Cellulose doping

Some textile materials and products are designed for medical and surgical applications in which a combination of strength, flexibility, and sometimes moisture and air permeability is required. Ihe optimiun conditions for these textile materials have resulted from the examination of some structural properties of hydroxypropyl cellulose doped with poly(vinyl alcohol) (PVA) in different weight percentages [149]. Ihe main observations made were that the modifications in the properties of the host polymer (cellulose derivative) depend on the chemical nature of the doping agent (poly(vinyl alcohol)) and also on the manner in which they interact with the host matrix. 

Qi, H., Cai, J., Zhang, L., Nishiyama, Y., and Rattaz, A., Influence of Finishing Oil on Structure and Properties of Multi-Filament Fibers from Cellulose Dope in NaOH/Urea Aqueous Solution , Cellulose, 15, 81-89, 2008. 

Chae, D. W., et al. (2002). Physical Properties of Lyocell Fibers Spun from Isotropic Cellulose Dope in NMMO Monohydrate. Textile Research Journal, 72(4), 335-340. McCormick, C. L. (1981). Novel Cellulose Solutions, U.S. Patent 4,278,790, Jul. 14. Turbak, A. (1993)., Newer cellulose solvent systems, in Wood and Agricultural Residues, E.J. Soltes (Editor), Academic Press. 87-99. 

The first successhil attempt to make textile fibers from plant cellulose can be traced to George Audemars (1). In 1855 he dissolved the nitrated form of cellulose in ether and alcohol and discovered that fibers were formed as the dope was drawn into the air. These soft strong nitrocellulose fibers could be woven into fabrics but had a serious drawback they were explosive, nitrated cellulose being the basis of gun-cotton (see Cellulose esters, inorganic esters). 

The dark blue solution containing 5—10% of cellulose with a DP of 1000—2000 is filtered through a series of plate-and-frame filter presses using fine mesh metal screens to remove any particles that might block the spinneret holes. It is then deaerated under vacuum and stored ready for spinning. Unlike viscose dope, the cuprammonium cellulose [9050-09-3] solution is relatively stable. 

Other patents (81,82) coveted the preparation of cellulose solutions using NMMO and speculated about their use as dialysis membranes, food casings (sausage skins), fibers, films, paper coatings, and nonwoven binders. NMMO emerged as the best of the amine oxides, and its commercial potential was demonstrated by American Enka (83,84). Others (85) have studied the cellulose-NMMO system in depth one paper indicates that further strength increases can be obtained by adding ammonium chloride or calcium chloride to the dope (86). 

Fig. 8. (a) Cross section of cellulose acetate isotropic porous hoUow-fiber dry-jet wet spun at incipient gelation point of dope mixture (b) magnification at... 

Cellulose acetate [9004-35-7], prepared by reaction of cellulose with acetic anhydride, acetic acid, and sulfuric acid, is spun into acetate rayon fibers by dissolving it in acetone and spinning the solution into a column of warm air that evaporates the acetone. Cellulose acetate is also shaped into a variety of plastic products, and its solutions are used as coating dopes. Cellulose acetate butyrate [9004-36-8], made from cellulose, acetic anhydride, and butyric anhydride in the presence of sulfuric acid, is a shock-resistant plastic. 

During the time of the development of the urea-based resins, a thermoplastic, cellulose acetate, was making its debut. The material had earlier been extensively used as an aircraft dope and for artificial fibres. The discovery of suitable... 

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-... 

Sensors based on the above reaction scheme have been developed for Al3+, Zn2+, Cu2+, Ca2+, Pb2+, Hg2"1", K+, Li+, etc. A polycation, protamine sensor has also been developed using 2/7/-dichlorofluorescein octadecyl ester (DCFOE) doped in polymer membranes. However, most of these sensors are pH dependent due to the pH dependence of the cation complexation reactions. The cation ion indicators can be immobilized on any solid support, such as silica, cellulose, ion-exchange resin, porous glass, sol-gel, or entrapped in polymer membranes. 

Uses Solvent for cellulose acetate, nitrocellulose, various gums, resins, waxes, oils textile printing lacquers dopes textile printing photographic film. 

Figure 4. Flux and refection of cellulose diacetate membranes doped with organo-philic bentonite as a function of bentonite concentration...

Preparation of Hollow Fiber Membrane. CTA (Cellulose Tri-Acetate) hollow fiber membranes were prepared by aplnning a dope solution of CTA followed by soaking and anealing. 

In the case of cellulose acetate (CA) casting dopes the solution structurization is mainly due to hydrogen bonding between polymer molecules and additives (swelling agents) in the solution. Therefore, a choice of a proper additive is an important step in the casting dope formulation. 

Eastman cellulose acetate E-398-3 and reagent-grade acetone and phosphoric acid, Merck, Darmstadt, W. Germany were employed for the casting dope preparations. 

The manufacture of cellulose acetate involves the acetylation of cellulose from cotton linters or wood pulp by acetic anhydride and acetic acid. Production started about 30 years ago, and early products that were developed include safety photographic films, airplane dopes, and acetate fabrics. It is now also produced in the form of sheeting, rods, and tubes and is widely used as a molding compound. 

Among the dopes used may be cited the following combustibles colophony (used by Nobel in his Dynamites of 1869 1873) (Vol 3 of Encycl, p C403R) wood-meal, woodpulp and sawdust in Grisounite and in some Amer Dynamites cork,charcoal (in "Carbodynamite , described in Ref 60, p C52-L) naphthalene (in Rheinischdynamit) and cotton or other forms of cellulose (in "Forcites ). Less frequently have been used peat moss, ivoty nut meal, unbaked com flakes, starch, pulverised peanut hull, pulverized cottonseed hulls and sunflower seed shells... 

Benzyl Alcohol Phenylmethanol or Hydroxytol-uene (called l -Oxy-T-methyl-benzol and benzyl chloride with Na or K carbonate in soln or by other methods. There are two commercial products technical grade and "FFC (free from chlorine) grade(Ref 3). Toxicity and fire hazard are discussed in Ref 5. It is used extensively in many branches of the chem industries, such as, for the manuf of esters(acetic, benzoic, sebacic, etc), as a solvent for cellulose esters ethers, etc. During WW I, it was used in a "dope for airplane fabrics... 

Fig. 11 Cellulose (beech sulfite pulp) dissolved in NMMO (Lyocell dope). Left DSco and differential MWD of the starting pulp, molecular weights of DP = 50 and DP = 200 are indicated by vertical dashed lines. Right Time course of the overall carbonyl content for three selected molecular weight ranges. Reprinted with permission from Biomacromolecules (2002) 4 743. Copyright (2002) American Chemical Society...

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