High molecular mass poly(lactide), (PLA), is an attractive polymer family because in addition to being thermoplastic, biodegradable, compostable, and produced from annually renewable resources, it shows mechanical and barrier behavior comparable to synthetic polymers like polystyrene (PS) and polyethylene terephthalate (PET). Furthermore, technology for large-scale fabrication of PLA has been fully developed. However, there is still a need to better understand the properties of PLA as this polymer is adapted to packaging applications, especially for food packaging. In this work, films from two PLA resins were studied by tensile testing; differential scanning calorimetry (DSC); and permeation of carbon dioxide, oxygen, and water vapor. The data from these two PLA film samples are compared to those of PS and PET.

The sorption of selected polychlorinated biphenyl (PCB) congeners (from tri to deca chlorinated) by three food-packaging plastic films [polyethylene, polyvinyl chloride (PVC), and polystyrene] from an aqueous solution was investigated. From the data generated, PCB uptake, partition, and diffusion coefficients were calculated for the various films. Polyethylene exhibited the highest PCB uptake, diffusion, and partition coefficients when compared to the other materials. Although PVC indicated larger sorption diffusion and partition coefficients for the lower chlorinated congeners than polystyrene, a reversal of this trend was observed for the higher congeners. For polyethylene and PVC, the PCB uptake decreased as the chlorine numbers in the congeners increased, confirming the correlation between increasing chlorination and increasing cohesive density within the PCB molecules. For polystyrene, the uptake decreased from tri to penta congeners, but showed an increase for the hexa, and then a decreased uptake until the deca chlorination. A comparison of the molecular sizes of the PCB congeners showed that the partition (Ke) and sorption diffusion (Ds) coefficients generally decreased with their increasing molar volumes. The resulting Ke values were used to determine the extent of sorption because these values indicate the affinity of PCBs for the plastic films. Results from this study can be of practical importance for cases of product quality related to the transfer of contaminants from the product to the packaging materials.

Modified-atmosphere packaging was used to provide respiratory data for apple (Malus xdomestica Borkh.) slices at 0, 5, 10 and 15°C. The maximum rate of O 2 uptake increased with increasing temperature. The lowest O 2 partial pressure to which fruit could be exposed without fermentation also increased with increasing temperature. A mathematical model of film permeability data characterized the effect of fruit mass, film permeability to O 2 , activation energy of O 2 permeation, temperature, and the film type, area, and thickness on O 2 partial pressure for hermetically packaged apple slices. The model identified a minimum (fruit mass × film thickness)/(film area) ratio for apple slices, which would simplify package design calculations.

Sorption and transport properties of water through films of Nylon‐6 were obtained at 5, 23, and 40°C. Commercially available films were used and a Cahn electrobalance was employed for measuring the water uptake by the polymer samples. Values of the water sorption isotherms are accurately described by the Langmuir/Flory‐Huggins dual‐mode sorption model. At water activity values below 0.15, the volume fraction of water described by the Langmuir portion of the model was greater than the Flory‐Huggins population. Solubility and diffusion coefficients of water, as well as the diffusion activation energy and enthalpy of dissolution of water for Nylon‐6, were determined from the sorption experiments. Values obtained support the hypothesis of a bimodal water sorption mode, and the formation of water clusters. © 1994 John Wiley & Sons, Inc.