SUMMARY AND CONCLUSIONS 



The major conclusions from this study are: 



1. The major component of western Cottonwood hemicellulose is 0-acetyl -4-0-methyl 

 glucuronoxylan (xylan) , making up about 95 percent of the noncellulose carbohydrate. 



2. The three major components of western Cottonwood, cellulose, xylan, and lignin 

 have quite dissimilar thermograms, but all three are reflected in the thermogram of the 

 whole wood. This independent behavior makes it quite likely that each component can be 

 studied independently and the results used to predict its behavior within whole wood. 

 This greatly simplifies the study of the complicated pyrolysis of wood. 



3. The hemicellulose 0-acetyl-4-0-methyl glucuronoxylan is almost completely 

 pyrolyzed prior to the beginning of cellulose pyrolysis. This makes the hemicellulose 

 component more important to the fire problem than generally thought, especially since 

 the pilot ignition temperature is around 300° to 340° C. 



4. Lignin is the least important component in the pyrolysis of wood because of 

 its products, rate of decomposition, and high yield of char. Since the char probably 

 contributes mainly to glowing, lignin may be quite important to the hold-over fire in 

 punk or decomposed plant material. 



5. Contrary to past work (Schwenker and Beck 1963), no formaldehyde from the 

 pyrolysis of these carbohydrates was found. This agrees with Wodley (1969). 



6. Cellulose, xylan, and wood all exhibit dissimilar thermograms and volatile 

 products between zinc chloride and sodium hydroxide treatment. The zinc chloride 

 produces more of the furan compounds, especially 2-furaldehyde , and a decrease in 2 



and 3 carbon compounds. The sodium hydroxide decreases the furan compound and increases 

 2 and 3 carbon compounds. Obviously these two model retardants are acting by dissimilar 

 mechanisms . 



7. Zinc chloride and sodium hydroxide both cause an increase in char and water 

 production. This probably means they both lead to more glowing combustion than would 

 occur with the untreated fuel. However, any flame retarding effect is due to a com- 

 bination of decreases in volatilization amount and rate as well as increases in water 

 and char production. Since these two compounds act differently, each effect must be 

 weighted accordingly. 



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