Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms. Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fiber is 90 – 95% and that of wood is 40 – 50%
Cellulose is mainly used to produce paperboard and paper. Smaller quantities are converted into a wide variety of derivative products such as cellophane and rayon. Conversion of cellulose from energy crops into biofuels such as cellulosic ethanol is under investigation as an alternative fuel source. Cellulose for industrial use is mainly obtained from Wood Pulp and Cotton Linters.
STRUCTURE & PROPERTIES
Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20 – 30, is insoluble in water and most organic solvents, is chiral and is biodegradable. It can be broken down chemically into its glucose units by treating it with concentrated acids at high temperature.
Cellulose is derived from D-glucose units, which condense through β (1→4) – glycosidic bonds. This linkage motif contrasts with that for α (1→4) – glycosidic bonds present in starch, glycogen, and other carbohydrates. Cellulose is a straight chain polymer: unlike starch, no coiling or branching occurs, and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbor chain, holding the chains firmly together side-by-side and forming micro fibrils with high tensile strength. This confers tensile strength in cell, where cellulose micro fibrils are meshed into a polysaccharide matrix.
Cotton fibers represent the purest natural form of cellulose, containing more than 90% of his polysaccharide.
Compared to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water.
Several different crystalline structures of cellulose are known, corresponding to the location of hydrogen bonds between and within strands.
Many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units, cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units. Molecules with very small chain length resulting from the breakdown of cellulose are known ascellodextrins, in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents.
Plant-derived cellulose is usually found in a mixture with hemicellulose, lignin, pectin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths.
Cellulose consists of crystalline and amorphous regions. By treating it with strong acid, the amorphous regions can be broken up, thereby producing nano-crystalline cellulose, a novel material with many desirable properties. Recently, nano-crystalline cellulose was used as the filler phase in bio-based polymer matrices to produce nano-composites with superior thermal and mechanical properties.
Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called cellodextrins or completely into glucose units; this is a hydrolysis reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides. However, this process can be significantly intensified in a proper solvent, e.g. in an ionic liquid. The bacterial mass is later digested by the ruminant in its digestive system (stomach and small intestine). Similarly, lower termites contain in their hindguts certain flagellate protozoa which produce such enzymes; higher termites contain bacteria for the job. Some termites may also produce cellulase of their own. Fungi, which in nature are responsible for recycling of nutrients, are also able to break down cellulose. The enzymes utilized to cleave the glycosidic linkage in cellulose are glycoside hydrolases including endo – acting cellulases and exo – acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerins and carbohydrate-binding modules.
The hydroxyl groups (-OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (-OR).
In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.
ESTER DERIVATIVES INCLUDE
|Cellulose Ester||Reagent||Example||Reagent||Group R|
|Organic Esters||Organic Acids||Cellulose Acetate||Acetic Acid and AceticAnhydride||H or -(C=O)CH3|
|Cellulose Triacetate||Acetic Acid and Acetic Anhydride||-(C=O)CH3|
|Cellulose Propionate||Propanoic Acid||H or -(C=O)CH2CH3|
|Cellulose Acetate Propionate (CAP)||Acetic Acid and Propanoic Acid||H or -(C=O)CH3 or – (C=O)CH2CH3|
|Cellulose Acetate Butyrate (CAB)||Acetic Acid and Butyric Acid||H or -(C=O)CH3 or – (C=O)CH2CH2CH3|
|Inorganic Esters||Inorganic Acids||Nitrocellulose (Cellulose Nitrate)||Nitric Acid or another powerful Nitrating Agent||H or -NO2|
|Cellulose Sulfate||Sulfuric Acid or another powerful Sulfuring Agent||H or -SO3H|
The cellulose acetate and cellulose triacetate are filmand fiberforming materials that find a variety of uses. The nitrocellulose was an early film forming material. With camphor, nitrocellulose gives celluloid.
ETHER DERIVATIVES INCLUDE
|Cellulose Ethers||Reagent||Example||Reagent||Group R = H or|
|Ethyl Methyl Cellulose||Chloromethane and Chloroethane||– CH3 or – CH2CH3|
|Hydroxyalkyl||Epoxides||Hydroxyethyl Cellulose||Ethylene Oxide||– CH2CH2OH|
|Hydroxypropyl Cellulose (HPC)||Propylene Oxide||-CH2CH(OH)CH3|
|Hydroxyethyl Methyl Cellulose||Chloromethane and Ethylene Oxide||– CH3 or -CH2CH2OH|
|Hydroxypropyl Methyl Cellulose (HPMC)||Chloromethane and Propylene Oxide||– CH3 or – CH2CH(OH)CH3|
|Chloroethane and Ethylene Oxide||– CH2CH3 or – CH2CH2OH|
|Carboxyalkyl||Halogenated Carboxylic Acids||Carboxymethyl Cellulose (CMC)||Chloroacetic Acid||– CH2COOH|
The Sodium Carboxymethyl Cellulose can be cross-linked to give the Croscarmellose Sodium.
Cellulose for industrial use is mainly obtained from wood pulp and cotton linters. The kraft process is used to separate cellulose from lignin, another major component of plant matter.
- Paper Products : Cellulose is the major constituent of paper, paperboard, and card stock.
- Fibers : Cellulose is the main ingredient of textiles made from cotton, linen, and other plant fibers. It can be turned into rayon, an important fiber that has been used for textiles since the beginning of the 20th century. Both cellophane and rayon are known as “regenerated cellulose fibers”; they are identical to cellulose in chemical structure and are usually made from dissolving pulp via viscose. A more recent and environmentally friendly method to produce a form of rayon is the Lyocell process.
- Consumables : Microcrystalline Cellulose and powdered Cellulose are used as inactive fillers in drug tablets and as thickeners and stabilizers in processed foods.
- Science: Cellulose is used in the laboratory as a stationary phase for thin layer chromatography. Cellulose fibers are also used in liquid filtration, sometimes in combination withdiatomaceous earth or other filtration media, to create a filter bed of inert material.
- Energy Crops: The major combustible component of non-food energy crops is cellulose, with lignin second. Non-food energy crops produce more usable energy than edible energy crops (which have a large starch component), but still compete with food crops for agricultural land and water resources. Typical non-food energy crops include industrial hemp (though outlawed in some countries), switchgrass, Miscanthus, Salix (willow), and Populus (poplar) species.
- Biofuel: TU-103, a strain of Clostridium bacteria found in zebra waste, can convert nearly any form of cellulose into Butanol fuel.
- Building Material: Hydroxyl bonding of cellulose in water produces a sprayable, moldable material as an alternative to the use of plastics and resins. The recyclable material can be made water- and fire-resistant. It provides sufficient strength for use as a building material. Insulation made from recycled paper is becoming popular as an environmentally preferable material for building insulation. It can be treated with boric acid as a fire retardant.
- Miscellaneous: Cellulose can be converted into cellophane, a thin transparent film. It is the base material for the celluloid that was used for photographic and movie films until the mid-1930s. Cellulose is used to make water-soluble adhesives and binders such as methyl cellulose andcarboxymethyl cellulose which are used in wallpaper paste. Cellulose is further used to make hydrophilic and highly absorbent sponges. Cellulose is the raw material in the manufacture of nitrocellulose (Cellulose Nitrate).
Packing is done in poly laminated 25 Kg HDPE bags with 2 (Two) Liners inside. Any modifications in packing can be made as per the customer’s requirement. Cellulose Powder is non – hygroscopic and considered to be stable product and is packaged in a sealed manner. The product has no specific requirement for storage, and there is no expiration date. However, it may absorb moisture if exposed to the atmosphere with a relative humidity higher than 65%.
Because of the numerous factors affecting results, and being used in numerous Industries, Suhal Cellulose LLP products are sold on the understanding that purchasers will make their own tests to determine the suitability of this product for their particular purpose. The several uses suggested by us are presented only to assist our customers in exploring possible applications. All information and data presented are believed to be accurate and reliable but are presented without the assumption of any liability of Suhal Cellulose LLP. The information contained is intended to be general in nature.