Contributions to the dynamic-mechanical thermoanalysis of adhesives

The transition zones of polymers can be described with respect to the mechanical properties and their changes by means of the dynamic mechanical thermoanalysis (DMTA). This mechanical spectroscopy sensitively shows changes in the polymer structure and thereby gives essential information for characterisation, development and qualification of adhesives. The possibilities to control the secondary transition with suitable plasticizers is shown for model systems based on epoxy resins. The changing of the softening characteristic in the primary and the secondary relaxation zones, caused by the diffusion of water, is demonstrated. The redrying of the specimen during the test is shown in isothermal measurements. The real progress in curing in the bondline is characterized by isothermal measurements of bonded steel sheets. This method is also used to descrirbe the thermomechanical properties of anaerobic adhesives.