| The cure kinetics and cure behavior of phenolic novolac resin with epoxy resin and with cyanate ester were compared with conventional hexamethylenetetramine (HMTA) curing agent, by means of DSC. Novolac-epoxy and novolac-cyanate systems offer volatile-free cure processes as well as higher thermo-oxidative stability. It was found that these two systems had higher reactivity, longer gel times and wider process windows than a conventional novolac-HMTA system.; The study revealed that the reaction rate expressions could be described as follows:(UNFORMATTED TABLE OR EQUATION FOLLOWS){dollar}{dollar}vbox{lcub}halign{lcub}#hfil&&quad #hfilcr Novolac-epoxy &{dollar}rm dalpha/dt=1.7times10sp6 exp ({lcub}-{rcub}59/RT)(1-alpha)sp{lcub}0.96{rcub}{dollar}cr Novolac-cyanate &{dollar}rm dalpha/dt=2.2times10sp8 exp ({lcub}-{rcub}76/RT)(1-alpha)sp{lcub}1.21{rcub}{dollar}cr Novolac-HMTA &{dollar}rm dalpha/dt=2.3times10sp{lcub}15{rcub} exp ({lcub}-{rcub}126/RT)(1-alpha)sp{lcub}1.66{rcub}{dollar}cr{rcub}{rcub}{dollar}{dollar}(TABLE/EQUATION ENDS)The results of the calculation correlated well with the experimental data obtained by dynamic temperature scans at constant rate.; The effect of HMTA concentration was also examined. There was an orderly increase in heat of reaction with HMTA/novolac molar ratio up to 1.0; above this value, heat of reaction decreased again. |
