This document describes a method for the determination of the glass transition temperature (Tg) of kraft lignin. The procedure utilizes differential scanning calorimetry (DSC).

This procedure is applicable to solid lignins (e.g., powdered form) isolated using different isolation techniques (e.g., acidification with hydrochloric acid, sulfuric acid, etc., and carbonation using gaseous carbon dioxide) from the spent liquor (black liquor) generated from the kraft pulping process.

It does not apply to raw black liquor and lignin in the alkali form, (lignin that is separated from wood chips and dissolved in sodium sulfide and sodium hydroxide liquor such as that originating from black liquor).