Biomedical Engineering Reference
In-Depth Information
physical properties. The results revealed that soy polyols react similarly to synthetic polyols,
and the foams prepared with MDI were more rigid than those synthesized with TDI. Guo
and co-workers (2002) reported that the rhodium-catalyzed hydroformylation resulted in a
polyol with 95% conversion producing rigid polyurethane, while the cobalt-catalyzed reac-
tion gave a polyol with 67% conversion leading to a material with lower mechanical strength.
Recently, a similar route, but with partial esterification of the hydroxyl groups with formic
acid, was also examined (Petrovi ´ et al ., 2008). In addition to hydroformylation, soybean oil
epoxidation followed by ring opening with methanol (Guo et al ., 2006 ; Lu and Larock,
2008) or phosphoric acid (Dwan'Isa et al ., 2003 ) and ozonolysis (Petrovi ´ et al ., 2005 ) are
other methods for synthesizing polyols.
The soybean oil-based polyols were studied in detail in order to establish structure-
property relationships of the polyurethanes produced thereof. The polyols synthesized
through hydroformylation, bearing primary alcohols, showed higher reactivity towards PU
formation and resulted in less rigid PU materials than those obtained through epoxidation.
On the other hand, the polyols synthesized from soybean oil via ozonolysis, free from long
pendant alkyl chains, resulted in PUs which displayed better mechanical properties and
higher T g . A different approach to synthesize PUs from soybean oil excluding isocyanates is
the cyclic carbonation of epoxidized soybean oil (ESBO) (Türünç et al ., 2008 ) (Figure 11.8 ),
a successfully commercialized product, and curing with primary amines to yield
-hydroxy
urethanes (Tamami et al ., 2003 ; Javni et al ., 2008 ). Additionally, thermal and mechanical
properties of these polyurethanes were enhanced by incorporation of silica nano-particles
via nano-composite formation (Türünç et al ., 2008 ).
Eren and co-workers (2003) modified soybean oil via anhydride functionalization of the
double bonds and polymerized the resulting monomers by polycondensation with low
molecular weight polyols and long diols (Figure 11.8). These polyesters, which were resil-
ient soft rubbers at room temperature, could find application as adhesives, film formers,
textile and paper sizes, and tackifiers.
In 2008, Biswas and co-workers reviewed nitrogen containing monomers, for example fatty
amines, fatty amides, fatty imidazolines, and polymers (PUs) made from soybean oil-based
β
G = Glycerol
O
G
O
Soybean oil
Epoxidation
Maleination
O
O
O
O
O
O
G
O
G
O
Cyclic carbonation
+
O
Regioisomers
O
O
O
G
O
Figure 11.8 Modification possibilities of soybean oil (G: glycerol moiety with two more fatty acid
derivatives attached).
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