Meaning
Post-consumer or post-industrial waste streams provide the polymer feedstock known as recycled polyamide 66, which is processed into pellets for injection moulding and extrusion. This material specification governs intrinsic viscosity, moisture content, and contaminant levels, distinguishing the reprocessed resin from virgin polymer datasheets. Strict boundaries apply when thermal history degrades chain length during multiple melt cycles, causing mechanical property loss if processing temperatures exceed specific limits.
Thermal Degradation
Chain scission occurs during reprocessing because residual moisture hydrolyztes the polymer backbone at elevated barrel temperatures. Melt temperature control during plasticising prevents molecular weight reduction and preserves tensile strength across a production run. Part specifications suffer when polymer degradation shifts the shrink rate, resulting in dimensional warping and out-of-tolerance moulded components.
Moisture Control
Hygroscopic behaviour requires predrying pellets to less than two tenths of one percent moisture before material enters the hopper. Processing wet resin causes polymer breakdown and gas blistering on the surface of finished parts. Dried feedstock prevents barrel pressure fluctuations, ensuring consistent shot weights and stable packing phases during cavity filling.
Regrind Economics
Purchasing regrind or recycled grades reduces raw material costs compared to virgin polymer procurement, though batch-to-batch property variance demands tighter process monitoring. Moulders must adjust injection speed and holding pressure to compensate for melt flow index shifts caused by prior thermal cycles. Part cost calculations balance material savings against scrap rates generated by viscosity instability during long production runs.
