Celluloses decomposition temperature

Determination of the thermal decomposition temperature by thermal gravimetric analysis (tga) defines the upper limits of processing. The tga for cellulose triacetate is shown in Figure 11. Comparing the melt temperature (289°C) from the dsc in Figure 10 to the onset of decomposition in Figure 11 defines the processing temperature window at which the material can successfully be melt extmded or blended. 

Although the prime function of plasticisers in cellulose acetate is to bring the processing temperature of the compound below the polymer decomposition temperature, it has additional values. An increase in the plasticiser content will reduce the melt viscosity at a given temperature and simplify processing. The physical properties of the finished product will be modified, increasing toughness... 

Orientation, wet stretching For plastics whose glass transition temperature (Tg) is above their decomposition temperature, orientation can be accomplished by swelling them temporarily with plasticizing liquids to lower their Tg of the total mass, particularly in solution processing. As an example, cellulose viscous films can be drawn during coagulation. Final removal of the solvent makes the orientation permanent. 

The same may be observed with magnesium carbonate in cellulose [70] (Figure 26). The chemiluminescence intensity at a given temperature increases with pH of the sample almost linearly. As it is evidenced by DSC, the sample with pH 7.2 is the least stable. Figure 26 is also a demonstration of the much higher sensitivity of the chemiluminescence method when compared with DSC. DSC exotherms, which accompany the final stages of the cellulose decomposition... 

The dramatic reduction of hydrogen bonding renders cellulose acetates thermoplastic. However, their softening points are very close to their decomposition temperatures (around 300 °C). The use of external plasticizers (e.g. phtalates) is often used to process cellulose diacetate in plastic applications (eyewear, screwdriver handles, etc.). 

Some polymers, such as cellulose, although linear in structure, have such a strong molecular interaction, mostly due to hydrogen bridges and polar groups that they do not soften or melt. Consequently, the transition temperatures as such are less important to this class of polymers. Normally they are highly crystalline, with a crystalline melting point (far) above the decomposition temperature. Their physical behaviour - except for... 

Recent approaches directed toward preventing oxidation of cotton cloth included using accelerated aging of alkaline-treated cotton cloth for neutralization of acidic, oxidized, cellulose decomposition components that in cellulosic textiles and in paper are responsible for age tendering and yellowing. Conclusions regarding the relative effectiveness of treatments at room temperature were based on results of treatments at one elevated temperature (8). Predictions of long-term effects of these treatments are unknown (9). 

In our previous work, hydrolysis is played an important role at the first step of cellulose decomposition in hot-con ressed water without catalyst. In this study, the sugar, which is the hydrolyzed products of cellulose, was detected at low reaction temperature of 260 and 280 °C, and its concentration was about 40% in the water-soluble products. This means that hydrolysis also plays an important role for gasification with the nickel catalyst, and the obtained sugar can decomposed quickly to non-sugar products. 

Results to date strongly imply that, depending on the residence time, the tar yields for final pyrolysis temperatures above 300 0 will be independent of heating rates. This observation is strengthened by the finding from TGA data analysis that the apparent activation energy for cellulose decomposition is similar to that for tar formation. 

The dose level for plasticisers in non-PVC polymers is generally low, although polyvinyl butyral can take 40 phr and cellulose acetate may need 50 phr of diethyl phthalate or dimethyl phthalate to facilitate processing below the decomposition temperature. 

CgIIuIOSIC Resins. In general, phosphorylation of cellulose or treatment of cellulose with phosphorus-containing resins produces a flame-retardant effect by increasing char 5deld although lowering the decomposition temperature somewhat. The mechanism has been extensively studied (209-211). 

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