Cellulose Plastics

8/14/2019 Cellulose Plastics

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INTRODUCTION

Cellulose is an organic compound with the formula(C6H10O5)n , a polysaccharide consisting of a linearchain of several hundred to over ten thousand (14)linked D-glucose units.Cellulose is the structural component of the primarycell wall of green plants, many forms of algae and theoomycetes. Some species of bacteria secrete it to form

biofilms. Cellulose is the most common organiccompound on Earth. About 33 percent of all plantmatter is cellulose (the cellulose content of cotton is 90percent and that of wood is 50 percent).


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For industrial use, cellulose is mainly obtained fromwood pulp and cotton. It is mainly used toproduce cardboard and paper; to a smaller extentit is converted into a wide variety of derivativeproducts such as cellophane and rayon.Converting cellulose from energy crops intobiofuels such as cellulosic ethanol is under

investigation as an alternative fuel source. Some animals, particularly ruminants and termites,

can digest cellulose with the help of symbioticmicro-organisms that live in their guts. Humanscannot digest cellulose; it is often referred to as'dietary fiber' or 'roughage' (e.g. outer shell ofMaize) and acts as a hydrophilic bulking agentfor feces


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NOMENCLATURE OF CELLULOSE

cellulose was discovered in 1838 by the Frenchchemist Anselme Payen, who isolated it from plantmatter and determined its chemical formula.Cellulose was used to produce the first successful

thermoplastic polymer, celluloid, by HyattManufacturing Company in 1870. HermannStaudinger determined the polymer structure ofcellulose in 1920. The compound was first

chemically synthesized (without the use of anybiologically-derived enzymes) in 1992, byKobayashi and Shoda


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Cellulose has no taste, is odourless, is hydrophilic, is insolublein water and most organic solvents, is choral and is

biodegradable. It can be broken down chemically into itsglucose units by treating it with concentrated acids at hightemperature.


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SOURCEOF RAW MATERIAL

Cellulose is the major constituent of paperand cardboard and of textiles made fromcotton, linen, and other plant fibers.Cellulose can be converted into

cellophane, a thin transparent film, andinto rayon, an important fiber that hasbeen used for textiles since the beginningof the 20th century. Both cellophane and

rayon are known as "regenerated cellulosefibers"; they are identical to cellulose inchemical structure and are usually madefrom viscose, a viscous solution made from

cellulose. A more recent and


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Cellulose is derived from D-glucose units, which condensethrough (14)-glycosidic bonds. This linkage motif

contrasts with that for (14)-glycosidic bonds present instarch, glycogen, and other carbohydrates. Cellulose is astraight chain polymer: unlike starch, no coiling orbranching occurs, and the molecule adopts an extendedand rather stiff rod-like conformation, aided by the

equatorial conformation of the glucose residues. Themultiple hydroxyl groups on the glucose residues from onechain form hydrogen bonds with oxygen molecules on thesame or on a neighbor chain, holding the chains firmlytogether side-by-side and forming micro fibrils with hightensile strength. This strength is important in cell walls,where the micro fibrils are meshed into a carbohydratematrix, conferring rigidity to plant cells.


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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 incooking), cellulose requires a temperature of 320 C andpressure of 25 MPa to become amorphous in water.

Many properties of cellulose depend on its chain length ordegree of polymerization, the number of glucose unitsthat make up one polymer molecule. Cellulose from wood

pulp has typical chain lengths between 300 and 1700units; cotton and other plant fibers as well as bacterialcelluloses have chain lengths ranging from 800 to 10,000

units. Molecules with very small chain length resultingfrom the breakdown of cellulose are known ascellodextrins; in contrast to long-chain cellulose,cellodextrins are typically soluble in water and organicsolvents.


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RAY DIAGRAM OF CELLULOSE

-Cellulose is the raw material in the manufacture ofnitrocellulose (cellulose nitrate) which was historically used in

smokeless gunpowder & as the base material for celluloidused for photographic and movie films until the mid 1930s..


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TYPES OF CELLULOSE

Four major types of loose-fill cellulose productshave been developed under a variety of brand

names. These are generally characterized as drycellulose, spray applied cellulose, stabilizedcellulose and low dust cellulose. These types areused in different parts of a building and for

different reasons.


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Dry Cellulose (Loose Fill)

Dry cellulose is used in retrofitting old homes by blowing thecellulose into holes drilled into the tops of the walls. It canalso be blown into a new wall construction by usingtemporary retainers or netting that is clamped in place thenremoved once the cellulose has reached the appropriate

density. This form of application does settle as much as 20%but the stated R-value of the cellulose is accurate aftersettling occurs. In addition, a dense-pack option can be usedto reduce settling and further minimize air gaps. Dense-pack

places pressure on the cavity, and should be done by an

experienced installer.


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Spray Applied Cellulose (Wet-Spray)

Spray applied cellulose is used for applying cellulose to new wallconstruction. The only difference is the addition of water to thecellulose while spraying. In some cases the insulation might alsomix in a very small percentage of adhesive or activate a dryadhesive present in the cellulose. Wet-spray allows applicationwithout the need for a temporary retainer. In addition, wet-sprayallows for an even better seal of the insulated cavity against airinfiltration and eliminates settling problems. Wet-spray installationrequires that the wall be allowed to dry for a minimum of 24 hours(or until maximum of 25% moisture is reached) before beingcovered.

Stabilized Cellulose

Stabilized cellulose is used most often in attic/roof insulation. It isapplied with a very small amount of water to activate an adhesive

of some kind. This reduces settling and decreases the amount ofcellulose needed. This can prove advantageous at reducing theoverall weight of the product on the ceiling drywall helping preventpossible sag. This application is ideal for sloped roofs and has beenapproved for 5:12 (41.66%) slopes.


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Low-Dust Cellulose The last major type of cellulose insulation on the

market is low dust variety. Nuisance levels of dustare created during application of most types of dryinsulation causing the need for simple dust masksto be worn during installation. This kind of

cellulose has a small percentage of oil or similardust dampener added. This may also be appropriateto homes where people are sensitive to newsprintor paper dust (though new dust will not be createdafter installation).

C O O


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APPLICATION OFCELLULOSE

Cellulose is used to make water-soluble adhesives andbinders such as methyl cellulose and carboxymethyl

cellulose which are used in wallpaper paste.Microcrystalline cellulose (E460i) and powderedcellulose (E460ii) are used as inactive fillers in

tablets and as thickeners and stabilizers in processedfoods.

Cellulose is used in the laboratory as the stationaryphase for thin layer chromatography. Cellulose fibers

are also used in liquid filtration, sometimes incombination with diatomaceous earth or otherfiltration media, to create a filter bed of inertmaterial. Cellulose is further used to makehydrophilic and highly absorbent sponges.


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For industrial use, cellulose is mainly obtainedfrom wood pulp and cotton. It is mainly used to

produce cardboard and paper; to a smallerextent it is converted into a wide variety ofderivative products such as cellophane andrayon. Converting cellulose from energy cropsinto biofuels such as cellulosic ethanol is underinvestigation as an alternative fuel source.

Cellulose is soluble in cupriethylenediamine(CED), cadmiumethylenediamine (Cadoxen),N-methylmorpholineN-oxide and lithium

chloride / dimethylformamide. This is used inthe production of regenerated celluloses (asviscose and cellophane) from dissolving pulp.


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MANUFACTURE OF CELLULOSE

Products of chemical processing Cellulose is produced from chemical pulp after complete

removal of the other constituents (lignin,hemicelluloses, and extractives). It is used in theproduction of synthetic fibers (e.g., rayon), cellophane,plastics, varnishes, lacquers, inks, adhesives,photographic films, magnetic tapes, artificial sponges,explosives, and many other products. The uses forlignin continue to grow, although great quantities arewasted or burned as fuel because its molecularstructure and chemistry are not completely known.

Lignin is used in making vanillin (synthetic vanilla),pharmaceuticals, plastics, solvents, ceramics,adhesives, synthetic rubber, foam materials,insecticides, fungicides, herbicides, soil conditioners,and other products.


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