Page 651 - Handbook of Thermal Analysis of Construction Materials

Section 4.0 - Applications 619

properties. Three commercially available non-reinforced EPDM roofing
membranes were selected for the study. They were heated in air-circulating
ovens to 100°C and 130°C. Specimens were removed from the oven after 1,
7, and 28 days.
Thermogravimetry (TG) was used to measure the weight loss of the
unheated and heated specimens. The glass transition temperature was
measured by DMA and tensile testing was used to measure the mechanical
properties of the specimens before and after heating. The TG results
showed that degradation of the unheated (control) and heated EPDM
specimens from two of the manufacturers occurred in one step (52–54%)
in the 300–500°C range, which is well above the aging temperatures used
in the study. Hence, no significant changes were observed between the
unheated and heated specimens. This supported the findings reported by
other researchers and discussed above.
The EPDM specimens from the other manufacturer showed, how-
ever, two-step degradation with 20% of the unheated (control) material
being volatized between 150° and 430°C while the polymer decomposition
(22.5%) occurred in the 440–550°C range. The lower temperature weight
loss was attributed to the loss of oils and/or plasticizers of low volatility,
which are typical ingredients in EPDM roof membranes. It was observed by
TG that the specimens heated at 100°C and 130°C displayed a decrease in
the oil content with exposure time. For example, after 28 days at 100°C,
only 4.9% was detected (~75% of oil was lost during the heat treatment)
compared to 13.2% (~ 34% oil lost during heat-aging) after 1 day of the
same heat-treatment. Similarly, after 28 days of heating at 130°C, only
1.6% (~ 92% oil lost) was detected versus 5 % of oil (75% oil was lost during
heat aging) after 1 day of heating. The TG results also showed (Fig. 1) that
there was an increase in the polymer loss with decreasing oil loss for
specimens from this manufacture. An increase in hardness was also
observed.
The dynamic mechanical analysis results for the EPDM roof
membrane samples from the three different manufacturers (S1, S2, S3)
showed a similar trend to that observed by TG. The glass transition
temperature (T ) of the unheated specimens from S1 and S2 manufacturers
g
was -49° and -46°C, respectively. The T of heated specimens did not

g
change significantly (-48° to -42°C range) even after 28 days of exposure
at 100° and 130°C. As predicted by TG, the EPDM specimens from the S3
manufacturer showed an increase in T with the number of days of heating.
g
For example, the T changed from -61°C for the unheated to -46°C after 28
g
days at 100°C and to -43°C after 28 days at 130°C.