Glass Transition of Lignin

Irvine, G.M. The glass transitions of lignin and hemicellulose and their measurements by differential thermal analysis. TAPPI 67(5), 118-121 (1984)... 

Geoffrey, M.I., 1984. The glass transition of lignin and hemicellu-lose and their measurement by differential thermal analysis. Wood Chem., 67(5) 118-121. 

Figure 8.6 indicate, dry cellulose shows no transition in a temperature range from 0 to 200°. On this account, it is reasonable to consider that the baseline gap observed in Figure 8.11 is attributed to the glass transition of in situ lignin. As reported previously [1,7,21,22], Tg s of isolated lignin are usually observed in a temperature range from ca. 90 to 190°C. 

Hirose S, Hatakeyama T, Hatakeyama H (2005) Curing and glass transition of epoxy resins from ester-carboxyUc acid derivatives of mono- and disaccharides and alcoholysis lignin. Macromol Symp 224 343-353... 

It is anticipated that the possibility of producing elastomeric lignin-containing PU s strongly depends on whether crosslink density can be held on a low level or not. It is also necessary to include soft segments, so that the glass transition temperature (Ta) of the PU falls below room temperature. 

Figure 1. Effect of lignin content on the glass transition temperature (Ta) of networks crosslinked with HDI. Formulation type A ( ) type B ( ) and type C (0).

Table I. Hydroxyl content and glass transition temperature of lignins derivatized with acetic anhydride (Ac), diethyl sulfate (Et), and propylene oxide (Pr)...

As an amorphous polymer, lignin undergoes chain segment motion upon heating. This motion, a glass transition, is characteristic of all amorphous polymers, and is indicated by an endothermic shift in the DTA or DSC curves. This glass transition is accompanied by abrupt changes in free volume, heat capacity, and thermal expansion coefficient. 

Fig. 4.8.12. Diagram showing the effect of degree of acetylation and water content on the glass transition temperature, Tx, of dioxane lignin. (Hatakeyama and Hatakeyama 1983)...

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