Meaning
Chemical additives used to protect polymers from thermal oxidation during the high-heat stages of processing. These secondary antioxidants work by decomposing hydroperoxides into non-radical, stable products before they can cause chain scission. Including phosphite stabilizers in a resin formulation prevents the yellowing and loss of molecular weight that occurs in the extruder or injection barrel.
Processing Protection
Heat exposure during the first pass of melting can consume a significant portion of the initial additive package. If the concentration of phosphite stabilizers is too low, the polymer will degrade during subsequent heat cycles, such as when regrind is added. These chemicals are particularly effective when paired with hindered phenols to provide protection.
Hydrolytic Stability
Resistance to moisture is a key differentiator between different types of these additives. Some phosphite stabilizers are prone to breaking down in humid environments, which can lead to the formation of acidic byproducts. Modern grades are engineered to resist hydrolysis, making them suitable for long-term storage in bulk silos.
Optical Clarity
Maintaining the original color of the resin is a primary function of these compounds. Without phosphite stabilizers, clear polymers like polycarbonate or PET would develop a brown tint after a single trip through the machine. Their presence ensures that the final product meets the aesthetic standards required for consumer packaging or optical lenses.
