Causes And Analysis Of Yellowing Of Plastic Film Or Product

- Jan 15, 2019-

After the color masterbatch is made into plastic film or product, the yellowing phenomenon mainly has the following aspects: 1. Immediate yellowing after plastic processing: Reasons may be: 

1. The processing temperature of plastic is too high, and the antioxidant in the material is consumed in advance. And lose the protection;

2, due to the stagnation of the extrusion process, the heating time in the equipment is too long to oxidize;

3, corona will accelerate the surface oxidation of the product; 

4, the content of small molecules in the material is high, Poor temperature and oxygen resistance; 


Solution or suggestion: 

1. Add appropriate amount of macromolecular main antioxidant in the formula; 

2. Add low-precipitation fluororubber processing aid to improve the extrusion process, reduce processing temperature setting and actual Melt temperature, reduce high temperature yellowing of stagnant materials; 

3. Formulation to minimize the proportion of raw materials added with low molecular content; Second, yellowing of plastic products after being subjected to ultraviolet radiation after processing: Reasons may be: Storage in ultraviolet environment, Lead to oxidation yellowing reaction of additives such as brighteners, and accelerate the oxidation reaction of the material, thereby causing yellowing; Solution suggestion: Add appropriate amount of low precipitation type Anti-UV agent; or the masterbatch in the formula does not contain whitening agent and dispersing agent; 

3. Long-term storage or use of yellowing: Reasons: 

1. Storage and use environment: high temperature, high humidity and sun exposure; : After storage or use, yellowing is a natural phenomenon caused by aging or degradation of materials. It improves the storage environment to be cool and dry, and reduces sun exposure. 

2. Storage environment: carbon monoxide and vehicle exhaust in the warehouse are induced by plastic yellow. One of the important factors to change; Solution Suggestions: Strengthen ventilation, disable diesel-powered handling vehicles;

3. BHT content in product formula exceeds the standard: BHT exceeds standard in raw materials, and the yellowing index exceeds the standard after processing; A BHT concentration of about 50 ppm is the critical point of material yellowing, and the resin supplier confirms the BHT concentration of each material in the formulation, preferably less than 20 ppm; 

4. The product contains an oxidizing active ingredient: Solution suggestion: The plastic formula can be added in an appropriate amount. A nitrite antioxidant is used in combination with the primary antioxidant. The above is the phenomenon and cause analysis of yellowing of plastic film or product. The solution is recommended. It needs analysis and confirmation, and the elimination method is used. But we know that the most important thing is that some elements in the material are oxidized, so the addition and selection of antioxidants is particularly important; whether the data can be found and related to the BHT concentration problem. The product has plastic film cleaning equipment.