The key compositional parameters involved in developing addition-curable silicone
PSAs include variations in the functional group type (SiH or Si-Vi), the number
of functional groups and molecular weights of the polymer, crosslinker and MQ
resin. An additioncure silicone PSA composition may also include organic diluents
and additives for specific requirements, e.g., for lowering the thermal expansion coefficient,
enhancing anchorage with the substrate, or improving high-temperature
properties. Temperature requirement for curing these silicone PSAs is also lower,
thus allowing the use of temperature-sensitive substrates. However, addition-cured
silicone PSA systems do suffer from generally lower heat stability than peroxide
systems. To overcome this deficiency, some patents describe improved compositions
that utilize peroxide and addition dual-cure mechanisms or the use of antioxidants
to improve high-temperature performance [9, 10, 16].
Other approaches to cure silicone PSAs were also found in our survey. Guo et
al. [41] described a silicone PSA system that uses a tin catalyst. The ability of
organic tin to catalyze a condensation reaction among the silanol-functional groups
is well known. Ultraviolet (UV) and electron-beam (EB) cure mechanisms are also
used with silicone PSAs, with the advantages of much lower energy requirements
and a smaller equipment footprint. Two recent patents describe the use of UV and
EB cures with, and without, thermal activation of the initiator [1]. A silicone PSA
composition is described that uses a thermal/UV dual-cure mechanism to leverage
the benefits of UV cure and the properties of thermal-cured silicone PSAs [16].