Low-Temperature Epoxy Adhesives and Sealants

Most conventional low-modulus adhesives and sealants, such as polysulfides, flexible epoxies, silicones, polyurethanes, and toughened acrylics, are flexible enough for use at intermediate low temperatures such as -40°C. Low-temperature properties of common structural adhesives used for applications down to -129°C are illustrated in Fig. 15.9, and the characteristics of these adhesives are summarized in Table 15.12. 

When the epoxy adhesive cannot be made flexible enough, the thermal conductivity and thermal expansion coefficient are controlled by appropriate fillers. General-purpose room temperature cured epoxy-polyamide adhesive systems can be made serviceable at low temperatures by the addition of appropriate fillers to control thermal expansion. 

Modified epoxies are generally selected for lower-temperature applications. The unmodified epoxy-based systems are not as attractive for low-temperature applications as some 

FIGURE 15.10 Tensile shear strength versus temperature for aluminum-filled DGEBA epoxy cured with DEAPA.21 

Advantages Highest shear strength in cryogenic range Uniform properties moderate cost RT cure easy handling low cost Adhesion to many materials easy handling 

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