relating near infrared spectra of Oryza sativa pulps to paper mechanical strength and brightness

• Rice straw was pulped under 27 different sets of conditions.
• We made handsheets from rice straw pulps, subjecting them to mechanical tests.
• Each pulp was analysed by spectroscopy between wavelengths 400 and 2500 nm.
• Spectra in the NIR and visible regions were related to key paper properties.
• Prediction of brightness and the tensile and tear indices was satisfactory.

Rice straw pulps produced under different conditions were subject to near infrared (NIR) spectroscopy. At the same time, samples from those pulps were used to make handsheets, whose mechanical properties were measured. These values and those of brightness were successfully fitted to the pulping variables. Relating them to the NIR spectra, we found valid correlations for all parameters except the burst index, concluding that NIR spectroscopy could be used as an economical, timesaving and non-intrusive way to predict the mechanical strength of pulps before the paper sheet is made.