Oxygen permeation has been measured in flat sheet as a function of degree of orientation, and oxygen and water transport have been measured in oriented polyester bottles. O2 permeability in flat sheets decreases gradually with orientation on either side of an abrupt decrease by about a factor of 2 after moderate orientation. The bottles tested were all more highly oriented than that critical decree; no significant effect of orientation on water or O2 transport in bottles could be found. Only container intrinsic viscosity (IV) (which is determined by molecular weight, and is therefore a convenient measure of polymer degradation) was significantly related to the transport properties of the bottles. It was found that O2 transport is increased with increasing IV while H2O transport decreased. The explanation for these seemingly contradictory data can be found in the chemistry of degradation of the polyester.

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Evidence of a negative-resistance characteristic in a circuit consisting of a thin film of Mylar, in series with a high resistance, at high dc fields is reported. This characteristic is a result of a reversible electrical breakdown of Mylar films at a temperature-dependent high dc field, which precedes an irreversible thermal breakdown. Without an adequate series resistance these two types of breakdown occur essentially simultaneously and in this event the negative-resistance characteristic cannot be observed.