Polyester films, surface pretreatment

Polyethylene terephthalate cannot be solvent-cemented or heat-welded. Adhesives are the prime way of joining PET to itself and to other substrates. Only solvent cleaning of PET surfaces is recommended as a surface treatment. The linear film of polyethylene terephthalate (Mylar) provides a surface that can be pretreated by alkaline etching or plasma for maximum adhesion, but often a special treatment such as this is not necessary. An adhesive for linear polyester has been developed from a partially amidized acid from a secondary amine, reacted at less than stoichiometric with a DGEB A epoxy resin, and cured with a dihydrazide.72... 

A major factor influencing the extrusion bonds is the specific adhesion. That is, the capability of the molten polymer to conform to or match the chemical composition of the substrate. In the composite polyester/PE/foil/PE, for instance, the actual construction to consider is more likely polyester/interface/PE/foil/PE, where the interface between the polyester and PE film must be considered as a true layer. At the polyester-polyethylene interface, a primer and adhesives, after surface modifications, are necessary so that the polyester will adhere properly to the PE. Likewise, a pretreatment between the foil and PE is necessary to form a sufficient bond between those two substrates. 

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