Flow and Cure of an Aerospace Adhesive

The rheological changes in a material during complex thermal histories can provide valuable information about processing, chemical structure, and end-use performance. Dielectric analysers can characterise dramatic and rapid changes in a polymer s physical state, even into the final stages of cure, which can significantly influence the physical and chemical properties of the finished product. 

As the temperature is held isothermally at 80 °C for 30 minutes, log e remains constant. Then, between 60 and 75 minutes as heat is applied at a rate of 1 °C/min, temperature-induced fluidity causes the viscosity of the resin to decrease. After 75 minutes, the resin polymerises and develops a three-dimensional network, as indicated by the decrease in log e . 

By comparing log ionic conductivity profiles with loss factor measurements, the operator can identify the window in the process during which the material is fluid (and therefore workable), develops molecular weight and crosslinks (which is critical to product performance and appearance), and is completely cnred (which identifies the proper time to demonld the product or remove jigs). The dielectric analyser can also record the dielectric properties of the resin dnring cooling. 

---