EAP - Proceedings of the Estonian Academy of Sciences

PUBLISHED
SINCE 1952

proceedings
of the estonian academy of sciences

ISSN 1736-7530 (Electronic)
ISSN 1736-6046 (Print)

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Structure and curing mechanism of resol phenol–formaldehyde prepolymer resins; pp. 225–232

PDF | doi: 10.3176/proc.2010.3.05

Authors

Peep Christjanson, Tõnis Pehk, Jane Paju

Abstract

Prepolymer resol resins with different phenol/formaldehyde/NaOH molar ratios were synthesized and characterized by technical analysis as well as by ¹³C NMR spectra for samples in CD₃OD solution. Larger amounts of NaOH promoted the binding of formaldehyde and para substitution including the formation of benzoquinone rings with two o, p'-methylene groups in the para position. The polycondensation between ortho-hydroxymethyl groups and one-substituted aromatic para positions as the main thermosetting curing process continued in the heat treatment of resol resins. The self-condensation between ortho-hydroxymethyl groups, the release and oxidation of formaldehyde, and the formation of hemiformals are processes of low significance in curing resol resins. The assignment of ¹³C NMR resonances depending on the presence of phenolic hydroxyl groups, phenoxide ions, and substituted quinone rings is discussed.

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