Today we’ll talk about pultrusion mold temperature and speed.
Determination of pultrusion mold temperature
The heating condition of the pultrusion mold is determined according to the type of the resin system and the curing agent. We’ll take the polyester resin formula as an example, firstly, we start the dynamic scanning of the differential scanning calorimeter (DSC) to obtain the heat release curve. Generally speaking, the mold temperature should be greater than the heat release of the resin, the max temperature limitation is the degradation of the resin temperature. At the same time, it should be matched with the resin gel test, temperature, gel curing time and pulling speed. The temperature of the preheating zone can be lower, and the temperature in the gel region is similar to that of the curing zone. Generally, the temperature difference of the three zones should be controlled at 20~30℃.
The length of the pultrusion mold is generally 0.5-1.2m per piece. The temperature of the mold is determined by the curing reaction of the resin system, and other relevant factors must be considered under this temperature.
At a certain temperature, the curing time of the resin system is very important to determine the process parameters. Generally speaking, when we choose the pultrusion speed, we should consider the product is cured in the middle of the mold and that’ll directly affect the product quality, product surface will have nonsolid resin layer. However, if the pultrusion speed is too slow, profiles in the mold for a too long time, that’ll cause the excessive cured product and reduce the production efficiency.
The typical experimental pultrusion speed is about 300mm/min, the speed should be slowed down when starting pultrusion process, and then gradually increase to the normal pultrusion speed. General speed is 300-500mm/min, one of the development direction of modern pultrusion technology is a high speed, the fastest pultrusion speed might reach to be 1.5m/min.