A non-destructive method for determination of the mechanical strength of virgin and recycled pulps

Fibre-fibre bonding plays an important role in the mechanical strength of paper and board products and is often improved by refining. In this study, pine and eucalypt pulps obtained from commercial pulp mills are refined to different freeness. It is evident that refining increases the surface area of fibres and hence improves elastic modulus of handsheets significantly. FTIR spectra obtained for these pulp samples have implied that the number of hydrogen bonds in the fibre network also increases with the degree of refining. A multivariate analysis (PLS) is used to establish a correlation between the elastic modulus and FTIR spectral data of the handsheets. It is clearly shown that the PLS model is statistically robust to predict the elastic modulus for the virgin pulp samples. An attempt to predict the elastic modulus of recycled pulps using the PLS model is also addressed in this study.