We have about six million olfactory receptors in our noses (compared to about 300 million in dog noses). These olfactory receptors are always scanning for scents that smell—well…just off. And despite our disadvantage to dogs, we’re still pretty good at it. So good that if a polymer based product has even low levels of particularly smelly compounds, there’s a good chance we can pick those smells up (and probably complain to the manufacturer!).
Compounds picked up as odd smells in plastic parts are low molecular weight, volatile organic compounds (VOCs) that can easily escape into the surrounding atmosphere and get detected by those olfactory receptors. Not making matters easier—for either the consumer, manufacturer, or analytical scientist—is that many such compounds have odor thresholds in the parts per billion range.
Unfortunately, as good as our noses are, they fall well short of identifying exact chemical compounds and concentrations in “good” vs “bad” parts. To bridge such gaps, scientists at Cambridge Polymer Group leverage a detailed understanding of the polymer system as well as a variety of analytical techniques to identify the root cause of an elevated VOC level or unpleasant odor.
There are a variety of potential causes of unpleasant odors or elevated VOC levels. The processing of finished polymer-based products often involves the input of many materials of varying purity. Such materials may include inherently volatile compounds (e.g. solvents), as well as processing by-products or impurities in the source material. The equipment used for the manufacturing itself may be used for the production of multiple, unrelated products and cross-contamination may occur between runs. Changes in resin or masterbatch purity or formulation may result in unexpected reaction byproducts or degradation during processing. Inclusion of recycled polymer resin into a production line introduces a complex and potentially variable input material stream. Changes in material handling may introduce contamination from an outside source or unexpected contact material.
CPG scientists can work with you to understand your process, material chemistry, and help design an experimental plan to carefully select samples throughout your process to understand the root cause of the odor compounds.
Using techniques like headspace gas chromatography coupled to mass spectrometry (HS-GCMS), analytical testing allows for the separation of complex sample mixtures and exceptionally sensitive detection, structural identification, and quantitation at the sub-ppm level. Such experiments, conducted with carefully selected samples and controls and combined with a knowledge of your process, yield a root cause for the the off-odor as well as potential corrective action solutions.
More generally, CPG can assist with the characterization of volatile organic compounds in polymers and finished products. Such compounds may be characterized with techniques like GCMS and TGA-FTIR, and such analysis includes categories such as: