A dismantlable
adhesion system satisfies both a strong bonding
strength during use and a quick debonding process on demand in response
to an external stimulus as a trigger for dismantling. In this study,
we synthesized acrylate copolymers consisting of 2-(
tert
-butoxycarbonyloxy)ethyl acrylate (BHEA), 2-ethylhexyl acrylate (2EHA),
and 2-hydroxyethyl acrylate (HEA) as the repeating units and evaluated
the properties as dismantlable adhesives. First, the thermal degradation
behavior of the obtained polymers was investigated by thermogravimetric
analysis and IR spectroscopy. The BHEA-containing polymers were thermally
stable during heating at a temperature below 150 °C, but they
rapidly degraded, i.e., the deprotection of the
tert
-butoxycarbonyl groups occurred during heating at 200 °C. The
onset temperatures for the deprotection depended on the BHEA and HEA
contents and their sequence structures because the hydroxy group in
the side chain accelerated the deprotection via an autocatalytic reaction
mechanism. Shear holding power and 180° peel tests were carried
out with the pressure-sensitive adhesive tapes using the BHEA-containing
copolymers as the adhesive materials. The copolymers consisting of
the BHEA, 2EHA, and HEA units with 25.7, 35.0, and 39.3 mol %, respectively,
exhibited the highest adhesion strength and the subsequent quick reduction
of the adhesion strength by heating during the dismantling process.
The addition of hexamethylene diisocyanate as the cross-linker and
Zn(acac)
2
as the Lewis acid to the adhesive polymers was
demonstrated to be valid for the design of high-performance dismantlable
adhesion systems. A change in the rheological properties during the
dismantling process was important for a quick response and selective
interfacial failure between the substrate and the adhesive.
Novel photolabile crosslinkers bearing O-acyloxime moiety are proposed. The crosslinkers were polymerized with methyl acrylate in film state, and the photodegradation of resulting films are demonstrated.
Energy transfer to aromatic ketone oximes can exhibit nonvertical behaviour depending on the planarity of ground state equilibrium geometry, a fact discussed in terms of structural changes of ground and triplet states.
Rheological studies of reworkable photocuring resins were carried out using reworkable monomers. A dimethacrylate monomer containing tertiary ester units in a molecule and a methacrylate monomer, which has both an epoxy moiety and a thermally-cleavable tertiary ester moiety in a molecule, were employed as the reworkable monomers. When the cured reworkable monomers were irradiated and baked in the presence of a photoacid generator, the storage moduli of the cured resin decreased at elevated temperatures. The decreased storage moduli revealed by the rheological studies were due to the acid-catalyzed decomposition of the tertiary ester linkages in the cured reworkable monomers.
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