Mr. Rao et al., THERMOCHEMICAL CHARACTERIZATION OF PHENOLIC RESINS - THERMOGRAVIMETRIC AND PYROLYSIS-GC STUDIES, Journal of thermal analysis, 49(1), 1997, pp. 261-268
Phenol-formaldehyde resins (I and II), synthesised at a monomer feed r
atio of F/P=1.0 and 1.5, were cured at 130 degrees C for 48 h without
any catalyst (Ia, IIa), with 0.1% ferric acetyl acetonate (Ib, IIb) an
d with 0.1% p-toluenesulphonic acid (Ic, IIc). Thermogravimetric studi
es indicate that the decomposition of the cured products takes place i
n two distinct stages: The first stage (T=340-480 degrees C; alpha=0.0
45-0.16; Delta E-1=140+/-10-239+/-24 and 60+/-3-65+/-2 kJ mol(-1) for
series I and II respectively) was attributed to the predominant cleava
ge of formal linkages. The main stage decomposition (T=460-640 degrees
C; alpha=0.114-0.393; Delta E-2=115+/-8-169+/-8 and 91+/-6-103+/-7 kJ
mol(-1) for series I and II respectively) was attributed to reactions
leading to graphitisation. Delta E-2 values were correlated to the ex
tent of cure as measured by IR spectroscopy and pyrolysis-GC. The effe
ct of catalysts on the extent of cure and on the activation energy was
evaluated.