Process characteristics of bamboo plywood

1. Preparation of bamboo strips with grooves and other thickness

The large-diameter moso bamboo is cross-sectioned into bamboo segments, and the outer section is milled into 2-4 pieces after milling, and then the inner section is milled for cooking and softening. Shaped bamboo blocks unfold into a flat surface. Finally, it was processed into double-thick bamboo chips without bamboo green and bamboo yellow by double-sided planing.

2. Styling and drying

In order to prevent the bamboo sheet from curling and deforming under the action of the horizontal elastic restoring force during the drying process, the process and equipment of pressure drying must be used to heat the wet bamboo sheet under pressure. Moisture and free shrink.

3.Bamboo sizing

A four-roll gluing machine is used to apply water-soluble phenolic resin glue to the bamboo rolls, and the amount of glue is 300-350g / ㎡ (double-sided). 1% -3% flour, soy flour, etc. can be added as a filler in the adhesive. The filler can make the bamboo sheet easily form an adhesive film on the surface after the glue is applied, and it is not easy to cause the glue flow phenomenon during hot pressing. The brittleness of the adhesive layer can be improved after curing.

4. group billet

The manual blank is assembled, and the blanks are assembled strictly according to the principle of symmetry, the principle of odd layers, and the principle that the texture of adjacent bamboo slices is perpendicular to each other. It is required that the panel be made of a good-quality bamboo sheet, and the inferior material bamboo sheet as the backboard. The face and back of the bamboo green face outward, and bamboo yellow face inward; when the core board is assembled, it is required that the orientation of adjacent bamboo pieces should be alternately arranged in order of bamboo green and bamboo yellow.

5.Pre-pressing and hot pressing

⑴Pre-pressing In order to prevent defects such as stacking cores and seams caused by displacement of the slab when it is loaded into the hot press, the slab must be pre-pressed at room temperature to make it sticky before hot pressing after assembly. Synthesize a whole material.

⑵Hot pressing The hot-hot bonding process is adopted. The hot-pressing temperature is about 140oC, and the unit pressure is 2.5-3.0MPa. The hot-pressing time is calculated based on the thickness of the finished product, which is generally 1.1min / mm.

In order to prevent the "bubble" phenomenon, a three-stage pressure reduction process is usually used in the later stage of hot pressing. The first section is reduced from the working pressure to the "equilibrium pressure", the second section is reduced from the "equilibrium pressure" to zero, and the third section is opened from zero to the hot platen.

6. Extension and surface treatment of sheet

Bamboo plywood is mainly used as the floor of the carriage, so the length of the board is required to be the same as the length of the carriage, and the pressed board is short, so it needs to be extended.

The joint length and surface treatment of the board include end milling bevel, bevel coating and overlap, hot-press bonding length, longitudinal trimming, board coating and overlaying wire mesh, and hot pressing again to cure the board adhesive layer. Steps such as extruding net marks.