1. Compatibility
The polymers of plastic polymers are generally non-polar, while the molecules of antioxidants and light stabilizers have different degrees of polarity, and the two have poor compatibility. Usually, the antioxidants, light stabilizers and The polymer melt is combined, and the antioxidant and light stabilizer molecules are dissolved between the polymer molecules when the polymer is cured. Within the formula dosage range, the antioxidants and light stabilizers must be melted at the processing temperature. Special attention should be paid. When designing the formula, the melting point or melting range of the solid antioxidant and light stabilizer should not be lower than the plastic polymerization. The processing temperature of the object.
2. Migration
For plastic products, especially opaque products with relatively small surface area to volume ratio (or weight ratio), the oxidation reaction mainly occurs on the surface of the product. This requires antioxidants and light stabilizers to continuously migrate from the inside of the plastic product to Play a role on the surface of the product. However, if the migration speed to the surface of the product is too fast and the migration amount is too large, the antioxidant and light stabilizer will volatilize into the environment of the product surface, or diffuse into other media in contact with the product surface and lose. In fact, it is inevitable and should be considered when designing the formula. When there is room for selection of antioxidants and light stabilizers, the ones with relatively large molecular weight and appropriately high melting point should be selected, and the antioxidants and light stabilizers should be determined on the premise of the most severe processing conditions and use environment. Add amount.
3. Stability
Antioxidants and light stabilizers should remain stable in plastic materials, have little volatilization loss under the use environment and high temperature processing, do not change color or develop color, and do not decompose (except for the antioxidants used for processing heat stabilization ), does not cause adverse chemical reactions with other additives, does not corrode mechanical equipment, and is not easily extracted by other substances on the surface of the product. Hindered amine light stabilizers are generally low-alkaline chemicals. When hindered amines are selected as light stabilizers in plastic materials, other acidic additives should not be included in the formulation, and corresponding plastic products should not be used in acid environments.
4. Processability
When processing plastic products, adding antioxidants and light stabilizers may change the melt viscosity of the resin and the stalk torque. If the melting point of antioxidant and light stabilizer differs greatly from the melting range of resin, the phenomenon of anti-oxidant and light stabilizer drift or screw holding will occur. The melting point of antioxidants and light stabilizers is lower than the processing temperature of 100. When C is above, the antioxidant and light stabilizer should be made into a certain concentration of masterbatch, and then mixed with the resin to process the product. In order to avoid uneven distribution of antioxidants and light stabilizers in the products and decrease in processing output due to drift.
5. Environment and hygiene
Antioxidants and light stabilizers should be non-toxic or low-toxic, no dust or low dust, no harmful effects on humans in the processing, manufacturing and use of plastic products, no harm to animals and plants, and no pollution to air, soil, and water systems . For agricultural films, food packaging boxes, children's toys, disposable infusion sets, and other plastic products that indirectly or directly contact food, drugs, medical devices, and the human body, not only should be selected and approved by the U.S. Food and Drug Administration (FDA). Or the types of antioxidants and light stabilizers permitted by the decree of the Commission of the European Communities, and the amount added should be strictly controlled under the maximum allowable limit.
