Chemistry Reference
In-Depth Information
Figure 1.15 The
photo-initiated
cationic
polymerization
of
aliphatic
dicycloepoxide.
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and adhesives.
7
The mechanism of photo-initiated cationic polymerization
is illustrated in Figure 1.15.
The Soucek group
75
have reported the preparation and photo-polymer-
ization of cyclohexene-derivatized linseed oil (CLO) and epoxycyclohexene-
derivatized linseed oil (ECLO). The structures of CLO and ECLO and the
photo-polymerization kinetics are shown in Figure 1.16. It was found that
the addition of reactive or non-reactive diluents could reduce the viscosity of
the formulations and increase the final epoxy conversion and the polymer-
ization rate (Figure 1.17).
76
The properties of UV-curing hybrid films derived
from epoxynorbornane-functionalized linseed oil and tetraethylorthosilane
(TEOS) were also studied. The results indicated that the incorporation of
TEOS can improve the performance of the films and enhance the tensile
strength, thermal stability, fracture toughness, and general coating prop-
erties of epoxynorbornane-modified linseed oil.
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Ortiz's group studied the acceleration effect of substituted benzyl alcohols
on the cationic photo-polymerization rate of epoxidized natural oils.
78
The
Crivello group described the effect of the structure of both the cation and
anion of diaryliodinium and triarylsulfonium photo-initiators on the poly-
merization rate of epoxidized triglycerides as renewable monomers. The
obtained cured raw vernonia oil films based on this system exhibited a high
degree of flexibility and impact strength.
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Johansson's group has prepared
UV-curable resins from a hydroxy functionalized hyperbranched polyether
onto which an epoxy functional fatty acid, vernolic acid, had been grafted
(Figure 1.18).
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The Lalev´e group
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explored the cationic polymerization
process of epoxidized soybean oil (ESO) using various photo-initiators under
air and solar irradiation. A fundamental research study on photo-initiators
was described for the case of the cationic photo-polymerization of trigly-
cerides. Their newly developed photo-initiating systems are highly ecient
under air upon solar irradiation, leading to 60% conversion, and form a
completely tack-free and uncolored coating after 1 h.
