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Publisher Summary This chapter focuses on multilayer flexible packaging, which involves the combination of two or more layers into a composite web or tube that provides functional, protective or decorative properties. For this, polymer materials are selected and the entire packaging structure is designed to meet the performance requirements specific to that particular application. Multilayer flexible packaging structures can lower the cost of many film structures by reducing the expensive polymer used, increasing the less costly polymers, using recycled material, or reducing film thickness. Competitive advantages can be achieved for many film structures ranging from the high technology barrier food packaging films to the heavy duty shipping bag market. A critical factor in developing successful flexible packaging applications has always been a good understanding of the target application. The performance properties required by the application and economic comparisons should be evaluated against the many alternative structures. Flexible packaging films are used to provide barrier to gases such as oxygen, nitrogen, carbon dioxide, and water vapor. Other applications may require taste and odor resistance properties. Heat sealability is also a critical property for various packaging applications. A polymer that exhibits low temperature sealability and maintains seal integrity over a broad seal temperature, dwell time, and seal pressure can significantly increase packaging line speeds, improve efficiencies, and minimize seal failures. Heat seal properties are influenced by a polymer's thermal and rheological properties as well as factors such as seal bar temperatures, seal bar pressure, dwell time, sealing bar configuration, and package design. |
