Thermal Properties

Vectran®, HT shows robust performance in a broad spectrum of responses to thermal loading.These responses are summarized below and in Table 3:

• Good LOI (equivalent to aramids) and low smoke generation
• Low thermal shrinkage (hot air,boiling water and laundry)
• No dripping in vertical flammability tests
• Good strength retention after hot air and radiant energy exposures
• Low,negative coefficient of thermal expansion
• Excellent property retention in a broad temperature range
• No measurable volatile condensable mass (VCM) and 0.3% maximum weight loss (TML or TWL) in testing for aerospace applications (see also “Offgassing/Outgassing”)

Mechanical property retention during or after thermal exposure is a key concern in many applications. Most commonly, high temperatures are encountered during a downstream processing step, such as coating or laminating. Care must be taken to minimize line tensions or other mechanical loads during the high temperature step. Figure 3, which describes Vectran's®,  tensile strength at temperature, should be used as a reference in selecting process conditions. For high temperature processing at low mechanical load, Figure 4 shows that Vectran will have excellent strength after processing; in fact, superior to aramids.
 

Figure 3: Strength At High Temperatures: Simultaneous Mechanical and Thermal Loading	Figure 4: Strength After Thermal Exposure 24 Hour Exposure To Temperature, Followed by Testing at Ambient Temperature

For end uses that call for longterm or cyclic thermal exposure, Vectran®,  can also offer increased product lifetimes. Figure 5 illustrates that Vectran™ has little-to-no strength loss in cyclic exposures to 120°C. Vectran’s™ resistance to cyclic thermal loads is confirmed at higher temperatures in Figure 6, which also illustrates Vectran’s™ superiority to aramids in this respect. Note that the aramid in Figure 6 suffered 30% strength loss in roughly a dozen 8-hr cycles, or 4 days of exposure (in total). Similar trends are observed when Vectran® is held at 250°C continuously (Figure 7) and after 120°C steam exposure (Figure 8).
 

Figure 5: Vectran® HT Tenacity vs Cycles At Temperature	Figure 6: Vectran® HT 1500/300 Filament Yarn Tenacity – Cycles at 195°C
Figure 7: Tenacity After Thermal Exposure (250°C)	Figure 8: Tenacity After Steam Exposure (120°C)

 Vectran® fiber's performance at low temperature was evaluated by ILC Dover during the design of the airbag system for the 1997 Mars Pathfinder mission. ILC reported that Vectran® actually increased in strength in tests at -62°C, leading to its selection for the airbag fabric and external assembly tendons (Development and Evaluation of the Mars Pathfinder Inflatable Airbag System, D. Cadogen et al, ILC Dover,Inc., 49th International Astronautical Congress, 1998.) This distinguishing characteristic of Vectran® is shown in Figure 9. 

Figure 9: Low Temperature Properties of Vectran® Fiber

Vectran®,  has a low, negative coefficient of thermal expansion (Table 5). This is particularly beneficial for dimensional control of composites. Thermal conductivity properties are given in Table 6.