Peelable structures for PP, PS, PET and PVC. Understanding how multilayer construction influences seal and peel properties, 2008 PLACE Conference

Please Note: This document will be available in PDF format in the "My Electronic Documents" link on the home page once your order has been completed. Please make sure you have the latest version of Acrobat Reader. Click on the Acrobat Reader icon to check for the latest version, it’s FREE. To print a hardcopy of a PDF file correctly you must have a postscript printer. If you are not sure if your printer is a postscript printer please refer to your owner’s manual.

Extrusion processes are attractive to design multilayers offering heat sealing as well as easy peeling properties to typical plastics used for trays and cups like PS, PP, PET and PVC. Versatile sealing properties, controlled peeling behaviour, as well as ease of processing at all converting stages are strong prerequisites, which are not so easy to meet all together. Whatever the technology used, some tricky issues have to be solved at the processing stage, all related to the stickiness of the sealant top layer : chill roll release, bubble splitting after collapsing, blocking, and friction properties.

Beside these processing issues, the development of peelable structures is sometimes considered as just a question of selecting a peelable resin. Actually, the whole construction is important. Each layer may influence the final seal and peel peformance through the thermal and rheological properties of the different materials involved. First, because sealing is a converting process which induces flows of materials under the effect of thermal and mechanical energy transfers. Second, because peel strength, which is a matter of both adhesion and plastic dissipation, will be controlled not only by the sealant but also by the combination of the different layers, each one with its own elastic modulus and yield stress.

Using different examples, this paper will try to provide a better understanding of these effects and illustrate the possibilities of a recently introduced versatile heat seal resin.