Controlled Oxidation of a Tetrafunctional Thiol to Obtain a Poly (Thiol- disulfide) Oligomer and Its Use as Self-healing Agent for Epoxy/Thiol-ene Photocurable Systems | Chapter 02 | New Advances in Materials Science and Engineering Vol. 2
In this work the pentaerythritol
tetrakis (3-mercaptopropionate) was partially oxidized to obtain an oligomer
with both thiol and disulfide functional groups in its structure, by using
iodobenzene diacetate (IBDA) as oxidant. This oligomer was used to introduce
disulfide bonds into the crosslinked network of a polyether-polythioether
matrix obtained by photopolymerizing an epoxy/thiol-ene system. The presence of
the disulfide bonds induced self-healing properties bonds in the obtained
co-network. The oligomer was a joint component of the thiol-ene system along
with a tetraallyl-functionalized ditertiary amine curing agent and a radical
photoinitiator. The thiol groups of the oligomer reacted with the double bonds
of the curing agent to form polythioethers, while the tertiary amine groups of
the curing agent induced the anionic ring opening polymerization of the oxirane
groups of an epoxy resin to produce polyethers. The kinetics of
photopolymerization of the epoxy resin diglycidylether of bisphenol A (DGEBA),
revealed that conversions of the epoxy groups as high as 80 % were achieved in
only fifteen minutes by increasing the concentration of the thiol-ene system in
the formulation. The disulfide bonds introduced in the co-network by using the
thiol-disulfide oligomer, allowed the repairing of the test specimens in as
little as 10 minutes when the specimens were heated at 80 °C or for 500 minutes
at room temperature. The analysis of mechanical properties using dynamic
mechanical analysis (DMA) showed that the healed specimens, retained their
mechanical properties depending on the amount of polythioethers present in the
co-network.
Author(s) Details
Dr. Ricardo Acosta Ortiz
Centro de Investigación en
Química Aplicada, Blvd Enrique Reyna #140, C.P. 25294, Saltillo, Coahuila,
México.
View Book: http://bp.bookpi.org/index.php/bpi/catalog/book/123
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