize a monolithic material.

(2) Hot pressing The hot-hot bonding process is adopted. The hot-pressing temperature is about 140oC, the unit pressure is 2.5-3.0MPa, and the hot-pressing time is calculated according to the thickness of the finished plate, generally 1.1min/mm.

In order to prevent the occurrence of "bubbling" phenomenon, a three-stage depressurization process is usually adopted in the later stage of hot pressing. The first section drops from the working pressure to the "balance pressure", the second section drops from the "balance pressure" to zero, and the third section goes from zero to the hot pressing plate to complete the opening.

6. Plywood extension and surface treatment

Bamboo plywood is mainly used as the floor of the carriage, so the length of the sheet is required to be consistent with the length of the carriage, and the pressed sheet is short and needs to be lengthened.

The extension and surface treatment of the board include end milling bevel, bevel gluing and lap jointing, heat-pressing lengthening, longitudinal trimming, board surface gluing and overlaying wire mesh, and heat-pressing again to cure the board surface glue layer and  pressing out the net marks.


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