A study on carbonization of phenol-formaldehyde resin labelled with deuterium and 13C

The carbonization mechanism of phenol-formaldehyde resins has been studied by using three types of isotope-labelled resin, which hold (1) deuterium atoms in hydroxyl groups, (2) deuterium atoms in methylene groups, (3) 13C atoms in methylene groups, respectively. The resins were carbonized in vacuum, and evolved gases were found to consist mainly of water at temperature below 400°C, whereas of water, methane, carbon monoxide and hydrogen above it. The isotope ratio was determined using a mass spectrometer. From the D/H ratio in water produced at temperatures below 400°C, it is concluded that the dehydration process involves two major reactions: a series of curing reactions and dehydration between methylene and hydroxyl groups. Also, from the 13C12C ratio in methane and carbon monoxide produced from the 13C-labelled resin, it is suggested that methane comes mainly from the methylene groups, while carbon monoxide from the benzene rings. Using this information, the carbonization mechanism is discussed in detail.