Infrared Studies of Carbons-VII. The Pyrolysis of a Phenol-Formaldehyde Resin

摘要

Infrared spectra were recorded of the chars produced by pyrolyzing a Novolac phenol-formaldehyde resin in vacuum and in nitrogen, using photothermal beam deflection spectroscopy. The two pyrolysis techniques led to the same results. Thermal branching and cross-linking occurred near 350 C, with the formation of diphenyl ether structures. These reactions continued at higher temperatures when aryl-aryl ethers were formed. Auto-oxidation is not an important degradation pathway. Although some changes occur, the polymer network remains essentially intact until 500 C, the aromatic systems being held apart and stabilized by aliphatic bridges. In the 500-560 C range, however, drastic changes occur in that the network collapses, aliphatic bridges are destroyed, hydrocarbonaceous residues are eliminated and those remaining are altered, polyaromatic domains form, and the resulting char is much like other intermediate temperature chars.