Thermal analysis of cellulose acetate solids with total degrees of substitution of 0.49, 1.75, 2.46, and 2.92

Abstract

The effects of the total degree of substitution ‹‹F›› and average-molecular weight on glass transition temperature (Tg), melting point (Tm) and the onset point of thermal decomposition (Td) for cellulose acetate (CA) solids were studied using DSC, TG, and X-ray diffractometry. Fractionated and whole CA polymers with ‹‹F›› of 0.49, 1.75, 2.46, and 2.92 were used. All whole and fractionated CA showed Tg. Tg of CA fractions do not depend on average-molecular weight significantly, except for CA(2.92) (the number in parentheses denotes ‹‹F››). Tg of CA fractions increases monotonously with a decrease in ‹‹F›› as follows Tg(K)=523-20.3‹‹F ››To derive the above equation, the Tg value of a CA(2.92) fraction with a viscosity-average molecular weight of 1×105 was employed. ‹‹F›› dependence of Tg was considered related to the difference in the density of intermolecular interactions in CA solids. For CA(2.92) and some CA(2.46) fractions, cold crystallization occurs at a temperature about 30 and 20 degree higher than their Tg, respectively. Tm and Td of CA fractions were mainly determined by CF ‹‹F››, being independent of the average-molecular weight. Tm as well as Td of CA(2.92) were highest among those of four kinds of CA, and CA(2.92) was thermally the most stable polymer among CA. © 1985 The Society of Polymer Science, Japan.