Different phenolformaldehyde novolak resins were characterised by
various methods. Gel permeation chromatography (GPC) was used to show
the different molecular weight distributions among the different resins, as
well as to give a quantitative analysis of the lower molecular weight
species of the resin. Infra-red spectrophotometry along with GPC were
used to show that the different molecular species of the resins were
predominantly hydrogen bonded via the phenolic hydroxyl group. Thermal
analysis methods, infra-red spectroscopy and x-ray diffraction techniques
were utilised to elucidate certain characteristics of the different resins.
Differential thermal analysis, Shawbury curometry and infra-red
spectroscopy were used to study the factors affecting the cure of
phenolformaldehyde resins. By various methods it was shown that the
phenol content had marked effects on the cure properties of the resins,
affecting not only the cure rate and the cure temperature but also the
extent of cure. Further investigations into the reaction of phenol with
hexamine indicated that the initiation of cross-linking by hexamine
decomposition was not solely a heat dependent process. By varying the
water content of phenolic resins it was shown that the water content
affects both the cure of the resins and the formation of low molecular
weight intermediates. Various methods of heat treating resin:hexamine
mixtures indicated that under certain conditions components of a
molecular weight intermediate between phenol and dihydroxydiphenylmethane
could be produced.
Finally a selection of commercially available moulding powders
was obtained and the resin constituents characterised by the methods used
previously for pure resin samples. From these results an attempt was made
to predict the cure properties of the different moulding powders and to
show how differences in the moulding powder compositions affects the
moulding behaviour of these compounds.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.