2021.11.15
If the board is broken, the first thing to look at is whether the foam is good? If the foam is broken, the quality of the board will not improve there. Generally, we talk about influencing factors, and we talk more about temperature.
The temperature of the foam particles just pre-emitted from the pre-expansion machine is generally between 40 and 50 ℃, and during the pre-expansion process, part of the steam penetrates into the inside of the foam particles, and the bubbles are relatively moist. Because of the large temperature difference between the foam and the environment, the residual foaming agent and steam inside the foam will quickly condense into liquid, and the liquid foaming agent will dissolve into the polystyrene foam, and the internal pressure of the foam will drop quickly. There is negative pressure (or partial vacuum) inside, at this time the foam particles appear soft and easily deformed, and it is impossible to make EPS foam products at all. It must be matured for a period of time;
After curing, it is dried on the one hand, and air penetrates into the bubble to eliminate negative pressure on the other hand, so that the pressure inside and outside of the bubble is balanced, the bubble is rounded and elastic, and the expansion and beading of the bubble are ensured during molding. The inter-particle fusion property improves the quality of EPS products.
After understanding the mechanism of pre-expansion and maturation, if the winter pre-expansion and maturing workshop has a poor thermal insulation effect, the temperature is low, the heat expands and contracts, and the particles are easily collapsed, destroying the foam structure, then it cannot rebound during maturation. At this time, when making lighter-weight plates, the plates are prone to shrinkage, cracking, and the plates become heavier. Generally, there is an optimal value for the curing temperature. Generally, the temperature of the curing environment is 18~22℃. Air penetrates into the foam particles, while the pentane inside the foam particles basically does not diffuse outward. If the temperature exceeds 22℃, the air infiltration rate increases and speeds up. At the same time, the rate of outward diffusion of pentane is also accelerated; on the contrary, if the temperature is lower than 20℃, the air infiltration rate will also be significantly reduced, and the curing time will be lengthened. Therefore, it is generally best to control the curing temperature between 20~25℃. ; If you mainly produce light board customers, the temperature of the curing workshop can be appropriately increased to about 28. (The data is for reference only, subject to actual workshop conditions.)
Therefore, if the temperature of the maturation warehouse is too low, especially in winter, it is rainy and cold, it may be that the insulation facilities of the foam factory are not doing well, and there is air leakage on all sides. The outside temperature of the workshop is basically the same as the outdoor temperature, so the foaming agent in the foam particles is liquid and cannot be gasified and expanded, causing the foam particles to shrink and the finished product feels poor. If you want to make light boards, you will make it heavier.
Summary: Entering winter, the temperature drops significantly, which will directly affect the production of foam products, especially light-weight panels. If the summer production process is still used, the foam particles of the first foam will not rebound in place, and the second foam will appear. Dead bubbles, sandwiching, cracking, shrinkage, overweight and other problems in sheet molding. Here is a suggestion: increase the foam weight, do a good job of heat preservation in the workshop (suggest the curing temperature is 35-45℃), and improve the curing effect. At the same time, due to different raw material manufacturers and different raw material properties are also different, please avoid mixed use.
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