Meaning
Systematic testing protocols for reclaimed polymers identify foreign materials or degraded chains before the stock enters a production line. Post-consumer resin screening acts as a quality gate to prevent contaminated material from damaging processing equipment or ruining a production run. This process involves melt flow testing and infrared spectroscopy to verify the composition of the recycled pellets.
It identifies the presence of incompatible polymers that would cause delamination in the final part.
Contamination Detection
Sorting systems use optical or density-based methods to remove metal and other foreign polymers from the waste stream. Residual adhesives or inks can create gases during moulding that result in surface silvering. Even a small percentage of PVC in a PET stream can cause severe acid degradation of the melt.
Batch Homogenization
Reclaimed materials vary from one bale to the next, creating a need for large-scale blending before use. Mixing different lots together creates a more consistent feedstock for the injection moulding machine. This reduces the frequency of process adjustments needed to maintain part weight and dimensions.
Moulders often use mechanical blenders to combine virgin resin with the screened recycle to hit a specific cost and performance target. Consistent flow properties are necessary for maintaining a stable process over several days.
Feedstock Stability
Frequent testing of the melt flow index ensures that the molecular weight of the recycle has not been compromised by previous heat cycles. Low viscosity indicates excessive degradation.
