Influence of fillers on epoxy resins properties: a review

Epoxy resins (ERs) are one of the main types of resins used as structural adhesives; however, they present some weakness, which are mostly related to their highly cross-linked network after the curing process. Low electrical and thermal conductivity and low fracture toughness are the major drawbacks of these type of materials, and several efforts have been made over the past few years to overcome them. A critical survey regarding the use of different fillers in ERs systems and the outcome is highlighted and discussed in the present review. The incorporation of fillers into ERs matrix is one of the most successfully explored alternatives to improve the properties of ERs. It is worth to mention that even though ER composites are a widely explored topic, few reports have been focused on a compilation of the most relevant fillers and the main changes on ERs composites performance. Therefore, the present review gives an overview of a vast selection of fillers—natural, metallic, carbon fillers—incorporated in ER matrices to enhance or to meet the requirements for a desired application, such as the increase in the final adhesive toughness. The combination of the top characteristics of fillers and polymers is accomplished, leading to high-performance composites. Among the most promising fillers, carbon nanomaterials, fiber-reinforced polymers, carbon fiber-reinforced polymers, biofillers and metallic and ceramic fillers are described which have the ones having higher application potential. The influence of the addition of these different types of fillers in ERs system properties such as flame retardancy, mechanical and thermal and electrical performance is discussed and reviewed in detail.