Cellulose microcrystals

Similarly MFC were obtained applying a high-pressure homogenizer to commercial microcrystal cellulose previously dispersed by a Turrax. The cellulose fibrils were in the range from 28 to 100 nm (Lee et al. 2009). 

Nanocrystalline cellulose (NCC), cellulose nanocrystals (CNC), crystallites, rodlike cellulose microcrystals, cellulose whiskers (CW) or cellulose nano whiskers (CNW) 2-20 100-600 10-100... 

By casting films from suspensions of cellulose microcrystals, cellulose films with the optical properties of chiral nematic liquid crystals can be prepared. The films can be tailored to give different colors of reflected light by altering the salt content of the suspension for a given source of cellulose and set of hydrolysis conditions. Possible areas of application include optical variable films and ink pigments for security papers [81]. 

Over 250,000 metric tons of microcrystaUine cellulose have been sold siace its commercialisation ia 1962 and demand continues to iacrease. Its utihty has led to development of other coUoidal polymer microcrystals (see Colloids). For example, polyamides and polyesters from recycled materials can be biodegraded to give microcrystals having a size of 30 nm (37). 

Baker AA, Helbert W. Sugiyama J, Miles MJ. High-resolution atomic force microscopy of native Valonia cellulose I. Microcrystals. J Struct Biol 1997 119 129-138. 

By analogy with the works which dealt with cellulose micro crystal-reinforced nanocomposite materials, microcrystals of starch [95] or chitin [96, 97] were used as a reinforcing phase in a polymer matrix. Poly(styrene-co-butyl acrylate) [95,96], poly(e-caprolactone) [96], and natural rubber [97] were reinforced, and again the formation of aggregates or clustering of the fillers within the matrices was considered to account for the improvement in the mechanical properties and thermal stability of the respective composites processed from suspensions in water or suitable organic solvents. 

In natural cellulose, the microcrystals are packed tightly in the fiber direction in a compact structure resembling bundles of wooden match sticks placed side by side. Unhinging the interconnecting chains by acid treatment does not destroy this structure. However, the unhinged crystals are now free to be dispersed by mechanical disintegration.. . . We immediately set out to explore this new avenue, developing uses for colloidal dispersions of microcrystalline celluloses, known commercially as Avicel. 

Betcn DB, YUksel N, Baykara T. The changes in the mechanic properties of a direct tableting agent microcrystal line cellulose by recompression. Drug Dev Ind Pharm 1994 20 2323-31. 

FIGURE 23 Heckel plots for binary mixtures of microcrystal-linc cellulose. Source Adapted from Ref. 48. 

HPMC Microcryst. Povidone Copovidone 11000 Cellulose K30 VA64... 

Cellulose microcrystals extracted from valonia ventricosa are prepared according to [97] to yield cellulose suspensions. For AFM, a 5-pl drop of a 100-fold diluted (water) suspension is deposited onto freshly cleaved mica and left to dry under ambient conditions. For imaging under propanol, the samples are deposited onto 3-aminopropyltriethoxysilane-functionalized mica [98]. 

Sugiyama J, Chanzy H, Maret G (1992) Orientation of cellulose microcrystals by strong magnetic fields. Macromolecules 25(16) 4232-4234... 

Colloidal, aqueous dispersions of microcrystalline cellulose can be prepared by boiling cotton linters for 15 minutes with 2.5 N hydrochloric acid, followed by subjecting the resulting (level-off D.P.) cellulose to vigorous mechanical agitation. The microcrystals ( Avicel ), which are thereby freed from their fibrous packed structure, have been put to a variety of uses in the production of food gels and structural materials. ... 

---