About The Whitening Problem Of PVC Products

Bleaching by water immersion. Many types of transparent PVC products, when exposed to water or water vapor for a long time, take on a white, fog-like turbid appearance. Soft products are more powerful than hard products. Due to the water penetration, the plasticizer and stabilizer precipitate from PVC, and hydration occurs, forming hydration precipitate on the surface (affecting transparency), even if the saturated water is not, the plasticizer and stabilizer can not return the original, only by increasing the temperature, the compatibility of the plasticizer and stabilizer has been restored, in order to become transparent. It is proved that stabilizers, plasticizers, lubricants, impact-resistant modifiers and processing AIDS can cause this phenomenon.

Bleaching by exposure to sunlight. PVC products in outdoor exposure, due to the action of water, carbon dioxide, sulfur dioxide and light in the air, will also present bleaching phenomenon. This is related to the compatibility of the stabilizer. In metal soap, benzoate with good compatibility with PVC has less bleaching than stearate. Organic tin is not easy to produce bleaching, sulfur organic tin is the best, followed by laurate, maleate. The addition of light stabilizer, phosphite ester and liquid compound stabilizer can prevent or alleviate the bleaching phenomenon of PVC due to exposure to the sun to a certain extent.

Stress bleaching. Stress whitening refers to PVC transparent hard products under the action of mechanical external forces, such as bending and stretching, PVC products such as bending creases, tensile parts appear bleaching phenomenon. This may be due to changes in molecular structure caused by external force, orientation of polymer molecular chains, changes in PVC density, and gaps between some molecules, forming light scattering, so that PVC products appear white.

Other albinos. PVC transparent products processing process, if the use of excessive lubricant, more lubricant precipitates will also lead to transparent products white turbidity phenomenon, this phenomenon is sometimes known as bleaching. This bleaching phenomenon, the product surface will generally have a more obvious waxy substance. The solution is to reduce the amount of lubricant, or replace with a more compatible lubricant variety, so that the formula inside and outside the slip to achieve a balance.