Effect of water presence on the sorption of organic compounds in ethylene–vinyl alcohol copolymers

Abstract

Sorption isotherms of methanol, ethanol, propanol, butanol, hexanol, ethyl caproate, and limonene in 4 ethylene-vinyl alcohol (EVOH) copolymers with different ethylene contents were determined by inverse gas chromatography (IGC) at 25°C and different relative humidity conditions. From sorption isotherms, solubility coefficients were determined and used as a tool for comparison. Besides affecting the morphology of the polymers by plastification, sorbed water seems to increase the polarity of the medium. Sorption of alcohols increases at high relative humidity; both plasticization and polarity cause this behavior. The effect is more important for the smaller alcohols and among polymers for those with low ethylene content. As the sorbant becomes nonpolar, plasticization and polarity effects become antagonistic. Indeed, the effect of water presence in sorption of hexanol is not significant, and sorption of limonene and ethyl caproate is even reduced at high water content.

Surface characterization of standard cotton fibres and determination of adsorption isotherms of fragrances by IGC

“…Hence, in the last decades, research works in the textile industry has focused on the surface characterization and fragrance interactions of natural and synthetic materials . In food science, IGC has mostly been used to study interactions between aroma compounds and food matrices, and it has been used to measure the sorption of aroma compounds on food packing polymers …”

Effect of Sorbed Oil on Food Aroma Loss through Packaging Materials

“…This difference in behavior can be interpreted as a question of compatibility. In a previous paper, the sorption of water was found to increase the solubility of polar substances and reduce that of nonpolar compounds (Aucejo et al, 1998). HxOH and PhEtOh are polar substances while both the polymers and the sorbed oil are nonpolar, and consequently the presence of oil may reduce the already low compatibility between these aromas and the polymer matrixes.…”

Effect of Humidity on the Permeability of Alcohols in Hydroxypropyl Xylan Films

“…By increasing the RH, Loṕez-Carballo et al 7 observed a minimum in the permeability of α-pinene and ethyl butanoate in EVOH-32 over a RH range of 0−100% while Zhang et al 8 reported increase in the permeability of limonene in EVOH and nylon-6,6 with increasing RH. Moreover, Aucejo et al 9 showed that sorption of alcohols in EVOH was increased at high levels of RH due to the water plasticizing effect and increased polarity of the medium as a result of increasing amount of water in the system. Generally, transport of aroma in hygroscopic materials such as nylon, poly(vinyl alcohol), poly(vinyl acetate), EVOH, polyamides, and uncoated cellophane are mostly affected by humidity because they all contain a high number of hydroxyl moieties (OH) while hydrophobic polymers such as poly-(ethylene terephthalate) (PET), low-density polyethylene (LDPE), and acrylonitrile copolymer are less-or unaffected by humidity.…”

“…Increase in the diffusivity of alcohols over the range of 0−50% of RH is likely due to the plasticizing and swelling effects. According to Aucejo et al, 9 absorbed water molecules are able to form hydrogen bonds with the polymer chains, such as HPX, that contain hydrogen bond forming moieties and break the interchain hydrogen bonds. This will in turn increase the chain flexibility and the corresponding free volume redistribution rate, thereby favoring the diffusion of the alcohol molecules.…”