Nano- and microfiber composites reinforced with cellulose nanocrystals

Abstract

The integration of reinforcing materials in composites with synthetic polymers has gained increased attention in recent years, especially in the area of nanocomposites. Most of the efforts in this respect have focused on inorganic reinforcing agents and mostly by using the casting method. Recently, the developments based on renewable materials have become increasingly popular because of the need for finding alternatives to nonrenewable fossil carbon resources. Among such materials, readily available cellulose nanocrystals (CNs) have attracted great interest because of their availability, renewability, biodegradability, and excellent mechanical properties. Furthermore, CNs are relatively easy to produce and are much less expensive than most of the particles currently used for reinforcement purposes. An additional advantage of CNs and “lignocellulosics” fillers compared to equivalent inorganics include high specific strength, surface reactivity, and the option of surface modification to give better compatibility with the matrix materials. On the other hand, the development of fibers with diameters in the micro- and nanoscale has gained vitality, because of the unique properties that they present, for example, their very high surface area-to-volume ratio. This characteristic along with the remarkable flexibility in surface functionalities and superior mechanical performance determine their importance in many fields, such as medicine, pharmacy, and nanocomposites manufacture. The production of fibers by using the electrospinning technique, which can be used in the spinning of either synthetic or natural polymer solutions, polymer alloys, and polymers filled with nanoparticles, metals, and so on, is a fascinating platform that has been utilized since several decades ago. Electrospinning is carried out with the help of electrostatic forces and allows manufacture of continuous nanofibers. Electrospun nonwoven mats provide very porous and interconnected structures, with an overall high surface area compared to regular textiles. After briefly discussing the electrospinning process, this chapter introduces the subject of CNs as the dispersed reinforcing phase in green composite fibers. Finally, results from our research with nano- and microfiber composites are discussed using some examples of interest for green applications.