Causes and control measures for delamination and coarse particleboard surface

1. Causes and control measures for delamination in thin plates

Causes:

Delamination refers to the separation of the bonded surfaces in particleboard due to insufficient glue or poor bonding. Delamination is a common defect in thin-sheet production, and its main causes are as follows.

1) The slab has too high a moisture content. Because the slab moves continuously in a continuous press, the steam generated during hot pressing can only be discharged from both sides of the slab. If the moisture content of the slab is too high, a large amount of steam will be generated in the core layer of the slab during hot pressing, increasing the difficulty of venting the slab and easily causing delamination.

2) Poor adhesive curing. Low degree of curing, long curing time, insufficient or uneven application of adhesive, insufficient or excessive hardener can all lead to poor adhesive curing and easy delamination.

3) Inappropriate hot-pressing process. If the hot-pressing temperature is too low or the hot-pressing speed is too fast, the adhesive in the middle part of the board cannot be completely cured, resulting in delamination of the board.

Control measures:

1) Control the moisture content of the slab. A low moisture content of wood shavings is required when producing thin slabs. After drying, the moisture content of wood shavings should be controlled at 2.0% to 3.0%. After applying glue, the moisture content of the surface wood shavings should be controlled at 12.5% ​​to 13.5%, and the core layer at 6.5% to 7.0%.

2) Adjust the adhesive formulation. The amount of adhesive applied to the wood shavings must be precisely controlled. If the amount of adhesive is too small, the bonding strength of the thin boards will not meet the requirements; if the amount of adhesive is too large, delamination is likely to occur. In addition, adjusting the amount of hardener added and adding an appropriate amount of urea can help improve the bonding strength of the thin boards.

3) Set the hot pressing process reasonably. Appropriately increase the working pressure of the pre-press to promote the expulsion of air from the slab. Pay attention to the fluctuation of the slab moisture content. When the slab moisture content is high, appropriately reduce the amount of adhesive applied or the amount of water added to the particleboard surface adhesive, and significantly reduce the hot pressing speed, and correspondingly reduce the hot pressing temperature and pressure.

2. Causes and control measures for coarse wood shavings on thin sheet surfaces

Causes:

1) The screen of the grinding machine broke, causing excessively large shavings to enter the surface hopper directly.

2) The vibrating screen inside the paving machine has fallen off or is partially damaged or torn.

3) Improper setting of the power parameters of the surface airflow paving machine fan resulted in uneven surface shavings paving.

Control measures:

1) Check the screen of the grinding machine. If the screen is damaged, it should be replaced in time. Check if the screen mesh size is appropriate. If it is not appropriate, the screen should be replaced.

2) Inspect the vibrating screen inside the paving machine. If it is damaged, replace it in time. The position and mesh size of the screen should be appropriate. If they are not appropriate, replace the screen.

3) The surface airflow paving machine should be in normal working condition to ensure smooth and unobstructed airflow during paving.