Meaning
Class of primary antioxidants used to protect polymers from oxidative degradation by scavenging peroxy radicals. The structure of a sterically hindered phenol includes bulky chemical groups surrounding the hydroxyl group, which slows down the reaction and prevents the formation of coloured byproducts.
Chemical Shielding
Free radicals generated by heat or light are intercepted by the antioxidant before they can break the carbon bonds of the polymer chain. This sterically hindered phenol donates a hydrogen atom to the radical, transforming it into a stable species and halting the degradation cycle.
Moulding Benefit
Maintaining the molecular weight of the resin during the high temperature injection phase ensures that the mechanical properties of the part remain intact. Use of a sterically hindered phenol prevents the yellowing and loss of surface finish that occurs when the polymer is exposed to oxygen at processing temperatures.
Synergistic Interaction
Combining these molecules with secondary stabilizers like phosphites provides a defense against both immediate processing heat and long term environmental stress. The consumption of the stabilizer package is monitored to ensure that enough protection remains for the entire service life of the finished product. This dual approach minimizes the risk of catastrophic failure in structural components by maintaining the original ductile behavior of the resin.
