How is Particle Board Made?

Particleboard is also called particle board. It cuts various shoots, small-diameter wood, fast-growing wood, and wood chips into pieces of a certain size. After drying, it is mixed with rubber, hardener, waterproofing agent, etc., and pressed under a certain temperature and pressure A kind of artificial board with uneven particle arrangement. Although particle board is also called particle board, it is not the same board as solid wood particle board. The solid wood particle board is only similar in processing technology to particleboard, but it is much higher in quality than particleboard. ^[1]

Divided according to use: A-type particleboard; B-type particleboard

According to the particleboard structure, it is divided into: single-layer particleboard; three-layer particleboard; graded particleboard; directional particleboard; waffle particleboard; molded particleboard.

Divided according to the manufacturing method: flattened particleboard; extruded particleboard. According to the raw materials used: wood particleboard; bagasse particleboard; flax chipboard; cotton stalk particleboard; bamboo particleboard; etc .; cement particleboard; gypsum particleboard.

According to surface conditions:

1. Undecorated particle board: sanded particle board; unsanded particle board.

2. Decorated particleboard: impregnated paper facing particleboard; decorative laminate facing particleboard; veneer facing particleboard; surface coated particleboard; PVC facing particleboard, etc.

Particleboard is divided into three types according to the product: low density (0.25 to 0.45 g / cm3), medium density (0.45 to 0.60 g / cm3), and high density (0.60 to 1.3 g / cm3). Particleboard from 0.60 to 0.70 g / cm3. According to the slab structure, it can be divided into single layer, three layers (including multiple layers), and gradient structures. According to water resistance, it can be divided into indoor water resistance and outdoor water resistance. There are two types of shavings in the slab: directional and random. In addition, there are various particleboards made of non-wood materials such as cotton stalks, hemp stalks, bagasse, rice husks, etc., as well as cement wood wool boards and cement particleboards made of inorganic adhesive materials. Particleboards come in many specifications, ranging in thickness from 1.6 mm to 75 mm, with a standard thickness of 19 mm. When assessing the quality of particleboard, the physical properties that are often considered are density, moisture content, water absorption, thickness expansion rate, etc. The mechanical properties include static bending strength, vertical board surface tensile strength (inner bond strength), and nail holding force elasticity. Modulus and rigidity modulus, etc. In terms of process properties, there are machinability, adhesiveness, and paintability. For special purpose particleboard, electrical, acoustic, thermal, and anticorrosive, fireproof, and flame retardant properties must be considered according to different uses. ^[2]

The production method of particleboard is divided into the flat pressing method of intermittent production, the extrusion method of continuous production, and the rolling method according to the slab forming and hot pressing process equipment. In actual production, the flat pressing method is mainly used. Hot pressing is a key step in the production of particle board. Its role is to solidify the rubber in the slab and consolidate the loose slab into a sheet of a specified thickness after pressing. The process requirements are: appropriate moisture content. When the water content of the surface layer is 18-20%, it is beneficial to improve the bending strength, tensile strength and surface finish, and reduce the possibility of slab bubbling and delamination during pressure release. The moisture content of the core layer should be lower than that of the surface layer to maintain proper plane tensile strength. Appropriate hot pressing pressure. Pressure can affect the contact area between the shavings, the thickness deviation of the sheet, and the degree of rubber transfer between the shavings. According to the different density requirements of the product, the hot pressing pressure is generally 1.2-1.4 MPa. proper temperature. Excessive temperature will not only decompose the urea-formaldehyde resin, but also cause the slab to partially solidify in advance and produce waste when heating up. appropriate pressure time. If the time is too short, the middle-layer resin cannot be fully cured, the elastic recovery of the finished product in the thickness direction is increased, and the plane tensile strength is significantly reduced. The hot-pressed particleboard should undergo a period of humidity control to make the moisture content reach an equilibrium state, and then sawed and sanded to inspect the packaging. However, they cannot be stacked in a hot state after depressurizing, otherwise the brittleness of the sheet will be increased. Molding technology refers to the technology of forming a product in one operation. There are three mature processes. The hot mold method can use less or no glue and rely on the activation flow of lignin in a closed hot mold to form glue. However, it requires cooling and demoulding, large heat consumption, low productivity, and has been gradually eliminated. The box forming method is to use special press to press and make products with one press to make packaging boxes. The hot press molding method mainly manufactures furniture accessories, interior decoration accessories, and pallets. The adhesive is mainly urea-formaldehyde resin. The surface of the product is veneered or resin-impregnated paper and pasted. In addition, there is also a flat die pressing method using a template on the surface of the prepared particle board or a molding slab that has not been hot-pressed to make a relief pattern. ^[2]

1. From the appearance point of view, look at the large size and shape of the wood pellets in the center of the cross section. The length is generally 5-10mm. The length is too loose, the structure is too short, and the deformation resistance is poor. The so-called static bending strength does not meet the standard;

2. The moisture resistance of wood-based panels depends on their density and moisture-proofing agent. It is not good to be soaked in water. Moisture-proof refers to moisture-proof, not water-proof, so it should be distinguished in future use. Northern regions, including In North China, Northwest China, and Northeast China, it is generally appropriate to control the moisture content of 8-10%; in the southern region, including coastal areas, it is necessary to control between 9-14%, otherwise the plate is liable to absorb moisture and deform.

3. In terms of surface flatness and smoothness, generally, the sandpaper light is about 200 # when leaving the factory. Generally, the fine points are good, but in some cases, such as sticking to fireproof boards, it is too thin and not good. Hang plastic. ^[2]

Innovation is the source of enterprise development. The enterprise is the main body of innovation activities and the main body of the application of innovation results. From a national perspective, the number of patents, patent applications, and patent applications for wood-based panel companies is very small. The research on wood-based panels is mainly concentrated in research institutes and universities, and high-tech research results are disconnected from production. The product structure of the wood-based panel industry is largely determined by market demand, resource conditions, and technological levels. The product structure of China's wood-based panel industry is unreasonable and it is difficult to adapt to market demand. The proportion of plywood with a wood utilization rate of only 50% is relatively large, accounting for 38% of the total output of wood-based panels, which is higher than the world average level of 30%; and the proportion of particleboards with wood utilization close to 90% based on the harvesting and processing residues On the small side, well below the world average of 37%. In addition, the technology of products such as oriented particle board, wood-plastic composite board, waffle board, and crop straw board is immature, accounting for a low market share; special-purpose board, special specification board, post-formed board and environmentally-friendly board have very little output. Not conducive to the comprehensive, coordinated and sustainable development of China's wood-based panel industry. ^[2]

Industry development

China's particleboard production has experienced an iterative process from the 1980s to the 1990s and then to the 2000s. After the particleboard was abandoned by the market due to poor quality and other reasons, many particleboard companies have learned lessons and introduced advanced foreign production lines and improved technology. After that, the quality of China's particleboard has improved significantly and has been accepted again by the market.

Particle board

Many furniture manufacturers have re-selected particleboard as the raw material. Furthermore, directional particleboard is gradually accepted by consumers. Therefore, in recent years, the demand for particleboard in China has increased year by year. As the demand for particleboard at home and abroad continues to increase, and the country has introduced preferential policies to encourage the development of the wood-based panel industry, it has created excellent conditions for the development of the particleboard industry.

From January to December 2006, China's particleboard manufacturing enterprises above designated size achieved a cumulative total industrial output value of 7,072,059 thousand yuan, an increase of 26.10% over the same period last year; a cumulative product sales income of 6,666,291 thousand yuan, an increase of 24.80% over the same period last year; The total accumulated profit was RMB 136,464,000, a decrease of 25.30% over the same period of the previous year.

From January to November 2007, China's particleboard manufacturing enterprises above designated size achieved a cumulative total industrial output value of 9,643,562 thousand yuan, an increase of 58.17% over the same period last year; a cumulative product sales income of 8,937,280 thousand yuan, an increase of 59.41% over the same period last year; The total accumulated profit was 409,659,000 yuan, an increase of 225.92% over the same period of the previous year.

China's particleboard industry has developed rapidly, but there are generally problems of small scale, backward equipment and technology. In addition, many companies do not pay attention to product quality, and use the dust produced by bark and MDF as raw materials for particleboard. The particleboard produced in China is generally of poor quality, and there is also a widespread problem of serious excess formaldehyde.

In this situation, the particleboard industry must quickly improve product quality and reduce costs, and actively participate in market competition. The market space for products is still huge. In addition to ensuring the supply of raw materials and improving product quality, enterprises need to increase technological innovation, vigorously recycle waste wood, and realize a circular economy. Efforts to develop new uses of particleboard, especially to strengthen the research on directional particleboard and the promotion of the use of particleboard. In order to improve the quality of particleboard, reduce costs, and improve research and development capabilities, the scale of project construction must be increased and small particleboard factories reorganized Reflect the economies of scale.

China's per capita consumption of particleboard is still relatively low, but with the advancement of China's construction of a well-off society, the demand for wood-based panel products continues to increase. The investment of 280 billion yuan in the Beijing Olympic Games and the direct investment of more than 25 billion yuan in the Shanghai World Games and the investment in fixed assets of Chinese urban utilities during the "11th Five-Year Plan" period have exceeded 1 trillion yuan. . Therefore, China's particleboard consumption is expected to increase year by year. ^[2]

Outlook

Particle board

The search for resource-rich and low-cost adhesives is an important factor in the development of particleboard production. Therefore, the effective use of forest resources and papermaking pulping waste liquor has received increasing attention. Tannin formaldehyde glue and sulfite pulp waste liquid glue have been successfully used as adhesives, and inorganic adhesives made of cement, gypsum, etc. have also been applied; and more attractive is the new technology of non-adhesive bonding, which appears Will fundamentally change the particleboard industry. As for the particle board itself, since the directional structure is significantly superior to the random structure in terms of mechanical properties, it can be used instead of plywood or even partly sawn board, so it has great development prospects. Particle board surface decoration processing will also see more new materials and new processes, and it is possible to form an independent emerging industrial category through the specialization of prefabrication of multi-variety and multi-functional finish materials. ^[2]

Environmental performance

Since formaldehyde-based adhesives are generally used in the production of particle board, the finished product will release more or less free formaldehyde. When the free formaldehyde content exceeds a certain limit, it will affect human health. Detecting the formaldehyde emission of particleboard is a complicated process. The formaldehyde emission of particleboard is simply judged by the following methods. First, stack unused particleboard boards in a cabin, close the doors and windows, and enter the room for observation after a period of storage. If there is no pungent nose odor, it means that the particleboard has a small amount of formaldehyde release, which will not affect human health. If the smell is large or there is a tear, it means that the particleboard may have a higher formaldehyde release. So how to deal with the high formaldehyde emission of particleboard? The most common method is to open the window to ventilate, which is beneficial to accelerate the emission of formaldehyde. In fact, placing green plants such as spider plants, tigertail orchids, and monstera plants in the decorated room can not only absorb formaldehyde but also beautify the environment. ^[2]