Optical Radiation Standards, National Physical Laboratory, K. S. Krishnan Road, New Delhi, 110012, India.
In this paper we report the results of the investigations made on the changes in near infrared (NIR) spectra and color parameters of pulp sample on heat treatment. Color change of pulp is analysed by the CIELAB color parameters. Near infrared (NIR) spectra of pulp at different temperatures are recorded using diffuse reflectance accessory. The color change in pulp on increasing temperature is related to the decrease in the content of hemicellulose and lignin. This can be seen by variation in infrared band markers at wavelength at 1580 nm (crystalline region in cellulose), 1705 nm (aromatic skeletal in ligin) and 1773 nm (furanose or pyranose ring constituent of hemicellulose) at different temperatures. We find that NIR spectroscopy is a powerful tool to probe the physicochemical structural changes in pulp on heat treatment.
