|
The overall objective was to develop a better quantitative
understanding of the mechanism of surface degradation of
polymeric materials and to develop improved test methods for
characterising environmental attack on polymeric surfaces.
The study concentrated on the effect of artificial weathering
cycles on the degradation of three formulations of window-grade
PVCU. The results were compared with samples which had been
naturally exposed for up to 16 years. Microhardness, filler loss,
carbonyl index, colour and gloss were used as measures of
degradation.
Samples tested in the laboratory exhibited surface degradation
and partial recovery predicted for these materials. Cyclic
variation of some properties was exhibited at long laboratory
exposures. However, naturally exposed material gave no definitive
indication of a recovery process. The techniques employed gave
reasonably consistent indications of degradation, particularly
with regard to the onset of partial recovery.
The complexity of the degradation process for these materials
inherently limits the establishment of quantitative rate
equations to predict durability of naturally exposed materials.
Nevertheless, four of the five cycles evaluated gave reasonably
consistent ranking of the different materials which compared well
with the ranking deduced from natural exposure. An optimum
artificial weathering cycle was derived.
It is recommended that laboratory tests should involve testing
of a reference sample in parallel for the purposes of quality
control, inter-laboratory comparison and, by choosing a material
with known outdoor history, as a basis for prediction of relative
service life.
Further Information
If you are interested in this, or any other project, please contact Richard Holman.
|
