Nonisothermal Curing Behaviors of Novolac-Type Phenolic Resins of Varied Ortho to Para Ratios

Abstract

Novolac resins of varied ortho to para (O/P) ratios were prepared and characterized with FTIR and ¹³C-NMR. The nonisothermal curing reactions of these novolac resins with hexamethylenetetramine (HMTA) were studied in detail using a dynamic differential scanning calorimetry (DSC) technique at a series of heating rates. The global activation energies of the reactions were determined with the Ozawa, Kissinger methods, respectively; additionally, Kissinger-Akahira-Sunose (KAS) isoconversional kinetic approach was used to obtain activation energy as a function of conversion. The results showed that the peak temperatures of the exothermic reactions and global activation energies decreased with increasing O/P ratios, which indicated that the higher the O/P ratio was, the faster the curing speed. In addition, the results from the KAS analysis exhibited that the activation energies increased quickly with conversion at the later reaction stage, which was likely associated with the diffusion-controlled kinetics.

Keywords:

• Activation energy
• Curing reaction
• Differential scanning calorimetry (DSC)
• Novolac resins
• O/P ratios

ACKNOWLEDGMENTS

The authors would like to appreciate the financial support of this work from the foundation of JiaXing city technological plan under Grant No. 2009AY201 and ZheJiang Province “NewMiao” talent plan.