In recent years, jumbo size wood based panels (including plywood, particle board and mdf board) have been used as wall panels and wardrobe panels more and more.
Large panels not only makes the entire decoration style high-end and atmospheric, and has a full sense of space and three-dimensionality, but also improves the space utilization of the wardrobe.
It is the new favorite of high-end decoration and is sought after by more and more Chinese consumers.
However, due to the excessive length of large-size panel, the change of deformation is increased.
This article analyzes sheet deformation from several angles and summarizes several methods to prevent large-size plywood deformation for industries.
1. Raw Board
1.1 Raw Board Type
Generally, the higher the density of wood-based panels, the greater the stress and tension in the panel, and the higher the probability of deformation.
Considering this aspect, particleboard is better than fiberboard for jumbo size boards.
This is because the density of particleboard is usually lower than that of fiberboard, and its resistance to deformation is better than fiberboard, and it is better than fiberboard in terms of environmental protection level and load-bearing capacity.
1.2 Raw Board Production Line
At present, the biggest difference in particleboard production equipment is the hot press.
From the perspective of the development history of particleboard production equipment, the hot press for particleboard production is going from multi-layer press→single-layer large-format press→continuous flat press. The 9-foot board currently circulating on the Chinese market are basically produced by continuous flat presses.
1.3 Raw Board Structure
One of the important reasons for sheet deformation is structural asymmetry, so there are many factors that cause sheet structure asymmetry.
From the analysis of the plain board, the factors that are most likely to cause deformation of the board are:
- Asymmetry of the upper and lower layers (the thickness of the upper and lower layers is inconsistent, or the peak density of the upper and lower surfaces are inconsistent)
- The density deviation of the board is too large. At present, the equipment investment of domestic particleboard factories above the designated size is more than 100 million yuan, and the equipment is relatively sophisticated. The above-mentioned situation is rare.
From the analysis of the core layer structure, in the past few years, the performance of the core equipment for particleboard production has been significantly improved. Some factories that have been put into production after 2017 can process the core layer of shavings into pieces with a length of about 3 cm and a thickness of about 1 mm. It effectively improves the length-to-thickness ratio of core shavings.
The flaky superimposed connection method increases the adhesive area of the core layer of shavings. The connection method is similar to oriented strand board (OSB), which makes the size of the board more stable and improves the resistance to deformation. This is also the most critical factor to improve the anti-deformation ability of particleboard plain board.
1.4 Impurity content
Many years ago, due to many factors such as impurities, poor production equipment, low environmental protection level, unqualified physical and chemical indicators, unsatisfactory use effects, and inadequate market supervision, the overall evaluation of particleboard by consumers was not high.
In recent years, with the upgrading of plywood production equipment and the improvement of market demand, some domestic high-end plywood factories have optimized the equipment configuration on the one hand, and removed the tree in the raw materials through equipment such as licker rollers, vibrating screens, and air sorting.
2. Melamine Face Lamination
The asymmetry of the plate structure is an important reason for the deformation of the plywood. The surface processing process of the panels easily destroys the symmetry of the board. The possible reasons are as follows:
- Hot pressing veneer process. Due to the difference in the time of contact between the upper and lower hot pressing plates, the upper and lower hot pressing plates often have an appropriate temperature difference, and according to different climates, different tree species, different moisture content, different thickness, etc., the temperature difference needs to be made accordingly Adjustment.
- The preservation process after lamination. The laminated board is very hot. If the melamine board is directly stacked for curing, the temperature of the board will not be released, which will not only easily cause the aging of the impregnated paper on the surface, but also easily cause the board to deform. If the heat is dissipated by the plate flipper, the temperature of the decorative panel will be greatly reduced, effectively avoiding the aging of the impregnated paper and the deformation of the board.
- Choice of surface finishing materials. Designers will work hard to create more beautiful works, including the combination of different finishing materials. However, the common use of different facing materials is particularly easy to destroy the structural symmetry of the facing panel, such as one side is impregnated adhesive film paper facing, the other side is glass products, or PET, UV paint. It is not obvious in a short time. As time goes by and the environment changes, the probability of deformation caused by asymmetry will increase. If the two sides of the same sheet choose the same finish material, it will effectively reduce the probability of deformation.
3. Storage and Transportation
There are also factors that cause deformation of plain boards or laminate board during storage and transportation.
The position of the cushion strip is not on a vertical line, which results in the position of the cushion strip of the plates stacked at a high place. Gravity is continuously applied to the boards underneath. However, there is no support point below the position of gravity, which will deform the boards under.
Climate change is also a common cause of deformation. In some areas with more rain and high humidity, or in hot and rainy seasons, the continuous moisture absorption of the plywood will reduce the physical and chemical indicators and use performance of the board, and it is easy to cause the plywood to deform.
At this time, keep dry and ventilated during storage and transportation to reduce moisture absorption of the plywood.
4. Installation & Use
The main cause of deformation is climate. Heavy rain, high air humidity, high temperature and other environments make the board easy to be damp. Even after the veneer and edge sealing process, if the punching area is not processed or the pre-milling before edge sealing is not enough, the edge sealing pressure is small, so inadequate sealing of the edges will also cause local moisture to the board.
In some areas in South China during the rainy season, the indoor air humidity is extremely high, and there will even be water drops on the wall. The plywood is equivalent to being partially immersed in water. This environment is particularly prone to deformation of the board and even mold. In this environment, you should pay attention to ventilation, dehumidification, and maintain a relatively dry indoor environment. If necessary, you can choose a moisture-proof plywood.
The main factors that cause the deformation of large format plywood are the asymmetry of the plain board structure, and the symmetry is broken during the processing, storage, and installation.
In view of these factors, it is recommended that when selecting large-size sheets, the preferred choice is the particle board with the core structure of flakes, high purity and continuous flat pressing line. The particleboard has strong plasticity, high flatness, and high environmental performance. The core layer of flakes makes the connection method more stable, and the high purity reduces the influence of impurities on the adhesive effect.
The continuous flat pressing line production is conducive to stable product performance and ultimately beneficial Improve the anti-deformation ability of the board. Do not destroy the original symmetry of the plywood during surface lamination. Strengthen management during storage and transportation to avoid deformation of the board due to human factors. When installing and using, reduce the impact of the environment on the board. Choose a moisture-proof plywood if necessary.