Near infrared spectroscopy for estimating properties of kraft paper reinforced with cellulose nanofibrils

ABSTRACT

Background:

The aim of this study was to investigate near infrared (NIR) spectroscopy ability to estimate nanofibril concentration, physical and mechanical properties of Kraft paper reinforced with cellulose nanofibrils (CNF). For this purpose, paper sheets were prepared by mixing unbleached Eucalyptus fibers and cellulose nanofibrils. Twelve treatments result from the combination of the nominal grammages 75, 85, 95 and 105 g m-² with the nanofibril concentrations of 1, 5 and 10wt%, with 7 sheets per treatment. NIR spectra measured directly on paper specimens were correlated with physical and mechanical properties values obtained through conventional laboratory analyzes.

Results:

Principal component analysis (PCA) revealed no separation among specimens related to nanofibril content. Partial least squares regression (PLS-R) models for estimating nanofibril content, tensile index, stretch and resistance to air passage yielded R ²cv ranging from 0.73 to 0.98. Partial least squares - discriminant analysis (PLS-DA) correctly classified up to 93% of the paper specimens both by grammage and nanofibril content using NIR spectra.

Conclusion:

This approach appears to be suitable for predicting physical and mechanical properties of Kraft papers and can detect cellulose nanofibril content in the cellulose handsheets.

Keywords:
Mechanical resistance; Nanocellulose; Machine learning; Papermaking; Quality control

HIGHLIGHTS

Models were able to successfully estimate paper properties.

NIR spectroscopy can quickly evaluate paper handsheets quality.

NIR spectrum contains information about CNF content within the paper.

Tensile index, stretch and resistance to air passage can be estimated by NIR-based models.