Polyhydroxyalkanoates and Their Nanobiocomposites With Cellulose Nanocrystals

Cellulose nanocrystals produced from different natural sources, are emerging renewable nanomaterials that can be applied in many different ways due to their properties of high strength and stiffness, combined with low weight, biodegradability and the environmental benefits arising from its use. Due to their nanoscale and specific intrinsic properties, cellulose nanocrystals are very promising for use as reinforcement in high-performance nanocomposites with sustainable appeal. Many biodegradable polymers are used as a matrix in the manufacture of these nanocomposites, among them the poly(3-hydroxybutirate) and its copolymer poly(3-hydroxybutirate-co-3-hydroxy valerate) (PHBV). These polymers are characterized as polyhydroxyalkanoates (PHA) class and are unique considering they can be produced on a large scale. PHA family polymers are natural polyesters, basically composed of carbon, hydrogen and oxygen atoms and synthesized from the fermentation of at least 75 different species of bacteria. PHBV has been studied for different applications as a matrix of nanocomposites due to its biodegradability and biocompatibility characteristics; however, it presents some disadvantages, such as high cost, low thermal stability, brittleness and low crystallization rate, which hinders its use in many applications. In addition, the nanocrystalline cellulose reinforcement has the main objective of acting as a nucleating agent increasing the polymer crystallization rate, and also of providing increased mechanical properties, such as tensile strength, Young's modulus and storage modulus. In this context, this chapter describes recent progress evidenced in the literature that deals with cellulose nanocrystal obtention, its use as a reinforcement of PHBV and, the use of its biodegradable nanocomposites in different applications.