Abstract
The process of curing epoxides with amines has been for many years a route to obtain many useful materials, from everyday substances such as adhesives right through to thermoset resins used in advanced composite manufacture. This work will try to highlight how a combination of chemical and numerical techniques come together to aid the further understanding, of what is an extremely complex reaction. Chapter 1(a) is a general review of epoxy resin curing chemistry, paying particular attention as to how our understanding of the process has developed over several decades, and highlights the various techniques used to study the reaction. Chapter 1(b) describes the experimental approach taken in this work, namely that of using model reactants in combination with radiochemical techniques in order to gain kinetic information about cure reactions. In Chapter 2 the development of the various kinetic models is discussed. It is first described how, and on what basis, various aspects of the cure chemistry are incorporated into the model. One then goes on to describe the numerical analysis applied to the rate equations, and how this is incorporated within the model. The results of the two major aspects of the work are divided into two distinct areas. The first (Chapter 3) deals with the modelling of those reactions using a low initial concentration of primary amine (usually <0.6M). These systems are devoid of many of the complicating features of cure reactions, and are shown to be modelled to a high degree of accuracy. In essence they are ideal systems, and ones which the initial model (KINET31) used in this study is able to describe. Chapter 3 also describes some studies carried using aromatic diamines, and the modelling performed of these reactions. Chapter 4 on the other hand deals with those reactions which used high initial amine concentrations. By contrast the standard of modelling shown here with KINET31 was much poorer. It is then described how various physical aspects of the cure reaction are investigated in an attempt to highlight the model's inadequacy. It is eventually shown how H-bonding of species, and the formation of pre-complexes, can play a very significant role in cure reactions. When the model is adapted to take these interactions into account a significant improvement is noted (KINET31H). Finally Chapter 5 deals with another interesting aspect of cure reactions, namely that of accelerators. With the model now taking into account the formation of the most are. significant pre-complexes, the reactivities of various -OH type accelerators are investigated.