Guide to Nylon Chemistry, Equipment & Processing (Coating and Casting), 1997 Polymers, Laminations & Coatings Conference Proceedings

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Packaging materials for perishable food products, like meats and sausages, ham and cheese products, must meet many requirements. They have to provide a gas and aroma barrier, moisture retention to prevent desiccation of the contents, oil and grease resistance, taste neutrality, optical properties like transparency and gloss, printability and ease of labelling, mechanical properties such as toughness and flex strength, thermoformability and sealability, ease for processing at high rates on modern packaging machinery, product presentation with high sales appeal, durability and freshness for the end users, as well as easy, non-polluting disposal after use. So many requirements can hardly be met by one material alone; however, by the combination of several materials with complementary properties, it is possible to produce packaging materials with an optimum price/performance ratio. Multilayer structures made from PA in combination with polyoiefines and papers, foils and kindred products, meet the relevant requirements for food packaging in an ideal way. In addition to the film characteristic, the processing efficiency, recyclability (edges and product), downgauging and price are in consideration for selected resin. Common resins utilised in film applications are: a small family of resins such as EVOH, PVDC, PA, PET provide the flavour and gas barrier properties required . Very important characteristic for PA resin family is downgauging through coextrusion cast process or by orientation-mono and biorientation-of the PA film itself or with PA/EVOH/PA structures. As flexible packaging is expanding more due to source reduction, PA film coextruded and extrusion coated-laminated structures start to be more important than in previous period of development. Because of this balance of properties that PA is in use more than any other resin for the production of film for the food and medical packaging market. Polyamide family of resins combines the ease of processing (only with proper extrusion equipment and knowledge) and mechanical strength to yield an efficient product. Also possibility to combine PA family of resins with other material are technologies of sophistication. More understanding of usability and processability of PA and (co)extrusion are subject of this paper.