Meaning
Standardised analytical protocol measures the percentage reduction of intentionally introduced chemical surrogate contaminants through a polymer recycling process. In food-contact packaging compliance, the decontamination efficiency challenge test spikes post-consumer flake with volatile and non-volatile surrogate compounds before running the material through super-clean extrusion, solid-state polycondensation or vacuum stripping. The test quantifies the cleaning threshold required to meet food safety standards established by regulatory authorities.
The evaluation ends once cleared flake or pellet stock transitions into conventional downstream bottle or sheet conversion.
Surrogate Spiking
Laboratory protocols introduce model contaminants representing volatile polar, volatile non-polar, non-volatile polar and non-volatile non-polar chemical classes. Toluene, chlorobenzene, phenylcyclohexane, benzophenone and methyl stearate represent standard surrogate cocktails applied to post-consumer polyethylene terephthalate or polyolefins. The flake absorbs these compounds at elevated temperatures until target contamination levels are reached.
Technicians measure baseline surrogate concentrations prior to feeding contaminated batches into decontamination equipment.
Cleaning Mechanism
High-vacuum devolatilisation, deep thermal desorption and solid-state polycondensation strip absorbed surrogates from the polymer matrix. Solid-state reactors operate near the polymer melting point under deep vacuum, accelerating surrogate migration out of amorphous regions. Polyolefin recycling requires aggressive vacuum extrusion or nitrogen purging due to higher diffusion rates in non-polar matrices.
Residual surrogate levels in the output resin are quantified via gas chromatography-mass spectrometry to determine cleaning percentages.
Regulatory Compliance
Food packaging authorities review challenge test data to grant non-objection letters for direct food-contact packaging applications. Challenge runs must match the lowest operating vacuum, lowest temperature and shortest residence time permitted in commercial production. Regrind feedstocks with higher initial contamination require robust cleaning margins to ensure finished containers comply with dietary exposure thresholds.
Recyclers maintain challenge test documentation as audit proof for food brand owners and global packaging converters.
