Cellulose nanowhiskers hydrolysis

Chen, Y., Liu, C., Chang, P. R., Cao, X., and Anderson, D. P. (2009). Bionanocomposites based on pea starch and cellulose nanowhiskers hydrolyzed from pea hull fibre Effect of hydrolysis time, Carbfj]fy ... 

There are basically two families of nanosized cellulosic particles (1) Nanofibrillar cellulose, which includes mechanically isolated microfibrils, chemically isolated microfibrils (TEMPO-oxidation), bacterial cellulose and can be considered spaghetti-like, and (2) Cellulose nanocrystals - rods of highly crystalline cellulose which are isolated by acid hydrolysis. Cellulose nanocrystals are represented in literature by synonyms like cellulose whiskers, cellulose nanowhiskers, cellulose microfibrils, micro-crystalline cellulose and nanocrystalline cellulose because they are not yet commercially available. These are needle-shaped (100 run to 200 run X 10 nm), highly crystalline, strong (E - 150 GPa) and form liquid crystal suspensions. 

Cellulose nanocrystals are rods of highly crystalline cellulose which are usually isolated by acid hydrolysis Cellulose nanocrystals are represented in literature by synonyms like cellulose whiskers, cellulose nanowhiskers, cellulose microfibrils. 

Recently bionanowhiskers have been extracted from jute by acid hydrolysis. Initially cellulose microfibrils were formed by alkali treatment then addition of an acid to the microfibrils triggered the formation of cellulose nanowhiskers. 

Rojas OJ, Montero GA, Habibi YJ (2009) Electrospun nanocomposites from polystyrene loaded with cellulose nanowhiskers. Appl Polym Sci 113 927-935 Roman M, Winter WT (2004) Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose. Biomacromolecules 5 1671-1677 Roman M, Winter WT (2006) Cellulose nanocomposites processing, characterization, and properties. In Oksman K, Sain M (eds) ACS symposium series 938. American Chemical Society, Washington, DC... 

At nanoscale thickness, fibrils are named as nanofibrillar cellulose (NFC) or nanocellulose [26-28]. Highly crystalline cellulose nanowhiskers, also called cellulose micelles, cellulose nanorods, cellulose nanocrystals, or nanocrystalline cellulose are produced under strong acid hydrolysis (e.g., mineral acids such as hydrochloric acid or sulphuric acid) combined with mechanical shearing [22, 29]. 

Different methods are presented in literature to obtained cellulose nanowhiskers chemical hydrolysis, high-pressure homogenization, and enzymatic hydrolysis. 

Regarding biodegradable polyurethanes, Luo et al. [35] synthesized polymeric nanocomposites by incorporating cellulose nanowhiskers (obtained by the classic sulfuric acid hydrolysis) into shape memory polyurethane based on poly (e-caprolactone) diol (PCL, Mw = 65000), 4,4 -diphenylmethane diisocyanate (MDI)... 

A method involving hydrolysis of bacterial cellulose by sulfuric acid has been undertaken in order to obtain nanowhiskers. These nanowhiskers can be dispersed in various solutions, however the nanowhiskers appear stiff and rod-like, and have been reported to aggregate to some degree [146]. Bacterial cellulose nanowhiskers have also been pre-pared by hydrochloric acid digestion [147]. 

Cellulose nanowhiskers were prepared by acid hydrolysis, following a procedure reported earlier (Liu et al., 2010). The oven-dried flax yams were hydrolyzed in sulfuric acid solution (60 wt%) at 55 °C for 1 h. Then the suspension was centrifuged and diluted with deionized water. The suspension was freeze-dried prior to being redispersed in deionized water. 

Cellulose nanowhiskers (CNWs), also known as cellulose nanocrystals (CNCs) or nanocrystalline cellulose, are usually produced by the acid hydrolysis of natural cellulosic material after removing nonceUulosic substances such as dewaxing, hemicelluloses, and lignin. Most CNWs show a high crystallinity index and a lower aspect ratio. Thus it is expected that CNWs extracted from tunicates exhibit a high... 

Satyamurthy P, Jain P, Balasubramanya RH, Vigneshwaran N (2011) Preparation and characterization of cellulose nanowhiskers from cotton fibres by controlled microbial hydrolysis. Carbohd Polym 83 122-129... 

Fahma F, Iwamoto S, Hori N, Iwata T, Takemura A (2011) Effect of pre-acid-hydrolysis treatment on morphology and properties of cellulose nanowhiskers from eoneonut husk. Cellulose 18 443-450... 

Bondeson et al. optimized the extraction process of NCC from MCC by varying the concentration of MCC and sulfuric acid, hydrolysis time, temperature, and ultrasonic treatment time [9]. It was found that an acid concentration of 63.5% (w/w) sulfuric acid can be used to produce cellulose whiskers of 200-400 nm length and 10 nm in diameter with 30% yield. Low yield of cellulose nanowhiskers has been attributed to the disintegration of amorphous cellulose and degradation of crystalline region during acid hydrolysis. 

The history of CNP began over 60 years ago, when Rmby (1952) reported for the first time that colloidal suspensions of cellulose can be obtained by controlled sulfuric-acid-catalyzed degradation of cellulose fibers. Currendy, CNP (nanowhiskers) are prepared by hydrolysis of cellulose samples with 55—65 wt% sulfuric or 25—30 wt% hydrochloric acids at moderate temperatures (40—60 °C) and subsequent mechanical or ultrasound disintegration of the hydrolyzed cellulose in aqueous medium (Habibi et al., 2010 Hubbe et al., 2008 loelovich, 2014a Li and... 

Several terms are used in the scientific literature to denote the rod-like nanoparticles isolated as a result of cellulose hydrolysis nanowhiskers, nanocrystals, or crystalline nanoparticles. Here we use predominantly the last term. 

StNs and chitin nanowhiskers have also been reported to produce PCL bionanocomposites with improved properties [296,298, 315]. For example, Habibi and Dufresne [316] prepared cellulose and StNs obtained from the acid hydrolysis of ramie fibers and waxy maize starch granules, respectively, which were subjected to... 

The interest on natural-based materials for reinforcement of polymer matrices has been increased in recent years. In this section, we focus the attention on the reinforcement effect of cellulose, starch or chitin fillers on the thermal properties of PU-based materials. These nanofillers can be obtained from natural and renewable sources and can be processed in several ways presenting different morphologies, such as nanowhiskers, nanofibers, or nanoparticles. In particular, cellulose can be processed by hydrolysis reaction of different cellulose sources in order to obtain cellulose nanocrystals (CNC) [72]. In Figure 7.3, the CNC structure is shown. The CNC present a diameter of about 19 nm. [72]. 

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