Chemistry Reference
In-Depth Information
increased from 0.91 to 1.23 GPa and from 26 to 36 MPa, respectively, while
incorporation of 10 wt% microcrystalline cellulose did not result in a sig-
nificant change in the mechanical properties. This is probably due to the
better particle dispersion of wood flour in the polymer matrix.
5.4.2 Applications of Tung Oil and its Derivatives
A tung-oil-based composite has been used as a sealing material for more
than 1000 years in China.
121
Fang et al.
121
conducted a study on a piece of
chu-nam putty discovered on an ancient ship in China, and revealed that the
putty was prepared by mixing tung oil, lime and oakum. This special or-
ganic-inorganic hybrid composite invented by ancient Chinese people had
excellent sealing performance including excellent waterproofing and bond-
ing properties. The application of chu-nam putty in a wooden ship led to
improvements in sailing technologies and ship safety issues.
Xiong et al.
132
used tung oil anhydride (TOA) as a plasticizer for PLA-starch
composites. The ready reaction between the MA on TOA and the hydroxyl
groups on starch resulted in an accumulation of TOA molecules on starch,
which increased the compatibility of the PLA-starch blends. A layer was
formed upon accumulation of TOA on starch, which had an effect on the
thermal behavior of PLA in the ternary blend. The T
g
and T
m
values of the
ternary blend were slightly lower than those of neat PLA, and increasing
the amount of tung oil from 5 to 12 wt% in the ternary blend did not affect
the T
g
and T
m
values of the blends. The enrichment of starch with TOA also
improved the toughness and impact strength of the PLA-starch blends. The
elongation-at-break reached a maximum value of 30% when 7 wt% of TOA
was used in the blend, and the impact strength of this blend was almost two
times of that of neat PLA.
Liu et al.
133
used tung oil as a reactive toughening agent for an un-
saturated polyester resin terminated with dicyclopentadiene (DCPD-UPR) via
an intermolecular Diels-Alder reaction occurring at the later stage of melt
polycondensation. These polymers were further blended with a styrene co-
monomer and cured via free-radical polymerization to give cross-linked
thermosetting polymers. The thermal and mechanical properties of these
bio-materials showed an enhanced toughness with increasing tung oil
content. With 20% tung oil, the matrix obtained from DCPD-UPR-tung oil
had maximum increases of 373% and 875% in impact strength and tensile
failure strain, respectively, due to the synergistic effects of phase separation
and cross-link density. The optimum amount of tung oil is 10% because a
stiffness-toughness balance can be achieved for the polymer matrix at
this point.
Ma et al.
134
used tung oil to modify rosins via a Diels-Alder addition re-
action and the modified rosins (GTR) were further used in the formulation of
glycerin esters with flexible characteristics. Increasing the amount of tung
oil resulted in a decrease in the bromine value and molecular weight, as well
as in the softening points and viscosities for GTRs. However, a slight
