The Importance of Thermal Transfer and Heat Retention in Designing Thermoformable Coextruded Film Structures, 2010 PLACE Conference

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Incomplete forming and excessive corner thinning are common problems in coex thermoforming films that result in loss of barrier and package integrity. Both problems can be avoided or minimized by designing coex structures that optimize thermal transfer and heat retention within the film and choosing interior polyethylene layers that soften at relatively low temperatures and extend or draw without neck-in.

These studies demonstrate the importance of maintaining heat in coex films immediately before and during forming. By considering the thermodynamic properties of the individual polymer layers used in the exterior and interior layers of a coex film, heat loss can be minimized and final forming quality improved. The results provide practical guidelines for using standard simple laboratory tests such as DSC and elevated temperature tensile tests to help choose polymers and design coex structures for thermoforming.