Chemistry Reference
In-Depth Information
Dipentarythritol pentaacrylate (DPPA), pentaerythritol tetrakis(3-mercapto-
propionate) (PETT) and Irgacure 2100 as the photo-initiator were mixed
with AESO and the photo-polymerization was conducted during the fiber-
formation process. This process can be viewed as replacing the thermal
energy needed for melting processing with light energy.
A bio-based polyurethane (PU) acrylate was blended with AESO
44
in order
to utilize the excellent properties of vegetable-oil-based PUs. Vegetable-oil-
based PUs have excellent chemical and physical properties such as enhanced
hydrolytic tendencies, high tensile strength and elongation and thermal
stability, combined by other advantages such as low toxicity, inherent bio-
degradability and high purity. Functional vegetable oils have been used as
constituent component materials to prepare polymer network materials. PU
and AESO are compatible due to the chemical cross-linking in these network
blends. With an increase in AESO content, the T
g
of the networks decreased
from 40 to
4.8 1C, the tensile strength increased from 1.7 to 9.8 MPa and
the elongation-at-break decreased from 470 to 70%.
AESO is also involved in the synthesis of composites. Albayrak et al.
45
synthesized nanocomposites from AESO combined with styrene monomers
and montmorillonite (MMT) clay by using an in situ free-radical polymer-
ization reaction. The nanocomposites had improved thermal and dynamic
mechanical properties compared with a neat AESO-based-polymer matrix.
Skrifvars et al.
46
on the other hand, mixed AESO with natural fibers without
using any co-monomer such as styrene to produce structural composites
with a high content of renewable material. The composites were prepared by
spray impregnation followed by compression molding at elevated tempera-
tures. The resin can be reinforced with up to 70 wt% of fibers without sac-
rificing its processability. The tensile modulus ranged between 5.8 and
9.7 GPa.
5.2.2.3 Soybean-oil-based Polyols
Soybean oil has no hydroxyl functional groups in its fatty acid chains.
However, the double bonds provide a starting point for introducing hydroxyl
groups to the soybean oil. Polyols are mostly used for the synthesis of PUs. In
order to get PUs with good properties, the polyols need to contain sucient
amounts of hydroxyl groups, which in turn requires a considerable number
of double bonds in the vegetable oil. Soybean oil has an average number of
double bonds of 4.6 per triglyceride, thus is suitable for conversion to polyols
for the synthesis of PUs.
Typically, soybean-oil-based polyols are synthesized by epoxidation fol-
lowed by oxirane ring opening.
5
Different catalyst systems are involved in the
second step. Recently, Bailosky et al.
47
developed a new catalyst for the
synthesis of soybean-oil-based polyols from ESO. Zinc triflate was a more
ecient catalyst in catalyzing the ESO hydroxyl reaction than methane-
sulfonic acid or BF
3
OEt
2
and gave the expected polyether polyols.
Only 0.01% zinc triflate was found to give over 99% conversion with ESO and
