Synthesis And Properties Of Tung Oil Modified Dicyclopentadiene Unsaturated Polyester Resin

Unsaturated polyester resin modified by dicyclopentadiene （hereinafter referred to asDCPD-UPR） is a new type of unsaturated polyester resin （briefly named UPR）, themodification of the resin with renewable tung oil has important implications for extending theapplication range of DCPD-UPR, improving the developing and utilizing value of tung oil andreducing the dependence of polymer on the petroleum resources. Hydrolysis addition methodwas adopted to manufacture DCPD-UPR and the tung oil modified DCPD-UPR with excellentmechanical properties, corrosion resistance and film properties was synthesized by theDiels-Alder （D-A） reaction between tung oil and the double bond of DCPD-UPR in the laterstage of polycondensation.The structural characterization of DCPD-UPR and tung oil modifiedDCPD-UPR was determined by¹H NMR, fourier transform infrared （FT-IR） and gelpermeation chromatography （GPC）. The casting and coating properties of tung oil modifiedDCPD-UPR were examined and the optimum material proportion of casting tung oil modifiedDCPD-UPR as well as the optimal amount of tung oil for coating tung oil modifiedDCPD-UPR were determined. Meanwhile the kinetic parameter of the curing reaction ofcasting tung oil modified DCPD-UPR was investigated using differential scanning calorimetry（DSC） technique.First, DCPD-UPR was synthesized by hydrolysis addition method and characterized byFT-IR and¹H NMR. The reaction conditions were as follows: n（MA）∶n（PA）=2∶1（mol/mol）, n（PG）∶n（DEG）=2∶1（mol/mol）, the styrene content was35%（mass fraction）,addition reaction was maintained at125¹35℃for2h, the acid value of polycondensationreaction end point was35mg/g or so,0.2%phosphoric acid by weight of polyester was usedas catalyst,0.02%hydroquinone by weight of total weight of resin was added aspolymerization inhibitor, the alcohol acid mol ratio was1.08∶1.Then, tung oil modified DCPD-UPR with different tung oil content （5%,10%,15%and20%） were synthesized by the Diels-Alder （D-A） reaction between tung oil and the doublebond of DCPD-UPR in the later stage of polycondensation. The mechanical and thermalproperties of the resin were examined and the results showed that the optimum amount of tungoil was10%. The influence of various raw materials dosage on the properties of the resin was investigated and it was concluded that the optimum raw material ratios of tung oil modifiedDCPD-UPR were as follows: n（MA）∶n（PA）=2∶1³âˆ¶1（mol/mol）, n（DCPD）∶n（MA）=0.6⁰.8（mol/mol）, n（PG）∶n（DEG）=2∶1（mol/mol）, the styrene content was35⁴0%（mass fraction）.Besides, coating tung oil modified DCPD-UPR was synthesized by change the rawmaterial ratio, and the effect of tung oil content on the coating properties and the thermalstability of the resin were examined. Compared with unmodified DCPD-UPR, tung oilmodified DCPD-UPR afforded better properties such as faster drying time, excellent adhesionand flexibility, good abrasion resistance and hardness and the resin with5%（mass fraction）tung oil showed best comprehensive performance.Finally, the cure kinetics of casting tung oil modified DCPD-UPR was studied by n ordermodel. The apparent activation energy of unmodified DCPD-UPR and tung oil modifiedDCPD-UPR were75.9kJ/mol and94.0kJ/mol respectively. The curing reaction order were0.92and0.94respectively, and the pre-exponential factors were6.98×10⁹and2.19×10¹²separately. Cure temperatures of tung oil modified DCPD-UPR were as follows: the geltemperature was97.6℃, the curing temperature was107.3℃and the treating temperature was120.7℃.