¹³C‐NMR‐Untersuchungen an Phenol‐Formaldehyd‐Harzen

Abstract

Mit Hilfe empirischer Substituentenparameter wurden die %-NMR-Spektren von zehn hIodellverbindungen, die 'als Zwischenprodukte bei der Phenol-Formaldehyd-Reaktion auftreten, berechnet und interpretiert. Durch vergleichende Betrachtung der cbemischen Verschiebungen der Modellverbindungcn lieljen sich fur die in Phenolharzen vermuteten Strukturelemente die Resonanzbereiche im Spektrum festlegen und erste Aussagen uber den aufbau und die Reaktionen einiger Harze treffen.IlapaMeTpOB 3aMeCTHTeJIefi 6b1nn BbIWiCJIeHbI H HHTepIIpeTHpOBaHbI CIIeKTpbI RMP l3C EeCHTH MOAeJIbHbIX COeEHHeHHfi, RBJIRRIqHXCFI IIPOMeXYTOYHbIMH IIpOAyKTaMH PeaKVHH @eHoJIa C (#OpMaJIbaerH~OM. CpaBHeHHeM XHMHYeCKHX CABIWOB MOAeJIbIIbIX COeAHHeHMfi 6~~1 1 2 OIIpeJ(eJIeHb1 pe30HaHCHbIe 06nac~a AJIH OXHEaeMbIX B QeHOJIbHbIX CMOJIaX CTPYKTYPHbIX 3JIeMeHTOB H AaHbI HH@OpMaqHH 0 CTpOeHHH H peaKqHFIX HeKOTOpbIX CMOJI. 13C-NMR investigations with phenol-formaldehyde resinsVia empirical substituent parameters the 13C-NMR spectra of ten model compounds which are intermediates in the phenol-formaldehyde-reaction were calculated and interpreted. Comparing the shifts of these model compounds it is possible to assign the resonance ranges of structural features expected in phenolic resins and to achieve information on structure and reactions of some studied resins.

A 13C NMR study of the methylol derivatives of 2,4′‐ and 4,4′‐dihydroxydiphenylmethanes found in resol phenol–formaldehyde resins

“…The bridge methylene chemical shift values have been used 4,8,9 as the easiest way to evaluate the amount and type of diphenylmethanes present in the various stages of cure found in PF resins. A methylene between two 4-hydroxyphenyl rings comes at 40.97 š 0.14 ppm, a methylene between a 4-hydroxyphenyl ring and a 2-hydroxyphenyl ring comes at 35.32 š 0.14 ppm, and a methylene between two 2-hydroxyphenyl rings comes at 30.5 ppm in acetone-d 6 .…”

“…6,7 Additional methylol groups can be added to these dihydroxydiphenylmethanes by further condensation reactions with formaldehyde. 4,8 Earlier, we reported a 13 C NMR method for the analysis of resol PF prepolymer resins based on nine model compounds. 9 In order to analyze the next cure stage (called prepreg) more comprehensively, it was necessary to extend the range of model compounds to include the methylol derivatives of the dihydroxydiarylmethanes, which are common intermediates found in this cure stage.…”

Optimizing the conditions of quantitative13C-NMR spectroscopy analysis for phenol-formaldehyde resol resins

“…[2][3][4][5] Solvent effects can be seen at 87.2-87.7 ppm in DMSO-d 6 , and it was also found in acetone-d 6 at 88.5-89.2 ppm. The intenin the spectra measured in different solvents (Table I).…”

“…the chemical structure of resins. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Due to the The raw materials of resins, phenol (purchased long spin-lattice relaxation times the measurefrom J. T. Baker) and formaldehyde (produced by ments of 13 C-NMR spectra of phenol-formaldeDynoresin Oy from methanol), were of high puhyde resins are quite time consuming to obtain rity grade. Formaldehyde was used as a formalin reasonable signal to noise ratios.…”

13C‐NMR‐Untersuchungen an Phenol‐Formaldehyd‐Harzen. 3. Zur Bildung von Dimethylenetherstrukturen in Phenol‐Resolen

“…Untersuchungen von YEDDANAPALLI und FRANCIS [6, 71 bestatigen dieses Ergebnis. Eine von den Autoren gemeinsam mit GRUNDEMANN vorgenommene Zuordnung der 13C-NMRSignale zu Strukturen in Phenolharzen ermoglicht, zwischen Hydroxymethylgruppen, Halbacetalen und Dimethylenethergruppen eindeutig zu unterscheiden [8]. In Resolen, die aus 1 mol Phenol, 1 mol Formaldehyd und 0,07 mol Katalysator bei 98OC nach 90min erhalten wurden, sind nur bei Magnesiumoxid-Katalgse Dimethylenetherstrukturen nachweisbar (sehr schwaches Signal bei 69 ppm im W-NMR-Spektrum).…”