NEW sHDPE with Ultra High Moisture Barrier Performance, 2008 PLACE Conference

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High-density polyethylene (HDPE) is commonly utilized to provide moisture barrier performance in flexible packaging. Improvements in moisture barrier performance have come by; modification of structure design(^1,2), changes in processing conditions(^3,4), and through development of new materials(^2,5). Most of these improvements have resulted in subtle changes moisture barrier performance.

Improvements in barrier properties can be achieved by increasing the crystallinity or density of a material. Recent findings relate to enhanced crystalline morphology in the final product. The morphology depends upon the microstructure, fabrication methods used in sample preparation and the thermal history. Many parameters influence the morphology development of blown films in a complex way(⁶). These parameters include molecular structure, molecular orientation, molecular weight, molecular weight distribution and equipment characteristics (such as die gap) as well as processing variables such as blow up ratio (BUR), draw down ratio (DDR), frost line height (FLH). Zhang et al.(⁷) showed that distinct orientation structure and morphology are found in Low-density (LDPE), Linear low density (LLDPE) and HDPE films. LDPE formed a row-nucleated structure with twisted lamellae where as HDPE showed non-twisted lamellar orientation. LLDPEs showed spherulite-like superstructure.