High Temperature Polymer Nanocomposites

Abstract

The chapter on High Temperature Polymer Nanocomposites mainly covers the advancements made in the research on varied composite materials and their novel innovations for high temperature applications. The chapter begins with a prelude on existing polymers of thermoplastic or thermosets and also a combination of the two to exploit the dual advantage of both high temperature thermoplastics and thermosets. The polymer composites are developed and implemented for varied temperature regimes in the range of 120–250°C, 250–350°C specially suited for aerospace applications. Further research work is under progress to explore the material suitable for temperatures above 350°C. The initial section explains on the applicability of polymer composites having matrices such as either liquid crystalline polymer, cyanates, polyimides or bismaleimides which are reinforced with either the carbon, glass or aramid fibres especially continuous fibre which provides improved material and physical properties. The polymer-composites are assessed for performance of the matrices and the composites not only for their strength or stiffness but also for their resistance to cracking, minimum loss of weight, brittleness due to cross-linking and other properties that may degrade the performance of the composites over the long period of high temperature applications. This section mentions on the literature reviews having come up with research in progress on other types of resins for high temperature applications namely the oligomers such as the acetylene terminated polyimides or the norbornene terminated polyimides. The second section is concerned with the polymer-nanocomposites for high temperature applications. In this section, the role of nanofillers in the enhancement of composite properties is discussed. The various forms of nanofillers are the nanoclay, nanofibres, carbon nanotubes, Polyhedral OligoSilsesquioxanes (POSS) and nano-oxides where they reinforce polymer chain at molecular scale as against the carbon fibres of macroscopic scale seen in polymer-composites. In a nanocomposite the thermal properties depends on the filler’s nature, rate and dispersion in a matrices. The applications have been as fire retardant materials or for re-entry applications in aerospace vehicles. Research on nanofillers is still at its nascent stage that ample scope is available for exploring the potential of various nanofillers for high temperature applications and as fire retardant materials. Some polymer thermosets such as PMR-15 (Polymerization from Monomeric Reactants) are the most extensively used resin for applications where long term thermal stability is required at 300°C. This section dwells on other progress under way in the field of nanocomposites as high temperature nanocomposites. The last section presents a review on advanced materials for high temperature applications, especially applicable for the next generation aerospace vehicles. The issues concerning adhesives for joining of surfaces exposed to high temperatures, the effective role of nano-fillers for improving fracture toughness at high temperature etc. It is seen that the most promising resin for high temperatures has been the polyimides (315°C). This resin has high Tg (400°C) and other good characteristics such as good micro cracking resistance, low moisture absorption and low toxicity. There are various grades of polyimides under development. Overall, the chapter provides a glimpse on the effective developments in the field of polymer-composites and nanocomposites for high temperature applications especially for aerospace vehicle and automotives.