Cellulose crystalline structure and thermal properties under heat treatment: An investigation by 2D correlation of near infrared spectroscopy and differential scanning calorimetry

This study investigated the thermal behavior and crystallinity of microcrystalline cellulose (MCC) under heat treatment using near infrared (NIR) spectroscopy and differential scanning calorimetry (DSC). The results showed that heat treatment reduced the crystallinity and thermal stability of MCC at a certain point, and that the changes in the chemical components and structure of MCC were correlated with the heat flow measured by DSC. The analysis was performed using two-dimensional correlation spectroscopy (2DCOS), which revealed the simultaneous changes in the NIR second-derivative spectra and the DSC thermograms of heat-treated MCC. Linear regression analysis showed a high r 2 value of 0.90 between the DSC enthalpy change at 270 °C–400°C and the PC1 score of NIR second-derivative spectra at 7500–4100 cm −1 . The 2DCOS synchronous map showed a positive correlation at 6656–6229 cm −1 with a r value of 0.70–0.98 for the endothermic reaction, and a negative correlation at 6229; 5620; 5401; 4844; 4535 cm −1 with a r value of −0.90 to −0.99 for the exothermic reaction. This study extended the knowledge on the thermal behavior and decomposition mechanisms of heat-treated MCC, and provided a useful method for cellulose characterization and identification.