About the whitening of PVC products
Water bleaching. Many types of transparent PVC products have a white, hazy appearance when exposed to water or water vapor for a long time. Soft goods are stronger than hard ones. Due to water penetration, plasticizer, stabilizer, precipitation from PVC, and the hydration, the surface forming hydrate deposition (affect transparency), even if it is not the saturated moisture, plasticizer, stabilizer, also can't return the same, only raise the temperature, the compatibility of the plasticizer and stabilizer was restored, can become transparent. The results show that stabilizers, plasticizers, lubricants, shock resistant modifiers and processing AIDS can all cause this phenomenon.
Exposure to the sun. PVC products are exposed to the sun outside. Due to the effects of water, carbon dioxide, sulfur dioxide and light in the air, there will also be albinism. This is related to the compatibility of stabilizers. In metal soaps, benzoate, which is compatible with PVC, has less albinism than stearate. Organic tin is not easy to whiten, the best containing sulfur organic tin, followed by lauric acid salts, maleate salts. The addition of light stabilizer, phosphite, liquid compound stabilizer and so on can prevent or alleviate the bleaching phenomenon of PVC caused by exposure to the sun to a certain extent.
Stress bleaching. Stress whitening refers to the whitening of PVC transparent hard products under the action of mechanical external forces, such as bending and stretching, where the parts of PVC products, such as bending creases and stretching parts, appear. This may be due to external force change the molecular structure, orientation of polymer molecular chain, PVC density change, and some appeared gap between molecules, light scattering, and make the white color PVC products.
Other bleaching. In the process of processing PVC transparent products, if excessive lubricant is used, more lubricant precipitates will also cause the transparent products to produce white turbidity, which is sometimes called bleaching. This kind of albinism phenomenon, product surface can have more apparent waxy substance commonly. The solution is to reduce the amount of lubricants, or to use a more compatible variety of lubricants, so that the formula inside and outside slip to a balance.