Adhesion between functionalized polypropylene and polyamide films
Claude Rustal, Hans-Gerhard Fritz
Institut fuer Kunststofftechnologie, University of Stuttgart, Germany
Germany

Keywords: polypropylene, polyamide, adhesion

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This study is a preliminary work on the generation of a three-layer coextruded film which could find an application in the
medical field for infusion or blood bags. The general aim is to use maleic anhydride grafted polypropylenes (PP-g-MAH) - a
copolymer and an homopolymer - as moisture barrier external layers and a polyamide PA6 or PA6-6,6 as an oxygen resistant
central layer without addition of tie layers.

Bond formation between PP-g-MAH and polyamides cast films was investigated. The polypropylenes were functionalized by
means of radical-initiated melt grafting reaction which was processed in a closely intermeshing twin screw extruder equipped
with a slit die. The grafted PP were characterized in terms of thermal, mechanical and rheological properties. Higher grafting
yields as well as a lower polymer degradation were achieved by using styrene as a comonomer during the grafting reaction.
The surface polarity of the PP-g-MAH cast films was analyzed by contact angle measurements.

The functionalized PP and PA cast films were subsequently bonded using an hydraulic hot press and the interfacial adhesion
between the PP-g-MAH and PA sheets was measured using T-peel tests. Results show that increasing bonding time and
pressure improved the bonding properties. The effect of the grafting formulations of the PP-g-MAH on adhesion was also
studied. The peeled surfaces were analyzed by electron scanning microscopy (SEM)