Meaning
Chemical fragments generated through the decomposition of hydroperoxides define this group of compounds. Secondary oxidation products consist of aldehydes, ketones, and carboxylic acids that arise when primary species break down during polymer degradation. These molecules accumulate within the matrix as the initial reaction chains terminate or branch into smaller volatile components.
Degradation Kinetics
Polymers exposed to heat or ultraviolet radiation undergo this molecular fragmentation. The process accelerates as the concentration of these species increases, creating feedback loops that further degrade the polymer backbone. Moulders observe this as yellowing or odor generation in parts processed at high residence times.
Moulding Economics
Virgin resin costs rise when regrind usage forces a reliance on high levels of antioxidants to prevent the formation of these contaminants. Excessive use of recycled material introduces higher concentrations of these products into the melt stream, forcing processors to lower melt temperatures to manage material stability. Higher scrap rates follow when these compounds compromise the physical integrity of the moulded part.
Structural Impact
Mechanical properties suffer as these small molecules act as internal plasticizers that weaken interchain bonding. Brittle failure modes emerge during tensile loading because these fragmented chains provide sites for crack initiation. Precise control of the extrusion environment mitigates this accumulation by limiting oxygen access during the melt phase.
