Chemistry Reference
In-Depth Information
Figure 1.9 Preparation of acrylated vegetable oils in one step.
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Acrylate moieties have also been attached to triglyceride structures by the
one-step addition of bromide and acrylate groups to a C
ΒΌ
C bond. Soybean
and sunflower oils have been modified in the presence of acrylic acid and
N-bromosuccinimide (NBS, Figure 1.9).
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The Patel group
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has synthesized a series of UV-curable polyurethane
acrylate pre-polymer monomers by reacting polyols from sesame oil (edible)
and using different ratio of polyols, aromatic isocyanate, and aliphatic
isocyanate, 2-hydroxy ethyl methacrylate (HEMA) and dibutyltin dilaurate
(DBTDL) as the catalyst. Polyols were prepared via the alcoholysis of trigly-
ceride oil using a proprietary method, which was further reacted with
toluene diisocyanate and isophorone diisocyanate in different ratios to
develop a series of polyurethanes (Figure 1.10).
Homan et al. also employed an acrylate-bearing isocyanate group to
produce acrylate castor oil.
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Patel et al. modified monoacylglycerol (MAG)
with the diisocyanate reagents methylene bis(4-phenylisocyanate) (MDI) and
toluene diisocyanate (TDI). The free terminal isocyanate groups of MAG
reacted with the acrylate monomer, which bears a free -OH group.
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A final
route for urethane-acrylated vegetable oils is the reaction of an acrylate
bearing an isocyanate group and fatty chains, with a hyperbranched
hydroxyl-terminated polyester.
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1.3 Photo-cured Materials from Vegetable Oil
Monomers
Photo-curing formulations are usually comprised of multifunctional
monomers and oligomers, with small amounts of a photo-initiator
which generates reactive species (free radicals or ions) upon UV exposure.
The overall process can be represented schematically as shown in
Figure 1.11.
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There are two major classes of UV-curable resins, and they
differ in their polymerization mechanism of monomers i.e. acrylates or
unsaturated polyesters (free radical polymerization) vs. photo-initiated cat-
ionic polymerization of multifunctional epoxides and vinyl ethers (cationic
polymerization).
Many researchers pay attention to the chemistry behind the photo-curing
process, and especially the photo-curing kinetics of ultrafast reactions for
both cationic-type and radical-type polymerization of the multifunctional
monomers from vegetable oils. Polymer networks based on vegetable oils
with different structures and tailor-made properties have been obtained by
photo-curing formulations containing one or more type(s) of monomer.
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