Oxygen Permeability Enhancements in Octene LLDPE Film Affected by LDPE Blending and Crystalline Orientation Changes, 2007 PLACE Conference

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The permeability of blown films made from Zeigler-Natta and single-site catalyzed octene linear low-density polyethylenes blended with branched low-density polyethylene was studied. At thinner film gauges, oxygen and moisture permeation rates of certain blends were significantly higher than the expected values. The films with the highest permeability had a corresponding higher degree of polymer crystal orientation in the film TD – ND plane. While PE film permeability rates typically decrease with increasing orientation, orientation in low crystallinity PE may align crystalline platelets parallel to the direction of permeant flow effectively increasing oxygen and moisture transmission rates. Certain blends of Octene LLDPE and LDPE showed higher levels of orientation and permeation in thin gauge films. Increased polymer relaxation times of these blends suggest that the LDPE helps induce and/or maintain orientation. Thus by increasing film draw-rate to maximize TD crystalline orientation and selectively blending LDPE to maintain orientation, the permeability of Octene LLDPE can be increased significantly.