The main problems and solutions of bamboo glue board in China

Bamboo rubber sheet formwork has been listed as a key promotion in the construction industry due to its advantages of large size, high strength, waterproof, wear-resistant, smooth surface, easy demoulding, quick demoulding, flat concrete surface, high repeated use rate and low cost. Among the 10 new technologies. It is also an important link in the implementation of bamboo, and its development is conducive to the protection of China's forest resources and in line with the strategy of sustainable development of China's forest resources. In recent years, although the bamboo glue board formwork production line has been increasing, but for various reasons, its sales volume and application range have not been expanded.

1 The status quo of bamboo sheet metal formwork production

Due to the huge market potential of bamboo plywood formwork, various places have been on the bamboo and bamboo board production line. At present, there are more than 70 bamboo glue board production lines in China, and the actual annual output has exceeded 20 million m2. Many production plants are still preparing to expand the production line. Fujian, Zhejiang, Anhui, Sichuan, Chongqing and other places are also in the new production line, coupled with the implementation of the national policy of logging ban on natural forests, many of the original wood plywood production enterprises may switch to bamboo slabs. Foreign wood plywood has begun to enter China; the emergence of new domestic template materials will compete with bamboo rubber sheets for the market. Therefore, the competition pressure of bamboo glue board templates is increasing. In order to reduce costs, many factories have not hesitated to blindly change the production process at the expense of quality, which has led to a sharp decline in the quality of bamboo sheet metal templates in recent years. Because the quality of bamboo rubber sheet can not meet the requirements of steel frame bamboo sheet formwork on the number of turns and thickness tolerance, many enterprises that originally produced steel frame bamboo plywood formwork had to re-use steel plate as the panel. This is the retrogression of the bamboo glue board template, and it also challenges the promotion and application of the new formwork.

2 The main problems and reasons for the current bamboo glue board template

(1) Thickness tolerance problem Whether it is used as a panel of steel frame bamboo board or as a frameless plywood formwork, users have corresponding requirements for the thickness tolerance of bamboo board. According to the industry standard "Bamboo Plywood Formwork Standard" (JG/T3026-1995) issued by the Ministry of Construction in 1995, the allowable tolerances for bamboo plywood thickness are: 9~12mm thick plate, superior product ±0.5mm, first-class product ±0.8mm , qualified product ± 1.2mm; 13 ~ 15mm thick plate, superior product ± 0.6mm, first-class product ± 1.0mm, qualified product ± 1.4mm. The measurement method generally measures 8 points around the board. If the measured data of the 8 points meets the corresponding requirements, the thickness of the board is determined according to the corresponding level. Since the bamboo curtains and bamboo mats used in the production of bamboo plywood are processed from different places and different farmers, the thickness of each piece of enamel has a large tolerance, and the thickness of more than 10 bamboo curtains and bamboo mats are superimposed. The tolerance is more obvious. Even if the thickness tolerance of the 8 points measured meets the standard, the part outside the 8 points may be out of tolerance. This problem is often difficult to detect when the product is shipped from the factory, and is exposed when the user uses it.

(2) Problems of bonding strength Bamboo plywood has problems of layered opening, vulnerability, and low repeated use rate, mainly due to insufficient bonding strength. In addition, the construction unit is not properly cared for during use, and it is also a cause of damage to the bamboo board. The bonding strength depends on the quality of the adhesive used and the hot pressing process. Since each bamboo board factory manufactures adhesives by itself, and the quality of the adhesives is closely related to the control of various reaction conditions in the production process, the quality of the adhesives produced by different factories in different periods is not exactly the same, and it is difficult to guarantee. Its quality is stable. Secondly, in the hot pressing process, some factories arbitrarily change the cooling and cooling time after hot pressing in order to increase the output, and unload the plate in advance when the temperature is not required to be specified, which is also one of the factors affecting the bonding strength.

(3) Surface quality problems JG/T3026-1995 has four types of bamboo rubber sheets, such as bamboo slabs, wood slabs, bamboo slabs and bamboo slabs. The bamboo mat pattern left on the concrete surface after the bamboo rubber sheet formwork is removed is mainly caused by the workmanship during the surface treatment. The reason why the surface is easily damaged is related to the rubber used for the film.

3 The main way to solve the problem of bamboo glue board quality

In order to develop high-quality bamboo glue board templates, in addition to technically solving the above problems, it is also necessary to improve quality awareness, strengthen quality supervision and management, establish quality control mechanisms, and increase investment in technological innovation.

(1) Solving the thickness tolerance of bamboo rubber sheet 1 Using mechanical processing to control the thickness of the bamboo curtain and bamboo mat processing, each production factory sets up a raw material processing base in the bamboo forest producing area to support the bamboo farmers to gradually use mechanical processing; 2 pairs of bamboo glue The board is subjected to secondary processing, and the extruded bamboo rubber sheet is first sanded to an equal thickness and then coated; 3, without affecting the strength, a piece of one to several sheets of relatively large wooden veneers are sandwiched therein to Reduce the thickness tolerance of bamboo chips; 4 each factory strictly checks and classifies bamboo curtains and bamboo mats, and try to make bamboo curtains with the same thickness.

(2) It is technically not a problem to increase the number of turns of the bamboo sheet template. The current product does not meet this requirement. The key is to change the rubber type at will, change the hot pressing parameters, and not produce according to the correct process conditions. The production technology of some factories has not been introduced through formal channels, and production technicians have not undergone rigorous training. Each factory shall organize production in strict accordance with the best production process of bamboo glue board.

(3) Solution of surface quality Each factory should produce various grades of bamboo glue board templates for the needs of users. For the panel used for the steel frame bamboo slab formwork, the paper film should be impregnated with modified melamine resin or alcohol-soluble phenolic resin. The number of sheets of impregnated paper can be determined according to the requirements of surface finish and flatness. If a wooden veneer can be placed on the surface of the bamboo glue board as a panel, the bamboo mat marks can be basically eliminated, but the melamine resin film should be used as much as possible to increase the wear resistance and surface hardness.

The stainless steel plate used for hot pressing should ensure its flatness and smoothness.

(4) Strengthening the quality inspection of bamboo glue board products At present, bamboo glue board production enterprises have few perfect testing equipments. Most have not undergone rigorous factory inspections. Even the detection of the thickness tolerance is not carried out according to the specified inspection method, and some even use the subjective judgment of the eye to carry out the thickness classification. A regional testing center can be set up in a concentrated area of ​​bamboo rubber sheet production enterprises to provide convenience for each factory.

(5) Establishing a quality restraint and supervision mechanism Bamboo glue board should implement a permit system like other building materials to fundamentally eliminate the inferior quality products from entering the market.

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