SAMPE Journal - March/April 2023 - 31

INTRODUCTION
Thermosetting compositions, such as unsaturated
polyesters, vinyl esters, epoxy resins, have
been widely used in coatings, adhesives and
composite materials. Historically, thermoset
resins have been synthesized using petroleumbased
chemicals as raw materials. However, due
to increasing environmental concerns, there is a
need for thermoset resins derived from bio-based
feedstocks.
Bio-based feedstocks include fatty acids derived
from plant-based oils such as soybean oil, canola
oil, tall oil, safflower oil, linseed oil, castor oil, etc.
Other bio-based feedstocks include rosin acids
including gum rosin acid, wood rosin acid, and tall
oil rosin acid. Rosin, a bio-renewable raw material,
is commercially available, and can be obtained
from pine trees by distillation of oleoresin (gum
rosin being the residue of distillation), by extraction
of pine stumps (wood rosin) or by fractionation of
tall oil (tall oil rosin). Rosin contains a mixture of
rosin acids, fatty acids, and other unsaponifiable
compounds.
A product of the Kraft process, crude tall oil
(CTO), can be further purified by distillation to
provide tall oil heads, tall oil fatty acids (TOFA),
distilled tall oil (DTO), tall oil rosin (TOR), and tall
oil pitch. These products have long been used in
traditional fields such as inks, adhesives, oil fields,
mining, paper sizing and detergents.
DTO mainly consists of a tall oil fatty acid
fraction (rich in oleic acid, linoleic acid, palmitic
acid, palmitoleic acid and stearic acid) and tall oil
rosin fraction (abietic acid, dehydroabietic acid,
palustric acid, neoabietic acid and isopimaric acid
being the primary isomers). Attempts have been
made to develop thermoset resins from tall oil
fatty acid or rosin. Thermoset resins derived from
tall oil fatty acid may have reduced mechanical
strength and thermal stability. Thermosets resins
derived from rosin might lead to rigid and brittle
materials. In contrast, we have utilized DTO to
develop a series of novel bio-based DTO vinyl ester
resins that provide balanced mechanical strength,
thermal stability and flexibility. These DTO vinyl
ester resins are liquid at room temperature and
have bio-content ranging from 20% to 66%. In this
paper, several DTO-based vinyl ester resins are
introduced. Their overall performance including
curing properties, mechanical properties and
thermal properties were investigated.
EXPERIMENTAL
Materials
The new DTO vinyl ester resins were synthesized
using reactors at Ingevity Corporation, and are
proprietary formulations and the intellectual
property of Ingevity Corporation based in North
Charleston, SC. Generally, these novel thermosets
consist
of DTO,
as
sourced
from Ingevity's
refineries, functionalized with an array of vinyl
ester functionalities, including acrylates and
methacrylate.
Clear cast resin specimen preparation: lab
specimens were unreinforced and fabricated by
curing the resin in a silicon mold. Methyl ethyl
ketone peroxide MEKP was used as a free radical
initiator and Cobalt (12%) and N, N-dimethylaniline
(DMA) were used as promoters to cure the DTO
vinyl resins at room temperature for overnight.
Test coupons were then de-molded and post cured
2 hours at 100°C oven for mechanical testing.
Characterization
Tensile testing was conducted according to the
ASTM D638 using an Instron 3365 universal testing
machine and at a crosshead speed of 10 mm/min.
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Advancing Composite Technology Since 1983
www. sampe.org
MARCH APRIL 2023
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SAMPE JOURNAL |
31
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SAMPE Journal - March/April 2023

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