242
R. Tesser et al.
PEUMH were characterized by spectral, physico-chemical, thermal (TGA and DSC)
and morphological analyses by standard methods. The potentiality of the same as
promising coating material was also evaluated. PEUMH are foreseen as prospective
candidates for application as antibacterial self-sterilizing protective coatings due to
oligodynamic effect of metal [198].
The Jatropha curcas Linnaeus (JCL) oil was extracted, refined and modified
through epoxidation, hydroxylation and dehydration steps in order to increase the
degree of unsaturation in the oil alkyl chain. The modified oil was subsequently used
for alkyd resin preparation (50% oil formulation) using a two-stage alcoholysispolyesterification method. Drying performances of white gloss paints formulated
from the desaturated oil alkyd gave improved results. The blending of the improved
50% JCL oil alkyd with acrylic further enhanced the drying properties to be comparable to the commercial standards. White gloss paint formulated from the improved
JCL alkyd–acrylic blends (1:3) dried hard within 2 h at an outdoor temperature of
37 °C ± 2 [151].
8.4.6 Vegetable Oils for Waterborne Paints and Coatings
Vegetable oil derivatives found applications as environment-friendly solvent-borne
or waterborne coating materials, leading to improved performances and reduction
or elimination of VOC emissions, due to the absence of organic solvents. VO-based
coatings are normally used when penetration is desired, i.e. for wood coating.
The formulation of solvent-borne paints is not a big issue, as VO is soluble in
organic solvents. On the contrary, the development of waterborne coatings is a challenging task due to the hydrophobic nature of oil chains. Several solutions to this
problem were proposed.
Water-soluble resins: are rare because most resins derived from oils are insoluble
in water. The real emulsions are obtained by using either a surfactant or a resin that
has a surfactant-like behaviour.
VO-modified latex: VO is incorporated in the latex resin. After application, the oil
portion, that lowers the glass transition temperature of the resin, of the resin crosslinks
to produce a hard, durable film [220]. Acrylated oils, soybean oil-urethane-acrylic
hybrids [166], epoxidized VO [197] are used in the synthesis of the latex.
Water-reducible resins: similar to the dispersions in that they are particles; however, the particle size, of spherical geometry, is generally less than 8 μm in diameter.
Adding water to the resin leads to a first viscosity drop-down, followed by a further rise to a very high level. After application, water evaporates and the solvent
re-dissolves leading to particles coalescence into a coating film. Even if these paints
started to be used only in the 1980s, due to the difficult formulation, they can be used
for many maintenance applications [220].
Radiation cures (radical UV, ionic and e-beam systems): the radical cure system
is nowadays the most popular owing in part to their cost and cure speed. As a matter
of fact, radical cure processes require only seconds to reach full cure, versus 20 min
R. Tesser et al.
PEUMH were characterized by spectral, physico-chemical, thermal (TGA and DSC)
and morphological analyses by standard methods. The potentiality of the same as
promising coating material was also evaluated. PEUMH are foreseen as prospective
candidates for application as antibacterial self-sterilizing protective coatings due to
oligodynamic effect of metal [198].
The Jatropha curcas Linnaeus (JCL) oil was extracted, refined and modified
through epoxidation, hydroxylation and dehydration steps in order to increase the
degree of unsaturation in the oil alkyl chain. The modified oil was subsequently used
for alkyd resin preparation (50% oil formulation) using a two-stage alcoholysispolyesterification method. Drying performances of white gloss paints formulated
from the desaturated oil alkyd gave improved results. The blending of the improved
50% JCL oil alkyd with acrylic further enhanced the drying properties to be comparable to the commercial standards. White gloss paint formulated from the improved
JCL alkyd–acrylic blends (1:3) dried hard within 2 h at an outdoor temperature of
37 °C ± 2 [151].
8.4.6 Vegetable Oils for Waterborne Paints and Coatings
Vegetable oil derivatives found applications as environment-friendly solvent-borne
or waterborne coating materials, leading to improved performances and reduction
or elimination of VOC emissions, due to the absence of organic solvents. VO-based
coatings are normally used when penetration is desired, i.e. for wood coating.
The formulation of solvent-borne paints is not a big issue, as VO is soluble in
organic solvents. On the contrary, the development of waterborne coatings is a challenging task due to the hydrophobic nature of oil chains. Several solutions to this
problem were proposed.
Water-soluble resins: are rare because most resins derived from oils are insoluble
in water. The real emulsions are obtained by using either a surfactant or a resin that
has a surfactant-like behaviour.
VO-modified latex: VO is incorporated in the latex resin. After application, the oil
portion, that lowers the glass transition temperature of the resin, of the resin crosslinks
to produce a hard, durable film [220]. Acrylated oils, soybean oil-urethane-acrylic
hybrids [166], epoxidized VO [197] are used in the synthesis of the latex.
Water-reducible resins: similar to the dispersions in that they are particles; however, the particle size, of spherical geometry, is generally less than 8 μm in diameter.
Adding water to the resin leads to a first viscosity drop-down, followed by a further rise to a very high level. After application, water evaporates and the solvent
re-dissolves leading to particles coalescence into a coating film. Even if these paints
started to be used only in the 1980s, due to the difficult formulation, they can be used
for many maintenance applications [220].
Radiation cures (radical UV, ionic and e-beam systems): the radical cure system
is nowadays the most popular owing in part to their cost and cure speed. As a matter
of fact, radical cure processes require only seconds to reach full cure, versus 20 min