Bamboo plywood Due to the advantages of large size, high strength, waterproof, wear-resistant, smooth surface, easy demoulding, fast demoulding, flat concrete surface, high repeated use rate, low cost and so on, formwork has been listed in the 10 new technologies that the construction industry focuses on promoting. It is also an important link to replace wood with bamboo. Its development is conducive to the protection of China's forest resources and conforms to the strategy of sustainable development of China's forest resources. In recent years, bamboo plywood formwork production line Although increasing, due to various reasons pin Sales volume and application scope have not been expanded.  
  

1. Current situation of bamboo plywood formwork production

Due to the huge market potential of bamboo plywood formwork, bamboo plywood production lines have been launched all over the country. At present, there are more than 70 bamboo plywood production lines in China, and the actual annual output has exceeded 20 million m2. Many manufacturers are still preparing to expand production lines. Fujian, Zhejiang, Anhui, Sichuan, Chongqing and other places are also building new production lines. In addition to the implementation of the national policy of banning the cutting of natural forests, many original wood plywood manufacturers may switch to bamboo plywood. Foreign wood plywood has begun to be imported into China; New domestic mold board The emergence of materials will compete for the market with bamboo plywood, therefore, bamboo plywood formwork is facing increasing competitive pressure. In order to reduce costs, many factories blindly change the production process at the expense of quality, which has led to a sharp decline in the quality of bamboo plywood formwork in recent years. Because the quality of bamboo plywood cannot meet the requirements of steel framed bamboo plywood formwork for turnover times and thickness tolerance, many enterprises that originally produced steel framed bamboo plywood formwork have to re adopt it steel plate Make panel. This is the retrogression of bamboo plywood formwork, and also challenges the promotion and application of new formwork again.

2. Main problems and causes of bamboo plywood formwork at present

(1) For thickness tolerance, whether it is used as the panel of steel framed bamboo plywood or directly as the formworks of frameless plywood, users have corresponding requirements for the thickness tolerance of bamboo plywood. According to the industrial standard Standard for Bamboo Plywood Formwork (JG/T3026-1995) issued by the Ministry of Construction in 1995, the allowable thickness tolerance of bamboo plywood is: 9~12mm thick board, high-quality products ± 0.5mm, first-class products ± 0.8mm, qualified products ± 1.2mm; 13~15mm thick plate, superior product ± 0.6mm, first-class product ± 1.0mm, qualified product ± 1.4mm. The measurement method is generally to measure 8 points around the plate. If the measured data of these 8 points meet the corresponding requirements, the thickness of this plate will be determined according to the corresponding grade. As the bamboo curtains and mats used in the production of bamboo plywood are processed from different places and farmers, the thickness of each strip has a larger tolerance. After more than 10 bamboo curtains and mats are stacked and heated, the thickness tolerance is more obvious. Even if the thickness tolerance of the measured 8 points meets the standard, the parts beyond the 8 points may still exceed the tolerance range. This problem is often difficult to find when the product is tested before delivery, but only exposed when the user uses it.

(2) The problem of bonding strength is that the bamboo plywood is delaminated, vulnerable, and has low repeated use rate. The main reason is that the bonding strength is not enough. In addition, the construction unit did not take good care of the bamboo plywood when using it, and littering is also one of the reasons why the bamboo plywood is easy to be damaged. The bond strength depends on the an adhesive Quality and hot pressing process. Since each bamboo plywood factory prepares its own adhesive, and the quality of the adhesive is closely related to the control of various reaction conditions in the production process, the quality of the adhesive produced by each factory in different periods is not exactly the same, and it is difficult to ensure the stability of its quality. Secondly, in the process of hot pressing, some factories arbitrarily change the cooling time after hot pressing in order to increase the output, and unload the board in advance when the temperature does not meet the specified requirements, which is also one of the factors affecting the bonding strength.

(3) Surface quality problems JG/T3026-1995 classifies bamboo plywood into surface bamboo plywood, composite wood bamboo plywood, film coated bamboo plywood and film covered bamboo plywood according to plain surface. The bamboo mat lines left on the concrete surface after the removal of bamboo plywood formwork are mainly surface treatment The reason why the surface is easy to be damaged is related to the glue used for film covering.

3. Main ways to solve the quality problems of bamboo plywood

In order to develop high-quality bamboo plywood formwork, in addition to solving the above problems technically, we must also improve quality awareness, strengthen quality supervision and management, establish a quality constraint mechanism, and increase investment in technological innovation.

(1) Solve the thickness tolerance of bamboo plywood ① use mechanical processing to control the thickness of bamboo curtain and bamboo mat processing links, and each manufacturer sets up raw material processing bases in bamboo forest production areas to support bamboo farmers to gradually use mechanical processing; ② The bamboo plywood shall be processed for the second time, and the pressed bamboo plywood shall be sanded to the same thickness before being covered with film; ③ On the premise of not affecting the strength, one or several pieces of wood veneer with large compression ratio shall be sandwiched to reduce the thickness tolerance of bamboo pieces; ④ Each factory strictly tests and classifies the bamboo curtains and mats, and tries to use the bamboo curtains of the same thickness to assemble the blanks.

(2) It is not a problem technically to increase the turnover times of bamboo plywood formwork. The current products cannot meet this requirement key The reason is that the rubber type and hot pressing parameters are changed at will, and the production is not in accordance with the correct process conditions. The production technology of some factories has not been introduced through formal channels, and the production technicians have not received strict training. All factories shall organize production in strict accordance with the better production process of bamboo plywood.

(3) To solve the problem of surface quality, each factory should produce various grades of bamboo plywood formwork according to the needs of users. For the panel used for steel frame bamboo plywood formwork, modified melamine resin or alcohol soluble phenolic resin Impregnated paper coating, the number of sheets of impregnated paper can be determined according to the requirements for board surface smoothness and flatness. If a layer of wood veneer can be placed on the surface of the bamboo plywood as the panel, the grain mark of the bamboo mat can be basically eliminated, but melamine resin coating should be used as far as possible to increase the wear resistance and surface hardness.

Integrity and finish.  


(4) Strengthen the quality inspection of bamboo plywood products At present, bamboo plywood production enterprises have perfect Testing equipment Not many. Most of them have not passed strict factory inspection. Even the detection of thickness tolerance is not carried out according to the specified inspection method, and some even classify the thickness according to the subjective judgment of the eyes. A regional inspection center can be set up in the area where bamboo plywood production enterprises are concentrated to provide convenience for each factory.

(5) The bamboo plywood should be like other As for building materials, the permit system is implemented so as to fundamentally prevent low-quality products from entering the market.