Chapter 18 - Development and Characterization of Roselle Nanocellulose and Its Potential in Reinforced Nanocomposites

Abstract

Over the following years, the number of scientific articles and patents published in nanocellulose has significantly risen. Nanocellulose has grown as a sustainable and promising nanomaterial owing to its superb properties, unique structures, low density, excellent mechanical performances, high aspect ratio, biocompatibility, and natural abundance. Nanocellulose has received massive attention in various applications as a nanoreinforcement for polymer matrices (i.e., optically transparent materials, coating films, biomimetic materials, aerogels, sensor, 3D printing, rheology modifiers, energy harvesters, filtration, textiles, printed and flexible electronics, composites, paper and board, packaging, oil and gas, and medical and healthcare). There are three types of nanocellulose, including nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC), and bacterial nanocellulose (BNC). These nanocellulose types can be obtained through top-down or bottom-up techniques. NFC and NCC are usually produced through the top-down approaches, such as chemical, mechanical, chemomechanical, and enzymatic processes for extraction and isolation from crops, higher plants, and by-products of forestry and agricultural residue. However, BNC is produced via the bottom-up approach, utilizes the fermentation of low-molecular-weight sugar by cellulose-producing bacteria. Natural fibers such as roselle fiber (Hibiscus sabdariffa) are abundantly found in nature and roselle is cultivated in Borneo, Guyana, Malaysia, Sri Lanka, Togo, Indonesia, and Tanzania. In Malaysia, after a year, the roselle plant will be cut to preserve the quality of the fruit and it subsequently becomes an agro-waste. The fiber is utilized as reinforcing material for polymer composites for more efficient use of this plant. This chapter focuses on the development and characterization of roselle nanocellulose and its potential in reinforced nanocomposites. This chapter also focuses on top-down techniques, such as acid hydrolysis, used in the preparation of roselle nanocellulose from agro-waste roselle fiber.