Oxidized cotton cellulose

By using this technique acrylamide, acrylonitrile, and methyl acrylate were grafted onto cellulose [20]. In this case, oxidative depolymerization of cellulose also occurs and could yield short-lived intermediates [21]. They [21] reported an electron spin resonance spectroscopy study of the affects of different parameters on the rates of formation and decay of free radicals in microcrystalline cellulose and in purified fibrous cotton cellulose. From the results they obtained, they suggested that ceric ions form a chelate with the cellulose molecule, possibly, through the C2 and C3 hydroxyls of the anhy-droglucose unit. Transfer of electrons from the cellulose molecule to Ce(IV) would follow, leading to its reduction... 

The selective oxidation of cellulose to dialdehyde by sodium periodate is well known. It has been postulated by Criegee (74) and by Waters (73) that this reaction proceeds by a free radical mechanism. Toda (76) and Morimoto, Okada, Okada, and Nakagawa (77) have concluded that sodium periodate oxidation should initiate graft polymerization. They succeeded in grafting methyl methacrylate and acrylonitrile onto cellulose substrates, such as rayon and paper. A similar procedure is recommended in a patent of Chemische Werke Huels (78) to graft vinyl monomers onto cotton, polyethylene oxide, copolymers of vinyl chloride-vinyl acetate, and others. 

Recently, the adhesion of MF microparticles on a cellulose film in air as well as in liquid media was characterised using AFM. The cellulose film was made by dissolving cotton powder in N-methylmorpholine-N-oxide (NMMO) solution, followed by spinning on a silicon wafer. Spectroscopic ellipsometry was employed to measure the film thickness, and AFM was also utilised for characterising the film roughness and material distribution (Figure 20). The cotton cellulose film was also... 

The discrepancies among reported data, besides possibly being caused by different analytic techniques employed, may be partly attributed to variations in the alkali concentration used as shown in Fig. 1. Rammas and Samuelson [197] also demonstrated that the reactivity of the 2-OH and 6-OH with ethylene oxide was quite comparable in dilute alkali and that the C6 hydroxyethylation was preferentially promoted by an increase in the alkali concentration. In etherification of cotton cellulose with sodium 2-aminoethyl sulfate [192], sodium allyl sulfate [193], or acrylamide [194], the 6-OH group was generally found to be more reactive than the 2-OH group. 

It was reported that the oxidative thermal degradation of the grafted fiber depended on the amount of grafted polymer and on the structure of the cellulose substrate (cotton cellulose, rayon, etc.). 

Other studies have shown that in the thermal treatment of cellulose at temperatures below 300 °C, the rate of weight loss can be accelerated by oxidation reactions such as the degradation of cellulose by atmospheric oxygen. When cotton cellulose was heated at 190 °C for 50 h, carboxyl and carbonyl groups formed at a linear rate. When rates of glycosidic bond scission at 170 °C in nitrogen and in air were compared, the rate in nitrogen was close to one-half of the rate in air (30). 

Figure 6. Rate of homogeneous hydrolysis of cotton cellulose in 81.25% phosphoric acid (D), chromate-oxidized cellulose (O), and SBH-reduced cellulose (R). (Reproduced with permission from Ref. 24. Copyright 1961...

Gel-permeation chromatography" is used to compare the pore structure of jute, scoured jute and purified cotton cellulose. Both native and scoured jute have shown greater pore volumes than cotton. The effects of alkali and acid treatment on the mechanical properties of coir fibers are reported." Scanning electron micrographs of the fractured surfaces of the fibers have revealed extensive fibrillation. Tenacity and extension-at-break decrease with chemical treatment and ultraviolet radiation, whereas an increase in initial modulus and crystallinity is observed with alkali treatment. FTIR spectroscopy shows that the major structural changes that occur when coir fibers are heated isothermally in an air oven (at 100, 150 and 200 °C for 1 h) are attributable to oxidation, dehydration and depolymerization of the cellulose component. 

G. F. Davidson, Properties of the oxycelluloses formed in the early stages of oxidation of cotton cellulose by periodic acid and metaperiodate, J. Text. Inst., 31 (1940) T81-T96. 

To obtain the modified ANP, the chemical pretreatment can be carried out, for instance by means of the selective oxidation with nitrogen tetroxide. The oxycel-lulose was prepared by the following method (Kumar, 2003) the starting cotton cellulose (100 g) was soaked with mixture of 85 wt% o-phosphoric and 70 wt% nitric acids (2 1), and after addition of 20 g of sodium nitrite the reaction system was kept at room temperature for 48 h. 

Reicher J (1992), Decomposition kinetics of the oxidizing agent and damage to cotton cellulose during metal-catalyzed bleaching with hydrogen peroxide , Melliand... 

Neukom, H. and Deuel, H. (1958) Alkaline degredation of pectin. Chemistry and Industry, xae, 683. Nevell, TP. (1951a) Oxidation of cotton cellulose by nitrogen dioxide./. Textile Inst., 42, 91-129. 

---