In the absence of global timber resources, bamboo has the characteristics of easy reproduction, fast growth, early production, high yield, and a successful afforestation, which can be selected annually and used continuously without destroying the ecological environment. The bamboo texture is straight, the color is light, the material is tough, and it has many advantages of hard and hardwood. It is an ideal material for producing furniture, flooring and various components. Pure bamboo furniture is not only a practical product, but also has considerable ornamental features, which makes people feel comfortable returning to nature, and can also feel the traditional Chinese culture of the face. At present, some manufacturers have developed a new type of bamboo laminated timber furniture combined with the characteristics of Chinese culture, and have opened up a new world in the international market.
Quality is at the heart of the product. Due to different production methods and different craft levels of various enterprises, bamboo laminated timber furniture exposes some problems in production. The outstanding thing is that bamboo laminated timber furniture is susceptible to insect frogs and mildew, and it is also prone to water absorption and cracking, and degumming deformation. How to solve these problems is a common concern of enterprises. Based on years of research and production practices, this paper discusses the quality problems that arise in the production of bamboo laminated timber furniture.
1. Characteristics of bamboo laminated timber
1.1, the characteristics of bamboo
The bamboo has a small diameter, the wall is hollow, and the sharpness is large, and its structural composition is very different from that of wood. The strength and density of bamboo are higher than that of ordinary wood, and the strength of bamboo products is greater than that of ordinary wood products. Bamboo products are smaller than wood products when used as structural materials. The bamboo texture is straight, the texture is smooth and self-sliding, the color is simple, and it is easy to be bleached, dyed and charred. It can be compared with some broadleaf wood. Bamboo glulam and bamboo flooring can replace precious broad-leaf leaf materials and have broad application prospects in the manufacturing fields of furniture, accessories and interior decoration.
1.2, good mechanics and physical and chemical properties
As a new type of furniture substrate, bamboo laminated timber maintains the characteristics of bamboo physical and mechanical properties and low shrinkage. It has the characteristics of large size, small deformation, stable size, high strength, good rigidity and wear resistance. It can be sawed, planed, inlaid, opened, drilled, sanded, assembled and surface decorated. Since the bamboo laminated timber is subjected to a certain hydrothermal treatment during production, the finished product has good sealing property, and can effectively prevent the frog and mildew. The bamboo laminated material adopts the modified UF resin glue, which is lower than the free nail of the artificial board and has good environmental protection.
2. Production technology of new bamboo laminated timber furniture
Bamboo laminated furniture can be divided into three types: one is traditional furniture based on enamel joints, and the shape and structure are similar to traditional hardwood furniture. The second is the modern plate-type bamboo integrated timber panel furniture, which can realize the standard part processing. The third is to bend the furniture. On the basis of the traditional round bamboo furniture, the bamboo is mainly used for the flexibility in the longitudinal direction. Bamboo laminated timber furniture can realize industrial production and modularization of furniture. The overall design advocates the characteristics of natural, simple and environmentally friendly. Through the choice and change of materials, it is diversified in style to meet the needs of consumers at different levels.
2.1. Production process of bamboo laminated timber and furniture
2.1.1. Production process of plate-shaped and square bamboo laminated timber.
2.1.2. The production process of flat and curved bamboo laminated timber.
2.1.3. Production process of bamboo laminated timber furniture.
3. Main technical problems and countermeasures of bamboo laminated timber furniture components
3.1, bamboo integrated materials anti-mildew, rot, frog treatment technology
To carry out the implementation of the "Bamboo-generation wood" project, we must first solve the problems of bamboo "mold, rot, frog, deformation". Because natural bamboo is rich in organic substances such as sugar, fat, protein, cellulose and lignin, it is easy to breed mold, mold, worm and other phenomena, which leads to deterioration of bamboo. The mold, rot and cockroaches of bamboo products often cause serious economic losses. At present, the fumigation method can only kill the eggs on the surface of the bamboo, it is difficult to kill the internal eggs, and has little effect on the nutrition and water in the bamboo, and the effect is not satisfactory. After many studies and experiments with the company, I have an understanding of bamboo wood mold.
Bamboo mold and rot type can be divided into four categories: sporadic distribution, uniform distribution, hyphae coverage and growth sub-entities. On the basis of the above classification, it can be subdivided into non-secreting pigment type, secreting light pigment type, and secreting dark pigment type. The fungi causing the mildew of bamboo are mainly Aspergillus, genus, Trichoderma, and Greenwood.
When the relative humidity is 95% and the temperature is between 20 °C and 30 °C, the mold is very active, the fecundity is extremely strong, and the bamboo will be mildewed and corroded.
In the warehouse with poor ventilation, the surface temperature of the bamboo is high and the relative humidity is close to saturation due to the continuous diffusion and evaporation of water from the bamboo. This provides favorable conditions for the spore germination hyphae.
Our comprehensive measures against bamboo mold, anti-corrosion and anti-mite are:
(1) Keep the environment clean: The processing and storage environment and nearby areas should avoid the presence of bamboo moldy waste, and the generated bamboo waste should be treated in time to reduce the chance of airborne mold.
(2) Improve storage conditions: Bamboo products and semi-finished products should be stored in a ventilated and dry place. Conditional ventilation and dehumidification equipment should be provided to make the indoor relative humidity below 75%. Bamboo products and semi-finished products should be stacked 500mm from the ground to facilitate ventilation and drying. The newly cut bamboo can be erected outdoors, reducing contact with the ground and improving ventilation.
(3) Cooking bath: For small bamboo and bamboo products, it can be cooked in a bath at a temperature above 70 °C. The boiling bath can effectively reduce the soluble nutrients of the mold in the bamboo and kill the potential mold and eggs.
(4) Bleaching: The cooking bath will affect the color of the bamboo. Bleaching also has the effect of killing latent molds. It can be bleached with 10% hydrogen peroxide, and the effect is good.
(5) Drying: The moisture content of bamboo is of great significance against mildew. Therefore, bamboo products should be dried immediately after being subjected to boiling bath, bleaching or hot dip, in order to prevent mold in the air from propagating on the surface of moist bamboo.
(6) Use of preservatives and paints: It should be selected according to the type and use of bamboo products. After drying, the bamboo products should be painted in time to prevent the bamboo from absorbing moisture and damp. The surface coating of bamboo is not only beautiful, but also has the effect of preventing mildew and insects. Commonly used bamboo mildew preservatives have a certain toxic or irritating odor, and paint can isolate the preservatives of bamboo.
3.2. Technical measures for anti-debonding and deformation of bamboo laminated materials
The moisture content of the bamboo strip, the viscosity of the rubber, the precision of the stamping die, the pressing method, and the processing technology all have an important influence on the bonding quality of the bamboo members, especially the curved members.
3.2.1, bamboo strip moisture content and rubber viscosity
The moisture content of bamboo strips is one of the important factors affecting the deformation and gluing quality of the plate. The moisture content is too low, the glue is not strong, the bending stress is large, the slab is brittle, and the waste is easy to produce; the moisture content is too high, and the bending is caused. Evaporation of water produces large internal stresses that cause deformation. When using a low-toxic suit to wake up the resin, the moisture content of the bamboo strip is preferably 6% to 8%. The bamboo strips should have a smooth surface and a small roughness, so that the amount of glue used is small, and the strips of bamboo strips can be fully adhered when pressed, and the bonding strength is high. When the thickness of the bamboo strip is above 15mm, the deviation is not more than 0.1mm. At the same time, the adhesive with high solid content and low moisture should be selected.
The process of controlling the moisture content of the bamboo strips and eliminating the internal stress is to send the bamboo strips to the digesting pool for mildew prevention and anti-frog treatment, and then stack them in an orderly manner and feed them into the carbonization kiln at 0.4MPa-0.5. The carbonization treatment was carried out for 3 hours to 4 hours under the conditions of MPa, 130 ° C - 160 ° C. Make the moisture content of the bamboo pieces meet the requirements. Then, the film selection, color matching, rubber coating and blanking are carried out; the bamboo strips are sent into the hot press glue and then synthesized into a slab, and the slab needs to be subjected to constant temperature qualitative treatment for 96 hours to fully eliminate the internal stress. The subsequent processing of bamboo products is only possible. Technical indicators are: moisture content 6%-8%, air dry density: 0.76g/cm3; static bending strength: thickness ≤ 15mm, ≥ 98MPa; thickness > 15mm, ≥ 90MPa; bonding strength: ≥ 9MPa.
3.2.2, shaping die accuracy
The bending and shaping process of bamboo strips is the key to the production process of curved bamboo laminated timber. The mold must be matched with precision to press out the glued and bent piece with firm glue and correct shape. The material of the stamper should have good dimensional stability, is not easily deformed, and has a certain rigidity. The surface of the mold must be smooth and smooth. The shape, curvature and structure of the mold directly affect the quality of the finished product. The greater the curvature of the bamboo product, the higher the difficulty of bending and shaping, and the greater the difference in compression over the length of the entire bamboo strip. During the bending process, it should be slowly and evenly pressurized, so that the bamboo strips are evenly stressed. In the operation, it is necessary to accurately position in the lateral direction to ensure that the bent bamboo strips are not twisted and skewed. Considering the elastic recovery of the curved bamboo laminated timber, the radius of curvature should be appropriately reduced during the design and manufacture of the mold, and the radius of curvature required by the design is reached after the elastic recovery of the bamboo strip.
3.3, pressure method and process
The bamboo strips are softened by cooking, and the heat is placed in the mold to be pressed and bent, so that the bamboo strips can be bent into a desired curved shape, and then dried or shaped to be sharply cooled. The time required for drying and setting is longer. As the amount of dry shrinkage increases, the pressing device needs to be tracked and tightened to make the setting accurate; the sharp cooling setting will produce a certain amount of rebound in the subsequent drying process, which is difficult to accurately reach. The radius of curvature of the design. The pressure of the pressure bending must be sufficient to bring the slab against the surface of the mold and the layers are in intimate contact.
The hot pressing process parameters are important factors affecting the bonding and bending of the bamboo strips. The pressure should be sufficient to keep the slabs bent to the specified shape and thickness to ensure the tight bonding of the veneers of each layer; the temperature and time directly affect the curing of the glue, too high The temperature will degrade the bamboo material, causing the mechanical properties to decrease, and at the same time, the rubber layer will become brittle. Similarly, if the temperature is too low, the curing speed of the glue will be slow, thereby reducing the production efficiency, and at the same time, the bonding strength is insufficient, and the defects such as easy opening of the rubber are easy. .
4, summary
The bamboo laminated timber furniture treated by the above technology has better effect on insect-proof frog, anti-mildew and anti-deformation. The relevant enterprises applied the above-mentioned technology to deal with bamboo laminated timber furniture for more than one year. No phenomenon of mildew and deformation of insects was found, and the old problems that have plagued the bamboo products industry for many years have been well solved. With the development of science and technology, many problems in processing technology will be gradually solved, and new bamboo laminated timber furniture that meets the requirements of green products will become a new category in furniture products.
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