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Thermoplastic elastomers can be readily crosslinked at ambient temperature by UV-irradiation in
the presence of a photoinitiator 1.2 These polymers, like styrene-butadiene block copolymers
(SBS), have a two-phase morphology, and are commonly used as pressure-sensitive adhesives,
in combination with a tackfying resin, and as flexographic printing plates. UV-curing creates
covalent bonds within the elastomeric phase, thus reinforcing irreversibly the already existing
physical network. As a result, the photocüred SBS becomes insoluble and more resistant to high
temperatures, the values of the Shear Adhesion Failure Temperature (SAFT) rising from 80°C to
over 160°C In SBS, the crosslinking process was markedly accelerated by the addition of a diacrylate monomer or a trifunctional thiol, which copolymerize with the polybutadiene double
bonds The use of light to induce the chain reaction has several advantages, namely high cure speed, low energy consumption, ambient temperature operations, dry processing without VOC emission and selective curing in the illuminated areas.
The work performed so far on SBS-type elastomers has now be extended to another type of
thermoplastic elastomer, an acrylonitrile-butadiene block copolymer (ABA), that we have tried to
crosslink rapidly by UV-irradiation. The same approach as for SBS has been used, by working
first with the neat polymer, and then by adding to it some acrylate or thiol monomers to achieve a
faster and more extensive curing and make the polymer more resistant to chemicals and heat.
The crosslinking reaction was quantitatively followed by infrared spe'ctroscopy, as well as by
insolubilization and hardness measurements.
