| 摘要 |
<p>A high density polyethylene (HDPE) film is provided having high-biaxial orieniation. The film includes HDPE having a density of at least about 0.940, and a melt index of from about 0.5 to about 10. The film is stretched in the machine (longitudinal) direction to a degree of from about 5:1 to about 8:1, preferably from about 6:1 to about 7:1. The film is also stretched in the transverse (lateral) direction to a degree of from about 6:1 to about 15:1, preferably from about 9:1 to about 13:1. Preferably, the film has an orientation imbalance, with a higher degree of transverse orientation than machine orientation. Skin layers such as heat seal layers can be provided. Preferably, the film contains one or more layers of a casting promoter material employed to promote casting of a high gauge HDPE sheet subsequently high biaxially oriented to provide the film. The film can also be cavitated, or otherwise modified (e.g., corona-treated, coated, metallized, etc.) to provide films suitable for special applications. The film of the invention has superior properties, including lower water vapor transmission rate, better dead-fold, higher tensile strength, and consistent gauge profile. Also provided is a method for making the biaxially oriented film.</p> |
