Case History; Considerations Made to Maximize Moisture Barrier Performance (Synopsis), 1996 Polymers, Laminations & Coatings Conference Proceedings
Converters of polyolefin resins into blown films regularly face challenges from end-users to improve film performance properties such as moisture vapor transmission rate (MVTR). Excessive moisture transmission through packaging film used to protect most dry products accelerates staling, oxidation, and flavor-loss mechanisms. Specifically, end-users want new generation box liners of high density polyethylene film (HDPE) for cereal, cookie and cracker products which will provide significant improvements in moisture barrier, or, will permit significant downguaging of liner film, thus reducing material costs. Polyolefin resin suppliers provide information on typical film properties, given general manufacturing conditions (extrusion temperature profiles, blow-up ratios, etc.). The moisture barrier film industry has, over the years, established standard expectations for MVTR of HDPE films in the range of 0.35 -0.40 g-mil/100SI/day, at 90% RH, 100F. Improvements over the standard pose two technical challenges: the determination of the best specific HDPE resins for moisture barrier which are fit for use by the end-user, and, manufacturing improved moisture barrier film on a consistent basis, as demonstrated by some form of statistical process control. Our first target for standard blown HDPE films in 2.0 - 2.2 mil thickness is 0.13 (0.265 g-mil basis) g /100 SI / day, or 2.0 g / M2 /day, at 90% RH, 100F, representing an approximate...