Alkyl Radicals

Radical Scavenging

Antioxidant stabilization relies on phenolic and phosphite additives that intercept alkyl radicals before they abstract hydrogen atoms from adjacent polymer chains. Moulders introduce these chemical stabilizers during the compounding phase to protect resin melt viscosity during multi-pass injection moulding operations. Virgin feedstock contains sufficient hindered amine light stabilizers to neutralise radical generation, whereas regrind material exhibits depleted additive packages that allow rapid polymer breakdown.

Unchecked radical activity causes severe molecular weight drop, resulting in structural brittleness and dimensional warp in finished moulded components.

Thermal Degradation

Melt temperature spikes inside the barrel exceed processing windows and trigger thermal homolysis that produces alkyl radicals at high rates. Extruder temperature profiles set along the feeding and metering zones govern the kinetic energy imparted to the polymer melt. Excessive residence time in the barrel intensifies thermal stress and multiplies radical concentrations until chain scission outweighs recombination.

Moulders mitigate this degradation by reducing screw speeds and installing barrel cooling jackets to maintain strict melt homogeneity across the production run.

Defect Mechanics

Surface blemishes and mechanical failure in moulded parts stem from viscosity shifts caused by alkyl radical recombination and chain scission events. Material specifications define melt flow rate limits that shift upward when excessive radical generation reduces polymer chain length during compounding. Part specifications establish impact strength thresholds that drop precipitously if degraded polymer domains propagate micro-voids under mechanical stress.

Viscosity variations across a production run force moulders to adjust injection pressure profiles to compensate for fluctuating melt behaviour caused by radical-induced degradation.