Cellulose Acetate and Mixed Esters

In the course of the recent revival of bio-based polymers [58], cellulose esters have gained attention as matrix materials both for macroscopic and nano composites. In a series of papers, Seavey, Glasser, et al. have investigated continuous cellulose fibre reinforced cellulose ester composites of which the last is dealing with commercial matrix and fibre options [59]. A sort of hand lay-up with acetone solutions was used as the manufacturing method. For various commercial CABs and Lyocell fibres moduli between 15 GPa and 21 GPa were obtained in unidirectional (UD) composites while for cross-ply (CP) architectures, the values were between 10 and 15 GPa. Strengths go up to 310 MPa for UD composites and to 210 MPa for CP materials. 

Heublein, B., Fink, H.-P. and Bohn, A. (2005) Cellulose fascinating biopolymer and sustainable raw material. Angewandte Chemie-Intemational Edition, 44, 2-37. 

(2004) Cotton fibers as natural raw materials for cellulose acetate production. Macromolecular Symposia, 208, 29-35. 

Kordsachia, O. and Sixta, H. (1997) Eignung von Rohstoffen und Verfahren zur HersteUung von ChemiezeUstoflen. Das Papier, 51, 637-643. 

Hessler, L.E., Merola, G.V. and Berkley, E.E. (1948) Degree of polymerization of cellulose in cotton fibers. Textile Research Journal, 18, 628-634. 

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Many cellulose esters, such as cellulose nitrate, cellulose acetate, and mixed esters of cellulose acetate butyrate, have found popularity in commercial scale production. Many new esters continue to appear in the market. Traditionally, esterification is conducted on a heterogeneous system (topo-chemical reaction) however, homogeneous systems employing mixed organic solvents have recently been developed. For example, Ikeda et al. [17] demonstrated that homogeneous esterification and acetalization of cellulose in LiCF DM AC can be achieved. 

Ill, Cellulose Acetate and Mixed Ester Plastics Continuous Sheets Under. 003". Figures on this classification are available on a monthly basis since June 1945 (4, 9). They are also available in the annual census of 1947 3),... 

Cellulose Acetate and Mixed Ester Plastics Continuous Sheets Equal... 

Cellulose acetate and mixed ester (include acetate butyrate and propionate plastics)... 

AND 113, Cellulose Acetate and Mixed Ester Plastics Sheets, Rods, and Tubes. Monthly data are available from 1933 to May 1945 (2). From February 1941 to the end of the period, cellulose acetate safety glass plastic was excluded. Since that time this total class can be computed by adding together the acetate sheet classifications, rods, and tubes. 

Cellulose Acetate and Mixed Ester Plastics Molding. Annual figures are available for 1939 (3). Monthly figures are available from 1938 to the present (2,4,9),... 

Synthetic Membrane Appropriate inert and commercially available synthetic membranes such as polysulfone, cellulose acetate/nitrate mixed ester, or Polytetrafluoroethylene 70 Fm membrane of appropriate size to fit the diffusion cell diameter (e.g., 25 imn in above case). 

Cellulose acetate, or mixed esters such as acetate-butyrate are widely used in photographic film, safety film, and lacquers. 

Cellulose esters, especially acetate propionate and acetate butyrate mixed esters, have found limited use in a wide variety of specialty appHcations such as in nonfogging optical sheeting (171), low profile additives to improve the surface characteristics of sheet-molding (SMC) compounds and hulk-molding (BMC) compounds (172,173), and controlled dmg release via encapsulation (174). 

A number of various esters of cellulose are known, for example, propionate and butyrate and mixed esters such as acetate-butyrate, propionate-isobutyrate, and propionate-valerate. The mixed esters have found use in plastic composites when good grease- and water-repelling properties are required. 

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. 

Cellulose acetate-propionate is used in flexographic ink formulations. The acetate-butyrate mixed esters are used in sheeting, molded plastics, hot melt dip coatings, lacquer coating and film products. The mixed proprionate-butyrate ester has excellent compatibility with oil-modified alkyl resins and is used in wood furniture coatings. 

Various other cellulose esters have been investigated and cellulose tripropionate and the mixed esters, cellulose acetate-propionate and cellulose acetate-butyrate are commercially available. Of these materials, which all have similar properties and applications (see Table 11.5 for some comparative properties), cellulose acetate-butyrate is probably the best known and is described below. These polymers have larger side-chains than cellulose acetate and with equal degrees of esterification, molecular weight and plasticizer content they have lower density and are softer and easier to mould. The larger hydrocarbon side-chain also results in slightly lower water absorption. 

Mixed esters of cellulose acetate and cellulose propionate, and cellulose acetate and cellulose butyrate can be formed by using mixtures of the anhydride of one acid and the acid of the other [4]. These mixed esters (60-65% acetate and 40-35% propionate or butyrate) give improved properties of toughness and shock resistance necessary for injection molding and special-purpose lacquers. 

Mixed Cellulose Esters. Only those containing acetate units and corresponding to terpolymers of cellulose, cellulose acetate, and a second ester are worthy of interest. Actually, the situation is even more complex since 3 degrees of substitution may be possible, along with 3 sites of substitution with 3 functional groups for each monomeric unit. 

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