High-Temperature Requirements of the Base Epoxy Polymer

1 High-Temperature Requirements of the Base Epoxy Polymer 

The base polymer, of course, is a key ingredient in a high-temperature epoxy adhesive system. For an adhesive to withstand elevated temperatures, it must have a high melting or softening point and resistance to oxidation. Materials with a low melting point, such as many of the thermoplastic adhesives, may prove excellent adhesives at room temperature  

FIGURE 15.2 Comparison of cured DGEBA epoxy with various other polymers in terms of weight loss after 15 h at 175°C.9 

Thermosetting adhesives, exhibiting no melting point, consist of highly crosslinked networks of macromolecules. Because of this dense crosslinked structure, they show relatively little creep at elevated temperatures and exhibit relatively little loss of mechanical function when exposed to either elevated temperatures or other degrading environments. Many of these materials are suitable for moderately high-temperature applications. 

For reasons as described above, some metal adhesive interfaces are chemically capable of accelerating the rate of oxidation. For example, it has been found that nearly all types of structural adhesives exhibit better thermal stability when bonded to aluminum than when bonded to stainless steel or titanium (see Fig. 15.3). 

---