Meaning
Polymer backbone degradation caused by energy input cleaves long carbon chains into smaller fragments, reducing molecular weight and melt viscosity. Polymer converters monitor polyolefin chain scission during extrusion to maintain mechanical strength and barrier performance in packaging films. The process applies to polyethylene and polypropylene resins during thermal processing or environmental exposure, stopping where cross-linking reactions dominate over molecular cleavage.
Degradation Chemistry
Shearing forces and high temperatures inside extruder barrels generate free radicals along the polymer backbone. Oxygen presence accelerates radical propagation, leading to rapid molecular weight reduction and altered flow properties. Secondary oxidation products form carbonyl groups that weaken physical film properties like tensile strength and impact resistance.
Antioxidant additives capture these free radicals to minimize structural damage during thermal processing.
Value Impact
Resin supply contracts establish melt flow index specifications to ensure material consistency across incoming polymer lots. Uncontrolled polyolefin chain scission alters processing characteristics, causing bubble instability during blown film production and inconsistent gauge control. Distributors reject resin shipments or finished film converted from degraded polymers due to increased risk of package failure in retail handling.
Reaction Boundary
Complete consumption of stabilizer additives leaves the polymer substrate unprotected against rapid mechanical failure during outdoor storage.
