Higher Tie Layer Adhesion in Machine Direction Oriented (MDO) Barrier Films, 2007 PLACE Conference

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Machine Direction Orientation (MDO) is a post-extrusion process used to enhance film properties such as barrier, stiffness and clarity. Orienting coextruded films containing EVOH or Nylon presents the special challenge of maintaining adhesion at the tie-layer barrier interface after orientation. When conventional tie-layer resins are used, the post-oriented adhesive bond force can decrease by up to 90% of the initial or pre-oriented levels. This decrease is due to a reduction in surface bond population as the interfacial area expands and a loss of interfacial strength as the film is stretched in the solid state below melting temperature. Why does the tie layer, which is primarily PE, lose interfacial strength between the tie layer and barrier materials when the other PE film layers are getting “enhanced film properties?”