Meaning
Foreign material introduction into a polymer batch represents recycling contamination, governing melt flow stability and molecular weight distribution across secondary resin processing runs. Processing variable degradation begins in the compounding extruder where rogue polymers or inorganic particulates disrupt thermal homogeneity. Extrusion temperatures above material thresholds trigger thermal oxidative chain scission when foreign debris acts as a local catalytic site.
Part specifications suffer structural failure because unbonded inclusions create stress concentration points under tensile load. Virgin resin economics rely on predictable rheological properties whereas regrind batches inherit variable contaminant profiles requiring constant machine parameter adjustments. Datasheet values represent ideal laboratory conditions that bear little resemblance to the actual viscosity window a moulder can hold across a production run using contaminated post consumer feedstock.
Thermal Degradation
Foreign matter deposition inside barrel heating zones causes localized polymer charring. Melt fracture appears at the die exit when degraded particles create turbulent flow disruptions. Screw shear rates increase sharply as high melting point plastics fail to soften alongside the bulk carrier resin.
Pressure spikes inside the nozzle indicate blocked gate geometry within the injection tool.
Mechanical Failure
Tensile strength drops precipitously when rigid contaminants cross component wall sections. Impact resistance values decline because micro voids form around hydrophilic paper fibers trapped inside the polymer matrix. Surface blemishes emerge during high pressure packing phases when trapped volatiles outgas through the skin layer.
Fatigue limits degrade rapidly under cyclic loading conditions due to premature crack propagation originating at inclusion sites.
Economic Penalty
Batch rejection rates escalate immediately when ash content exceeds machine tolerance limits. Filter screen pack changes occur with high frequency during processing runs utilizing unwashed regrind stocks. Tooling maintenance costs multiply because abrasive mineral fillers accelerate barrel wear and screw flight erosion.
Production downtime eats into operational margins when scrap ratios override acceptable plant thresholds.
