Thermal Analysis of Cellulose Acetate Solids with Total Degrees of Substitution of 0.49, 1.75, 2.46, and 2.92

Abstract

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 (Tctl 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 averagemolecular 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))

Probing the dependence of the properties of cellulose acetates and their films on the degree of biopolymer substitution: use of solvatochromic indicators and thermal analysis

“…The slope of this line is in good agreement with that previously calculated (20.3), based on the results of four CAs (Kamide and Saito 1985). Because of thermal annealing before recording the DSC trace, no exothermic event was observed before the endothermic peak, corresponding to sample melting.…”

“…Patel et al were unable to detect T g for CAs samples of DS = 0.9 and 1.6 (Patel et al 1970). Our T g values for CTA, 173°C, agrees with literature values of 172, and 187°C (Kamide and Saito 1985;Zugenmaier 2004). The linear dependence of T g on DS is described by Eq.…”

“…4. Figure 6b is satisfying because our data, as well as previous ones (Kamide and Saito 1985), can be fitted by employing the same polynomial. The decrease then increase of T m as a function of increasing DS maybe related to the corresponding structural change.…”

“…This (missing) event is attributed to the so called ''cold crystallization'' first observed for polyester fibers (Schwenker and Beck 1960). This behavior (disappearance of crystallization) was observed before for a CA sample (DS = 2.92) where an endothermic peak at 210°C disappeared after the sample was heated to 237°C, cooled to room temperature, then heated again (Kamide and Saito 1985). We were unable to determine the values of T m for the samples with DS = 0.83 and 1.13, because these temperatures were close to the corresponding T decomp ; the base lines of the corresponding TGA traces were not linear, showing some decomposition before melting.…”

“…The conclusions drawn here should apply to CAs with other molecular weights, MW. The reason is that TA analysis of CAs has indicated that the results are practically independent of MW, at the same DS (Kamide and Saito 1985;Takahashi et al 1979).…”