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.

Factors determining the transport coefficients of aroma compounds through polyethylene films

“…In this case, the presence of either water or aroma compounds could affect sorption. PE1 was more affected by water transfer than PE2 (Table 3) and water molecules could act as competitors for the same interacting sites as previously described (Aucejo et al, 1998). Therefore, additional studies are required to evaluate the impact of other aroma compounds on sorption.…”

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

“…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, 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 .…”

“…By increasing the RH, López-Carballo et al 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 reported increase in the permeability of limonene in EVOH and nylon-6,6 with increasing RH. Moreover, Aucejo et al 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. , …”

Ethyl hexanoate transfer in paper and plastic food packaging by sorption and permeation experiments

“…Gavara et al (1996b) showed that diffusion coefficients differed significantly using isostatic and quasi-isostatic permeation methods. Aucejo et al (1998) obtained close values for hexanol solubility in ethylene vinyl alcohol (EVOH) by the IGC technique and by isostatic permeation. Cava et al (2004) found comparable diffusion coefficients in polyethylene of a-pinene, limonene and linalool by the FT-IR technique and a conventional gravimetric method based on weight loss measurement.…”