Use of Rosin Acids as Rigid Building Blocks in the Synthesis of Curing Agents for Epoxies - Rosin-based Chemicals and Polymers - page 9

groups of BTCA have similar reactivity with epoxy due to the electronic effect of
the phenyl ring, therefore only one wide exothermic peak was noted in curing of
epoxy with BTCA. Based on the temperatures of the exothermic peaks, BTCA and
MMP seemed to be slightly more active than MPA and CHDA, respectively, towards
reacting with epoxy.
DER332/CHDA
DER332/BTCA
DER332/MMP
DER332/MPA
Temperature (°C)
Figure 1.7 DSC thermograms of nonisothermal (5 °C/min) curing of DER 332
with different curing agents. Reproduced with permission from X. Liu, W. Xin and
J. Zhang, Green Chemistry, 2009, 11 , 1018. 2009, Royal Society of Chemistry
[6]
Figure 1.8 shows the results of thermodynamic mechanical analysis (DMA) of the
cured DER332 with these curing agents. In the glassy state, MMP- and MPA- cured
DER332 exhibited a very similar storage modulus to that of their petrochemical
counterparts, CHDA- and BTCA- cured DER332, respectively ( Figure 1.8a ). However,
the epoxies cured with rosin-derived curing agents exhibited a lower modulus in the
rubbery state. This result might be attributed to the bulky hydrogenated phenanthrene
ring of rosin acids which reduced the crosslink density of the cured resins. The resin