Abstract
Curing behavior of resol in the presence of p-toluenesulfonic acid (PTS) or sodium hydroxide (NaOH) has been studied by Torsional Braid Analysis (TBA).
Resol (molar ratio of P/F was 1/1.2) prepared using NaOH as catalyst was pretreated with ion-exchange resin (Amberlite IRC-50) to eliminate the catalyst, and various amount of PTS or NaOH methanolic solutions as curing catalysts were added to the resol and pH of these resols were measured respectively.
The curing behavior of these resols were examined by TBA at constant temperature or at a heat programming rate of 1°C/min in air, respectively. In lower and higher pH region of resols, gelling and curing rate were much accelated compared with neutral region such as pH 4-6, and PTS was more effective than NaOH on gelling and curing of the resols containing same equivalent amount of each catalyst.
The order of apparent activation energy of the curing rates were as follow :
Resol with NaOH>with PTS> Without any catalyst
These results suggest that the curing reaction mechanism of resol in an alkaline region is considerably differ from those in an acid region.
