Plasma polymer adhesion promoters for metal-polymer systems - Polyimides and Other High Temperature Polymers - page 384

sive strength of pure pulsed plasma allylalcohol. The low cohesive strength of the
allylalcohol homopolymer was evidenced by the measured low peel strength and
the locus of failure, which was within the plasma polymer layer.
5. SUMMARY
The pulsed plasma polymerisation of vinyl, acrylic and allyl monomers is domi-
nated by a chemical (radical) polymerisation in the plasma-off periods. The prod-
ucts are similar to commercial polymers. In addition, pulsed plasma polymers also
contain a number of irregularities, especially branched structures. The
polymerisation of functional groups bearing monomers is also possible. A high
degree of the functional group of the monomer is retained in the plasma polymer
(65-95% retention), and OH, NH 2 , and COOH groups could be produced. The
yields were 30 OH, 18 NH 2 , and 24 COOH groups per 100 C atoms. Furthermore,
a plasma-initiated copolymerisation can be performed. This process allows to
vary the density of functional groups by the addition of a chain-extending
comonomer. Olefins, dienes or other hydrocarbon chain-extending comonomers
tend to branch and to trap C radical sites (up to 15% of all carbon atoms). Co-
polymer formation was observed if both comonomers had similar tendencies to
polymerise. Self-Exciting Electron Resonance Spectroscopy (SEERS) was used
as diagnostic technique for the pulsed plasmas. In Al-PP composites the peel
strength of Al proportionally increased with the density of OH functional groups
of the adhesion-promoting interlayer produced by the plasma-initiated
copolymerisation of allylalcohol and ethylene.
Acknowledgements
We thank the VDI-TZ in Duesseldorf for financing this work under grant
13N7779.
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