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The objectives of the work were to co-ordinate PRA, industrial
and academic resources to gain insight into how the air drying
mechanism of paint films is influenced by the choice of driers
and ambient conditions. The ultimate aim was to guide paint
formulators in the selection of drier systems that perform well,
even under conditions of low temperature and high humidity.
A variety of experimental techniques were employed, from
simple manual drying time tests to the use of the SERC 90 metre
Synchrotron Radiation Source, to study the chemistry of drier
materials in alkyd films.
The nature of the ligands in the immediate vicinity of cobalt,
lead and zirconium atoms were studied using Extended X-ray
Absorption Fine Structure (EXAFS) and Small Angle X-ray
Scattering (SAXS) in what is believed to be one of the first uses
of these techniques by the paint industry.
The main reason for the differences in the behaviour of
auxiliary driers would appear to be that different drier systems
give rise to different reaction routes. Some of these routes lead
to structures with high crosslink density which characterises the
hard dry state while others yield products where polymerisation
is terminated prematurely.
One of the most intriguing findings of the whole study was the
evidence that during alkyd autoxidation, most of the
polyunsaturated fatty acid chains undergo scission to leave C(9)
residues in place of the initial C(18) moieties. The loss of this
plasticising component must have a major effect on the physical
properties of the cured film.
Further Information
If you are interested in this, or any other project, please contact Richard Holman.
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