The sorption of limonene/ethyl acetate binary vapour mixtures by a biaxially oriented polypropylene film

Abstract

The sorption of ethyl acetate and limonene as individual sorbates and in binary vapour mixtures by an oriented polypropylene was determined by t w o independent methods, namely by gravimetric and thermal stripping/thermal desorption procedures. The t w o methods showed excellent agreement. The solubility coefficients for the t w o species were found t o be independent of sorbate concentration within the ranges studied, indicating that sorption followed Henry's law. Calculated and experimentally obtained sorption profile curves agreed well for both ethyl acetate and limonene at low vapour activities. At a limonene vapour activity of 0.29 there was a lack of agreement between experimental and calculated results. This was attributed t o the onset of non-Fickian relaxation effects occurring within the polymer matrix at this limonene concentration. The results of sorption studies involving binary vapour mixtures indicated that at the concentration levels evaluated, the co-permeant did not effect the sorption characteristics of the other sorbate.Keywords: sorption; diffusion; permeation; limonene; ethyl acetate; binary mixture; vapours; packaging material; polypropylene; thermal stripping; thermal desorption; electrobalanceLoss of flavour constituents from foodstuffs due to sorption into and permeation through plastic packaging materials can result in the loss of product quality and a concomitant reduction in shelf-life for the packaged product. Permeation is described by Equation 1. P = D x S(1)The permeability coefficient (P) expresses the transport rate at steady-state, the diffusion coefficient (D) describes how quickly the permeant molecules move in the film and the solubility coefficient *To whom correspondence should be addressed.( S ) is a measure of the amount of a substance that will be absorbed by the polymer. Various investigators have shown that the diffusion, solubility and, therefore, the permeability coefficients are dependent upon a number of parameters. Landois-Garza and Hotchkiss' reported that an increase in permeant molecular weight resulted in an increase in the solubility of ethyl esters in polyvinyl alcohol (PVA), while the diffusivity decreased. Similar effects were found by Shimoda et a1.,2 who studied the transport of esters, aldehydes, alcohols and alkanes in polyethylene (PE) films. The type of functional group characteristic of the penetrant molecule is also of great importance in determining the extent of sorption by the packaging material. For example, esters

Concentration and Interactive Effects on the Sorption of Aroma Liquids and Vapors into Polypropylene

“…The aroma vapors were not affected by interactions with other compounds at any concentration or mixture investigated (Table 4 and 5). This was consistent with the reports of Nielsen and Giacin (1994) and Baner et al (1991). Concentrations of aroma vapors were in the range of concentrations expected in foodstuffs (Maarse, 1991).…”

Sorption of ethyl acetate and d‐limonene in poly(lactide) polymers

“…Figure 7 compares the ethyl acetate permeability coefficient values of PLA, LDPE, 43 PP, 46 and PET. 47 Ethyl acetate permeability coefficients in PLA are lower than those for PP and LDPE and slightly higher than PET.…”

Packaging material as a source of taints

“…In a further paper by Nielsen and Giacin (1994) the absorption by a biaxially oriented polypropylene (OPP) film of limonene and ethyl acetate in binary vapour mixtures was studied. It was concluded that there was no concentration dependency for the solubility coefficients of ethyl acetate and limonene in OPP film and no observed synergistic effects attributed to the co-permeant of binary vapour mixtures.…”