The three elements of hot pressing technology are interdependent and mutually restrictive, and require unified analysis and adjustment when making process adjustments. The three factors have different effects on the adhesive panel, and the hot pressing temperature mainly catalyzes the chemical reaction of the impregnated resin, that is, accelerates the curing process. Based on the actual production requirements and the author's experience, a temperature range of 145-162 ℃ is more suitable for hot pressing plates. High temperature is beneficial for demolding after pressing, and can shorten the hot pressing period and increase production. However, excessive temperature prevents the resin from flowing evenly and solidifying, resulting in small pores on the surface of the board. According to the quality inspection data of impregnated film paper laminated artificial board in 1998 nationwide. A considerable number of enterprises have shortened the hot pressing time by increasing the hot pressing temperature in order to increase production, resulting in the board surface being prone to rebound and not smooth. Seemingly increasing production, it is actually at the cost of sacrificing product quality, while also causing an impact on legitimate product manufacturers.
Appropriate pressure can ensure a good bond between the substrate and the impregnated paper. Under appropriate temperature and pressure, the resin in the impregnated paper melts and solidifies, forming a closed and dense surface. It can also fill the unevenness and small gaps on the substrate surface. Usually, the pressure is between 2.0 and 3.0 MPa. Under the premise of not affecting product quality, it is advisable to use a lower pressure as much as possible, which is beneficial for the service life of equipment, hydraulic oil, and the internal structure of the substrate; However, excessively low pressure affects the adhesive strength and resin flow ability between the substrate and impregnated paper. Therefore, in actual production, the unit pressure should be adjusted appropriately according to the age of different substrates and buffer pads.
The length of hot pressing time depends on the curing speed of the impregnating resin and the hot pressing temperature, and is generally suitable between 40-50 seconds. Excessive curing time can cause resin to lose its elasticity, which can easily cause cracks or internal stress in the product, leading to cracking and warping during subsequent processing; If the time is too short and the resin curing is not sufficient, it is easy to produce sticking phenomenon, which affects the rational performance of the product surface and the durability of the product. The required time for different materials varies, and a curing degree test should be conducted on the surface of each new product, and then the hot pressing parameters should be adjusted based on the experimental results.
In addition, during the operation, the movement of the impregnated paper should be careful to avoid damage; Do not wear dirty gloves during operation; If the board surface is found to be unclean during the assembly process, it should be cleaned up in a timely manner; Careful inspection should be carried out when feeding the substrate. If defects such as large shavings, missing corners, damage, sand marks, etc. are found on the surface of the board, they should be promptly removed and rejected for use; The pressure rollers of the paving machine, the large suction cups for discharging, the small suction cups for stacking, and the various conveying rollers should be cleaned regularly to prevent suction cup marks and dust on the board surface from causing product degradation.