What is the ingredient of "white frost"?
1. In the production process of PVC calendering film, precipitation sometimes occurs, that is, a layer of "white frost" is produced on the surface of the film or on the calendaring roll
In the production of PVC calendered film, a certain amount of lubricant is added to the plastic in order to make the surface of the product smooth and beautiful, improve the fluidity of the plastic melt, and reduce and avoid the friction effect on the equipment. But improper use of lubricants, beyond its compatibility limit, easy to precipitate on the surface of the product, that is, commonly known as "frost", affect the appearance of the product, but also affect its ink absorption. The amount of lubricant is too small to play a lubricating role. Generally, the amount of lubricant is less than 1%.
Because the processing temperature of PVC is equal to the decomposition temperature, it will undergo severe thermal degradation in the process of processing. In order to improve its stability, stabilizers must be added in the process of processing. Many stabilizers not only have the function of stabilization, but also have the function of lubrication. The compatibility of stabilizers is poor, and the phenomenon of "frost" and migration will occur.
4. Filler (calcium carbonate)
In order to improve the mechanical properties of products and reduce the cost, it is necessary to add appropriate filling materials. The addition of appropriate amount of additives can reduce the molding shrinkage of plastics and improve their heat resistance, flame retardancy and strength. The amount of filler should be appropriate, too much will precipitate from the film surface. Increasing the fineness of fillers can increase the amount of additives, such as ultrafine calcium carbonate more than ordinary calcium carbonate. Calcium carbonate can also be treated with coupling agent to increase the compatibility between calcium carbonate and PVC.
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