Polymers cellulose triacetate

The photodegradation and photo-oxidation of poly(organosiloxanes), poly(iV-vinylcarbazole), polyCalkoxyphosphazones)," thymine-containing polymers/ cellulose triacetate, cellulose acetophthalate complexes with poly(vinyl alcohol)/ acrylonitrile-butyl acrylate-vinylene chloride terpoly-... 

Membrane polymer Cellulose triacetate TFC polyamide TFC polyamide TFC polyamide... 

Other Polymers Cellulose triacetate 145.7 Ethyl acetate 185-235 3.5-8.5 0.5-5 LCST [75] Visual CP, variable vol. 

Many ceUulosic derivatives form anisotropic, ie, Hquid crystalline, solutions, and cellulose acetate and triacetate are no exception. Various cellulose acetate anisotropic solutions have been made using a variety of solvents (56,57). The nature of the polymer—solvent interaction determines the concentration at which hquid crystalline behavior is initiated. The better the interaction, the lower the concentration needed to form the anisotropic, birefringent polymer solution. Strong organic acids, eg, trifluoroacetic acid are most effective and can produce an anisotropic phase with concentrations as low as 28% (58). Trifluoroacetic acid has been studied with cellulose triacetate alone or in combination with other solvents (59—64) concentrations of 30—42% (wt vol) triacetate were common. 

Polymer Plasticizer. Nylon, cellulose, and cellulose esters can be plasticized using sulfolane to improve flexibiUty and to increase elongation of the polymer (130,131). More importantly, sulfolane is a preferred plasticizer for the synthesis of cellulose hoUow fibers, which are used as permeabiUty membranes in reverse osmosis (qv) cells (131—133) (see Hollow-FIBERMEMBRANEs). In the preparation of the hoUow fibers, a molten mixture of sulfolane and cellulose triacetate is extmded through a die to form the hoUow fiber. The sulfolane is subsequently extracted from the fiber with water to give a permeable, plasticizer-free, hoUow fiber. 

It is difficult for dye solutions in water to penetrate synthetic fibers such as polyester, cellulose triacetate, polyamides, and polyacryUcs which are somewhat hydrophobic. The rate of water imbibition differs with each fiber as shown in Table 1 as compared to viscose (see Fibers, regenerated CELLULOSics), which imbibes water at the rate of 100% (1). The low imbibition rate is attributed to the high T obtained when the polymeric fibers are drawn. During this drawing operation the polymer chains become highly oriented and tightly packed, forming a stmcture practically free of voids. 

Strictly speaking, the term polyester ought to refer to a chemical compound containing many ester groups in each molecule. In practice, however, it usually refers to polymeric materials containing ester groups as major structural components of the main chains of the macromolecules of which the polymer is composed, and this is the sense in which it is used here. The term is not now usually applied to polymers that contain ester groups attached to the main chain either directly, as in cellulose triacetate, poly(vinyl acetate) or poly(methyl acrylate), or within short side-chains. 

In principle, molecular sieve carbons (MSC) can be achieved by the pyrolysis of thermosetting polymers such as polyvinylidene chloride, polyfurfuryl alcohol, cellulose, cellulose triacetate, polyacrylonitrile and phenol formaldehyde (Koresh 1980). An example is given by Trimm and Cooper (1970,1973) for the preparation of MSC (mixed with metallic compounds) for catalyst systems. A mixture of furfuryl alcohol, platinum oxide and formaldehyde was heated to 40°C and additional formaldehyde was added to ensure the... 

A literature survey ( 1 - 11) on the fractionation of cellulose triacetate by precipitation indicates that in most cases it has been unsuccessful due to the possibility of hydrogen bonding between polymer and solvent in solutions (10. 12). GPC has been applied to the fractionation of cellulose derivatives by many workers. Segal (13), Meyerhoff (14 - 16), Muller and Alexander (17) have reported the fractionation of cellulose nitrate by GPC. Muller and Alexander (17), Brewer, Tanghe, Bailly and Burr... 

Fractional Precipitation of Cellulose Triacetate. The reported partial or non-fractionation of cellulose triacetate from chlorinated hydrocarbons or acetic acid may be explained in terms of the polymer-solvent Interaction parameter x (1-11) The x values for cellulose triacetate-tetrachloroethane and cellulose triacetate-chloroform systems are reported (10,21) as 0.29 and 0.34 respectively. The lower values of x for such systems will result in a smaller or negative heat of mixing (AHm) and therefore partial or non-fractionation of the polymer in question results. 

Linear polymers, polystyrene and cellulose triacetate exhibit differences in hydrodynamic behavior in solution. Cellulose and its derivatives are known to have highly extended and stiff chain molecules below a Dp of about 300, but as the Dp Increases above 300 the chain tends to assume the character of a random coll (27,28). The assumption that hydrodynamic volume control fractionation in GPC may not be true for polystyrene and cellulose triacetate, though it has been found satisfactory for non-polar polymers in good solvents (29). 

Deters (14) vibromilled a blend of cellulose and cellulose triacetate. The acetic acid content of cellulose acetate decreased with grinding time (40 h) while that of the cellulose increased, suggesting the formation of a block or graft copolymer or of an esterification reaction by acetic acid developed by mechanical reaction. Baramboim (/5) dissolved separately in CO polystyrene, poly(methyl methacrylate), and poly(vinyl acetate). After mixing equal volumes of solutions of equivalent polymer concentration, the solvent was evaporated at 50° C under vacuum and the resultant product ball-milled. The examination of the ball-milled products showed the formation of free radicals which copolymerized. 

Fig. 7. Comparison of experimental phase boundary concentrations between the isotropic and biphasic regions for various liquid-crystalline polymer solutions with the scaled particle theory for wormlike hard spherocylinders. ( ) schizophyllan water [65] (A) poly y-benzyl L-glutamate) (PBLG)-dimethylformamide (DMF) [66-69] (A) PBLG-m-cresoI [70] ( ) PBLG-dioxane [71] (O) PBLG-methylene chloride [71] (o) po y(n-hexyl isocyanate) (PHICH°Iuene at 10,25,30,40 °C [64] (O) PHIC-dichloromethane (DCM) at 20 °C [64] (5) a po y(yne)-platinum polymer (PYPt)-tuchIoroethane (TCE) [33] ( ) (hydroxypropyl)-cellulose (HPC)-water [34] ( ) HPC-dimethylacetamide (DMAc) [34] (N) (acetoxypropyl) cellulose (APC)-dibutylphthalate (DBP) [35] ( ) cellulose triacetate (CTA)-trifluoroacetic acid [72]...

Materials. Cellulose Triacetate. Celanese cellulose triacetate was purified by dissolution in reagent grade methylene chloride, followed by filtration and reprecipitation into an excess of reagent grade 2-propanol. The polymer was collected on a Buchner funnel, washed with 2-propanol, and dried. Clear films of 5-mil thickness were cast from methylene chloride solution and used for the photolytic studies. 

Even though the two polymers have the same molecular weight, the cellulose triacetate has an intrinsic viscosity more than eight times greater than the polyisobutene. Note that the Mark-Houwink coefficient a is primarily responsible for this the intrinsic viscosities would be ranked oppositely if k were responsible. 

Polymer Poly(D- propylene oxide) Cellulose triacetate Cellulose diacetate Polyfy-methyl L-glutamate) (a-helix)... 

Cellulose triacetate (CTA) Polymer with complete acetylation of cellulose that is hydrophilic, but suffers from very narrow acceptable temperature (<30°C), and pH (4-6 nominal, 2-9 occasional) ranges. This material is also highly susceptible to microbial attack. (In-filco Degremont is the only manufacatuer using this material as of this publication.)... 

The starting material for this process is wood pulp, cloth, or paper waste and the acetic acid is added first to swell the material and allow it to take up the reagents better. Organic solvents often do this to polymers. The anhydride now carries out the acid-catalysed acetylation and the cellulose triacetate, unlike the cellulose, dissolves in the reaction mixture. The new polymer is often known simply as acetate . 

Fig. 3. Typical TLC chromatograms of cellulose triacetate (CTA) fractions and whole polymer (Ac w = 61.0wt%) having various Mw 12) solid lines fractions broken line whole polymer numbers on curves represent 10 4 Mw. (Rf = rate of flow.)...

The chromatograms of cellulose triacetate (CTA) whole polymer (Ac w = 61.0 wt %, dotted curve) and its fractions (solid curves) are illustrated in Fig. 3. For the cellulose diacetate (CDA) and CTA fractions, the TLC becomes apparently sharp with an increase in Mw. The double-peaked form of the chromatograms is characteristic of the CTA samples, although their gel permeation chromatography (GPC) curves have been found to be single-peaked. This fact implies that the peak at the lower end of Rf corresponds to fully substituted CTA and the peak at the higher end is obviously due to the existence of not-fully substituted acetate. In this sense, real CTA is a binary mixture of ideal CTA and CDA. 

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