Meaning
Synthetic phenolic antioxidants prevent the degradation of polymers through the termination of free radical chain reactions. The compound butylhydroxytoluene E321 functions by donating hydrogen atoms to reactive peroxyl radicals, thereby slowing down the oxidation of resins during heat history cycles. It terminates chain scission in polyolefins and prevents yellowing in styrenic plastics.
Processing Impact
Degradation occurs in extrusion and injection moulding because high temperatures break down chemical bonds within the polymer chain. Butylhydroxytoluene E321 acts as a sacrificial additive that absorbs thermal stress during these stages to maintain molecular weight consistency. Without sufficient levels of this antioxidant, parts experience premature embrittlement, loss of mechanical strength and significant colour shifts when exposed to shear forces.
Economic Value
Virgin materials contain established levels of stabilisers to ensure performance across long production runs. Regrind resin exhibits diminished antioxidant capacity due to the consumption of those additives during initial processing cycles. Manufacturers must reintroduce supplemental stabilisers into the melt to compensate for this depletion or face part failure in structural applications.
Performance Boundary
Stabiliser efficacy remains dependent on the ambient oxygen concentration and the specific metal content within the moulding equipment. Interaction between the additive and pigments can cause unexpected discolouration if the chemical compatibility is not vetted through laboratory trials. Concentration limits remain subject to strict food contact regulations that prevent leaching into finished goods.
The efficiency of the additive decreases as the concentration drops below the threshold required to counter the thermal load of the specific resin grade.
