Effect of temperature effect



At room temperature, the post-forming of the laminate can only be bent to a large radius of curvature, which requires a small change in the size of the trimeric amine layer or the phenolic layer. As the temperature of the laminate increases, the modulus of both the melamine and the phenolic layer decreases, while the phenolic layer decreases more rapidly than the melamine layer. This makes it possible to bend into a smaller bend radius. The neutral plane even moves closer to the trimeric amine layer. More phenolic resin layers bear most of the deformation that is both adapted to bend without breaking. Unfortunately, the post-forming process is much more complicated than just heating and bending the veneer. The condensation (polymerization) reaction is re-induced due to the increase in temperature. This increases the modulus of the resin and makes the laminate more brittle, making it more difficult to bend without cracking. Fortunately, as the temperature increases, the polymerization process is slower than the decrease in modulus. Rapid heating and bending of the laminate minimizes the embrittlement caused by this polymerization.
Another temperature negative effect is bubbling. Any volatile material, including moisture in the laminate (due to its equilibrium with the surrounding side), together with moisture generated by further condensation, can be converted to steam once the temperature exceeds 100 °C. This moisture is in the form of superheated water in most cases. However, any voids or cracks in the structure may activate the formation of vapor bubbles, thereby damaging the laminate structure. The higher the temperature, the higher the pressure at which the vapor is formed, and the lower the modulus of the surrounding material. Any bubbling of the press plate will completely destroy its use value, which in effect restricts the use of the industrial after post-forming. The molding process is generally carried out at a temperature of 149 - 177 °C. Such temperatures represent a compromise between large radius bends (otherwise fractures) and bubbling at high temperatures at low temperatures.
In order to meet the requirements of the user, when the laminate manufacturer produces the laminate for post-forming, the manufacturing process must be practically modified. These modifications typically involve the use of about 5% resin (resin to fiber plus resin) and a lower formaldehyde to phenol ratio (i.e., 1.1:1 for a general purpose of 1:1:1). Laminates for post-forming are generally cured at low temperatures, and often stacks of paper stacks (press press openings) are pressed to obtain a more uniform cure. A typical time for the post-forming press plate is obtained. Curve. Most manufacturers set the laminate at 40%^50% relative humidity and 21^-24 °C for at least 48 hours prior to post forming. This ensures that the laminate has a well-adjusted moisture content.

  • 11/01/2019
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