Water immersion bleaching. When many types of transparent PVC products are in contact with water or water vapor for a long time, they show a white fog-like appearance. Soft products are more powerful than hard products. Due to water immersion, plasticizers and stabilizers are separated from PVC and hydrated to form hydrated precipitates on the surface (affecting transparency). Even if the saturated water is gone, plasticizers and stabilizers cannot return to the original samples. Only by raising the temperature can the compatibility of plasticizers and stabilizers be restored can they become transparent. Tests have proved that stabilizers, plasticizers, lubricants, impact modifiers and processing aids can all cause this phenomenon.
Exposure to the sun. When PVC products are exposed to the sun outdoors, due to the effects of water, carbon dioxide, sulfur dioxide and light in the air, they will also appear albinism. This is related to the compatibility of Stabilizer. In metal soaps, benzoate with good compatibility with PVC has less whitening than stearate. Organic tin is not easy to whiten, and sulfur-containing organic tin is the best, followed by laurate and maleate. The addition of light STABILIZER, phosphite ester and liquid composite stabilizer can prevent or alleviate the bleaching phenomenon of PVC due to exposure to a certain extent.
Stress whitening. Stress whitening refers to the whitening phenomenon of PVC transparent hard products under the action of mechanical external forces, such as bending and stretching, and local parts of PVC products, such as bending, creasing and stretching parts. This may be due to the change of molecular structure caused by external force, the orientation of polymer molecular chain, the change of PVC density, and the occurrence of voids between some molecules to form light scattering, which makes PVC products appear white.
Other albinism. During the processing of PVC transparent products, if excessive lubricant is used, more lubricant precipitates will also lead to white and turbid phenomenon of transparent products, which is sometimes called whitening. This kind of whitening phenomenon, the product surface will generally have more obvious waxy substances. The solution is to reduce the amount of lubricant, or change the lubricant with better compatibility, so as to achieve a balance between the inside and outside of the formula.
We have done chemical products for over 30years. Our main products include PVC Resin, CPE, TIO2, STABILIZER, Pe Wax, Paraffin Wax etc.
