Cellulose nitrate applications

The doyen of the ester polymers is cellulose nitrate. Camphor-modified cellulose nitrate has been known for over 120 years and still retains its use in a few specialised applications. 

It will be observed from Table 22.1 that industrial cellulose nitrates or nitrocellulose (as they are often erroneously called) have a degree of substitution somewhere between 1.9 and 2.7 and that materials with lower degrees of substitution are used for plastics applications. 

Tliere is another type of application where the damping effect of plastic structures can be used to advantage. It has a long although not obvious history. The early airplanes used doped fabric as the covering for wings and other aerodynamic surfaces. The dope was cellulose nitrate and later cellulose acetate that is a damping type of plastic. Conse-... 

Cellulosic They are tough, transparent, hard or flexible natural polymers made from plant cellulose feedstock. With exposure to light, heat, weather and aging, they tend to dry out, deform, embrittle and lose gloss. Molding applications include tool handles, control knobs, eyeglass frames. Extrusion uses include blister packaging, toys, holiday decorations, etc. Cellulosic types, each with their specialty properties, include cellulose acetates (CAs), cellulose acetate butyrates (CABs), cellulose nitrates (CNs), cellulose propionate (CAPs), and ethyl celluloses (EC). 

Indeed it can be stated that the history of modern expls begins with the discoveries of nitroglycerin (NG) and nitrocellulose (or more correctly cellulose nitrate or NC) nearly 125 years ago, and their application to military and commercial usage. An excellent review of the early history of NC is given by. T.L. Davis (Ref 29, pp 244—56). The early histories of NG and EGDN (discovered in 1870) are summarized, respectively, in Vol 6, G99-R to G100-R and E259-R, and in the Naoum reference cited above... 

Natural fibers go back to prehistoric days. Probably one of the early applications was the conversion of a fiber (possibly wool or cellulose) into thread or rope strong enough to be used in a snare, net, or cage. Literature as far back as the 17th century notes that people attempted to make fibers out of something other than cotton, wool, or flax. The first man-made fiber, known as artificial silk, was made in the 19 th century, when wood pulp was treated with nitric acid. The result was known chemically as cellulose nitrate and (eventually) commercially as Rayon. The commercial name referred to the sheen that has the brilliance of the sun. ... 

Cellulose nitrate (pyroxylin) [9004-70-0], made from cellulose and a mixture of nitric and sulfuric acids, is called gun cotton and is used in explosives. Nitrates of lower DS find some application in coatings and adhesives. 

The principles behind ultrafiltration are sometimes misunderstood. The nomenclature implies that separations are the result of physical trapping of the particles and molecules by the filter. With polycarbonate and fiberglass filters, separations are made primarily on the basis of physical size. Other filters (cellulose nitrate, polyvinylidene fluoride, and to a lesser extent cellulose acetate) trap particles that cannot pass through the pores, but also retain macromolecules by adsorption. In particular, these materials have protein and nucleic acid binding properties. Each type of membrane displays a different affinity for various molecules. For protein, the relative binding affinity is polyvinylidene fluoride > cellulose nitrate > cellulose acetate. We can expect to see many applications of the affinity membranes in the future as the various membrane surface chemistries are altered and made more specific. Some applications are described in the following pages. 

A little of the sample is dissolved in pure concentrated sulphuric acid and a crystal of diphenylamine sulphate added to the solution with artificial silks based on cellulose nitrate, a blue coloration is obtained. This test is applicable only to undyed fibres. 

The first major application of microfiltration membranes was for biological testing of water. This remains an important laboratory application in microbiology and biotechnology. For these applications the early cellulose acetate/cellulose nitrate phase separation membranes made by vapor-phase precipitation with water are still widely used. In the early 1960s and 1970s, a number of other membrane materials with improved mechanical properties and chemical stability were developed. These include polyacrylonitrile-poly(vinyl chloride) copolymers, poly(vinylidene fluoride), polysulfone, cellulose triacetate, and various nylons. Most cartridge filters use these membranes. More recently poly(tetrafluo-roethylene) membranes have come into use. 

Membranes and composites from cellulose and cellulose esters are important domains in the development and application of these polymer materials. The most important segment by volume in the chemical processing of cellulose contains regenerated cellulose fibers, films, and membranes, hi the case of the cellulose esters mainly cellulose nitrate and cellulose acetate as well as novel high-performance materials created therefrom are widely used as laminates, composites, optical/photographic films and membranes, or other separation media, as reviewed in [1], The previously specified nanocelluloses from bacteria and wood tie in with these important potentials and open novel fields of application. 

Cellulose nitrate film cast from solution is highly brittle and is made flexible for surface coating applications bv the addition of plasticizers like dibutylphthalate, dioctylphthalate,... 

Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate.26 In vinyls (plasticized), arylphos-phates are frequently used with phthalate plasticizers. Their principal applications are in wire and cable insulation, connectors, automotive interiors, vinyl moisture barriers, plastic greenhouses, furniture upholstery, and vinyl forms. Triarylphosphates are also used, on a large scale, as flame-retardant hydraulic fluids, lubricants, and lubricant additives. Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. Blends of triarylphosphates and pentabromodiphenyl oxide are extensively used as flame-retardant additives for flexible urethane foams. It has been also... 

An early important commercial use for the cellulosics was to replace ivory in making billiard balls, and while today this certainly would win approval by green enthusiasts it is not far-fetched to imagine at the time some habitues of the tables grumbling that the plastic balls just were not the same . When perfected eventually in a commercial sense cellulose nitrate plastics were more consistent in appearance and quality than tusks, and duly replaced them too for uses such as piano keys and handles for table cutlery in products like these they were an economical and practical substitute but in stiff collars and cuffs— another important early application (eventually, millions were made) to help keep clerks, nannies, and others looking smart throughout the working... 

Natural products and transformed natural products can also be used as binding agents for packaging applications. These are shellac, dammar gum, dried unsaturated oils (linseed oil), rosin and hydrated esters of rosin, cellulose acetate and propionate acetate, cellulose acetobutyrate, cellulose nitrate and ethyl cellulose. 

Cellulose acetate has replaced cellulose nitrate in many products, for example, in safety-type photographic films. When a solution of cellulose acetate in acetone is passed through the fine holes of a spinneret and the solvent evaporates, solid filaments are produced. Acetate rayon is prepared from threads of these filaments. Some applications and solvents of commercial cellulose acetate grades are summarized in Table 9-5. 

Most practical applications of electrophoresis in biochemistry employ some form of zonal electrophoresis, in which the aqueous ionic solution is carried in a solid support and samples are applied as spots or bands of material. Paper electrophoresis, cellulose acetate strip and cellulose nitrate strip, and gel electrophoresis are all examples of zonal... 

For adhesive application, the acid mixture is made up of nitric acid (25%), sulfuric acid (55%), and water (20%). The function of sulfuric acid is to remove the water of reaction so that nitration may be carried to the desired degree more readily. The various products may be characterized by nitrogen content, which corresponds to the degree of substitution. The nitrogen content also determines the solubility of cellulose nitrate. With 11.8 to 12.2% nitrogen content,... 

Cellulose is the most abundant naturally oeeurring polysaccharide formed out of glucose-based repeat imits, connected by 1,4-beta-glucosidic linkages. Cellulose and its derivatives are widely used as tough versatile materials. Cellulose nitrate, cellulose acetate (CA) and cellulose xanthate (rayon) can be easily molded or drawn into fibers for textile applications, for designing composite materials (safety glass), as thermoplastics etc [80]. 

Hollow membrane fibers are required for many medical application, e.g. for disposable dialysis. Such fibers are made by usmg an appropriate fiber spinning technique with a special inlet in the center of the spinneret through which the fiber core forming medium (liquid or gas) is injected. The membrane material may be made by melt-spinning, chemical activated spinning or phase separation. The thin wall (15-500 xm thickness) acts as a semi-permeable membrane. Commonly, such fibers are made of cellulose-based membrane materials such as cellulose nitrate, or polyacrylonitrile, polymethylmethacrylate, polyamide and polypropylene (van Stone, 1985). 

From the point of view of water purification, one of tl earliest applications of MF is still the most important sterile filtration. Bacteria can be removed from drinking water, solutions for intravenous or parenteral injection, heat-sensitive liquid foods, and so on by MF. The earliest MF membranes were prepared from cellulose nitrate or from mixed acetate and nitrate esters of cellulose. 

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