The selection of powder in moisture absorption and defoaming masterbatch
Plastic raw materials contain a small amount of water that is adsorbed on or inside the material. At the material processing temperature (greater than 100°C), these waters are released to form water vapor, which is entrapped in the plastic melt. After the melt leaves the mold, the water vapor expands and volatilizes, forming pinholes on the surface and inside of the material. Holes, bubbles, and light affect the appearance of the product, and those that affect the continuity of production. If a material is selected, the moisture or moisture can be converted into a firm adsorption or completely converted into another form so that the blister can be eliminated. Alkali metal oxides or alkaline earth oxides absorb water and convert it into alkali. This eliminates free water and generates no bubbles.
Calcium oxide is calcined from high-quality calcium carbonate ore, which has high water absorption and is inexpensive, and can be used as a powder for moisture absorption masterbatch. Choosing calcium oxide produced in Yulin, Guangxi, the material is of high purity and has a calcium oxide content of not less than 96% (mass fraction). Uniform fineness, white amorphous powder.
It was found in the experiment that the particle size of the calcium oxide powder is too small and the particles will agglomerate, affecting the dispersibility of the moisture absorbent and affecting the appearance of the product. This will increase the coupling processing workload. If the treatment is not good, the filter will be blocked in the production process, resulting in the production of broken membranes. If the particle size is too large, the appearance of the product will be affected, and the feel will be rough. It will also affect the defoaming effect of water absorption. Therefore, the average particle size of the powder is preferably 10-15 μm.
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