Transfer phenomena of volatile organic compounds in thermoplastic polymers and polymer blends by supercritical carbon dioxide

The low-temperature uptake of the flavouring agents limonene and vanillin from supercritical carbon dioxide (CO2SCF) into films of a poly(ethylene terephthalate)-based copolyester (PET-G), polycaprolactam (PA6), and isotactic poly(propylene) (PP), also blended with hydrogenated oligo(cyclopentadiene) or polycaprolactam, have been investigated through thermogravimetric determination of the additive amount released in the temperature range 30-230 degrees C. The uptake of an additive strongly depends on its relative solubility in the polymer and in CO2SCF: limonene can easily be transferred into lipophilic PP-based and PET-G polymers, also due to the plastifying action of CO2SCF on PET-G, while only the more polar vanillin can be taken up by hydrophilic PA6. The CO2SCF treatment is particularly suitable for the low-temperature uptake of heat-sensitive flavours into polymeric substrates to be used in "active" packaging.