Civil Engineering Reference
In-Depth Information
a) The changes in glass transition (
T
g
) measured by TMA for
the exposed specimens from different manufacturers al-
lowed identification of the various products
b) Changes in
T
g
after exposure of 14°C or less, were
considered to be minor (compared to ±8°C recommended
by CIB/RILEM)
c) No differences between the black and white EPDM were
observed for the same exposure conditions
d) The changes in the
T
g
of the EPDM obtained from TMA
were not as large as those in the percent elongation found
by load-elongation measurement
As in their previous paper, Gaddy, et al.,
[34]
attributed this to the influence of the
surface characteristics and that TMA may be appropriate for determining
bulk properties and possible changes which result from exposure.
In March 1990, a workshop on the “Applicability of Thermal
Analytical Techniques to the Characterization of Roof Membrane Materi-
als”
[37]
was convened to address the issue of incorporating thermoanalytical
methods for characterizing roof membrane materials. The consensus of the
workshop was that TA methods are valuable tools in the laboratory for
research studies and troubleshooting as well as for tracking manufacturing
processes to ensure that they are in control. However, participants con-
cluded that thermoanalytical techniques or methods did not have immediate
use in roofing standards because they could not alone provide the in-service
performance of a product. In addition, the high cost of thermoanalytical
equipment may prohibit general use of the techniques or make their
incorporation in standards unattractive.
The fact that previous research
[31]-[34][36]
on the use of
thermoanalytical techniques to characterize roof membrane materials
showed little change in the materials analyzed does not indicate that the
thermoanalytical techniques were not a useful tool. If the materials such as
EPDM selected for the study were good, no changes would be observed.
This was probably the case for the research carried out by Gaddy, et al.
[34][36]
Research carried out by Paroli, et al.,
[38]
on the effect of heat-aging on three
EPDM roofing membranes showed that thermoanalytical techniques can
provide some insight as to why some roofing materials fail more prema-
turely than others. The objective of Paroli's, et al., study was to demonstrate
the utility of TG and DMA in establishing the durability of roofing
membranes and correlating the thermoanalytical results with the mechanical
