Abstract
Resorcinol-formaldehyde resins of various moleratios (F/R=0.30.7) were prepared in the absence of catalyst.
Each sample was evacuated in order to remove water and methanol, and the infrared spectrum was measured by KBr disk method. From the spectra, it was found that the ratio of the intensities, 1170 cm-1to 1150 cm-1, and 980 cm-1 to 960 cm-1 band, varied as the mole-ratio changes.
Assignments of the 1170 cm-1 and 1150 cm-1 bands were not clear. But the 980 cm-1band was assigned to be an absorption related to the free hydrogen atom at 2-position of 4-substituted derivatives of resorcinol, and 960 cm-1 band was assigned to be due to unreacted resorcinol.
2-Substituted derivatives of resorcinol had no absorption band in the region 950 cm-11000 cm-1.
There were linear relations between mole-ratio and intensities ratio D1170/D1150 and D980/(D980+D960).
The standard deviations of the calibration curves were nearly the same, and were 0.02 by mole-ratio (F/R).
These calibration curves were used to analyze the other samples which were obtained in the presence of various catalysts.
The result obtained by using acid catalyst (HCl) was the same as that obtained under no catalyst. But a large deviation was observed when alkaline catalyst (NaOH) was used.
From the above results, a possibility to determine the structures of resorcinol-formaldehyde resins prepared by various catalysts has been pointed out. The structures found in this resin were unreacted resorcinol (a) (960 cm-1), 4-, and 4·6-substituted derivatives (b) (980 cm-1) and 2-, 2·4-, and 2·4·6-substituted derivatives (c).
The determination of the structures was carried out by their acetone solutions.
The structural difference in the resin caused by the use of different catalysts were concluded as follows: about (a) NaOH>no>HCl, about (b) no>HCl>NaOH, about (c) HCl_??_NaOH>no.
These data were useful in order to interpret the difference of physical properties of various samples.
