Headspace Volatile Extraction Methods for Recycled Resin Testing
Headspace volatile extraction quantifies residual odorants and degradation products in recycled resin to establish compliance and prevent lot failures.
Terpene Residual
Meaning
Organic compounds from food packaging persist in reprocessed polyolefins, leaving a characteristic aromatic scent. The presence of terpene residual is a major quality issue when using recycled high-density polyethylene for household products. This contamination is limited to resins sourced from post-consumer sorting facilities.
Odor Issue
Volatile molecules migrate out of the polymer matrix during melt processing, filling the molding hall with strong odors. If a recycled resin contains high levels of terpene residual, the finished plastic articles retain this smell, making them unsuitable for cosmetic containers. This sensory defect reduces the market value of the recycled material.
Analytical Detection
Gas chromatography coupled with mass spectrometry measures the exact concentration of volatile aromatic compounds in the polymer pellets. This analysis helps compounders screen incoming batches of regrind before mixing them with virgin materials. Identifying these compounds is essential for setting the maximum limits allowed by consumers.
Removal Technique
Vacuum degassing and thermal stripping in solid-state reactors remove these volatile contaminants from the recycled flakes. Applying these methods reduces the terpene residual to levels below the sensory threshold of human detection. This purification step represents a significant processing cost that increases the premium charged for odor-free recycled resins.
Adding specific deodorizing masterbatches during extrusion can also encapsulate the scent, though this method is often combined with thermal treatment for maximum effectiveness.