Verifying Food Contact Migration Test Reports against Upstream Resin Specifications
Verifying food contact reports against resin specifications requires matching batch numbers, validating simulants, and recalculating surface contact ratios.
Polymer Melt Flow Rate
Meaning
Measure of the ease of flow of a thermoplastic resin under specific temperature and pressure conditions. Calculation of polymer melt flow rate involves extruding a sample through a standardized die using a fixed weight over ten minutes. This value indicates the average molecular weight and viscosity of the material.
High values signify a low-viscosity resin suitable for thin-wall injection moulding.
Lot Consistency
Monitoring the incoming resin ensures that the moulding process remains stable across different material deliveries. A polymer melt flow rate that varies by more than twenty percent from the datasheet value often causes filling fluctuations. This variance leads to defects such as short shots or excessive flashing.
Quality control labs use this test as the first screen for incoming raw materials.
Degradation Tracking
Changes in viscosity during processing reveal whether the polymer is undergoing thermal or oxidative breakdown. If the polymer melt flow rate of a regrind sample is significantly higher than the virgin resin, the chains have likely shortened due to excessive heat. This degradation reduces the mechanical strength and impact resistance of the final part.
Processors use this ratio to determine the maximum allowable regrind percentage.
Flow Selection
Tooling design depends on the expected flow behavior of the selected grade. The polymer melt flow rate dictates the required gate size and runner diameter to avoid excessive shear heating.