Comparative study of cellulose and lignocellulose nanopapers prepared from hard wood pulps: Morphological, structural and barrier properties.

The current research intended to explore the hardwood pulps capabilities to produce cellulose (CNPs) and lignocellulose nanopapers (LNPs) and feasible enhancement of their performance for possible utilization in sustainable packaging. The high-yield hardwood pulps were then bleached to show the fundamental role of residual lignin on the ultrafine fibrillation processes, structural and barrier properties of nanopapers. X-ray diffraction results demonstrated that the crystallinity and crystallite size of CNPs and LNPs were lower than the corresponding starting pulps. Field emission scanning electron microscopy analysis showed that the average nanofibril diameter of the CNPs and LNPs are 35 nm and 23 nm, respectively. Elastic modulus of LNPs was found to be 9.1 and 10.8 GPa for Chemimechanical and Neutral sulfite semichemical pulps, respectively. The semi-porous and consolidated structure of LNPs prepared from CMP fibers contributed to yield the lowest water vapor transmission rate i.e. 108 g/m2.day which is promising for potential applications in packaging materials.

Multivariate Analysis of Hemicelluloses in Bleached Kraft Pulp Using Infrared Spectroscopy.

The hemicellulose composition of a pulp significantly affects its chemical and physical properties and thus represents an important process control variable. However, complicated steps of sample preparation make standard methods for the carbohydrate analysis of pulp samples, such as high performance liquid chromatography (HPLC), expensive and time-consuming. In contrast, pulp analysis by attenuated total internal reflection Fourier transform infrared spectroscopy (ATR FT-IR) requires little sample preparation. Here we show that ATR FT-IR with discrete wavelet transform (DWT) and standard normal variate (SNV) spectral preprocessing offers a convenient means for the qualitative and quantitative analysis of hemicelluloses in bleached kraft pulp and alkaline treated kraft pulp. The pulp samples investigated include bleached softwood kraft pulps, bleached hardwood kraft pulps, and their mixtures, as obtained from Canadian industry mills or blended in a lab, and bleached kraft pulp samples treated with 0-6% NaOH solutions. In the principal component analysis (PCA) of these spectra, we find the potential both to differentiate all pulps on the basis of hemicellulose compositions and to distinguish bleached hardwood pulps by species. Partial least squares (PLS) multivariate analysis gives a 0.442 wt% root mean square errors of prediction (RMSEP) for the prediction of xylan content and 0.233 wt% RMSEP for the prediction of mannan content. These data all support the idea that ATR FT-IR has a great potential to rapidly and accurately predict the content of xylan and mannan for bleached kraft pulps (softwood, hardwood, and their mixtures) in industry. However, the prediction of xylan and mannan concentrations presented a difficulty for pulp samples with modified cellulose crystalline structure.