INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
One pot preparation and evaluation of self-heqling polyurethane coatings
Autor/es:
RIVERO GUADALUPE; NGUYEN LE-THU T.; HILLEWAERE XANDER; DU PREZ FILIP E.
Reunión:
Simposio; Macro Young Researchers' Meeting 2014; 2014
Resumen:
capability under mild temperature conditions will be presented. The material design
combines the main advantages of several cutting edge topics in a complex functional
system, but achievable in a straightforward, one-pot process. Diels-Alder thermoreversible
covalent bonds were introduced as crosslinkers into a shape-memory polyurethane
material, improving thereby the material mechanical properties.
The healing strategy applied is based on a synergetic combination of Diels Alder covalent
thermo-remendability with the simultaneous assistance of a shape memory agent to favor
the crack closure. When a crack occurs, Diels-Alder bonds will preferentially break,
regenerating free furan/maleimide functional groups. The shape memory effect favors the
crack closure upon heating, resulting in a reformation of the reversible crosslinking bonds.
In this way, the concept can be adapted as ?Diels Alder based shape memory assisted selfhealing?
(DASMASH).
The preparation method involves an initial Diels-Alder reaction among a commercial bismaleimide
and a diol with a pendant furan moiety, easily synthesized on large scale. After
the incorporation of polycaprolactone (PCL) as shape memory switching segments, the
polyurethane formation reaction takes place in the same reaction vessel.
The concept was proven and the healing performance upgraded after studying the role of
each component and testing different compositions. The hard segment content does not
only affect the physical/structural parameters such as crystallinity, toughness and
transparency but also the self-healing characteristics in accordance with the resulting
crosslinking degrees. Diels-Alder moieties are then proved to be the main responsible
factor for the polyurethane thermo-remendability.
Polyurethanes heal at 50°C after mechanical damage induced by either the application of
a large tensile deformation, macro and instrumented micro scratches. The PCL melting
provides enough mobility to recover the shape in a couple of minutes, enabling the
progressive Diels-Alder bonding reformation in this same condition. On-line FT-IR monitoring allowed the structural and kinetic description of the system reversibility for
numerous cycles. Furthermore, mechanical recovery was accomplished after multiple
cycles of large deformation. Complete disappearance of microscratches was also achieved.
The results were not only confirmed by by an optical inspection with scanning electron
microscopy but also by the comparison of the cross-section profiles before and after
healing with confocal microscopic mapping.