Evaluating Thermal and Oxidative Polyolefin Flake Degradation
Thermal and oxidative degradation alters polyolefin flake viscosity and residual stability, demanding MFR, OIT, and Carbonyl Index verification before processing.
Heterogeneous Flake Sampling
Meaning
Statistical collection methods obtain representative portions of post-consumer polymer flakes to ensure accurate testing of non-uniform recycled feedstocks. When processing regrind or ocean-bound plastics, heterogeneous flake sampling allows processors to evaluate the average moisture level and contamination across large bulk bags. Because recycled flake batches contain diverse polymer types and varying flake sizes, simple grab samples will not represent the whole batch.
This step is necessary to prevent extruder clogging and volatile outgassing during the compounding process.
Bulk Characterization
Variation in flake thickness and density leads to segregation during transport, with smaller, heavier pieces settling at the bottom of the container. If the batch undergoes testing without heterogeneous flake sampling, the laboratory results will deviate from the actual material composition. This discrepancy causes issues when setting drying times and extrusion temperatures.
Sample Collection
Specialized thief samplers or mechanical splitters extract material from multiple depths and locations within the bulk bag to build a composite sample. This mixture is then reduced using a riffler to achieve a portion small enough for laboratory testing while retaining the true distribution of the batch. Consistent extraction prevents high-purity virgin polymer from being incorrectly blended with highly contaminated regrind.
Quality Assurance
Maintaining a systematic sampling protocol ensures that resin suppliers and molders agree on the contamination limits of the incoming material.