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Gas Permeability and DSC Characteristics of Polymers used in Food Packaging

The work is an experimental study of gas permeability and DSC characterisation of polymers used in food packaging. For this purpose polyethylene (0.03 and 0.1 mm), polypropylene (0.03 mm), and coextruded polypropylene (0.1 mm) were studied. The permeabilities of polymers to oxygen and nitrogen were measured at 20 oC, 40 oC and 60 oC using the manometric method. From the obtained permeability data, permeation, diffusion and solubility constants were calculated while temperatures and enthalpies of the phase change were determined by the DSC method. Permeability of oxygen and nitrogen increase with temperature for all investigated samples. Permeation data for the polypropylene (0.03 mm) and polyethylene (0.03 mm) showed good agreement with the Arrhenius equation. Upon temperature increase starting from 40 0C all samples undergo phase change in the temperature range from 107 0C to 173 0C with enthalpies in the range of 40 to 85 J g^-1. Experiments, where simulated conditions of food sterilisation were used as well as exposition to radiation in a microwave oven, showed negligible changes in DSC indicating structural stability of the polymers.

Activation energy; Diffusion; DSC; Gas permeability; Heat of Sorption; Permeation; Polymers; Solubility.

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