Tailoring of epoxy material properties

Abstract

This research work is aimed to understand the effect of resin chemistry on the physical properties (e.g. moduli, viscoelasticity, moisture uptake, coefficient of thermal expansion) of cured aromatic epoxy-amine thermoset resins. This understanding will result into a good first approximation of the final properties. As a consequence in future it will be possible to design a resin with a well defined set of material properties. Although this research work cannot be generalized to all kinds of polymeric materials, it gives the knowledge to understand and predict the properties within the class of polymeric materials being under consideration. Motivation Look at the bottles of commercially available resins and hardeners and you will find that they are specified with the properties such as equivalent weight, functionality (f) and purity. The properties specified on the bottles of the same kind of resins and hardeners are not always the same. It is mainly because of batch-to-batch variations during the production of the resins and hardeners. Also initial properties such as the mixing ratio and the initial conversion can vary due to the processing schedule in the production unit. Small changes in these initial properties can lead to large changes in the final physical properties of the cured resin. For example if the average functionality of the reacting mixture is changed from 2 to 2.1 the final reacted product will change from thermoplastic to thermoset. So, the motivation behind this research is to understand the effect of batch-to-batch variation in the initial properties (i.e., average functionality, mixing ratio, cure schedule) of a resin-hardener mixture on the final properties of their cured products. The materials that are used for high-tech applications such as in aerospace and electronic industry must satisfy stringent specifications regarding dimensions and high temperature behavior. Usually, the materials used in the high-tech applications contain epoxy as adhesive layer or as matrix material. Hence any change in the initial epoxy composition immediately affects the end properties of these materials. Batch-to-batch variations can easily occur in the suppliers’ production process. An additional advantage of the present study on the effect of resin chemistry on the physical properties is that a good base for future molecular dynamics simulations on epoxy materials is obtained. Aim The aim of the present study is to understand the effect of the initial resin composition on the final properties of their cured products. This understanding will result in a good estimate of the final properties of polymeric materials and thus can help to save time by rightly choosing the initial components without the need of a full experimental characterization. If a good understanding of the relation between the resin chemistry and final properties is known it will be possible to tailor the properties to the customers’ demands.