Cellulose acetate characteristics

Mixed cellulose esters containing the dicarboxylate moiety, eg, cellulose acetate phthalate, have commercially useful properties such as alkaline solubihty and excellent film-forming characteristics. These esters can be prepared by the reaction of hydrolyzed cellulose acetate with a dicarboxyhc anhydride in a pyridine or, preferably, an acetic acid solvent with sodium acetate catalyst. Cellulose acetate phthalate [9004-38-0] for pharmaceutical and photographic uses is produced commercially via the acetic acid—sodium acetate method. 

The common commercial products are the primary (triacetate) and the secondary (acetone-soluble, ca 39.5% acetyl, 2.45 DS) acetates they are odorless, tasteless, and nontoxic. Their properties depend on the combined acetic acid content (acetyl, see Table 1 and Figure 4) and molecular weight. Solubihty characteristics of cellulose acetates with various acetyl contents are given in Table 4. 

Moisture sensitivity and vapor-permeabiUty rate of cellulose acetate increase with decreasing acetyl (increasing hydroxyl) content. Thermoplastic characteristics are gready improved as the acetyl content is increased from ca 20% (DS(acetyl) = 1) to ca 39% (DS(acetyl) = 2.4) (9). 

The cellulose esters with the largest commercial consumption are cellulose acetate, including cellulose triacetate, cellulose acetate butyrate, and cellulose acetate propionate. Cellulose acetate is used in textile fibers, plastics, film, sheeting, and lacquers. The cellulose acetate used for photographic film base is almost exclusively triacetate some triacetate is also used for textile fibers because of its crystalline and heat-setting characteristics. The critical properties of cellulose acetate as related to appHcation are given in Table 10. 

Table 11. Application and Characteristics of Commercial-Grade Cellulose Acetate Butyrate ...

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkaU than the usual acetate and may be scoured, generally, in openwidth, with aqueous solutions of a synthetic surfactant and soda ash. 

Compared with the major vinyls cellulose acetate plastics have a high water absorption, poor electrical insulation characteristics, limited aging resistance and... 

As the separation characteristics of liquid chromatographic and electrophoretic techniques markedly differ from each other, combined methods using the advantages of both procedures have been successfully used for the analysis of flavonoids. Thus, the use of CZE-UV, HPTLC-UV and GC-MS for the measurement of flavonoids in seeds and root exudates of Lotus pedunculatus has been reported. The rooting solution and seed exudate were passed through cellulose acetate filters to bind the flavonoids. After extraction,... 

Our Investigation on durability and membrane characteristics changes under adverse conditions have much contributed to development of RO applications. Among these applications are those for ultra-pure water in electronic and pharmaceutical industries. Even under the circumstance of pH 7 and with 2 to 4 times per year of sterilization by H2O2 of as high as 1 %, the cellulose acetate membrane proved to show membrane life of more than 3 years. 

Acetyl Celluloses (AC) (Acetates of Cellulose or Cellulose Acetates). According to Doree(Ref 3) the action of AcaO on cellulose (called acetylation) should theoretically yield the triacetate [CfiH702(00C. CH3)s]n. Actually, the products of acetylation are a mixture of tri-, di- and mono-acetate. A characteristic property of the lower acetyl-ated acetates is their sol in acetone, whereas the triacetate can absorb acetone only to the extent of causing swelling... 

Polybenzimidazolone membrane 21 developed by Teijin Ltd. had the following permeative characteristics Water permeation, 840 1/m2 - day salt rejection, 99.5% (1% NaCl aqueous solution, 80 kg/cm2)69). The membrane was less sensitive to plasticization with water than cellulose acetate and aromatic polyamide membranes... 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkali than the usual acetate and may be scoured, generally, in open-width, with aqueous solulions of a synthetic surfactant and soda ash. Triacetate is a hydrophobic liber, as compared to secondary acetate, and consequently does not dye rapidly. It is necessary to increase the rate of diffusion of the disperse dye into the fiber by increasing the dyeing temperature to 110— 130CC or using a dye accelerant or carrier, or both. 

Table II shows the effect of the carboxyl content on the adhesive characteristics of PMDA-extended polyesters in blends with K-l polycarbonate [4,4 - (2-norbomylidene) diphenol polycarbonate] (VIII), cellulose acetate butyrate, and poly (vinyl chloride). K-l polycarbonate is an experimental polymer which, like cellulose acetate butyrate and poly (vinyl chloride), is very sensitive to adhesive changes because only 1-2% of a carboxylated...

Cellulose acetate (CA), of poor chemical stability, tends to hydrolyze over time, is subject to biological attack, and can operate at only a limited pH range of 3.0 to 6.5 at 0 to 30°C. It is widely available at low cost and is tolerant of continuous low-level chlorine exposure, such as is found in city water). Often blended with cellulose triacetate (CTA), which provides reasonable hydrolysis and compaction characteristics. 

---