Meaning
Secondary antioxidant that reacts with hydroperoxides to prevent the initiation of oxidative degradation in thermoplastic resins. A triaryl phosphite is typically used during the compounding and moulding stages to protect the polymer from thermal stress.
Hydroperoxide Decomposition
Unstable molecules created by the reaction of oxygen with the polymer are converted into stable alcohols by the additive. This triaryl phosphite acts as a sacrificial agent, preventing the hydroperoxides from breaking down into more reactive free radicals that would cause chain scission.
Processing Stability
Elevated temperatures in the extruder barrel can lead to rapid shifts in the melt flow index if the resin is not properly stabilized. Including a triaryl phosphite in the formulation helps maintain a consistent viscosity, which is essential for achieving uniform part weights and dimensions across a long production run.
Material Compatibility
These additives are effective in polyolefins and polyesters, where they work in tandem with primary antioxidants to provide a stabilization system. The choice of a specific phosphite depends on its hydrolytic stability and its ability to withstand the moisture levels present during the drying and processing of the resin. This selection is based on the specific requirements of the application and the environment where the final part will be used.
Sensitivity to humidity necessitates the use of airtight storage containers to prevent the premature degradation of the phosphite before it enters the polymer melt.
