Cellulose acetate thermal degradation

The list of pyrolysis products of cottonwood shown in Table VII (llj reflects the summation of the pyrolysis products of its three major components. The higher yields of acetone, propenal, methanol, acetic acid, CO, water and char from cottonwood, as compared to those obtained from cellulose and xylan, are likely attributed to lignin pyrolysis. Other results are similar to those obtained from the pyrolysis of cell-wall polysaccharides. This further verifies that there is no significant interaction among the three major components during the thermal degradation of wood. 

Procedure for DTA peak analysis of dioxouranium [UO, [VI]] complexes with cellulose acetate [CA], using the equation of Prout and Tompkins [Table 7.9] showed that the increase of DS of cellulose acetate [from 2.2 to 2.86] and its chelation with uranium [VI] ions increased the activation energies for degradation. The increase in the thermal stabilities [activation energy] of cellulose acetate complexes can be attributed to the coordination bonds between dioxouranium and acetyl of cellulose acetate, i.e., to the formation of five-membered rings [14,29]. 

Esters of cellulose with interesting properties such as bioactivity and thermal and dissolution behavior can be obtained by esterification of cellulose with nitric acid in the presence of sulfuric acid, phosphoric acid, or acetic acid. Commercially important cellulose esters are cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Cellulose esters of aliphatic, aromatic, bulky, and functionalized carboxylic acids can be synthesized through the activation of free acids in situ with tosyl chloride, iV,iV -carbonyldiimidazole, and iminium chloride under homogeneous acylation with DMA/LiCl or DMSO/TBAF. A wide range of cellulose esters that vary in their DS, various substituent distributions, and several desirable properties can be obtained through these reactions. Recently, a number of enzymes that degrade cellulose esters have been reported. Some of them are acetyl esterases, carbohydrate esterase (CE) family 1, and esterases of the CE 5 [169-172] family. 

Table 1. Some products of the thermal degradation of cellulose acetate analysed by TGA/MS/MS...

Figure 5. Proposed scheme for the thermal degradation of cellulose acetate based on TGA/MS/MS analysis...

Other polymers which have been the subject of thermal degradation studies include ethylene-vinyl acetate [29, 66, 67], ethylene-vinyl alcohol [68], poly(aryl-ether ketone) [69], poly-2-vinyl-naphthalene-co-methyl maleate [34], polyphenylenes based on diethyl-benzophenone [70], polyglycollide [71-73], poly(a-methylstyrene tricarbonyl chromium [74], polytetrahydrofuran [75], polylactide [76-78], poly(vinyl) cyclohexane [79], styrene-vinyl cyclohexane [80], isopropenylacetate-maleic dianhydride [80], polyethylene glycol containing a 1,3-disubstituted phenolic group [81], poly-2-vinyl naphthalene-co-methacrylate [34], collagen biopolymers [82], chitin graft poly (2-methyl-oxazoline - polyvinyl chloride blends [83], cellulose [32, 83-88] and side-chain cholestric elastomers [89, 90]. 

Gilmore et al. reported the preparation of a blend of cellulose acetate esters and P(3HB-co-3HV) copolymer using a solvent-casting method. P(3HB-C0-3HV) copolymer and cellulose acetate esters were dissolved separately in chloroform and then dried under vacuum. Lotti and Scandola reported the preparation of a blend of cellulose acetate butyrate and P(3HB-co-3HV) copolymer whereby the components were mixed in an injection molding machine. The temperature was kept low in order to minimise the thermal degradation of P(3HB-co-3HV) copolymer. 

The thermal degradation of cellulose acetate hydrogen phthalate (CAP) and its blends with PMMA has been investigated by thermogravimetry [a.l75]. The TG/DTG curves showed two decomposition stages for pure CAP. The decomposition behaviour was changed with the addition of PMMA. For 90/10 and 70/30 CAP/PMMA blends, there were three... 

Madorsky, S. L., Thermal Degradation of Organic Polymers , Interscience, New York, 1964. A compilation of the existing knowledge on polymers and copolymers of styrene, alkenes, halo-carbons, vinyl acetate, acrylonitrile, butadiene, isoprene, poly(ethylene terephthalate), polybenzyl, polyxylene, phenol, formaldehyde resin and cellulosic polymers Polym, Rev, vol. 7). 

Chemical structure of cellulose (or regenerated cellulose) is shown in Scheme 1. Other important families of cellulose polymers are the cellulose esters, with the presence of groups such as nitrate, acetate, methyl or ethyl. All these polymers, also called cellophanes, are very sensitive to thermal, chemical and also biological degradation, since cellulose is a polysaccharide. 

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