Solid particles have a strong opening and breaking effect on the cell walls, which will cause cracking during the foaming process , sinking, collapse and other problems. Therefore, the amount of foam stabilizer must be increased accordingly in the formula, so that the foam stabilizer and filler can have a coupling adsorption effect and weaken the filler’s pore-opening and wall-breaking effect on the foam. Often 1kg of light calcium carbonate should be added with 10mL of foam stabilizer.
Generally, the water content of calcium carbonate is 0.4%, but during storage and transportation, its water content often increases due to its water absorption, and it is very likely to reach 0.5%-1.0%. When calculating the amount of water foaming agent, this small amount of water should be considered and calculated as part of the water foaming agent.
Adding fillers to the formula can improve the quality of soft foam Compressive load strength and overall density, but tensile strength, tear strength, etc. are reduced, and the service life is shortened, which should be carefully considered in actual use. It is rarely used in applications that require certain mechanical properties. In addition to poor performance, most foam manufacturers do not use this type of filler due to filler wear and other issues. .
At present, adding degradable materials and recycled materials in the polyurethane foaming process is an important research direction. The effects of solid particle size, solid addition amount, catalyst dosage, silicone oil dosage and other conditions on the foaming effect of the product were studied. When the solid particle size is large, due to its low density, it floats on the surface of the reaction liquid during the reaction, making it difficult to mix evenly. When the solid particle size is small, due to its large surface area, almost all of the reaction liquid sticks to the surface, destroying the foam. The stability of the surface causes the foam to burst, leading to foam collapse. When the amount of solid added is large, when foaming is completed, the foam cannot be supported and foam collapse occurs; after further addition, the reaction liquid completely sticks to the solid surface, making the reaction unable to proceed and foaming impossible. When the amount of catalyst is small, the gel reaction proceeds slowly and insufficiently, causing cracks on the surface of the product, the foam body collapses, and the foaming effect is poor; when the amount of catalyst is large, the reaction is too fast, the foaming speed is too fast, and the foaming effect is poor. The bubbles are uneven, resulting in uneven solid dispersion. When the dosage of silicone oil is small, the foam is easy to burst and serious collapse occurs; when the dosage is large, a closed cell structure is formed and the shrinkage is large after molding.
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