NEW GENERATION OF MULTIFUNCTIONAL CROSSLINKERS
Dr. Roland Milker
Managing Director
Chemitec GmbH, Germany
Dr. Zbigniew Czech
Consultant
Szczecin, Poland
Crosslinking is a most interesting process, attractive for the chemist, informative for
the physicist and helpful for the user- in the joint development of tailored PSAs. This
applies mostly also for acrylate based PSA dispersions.
In general PSAs are used increasingly for coating of labels, PSA tapes, decorative
films and similar self-adhesive articles. The PSAs have to have certain properties.
Besides a good surface adhesion the PSAs should have good stability against light,
oxygen, moisture and plasticizer and the adhesion characteristic should be constant
over a very large temperature range.
The crosslinking of PSAs is a useful process in the repertoire of general procedures
and is recognized like a red line going through the many applications in the areas of
PSAs. In the nomenclature "crosslinking" is the correlation of a network which relates
to a net of interconnected chains. Polymeric networks or crosslinked systems consist
of interconnected macro molecules, which expend into all three dimensions.
The individual molecule chains in a crosslinking are interconnected into "infinitely"
large molecules. Due to the huge length of the starting polymeric chains, only small
amounts of a crosslinking additive are needed to accomplish complete crosslinking,
i.e. a crosslinking covering the total volume of the PSA. The larger the starting
molecules, the larger the probability that they participate in the network concentration
at a given amount of crosslinking additive. Therefore, preferrably parts with lower
molecular weight remain without ties to the network when low crosslinking degree
applies because of the normally polydispersal characteristic of polymers.
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