Discoloration of representative phenolic antioxidants, such as BHT, AO-1076, and AO-1010, occurs due to various harsh work processes, work, and environmental factors.

• It prevents decomposition of plastic due to the heat and pressure generated during processing, but the final product may appear yellow or pink due to changes in its color. (Example: Pinking phenomenon of OPP roll film)

• The color changes when it reacts with trace amounts of residual catalyst ions present in the plastic.

• It varies depending on impurities in functional additives or fillers used when compounding plastic.

• The color changes due to pollutants present at the storage, distribution, or use of the final product, most notably nitrogen monoxide and nitrogen dioxide (vehicle exhaust).

• Antioxidants are selected considering their reactivity with pollutants such as impurities and NOx.

Data interpretation

• The discoloration sensitivity of phenolic antioxidants is confirmed by injecting nitric oxide into a heated oven to express and measure changes in plastic color under harsh conditions.

• Recommended antioxidants are highly effective against color changes caused by NOx.