Effects of orientation on the transport of d‐limonene in polypropylene

Abstract

SYNOPSISKinetics and equilibria of sorption and desorption of d-limonene in three polypropylene films (unoriented polypropylene [UN], uniaxially oriented polypropylene [ UA], and biaxially oriented polypropylene [BA]) were studied a t 30°C and various penetrant activities. The weight percent uptake of a saturated vapor of limonene in UN, BA, and UA films ranged from 12.5 to 19.0%. The kinetics of sorption of a saturated vapor of limonene in these polymers exhibits an increasing tendency toward Fickian transport as the degree of orientation increases, with the highly oriented BA approaching a Fickian response. As the penetrant activity is lowered, sorption kinetics tends to show a Fickian response more closely even for the U N and the UA films. Desorption of limonene from the three samples appears to be Fickian and considerably faster than sorption in the initial stages; however, the process decelerates after roughly half of the penetrant has desorbed. Subsequent exposure of the three oriented films to a saturated vapor of limonene resulted in identical sorption kinetics, suggesting the absence of crazing or other irreversible damage often associated with anomalous sorption in glassy polymers. These results illustrate that the concentrationdependent anomalies in kinetics of sorption of a large penetrant such as limonene in the unoriented polypropylene film may be influenced by orientation to yield Fickian transport even at the highest external surface concentration. Thus, the orientation processes appear to affect large-scale swelling-induced relaxations to a larger degree than it does the diffusional processes which are dependent on smaller-scale segmental motions. 0 1995 John Wiley & Sons, Inc.

Scalping of ethyloctanoate and linalool from a model wine into plastic films

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