Meaning
Recycled low density polyethylene designates a post consumer or post industrial polymer stream reprocessed into pelletized feedstock for film extrusion and blow moulding applications. Recycled low density polyethylene governs melt flow index variability and contamination loads across secondary conversion lines, setting limits on acceptable gel counts and volatile fractions during compounding. Conversion tolerances fail when recycled low density polyethylene contains cross linked polymer fractions or moisture exceeding regulatory thresholds, which generates bubble instability and die line tearing.
Thermal Window
Melt processing temperatures for recycled low density polyethylene demand narrower heater band tolerances than virgin polymer grades because thermal history degrades chain length distribution over successive reprocessing cycles. Extrusion pressures fluctuate when recycled low density polyethylene introduces varied molecular weight fractions into the screw barrel, producing surging output rates across the adapter zone. Operators adjust barrel heating profiles downward when recycled low density polyethylene exhibits lower intrinsic viscosity, preventing excessive sag during parison formation in hollow part production.
Rheological Shift
Melt flow rate instability in recycled low density polyethylene emerges from inconsistent polymer feedstock origins, altering shear sensitivity within the die gap during high speed film blowing. Viscosity curves flatten when recycled low density polyethylene blends contain degraded polymer fractions, reducing melt strength and causing bubble collapse on cooling rings. Injection pressure requirements drop when recycled low density polyethylene replaces virgin material in thin wall containers, yet dimensional shrinkage increases due to altered crystallinity kinetics.
Contaminant Penalty
Gel particle formation within recycled low density polyethylene creates localized stress concentration points that cause premature mechanical failure during drop impact testing of finished containers. Part specification standards restrict recycled low density polyethylene content in load bearing enclosures because foreign polymer fractions reduce environmental stress crack resistance across extended storage intervals. Scrap rates escalate when recycled low density polyethylene introduces moisture induced voids into thick walled mouldings, increasing production costs through necessary regrind separation steps.
