Beneath the low-pressure plasma technology and the atmospheric pressure plasma technology the IFAM uses the so called fluorination to activate plastics being difficult to bond or to varnish.
In this technique the surface of a workpiece is exposed at room temperature to a mixture of nitrogen, few percent fluorine and eventually some oxygen, whereby hydrogen atoms of the outer layers of the polymer are replaced by fluorine atoms in a strong exothermic process. In the exemplary case of treating polypropylene by this process the result is a replacement of approx. half of the available hydrogen atoms within a surface layer of some 10 nm after a few minutes of fluorination. The gas phase fluorination can be used as an inline- as well as an offline-procedure. Both possibilities are used in the industry and have been proved to be worthwhile for a great number of applications.
The activation effect is
based on the fact that by the replacement of a certain number of the hydrogen
atoms by fluorine atoms dipoles are generated within the polymer. By this
the surface energy is increased – the effect is a better wettability. Furthermore
the surface renders a lot of adhesion points at which the adhesives can
link at least by dipole interactions.
In the case of a fluorination
the activation is very long term-resistant due to the considerable depth
of penetration of the reaction. By this effect rotational motions of chain
segments are hindered below the softening temperature. These rotational
motions otherwise would make the activated part of the chain turning to
the inside of the polymer and by this spoil the activation effect.
If the fluorination process
is carried out in the presence of oxygen (residue concentration in the
reactor and/or use of a mixture of nitrogen, fluorine and oxygen) oxygen
atoms are inserted as well. This process is called oxifluorination. The
acid fluorine - and carboxyl-groups formed this way render additional linking
points for reactive adhesive components and therefore lead to improved
properties of the adhesive bond or the varnishing as well.
Within the bounds of its function as service provider in technology transfer, IFAM offers its resources for the processing of the above-mentioned industrial questions up to series production. Our service comprises consultation, process development, sampling and industrial installation through pilot terotechnology.
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