Views:0 Author:Site Editor Publish Time: 2020-07-10 Origin:Site
Polyethylene tarpaulin is prone to discoloration during use, and the main reason for this phenomenon is the following:
one. Tautomerization of color pigments under the action of light and heat causes color change: some color pigments are tautomerized by molecular configuration under the action of light and heat, such as the use of CIPig.R2 (BBC) pigments by azo type It is a quinone type, which changes the original conjugation effect and causes the reduction of conjugated bonds, resulting in the color changing from dark blue light red to light orange red; at the same time, it decomposes with water under the catalytic action of light. The co-crystal water changes to cause discoloration.
Second, the color change caused by the automatic oxidation of additives: the automatic oxidation of phenolic stabilizers is an important factor to promote the color change of white or light-colored products. This color change is often called "Pinking" (redness) in foreign countries. It is coupled by oxidation products such as BHT antioxidant (2-6-di-tert-butyl-4-methylphenol), and is in the form of 3,3′,5,5′-stilbene quinone pale red reaction product, This discoloration only occurs under aerobic and water conditions, and in the absence of light. When exposed to ultraviolet light, the pale red stilbene quinone quickly decomposes into a yellow monocyclic product.
Third, the reaction between additives: if many additives are used improperly, unexpected reactions may occur and the product will change color.
Fourth, the color change caused by the reaction of the colorant and the resin: the reaction of the colorant and the resin is mainly manifested in the processing of certain pigments or dyes and resins, these chemical reactions will lead to changes in hue, and make the polymer occur Degradation, thereby changing the performance of the product.
Fifth, the color change caused by atmospheric pollutants: when plastic products are stored or used, some reactive groups, whether they are resins or additives, or colored pigments, under the action of light and heat, will react with moisture or chemicals in the atmosphere. The action of contaminants such as acid and alkali causes various complex chemical reactions. Over time, it will cause discoloration or discoloration. It can be avoided by adding suitable thermal oxygen stabilizers, light stabilizers, or using good weathering additives and pigments. Or ease the discoloration of polyethylene tarpaulin during use.