Analytical Testing Methods for Quantifying Recycled Content in Polyolefin Compounds
Accurate quantification of recycled polyolefins requires combining DSC thermal integration, high-temperature GPC, ICP-MS trace metals, and melt rheology sweeps.
Heavy Metal Contamination
Meaning
Polymer compounds that incorporate recycled materials face strict purity limits when toxic elements like lead, cadmium, mercury, or chromium enter the melt stream from legacy additives. Uncontrolled heavy metal contamination restricts the use of recycled resins in food-contact and medical applications. This restriction governs the maximum allowable concentration of hazardous metals under global environmental regulations.
The limits apply to the finished moulded part and cannot be bypassed by dilution with virgin resin.
Poisoning Danger
Processing plastics that contain these toxic elements releases hazardous vapours during high-temperature injection moulding. This heavy metal contamination also poses a risk of leaching when the finished parts come into contact with acidic liquids or skin. The migration of these elements occurs over time as the polymer matrix degrades under ultraviolet light or mechanical stress.
For this reason, medical and food packaging resins must undergo rigorous chemical testing to prove the absence of these restricted elements.
Additive Heritage
Recycled polymers derived from old electrical housings or industrial pipes often contain legacy heat stabilizers based on lead or cadmium. Using these materials without certified screening introduces heavy metal contamination into new consumer products. Moulders must audit their regrind suppliers and demand batch-level spectroscopy reports to ensure compliance with international safety standards.
A single contaminated batch can compromise an entire production run and lead to expensive product recalls.
Measuring Technique
Inductively coupled plasma mass spectrometry provides the standard method to identify and measure these trace elements in polymer samples. When heavy metal contamination is suspected, the test laboratory dissolves the polymer sample in strong acid before vaporizing the solution. This process reveals the exact concentration of each restricted metal down to parts per billion.