Polyurethane−Epoxy Composites: Recent Developments and Future Perspectives

Composites are engineered materials used for advanced applications. Research on polyurethane (PU) composites has increased because of their versatile properties, including a broad array of characteristics such as chemical resistance, tensile strength, processability, and thermal stability for applications in the production of foams, elastomers, coatings, fibers, and other materials. On the other hand, epoxy (EP) resin is a thermoset with biodegradability, lightness, reduced cost, and favorable mechanical, adhesive, and chemical properties and can be used in coatings, adhesives, and matrices for advanced composite materials. Exclusive properties such as mechanical, thermal, and chemical properties of PUs (thermoset/thermoplastic) can be fabricated by the reactions from various nanomaterials that result from cross-linked PUs. One of the biggest challenges that researchers face is achieving the appropriate interfacial bonding with enhanced thermal and mechanical properties that will lead to product formation and development. Composites that exhibit superior thermal and mechanical properties could find more industrial applications and would have widespread commercial acceptance. This is difficult because of the hydrophobicity of polymers and hydrophilicity of fibers such as PU. In order to conquer such limitations, PU phase can be integrated into the EP network for toughening. Significant research has already been carried out to introduce a second reactive polymer onto the matrix for generating interpenetrating polymer networks. EP resins are usually rigid and brittle with a lower crack resistance. Consequently, the mechanical properties, thermal resistance, glass-transition behavior, and damping features of PU will also be enhanced by the introduction of EP to form PU/EP interpenetrating polymer network structures. It has been reported that different modifiers are employed to modify the properties of PU/EP interpenetrating polymer networks, such as conducting polymers, fibers, and montmorillonite nanoclay. The PU/EP cross-linked networks exhibit a wide range of high-performance applications in aircraft machines, engineering materials, ion-exchange resins, biomedical devices, and other commercial interpenetrating polymer network products. This chapter will be dedicated to discussing various types of PU/EP composites. In this chapter, comprehensive assessments about PU and its EP polymer composites are presented. The chapter also focuses on the effect of several natural and synthetic fibers on PU-based polymer composite products. In addition, the chapter illustrates the effect of nanocomposites for the enhanced interfacial bonding between PU/EP matrices for developing advanced materials with improved thermal and mechanical properties.