Table 1. Listing of materials selected for evaluation

How Can We Compare These Materials?

Tensile strength will be tested, just like before, to understand how elevated temperatures affect the mechanical properties of these materials. Mechanisms here can occur at different scales. At elevated temperatures, however, the mechanisms are similar to those mentioned in the weathering test. See Figure 1 for some examples of mechanism for degradation at elevated temperatures.

Experimental Test Set-Up

Four groups of samples were tested, all differing by the temperature the samples were subjected to for 21 days. See Figure 2 for the breakdown of groupings. Tensile strength was determined by a modified version of ASTM D638.

Results

It should be noted that typically fabric, elastomeric and non-elastomeric samples follow different protocols when measuring tensile strength. The values here should only be regarded as qualitative values for comparison, rather than actual values of measured tensile strength.


In this test, FEP-5 showed the most stable behavior. FSR-16 showed stable behavior after an initial increase from baseline at 50°C. Both 63-20 and PFR were not able to be tested at 150°C. PFR melted to the pan used in the oven and 63-20 was so brittle, that when placed into the grips for tensile testing, the samples crumbled. VHNLT-23 showed the largest decrease in tensile strength at 150°C. This isn’t surprising since this material is better suited for low temperature environments. Trevira and PVL-10 had similar tensile behavior, where the tensile strength significantly dropped off at 150°C. RPH-14 showed an initial increase, then held somewhat steady before decreasing at 150°C.