Adding a small amount of antioxidants in plastic processing can prevent or delay the aging process, thereby extending the service life of plastic products.
When selecting antioxidants, it should mainly be determined based on factors such as the type and model of plastic materials, processing equipment and process conditions, the variety and dosage of other chemical additives, the use environment and duration of the product, etc.
The selection of industrial antioxidants should be based on the following principles:
The compatibility between plastic polymers and antioxidants is often poor. Typically, antioxidants are combined with polymer melts at high temperatures. And during polymer curing, antioxidant molecules are compatible with the polymer molecules. Within the range of formula dosage, antioxidants need to melt at processing temperature. Special attention should be paid to selecting solid antioxidants and light stabilizers with melting points or upper melting range limits when designing formulas, which should not be lower than the processing temperature of plastic polymers.
Plastic products, especially those with smaller surface area to volume ratio (or mass ratio) values, undergo oxidation mainly on the surface of the product, which requires antioxidants to continuously migrate from the inside of the plastic product to the surface of the product to exert their effects. But if the migration speed to the surface of the product is too fast and the migration amount is too large, the antioxidant will evaporate into the environment on the surface of the product, or the diffusion agent will be lost in other media in contact with the surface of the product. This loss is actually inevitable, and should be considered when designing the formula. When there is room for selection of antioxidant varieties, it is recommended to choose varieties with relatively large molecular weight and appropriately high melting point, and the amount of antioxidant used should be determined based on the most severe usage environment.
Antioxidants should be stable in plastic materials, with minimal volatilization and loss during use and high-temperature processing. They should not discolor or develop color, decompose (except for antioxidants used for processing thermal stability), have no adverse chemical reactions with other additives, do not corrode mechanical equipment, and are not easily extracted by other substances on the surface of the product.
When processing plastic products, the addition of antioxidants may alter both resin viscosity and screw torque. If there is a significant difference in the melting range between antioxidants and resins, there may be a phenomenon of antioxidant bias or screw inhibition. When the melting point of the antioxidant is above 100 ℃ below the processing temperature, it should be first made into a certain masterbatch, and then mixed with resin to process the product, in order to avoid uneven distribution of the antioxidant in the product and a decrease in processing yield due to bias current.
5. Environment and Hygiene
Antioxidants should be non-toxic or low toxic, free from dust or low dust, and have no harmful effects on human health during the processing, manufacturing, and use of plastic products. They are not harmful to animals or plants, and do not pollute air, soil, or water systems. For plastic products that come into direct or indirect contact with the human body, such as food packaging boxes, children’s toys, and disposable infusion fluids, not only should they use antioxidant varieties that have been inspected and approved by the US Food and Drug Administration (FDA), or allowed by EC Commission regulations, but the addition amount should be strictly controlled within the maximum allowable limit.
1. Antioxidant 1010
It is widely used in PP as an additive with high thermal stability and is very suitable for use under high temperature conditions. In addition, it can also be used for most other resins. Generally, the addition amount should not exceed 0.5%.
2. Antioxidant 1076
It can be used as an antioxidant for resins such as PE, PP, PS, PVC, PA, ABS, and acrylic acid. It has characteristics such as good oxygen resistance, low volatility, and washing resistance. The general dosage should not exceed 0.5%.
3. Antioxidants 168
Can be used for PE, PP, PVC, PS, PA, PC, ABS, etc.
4. Antioxidant CA
Suitable for PP, PE, PVC, ABS, and PA resins. The general dosage should not exceed 0.5%.
5. Antioxidants 164
It is widely used in various resins. More suitable for food packaging molding materials (PP, PE, PVC, ABS, polyester, and PS). The general dosage is 0.01%~0.5%.
6. Antioxidant DNP
Used for PE, PP, HIPS, and ABS resins, it not only has antioxidant properties, but also has good thermal stability and suppresses the influence of metals such as copper. The general dosage should not exceed 2%.
7. Antioxidant DLTP
Used as an auxiliary antioxidant for PE, PP, ABS, and PVC resins, it can change the heat resistance and oxygen resistance of products. The general dosage is 0.05%~1.5%.
8. Antioxidant TNP
Used for PVC, PE, PP, HIPS, ABS, polyester and other resins, with good antioxidant performance at high temperatures. The usage should not exceed 1.5%.
9. Antioxidant TPP
Used as an auxiliary antioxidant for PVC, PS, PP, and ABS resins. The usage should not exceed 3%.
10. Antioxidant MB
Antioxidants for PE, PA, and PP resins; Non polluting, non coloring, can be used for white or bright colored products. The dosage should not exceed 0.5%.
11. Antioxidants 264
Universal phenolic antioxidant. Widely used in polymer materials.