Views:1 Author:Site Editor Publish Time: 2020-09-23 Origin:Site
Linyi Shengde tarpaulin manufacturer said that polyethylene tarpaulin is prone to discoloration during use, and the main reasons for this phenomenon are as follows:
1. Colored pigments undergo tautomerism under the action of light and heat: part of the colored pigments undergoes tautomerism in molecular configuration under the action of light and heat. For example, the use of CIPig.R2 (BBC) pigments changes from azo type It is a quinone type, which changes the original conjugation effect and causes the reduction of conjugate bonds, resulting in the color changing from dark blue light red to light orange red; at the same time, it is decomposed with water under the catalysis of light. Change the eutectic water and cause fading.
2. Discoloration caused by automatic oxidation of additives: The automatic oxidation of phenolic stabilizers is an important factor in promoting the discoloration of white or light-colored products. This discoloration is often called "Pinking" in foreign countries. It is coupled by oxidation products such as BHT antioxidant (2-6-di-tert-butyl-4-methylphenol), and is shaped like a light red reaction product of 3,3′,5,5′-stilbene quinone, This discoloration only occurs in the presence of oxygen, water and no light. When exposed to ultraviolet light, the reddish stilbene quinone rapidly decomposes into a yellow monocyclic product.
3. Reactions among additives: If many additives are used improperly, unexpected reactions may occur and the products may change color.
4. Color change caused by the reaction of colorant and resin: The reaction of colorant and resin is mainly manifested in certain pigments or dyes and resins during processing and molding. These chemical reactions will lead to changes in hue and make polymers occur. Degradation, so that the product performance changes.
5. Discoloration caused by atmospheric pollutants: When plastic products are stored or used, some reactive groups, whether resins or additives, or coloring pigments, will interact with atmospheric moisture or chemicals under the action of light and heat. Pollutants—acids, alkalis, etc., act to cause various complex chemical reactions. Over time, they will cause fading or discoloration. This can be avoided by adding suitable thermal oxygen stabilizers, light stabilizers, or choosing good weathering additives and pigments. Or alleviate this situation.