Capillary Rheology Qualification Protocols for High Strain Extrusion Regrind
Twin-bore capillary testing at 1,000 to 10,000 s⁻¹ qualifies high-strain regrind by isolating entrance losses, true wall slip, and elastic die swell shifts.
Regrind Qualification
Meaning
Polymer processing protocols define a technical evaluation method for establishing the physical property retention of surplus production scrap when reintroduced into a manufacturing stream. This regrind qualification procedure isolates the specific impact of thermal history and shear degradation on the melt flow index or mechanical performance of a thermoplastic resin. It establishes the upper limit for the percentage of recycled material that maintains compliance with the original part specification requirements.
By comparing samples of virgin material against blends containing increasing proportions of processed flake, technicians verify whether the additive or filler degradation compromises the final component integrity.
Process Variable
Melt flow rate serves as the primary metric for tracking molecular weight reduction throughout the remelting cycle. Excessive variance indicates that the regrind qualification threshold has been exceeded and necessitates a reduction in the recycled load. Precise control of this parameter prevents common defects such as brittle fracture or surface blemishes that emerge when chain scission dominates the polymer matrix.
Material Specification
Engineering datasheets define the acceptable range for virgin resin properties that remain stable during primary fabrication. Regrind qualification operates as a separate secondary standard because the material has already undergone at least one complete thermal excursion. This distinction ensures that the processor accounts for the cumulative loss of properties that occurs before the material enters the final mould.
Economic Consequence
Direct cost reductions appear when the proportion of high-value virgin pellets decreases in favor of reprocessed material. Proper execution of the qualification prevents the production of scrap parts that would otherwise force a total loss of the entire moulded batch.