Civil Engineering Reference
In-Depth Information
thermoanalytical group was to conduct interlaboratory testing to examine the
reproducibility of thermoanalytical techniques when applied to typical
roofing membrane materials, and to investigate further the feasibility of
using these methods for detecting changes, which occur in the aging
process.
In examining the application of thermoanalytical methods to the
characterization of roofing membrane materials, the task group defined
three criteria for selecting test procedures:
•
Testing be done under laboratory conditions
•
Results be available within a reasonable period of time
• Results be applicable to demonstrating the stability of
materials and to comparing performance of materials
under laboratory and outdoor exposure conditions
The members of the task group chose samples of EPDM, PVC, and
polymer-modified (SBS and APP) bituminous roofing membrane materials
to conduct the study. Thermogravimetry (TG), dynamic mechanical analy-
sis (DMA), torsion pendulum analysis (TPA), and differential scanning
calorimetry (DSC) were the techniques selected. The roofing materials
were tested “as received” (unaged) and after exposure in the laboratory to
heat and water submersion, and to natural weathering in climates of four
countries. The variability within and between laboratories was investi-
gated. Five, two, one, and four laboratories participated in the TG, DMA,
TPA, and DSC analysis respectively.
In September 1993, the task group issued a preliminary report
[49]
describing its activities and reporting aging conditions and experimental
parameters for each method and the interlaboratory results of unaged
roofing membrane materials. Based on their study and results from previous
research,
[31]-[48][50][51]
the Committee presented its final report in December
1995
[52]
reporting the results of studies and included recommendations for
conducting thermoanalytical methods under controlled test conditions.
The results of the inter-laboratory study showed that the exposures
produced only minor changes in the measured thermoanalytical properties.
The materials tested were generally stable under the outdoor and laboratory
exposure conditions. In the case of TG analysis of the pyrolyzable organic
constituents, it was found that the method showed rather good within- and
between-laboratory variability. The number of participants in the dynamic
mechanical/TPA analysis was limited; hence, no conclusion was made
regarding the variability within and between laboratories. In the case of
