Feedstocks, Synthesis, and Characterization of Cellulosic Materials for Advanced Applications with Emphasis on Microcrystalline Cellulose (MCC)

Cellulosic materials find applications in pharmaceutical, food, and cosmetic industry due to their surface, mechanical, and antimicrobial properties. Many investigations are reported on synthesis of cellulosic products from raw feedstocks that contains 40 to 80% cellulose. Microcrystalline cellulose (MCC) is synthesized from raw feedstock with a methodology involving alkali treatment, acid hydrolysis, and dewatering. Various modifications in terms of alkali, acid, and dewatering methods are explored for effective synthesis with desired characteristics. Also application-oriented research include combination of MCC with polymers to get better and customized materials. Microcrystalline cellulose is also used as an anticaking material, dispersing agent, and stabilizer. The properties of microcrystalline material depends on the synthesis conditions and the starting material. Being microcrystalline in structure, the characterization for its size, strength, crystallinity, pH, crystal size, stability, and flow properties is an important factor deciding the suitability of the material for specific applications. This review provides important insight on raw materials and MCC properties. The sisal fiber MCC was reported to have crystallinity index 81.5% and the Kraft pulp MCC, 88%, highest among the feedstocks. Carr’s index was highest, 29–26%, for cotton MCC. pH of the product ranged from 6 to 7. The yield of MCC for raw feedstock was reported to be satisfactory, the highest being 88% for Rabdosia rubescens residue. This article reviews the investigations on MCC to explore feedstocks, characterization methods, and applications of microcrystalline cellulose in pure and composite form.