Thermal Stability and Lifetime Prediction of an Epoxide Adhesive System
Epoxide systems, with diglycidyl ether of bisphenol A as the most popular representative, are known for their outstanding thermal stability. Nevertheless, lifetime predictions are indispensable for many applications. Therefore, the change of mechanical pr
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Thermal Stability and Lifetime Prediction of an Epoxide Adhesive System R. Tiefenthaller, R. Fluch, B. Strauß and S. Hild
Abstract Epoxide systems, with diglycidyl ether of bisphenol A as the most popular representative, are known for their outstanding thermal stability. Nevertheless, lifetime predictions are indispensable for many applications. Therefore, the change of mechanical properties of an epoxide adhesive system was analysed. The observed embrittlement of the system could be explained and shown by chemical degradation reactions. To determine the long-term stability accelerated testing methods had to be applied: Steel panels were bonded with a thin layer of the adhesive system and aged at elevated temperatures. Lifetime predictions were based on the adhesive strength, which can be evaluated by different methods like peeling or shearing tests. The lifetime was strongly depending on the chosen parameter for the adhesive strength. However, if only the time at the high temperature was calculated, cyclic thermal loads came to the same results as constant high temperature regimes.
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Introduction
Due to their remarkable properties epoxy resins are found today in many different fields of application. Industries for adhesives, coatings or electronics make use of these thermosetting materials [1–4]. They are commonly applied as matrices in polymer composites as well [2, 5–7]. Epoxide systems show outstanding adherence to a variety of substrates and have a good chemical and radiochemical resistance as well as a low degree of shrinkage at curing. Their excellent insulating properties in combination with a good thermal stability are beneficial for electrical applications. Still every application has its own requirements concerning processing or special properties in end-use. Since one system cannot fit all demands, there exists a range of different epoxy-based formulations. The mechanical properties can be tailored by R. Tiefenthaller (&) S. Hild Institute of Polymer Science, Johannes Kepler University Linz, Linz, Austria R. Tiefenthaller R. Fluch B. Strauß voestalpine Stahl GmbH, Linz, Austria © Springer International Publishing AG 2017 W. Grellmann and B. Langer (eds.), Deformation and Fracture Behaviour of Polymer Materials, Springer Series in Materials Science 247, DOI 10.1007/978-3-319-41879-7_21
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varying resin and hardener composition. These parameters can influence crosslinking kinetics as well [1–4, 8–11]. As binder diglycidyl ether of bisphenol-A (DGEBA) has gained greatest importance due to its low cost, easy processability and good stability caused by its aromatic structure [5, 12, 13]. In combination with dicyandiamide (DICY), which is an amine hardener with high latency, 1-K adhesive systems can be formulated [14, 15]. Although there is no doubt about the good thermal stability of epoxy systems compared to many other polymers, for many applications it is essential to determine the long-term stability of the material at increased temperatures. Testing at service
