Accurate measurement of the localized degree of grafting using thermogravimetric analysis

• Cryo-milling and thermogravimetric analysis used to measure degree of grafting (DG). • At low DG, difference between proposed method and gravimetric measurements was <1.0 %. • DG distribution can be detected for cotton fiber substrate with thickness of <1 mm. A method for accurately measuring the degree of grafting (DG) in a small area of several tens of square millimeters to several tens of square centimeters is proposed. This method employs thermogravimetric analysis to take advantage of the similarity in pyrolysis behavior of grafted materials with similar DGs. A pre-irradiation method is used for graft polymerization with an acrylic acid monomer to a cotton fibers substrate, and the proposed method is used to quantify the DG of the grafted material. Cryo-milling is used to homogenize the grafted material, and reference samples with known DGs (DG: 1.9 %–107.0 %) are prepared. Subsequently, localized DG is determined by measuring the pyrolysis behavior and comparing it to that of the reference samples. In experiments, the proposed method accurately predicts the DGs of test samples with a difference of <1.0 % from gravimetric measurements, especially at low DGs of 0 %–40.0 %. The proposed method can also detect the DG distribution of a cotton fiber substrate with a thickness of <1 mm. The proposed method is expected to be useful for detecting heterogeneous graft reactions and improving quality control of grafted materials in industrial applications.