Israel González

Effect of the combination of biobeating and NFC on the physico-mechanical properties of paper

The combined effect of enzymatic treatment (biobeating) and NFC addition on the mechanical and physical properties of a papermaking pulp suspension was investigated. The influence of pH, consistency of pulp and reaction time of the enzyme on the pulp strength was evaluated by measuring the breaking length of paper sheets made thereof. The results showed that the enzymatic treatment improved mechanical properties of fibres without modifying drainability. After biobeating, NFC was added to the enzyme-treated pulps. Mechanical properties were enhanced, obtaining length at break values similar to those observed in commercial printing/writing paper. Opacity remained constant, whereas porosity was gradually reduced as more amount of NFC was added. The presence of NFC also reduced drainability, although it remained at suitable levels for the papermaking industry. The results suggest that the combination of biobeating and NFC addition can be considered as an alternative to mechanical beating.

Nanofibrillated cellulose as an additive in papermaking process: A review

During the last two decades, cellulose nanofibres (CNF) have emerged as a promising, sustainable reinforcement with outstanding potential in material sciences. Though application of CNF in papermaking is recent, it is expected to find implementation in the near future to give a broader commercial market to this type of cellulose. The present review highlights recent progress in the field of the application of cellulose nanofibres as additives in papermaking. The effect of CNF addition on the wet end process is analysed according to the type of pulp used for papermaking. According to the literature consulted, improvement in papers overall properties after CNF addition depended not only on the type and amount of CNF applied, but also in the pulps origin and treatment. Bulk and surface application of CNF also presented significant differences regarding papers final properties. This review also revises the mechanisms behind CNF reinforcing effect on paper and the effect of chemically modified CNF as additives.

Suitability of wheat straw semichemical pulp for the fabrication of lignocellulosic nanofibres and their application to papermaking slurries

The present work studies the feasibility of wheat soda pulp as a raw material for the fabrication of cellulose nanofibres and their application as an additive in papermaking. Wheat straws were cooked under alkaline conditions and the resulting pulp was used as a raw material for the production of lignocellulosic nanofibres (LCNF). Nanofibres were fabricated by intense mechanical beating followed by high-pressure homogenization. The produced LCNF were characterized and applied to papermaking slurry based also on wheat straw soda pulp. Paper sheets made thereof were analysed for their physical and mechanical properties. The results indicated that paper strength was improved after addition of LCNF, whereas density increased and porosity was reduced. These improvements in properties (except the Tear Index) are significant because they were achieved using LCNF with lower fibrillation degree compared to previous works where chemically pre-treated LCNF were used as reinforcement.

On the morphology of cellulose nanofibrils obtained by TEMPO-mediated oxidation and mechanical treatment.

The morphological properties of cellulose nanofibrils obtained from eucalyptus pulp fibres were assessed. Two samples were produced with the same chemical treatment (NaClO/NaBr/TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation), but distinct mechanical treatment intensities during homogenization. It was shown that the nanofibrils production yield increases with the mechanical energy. The effect of mechanical treatment on the yield was confirmed by laser profilometry of air-dried nanocellulose films. However, no significant differences were detected regarding the nanofibrils width as measured by atomic force microscopy (AFM) of air-dried films. On the other hand, differences in size were found either by laser diffraction spectroscopy or by dynamic light scattering (DLS) of the cellulose nanofibrils suspensions as a consequence of the differences in the length distribution of both samples. The nanofibrils length of the more nanofibrillated sample was calculated based on the width measured by AFM and the hydrodynamic diameter obtained by DLS. A length value of ca. 600 nm was estimated. The DLS hydrodynamic diameter, as an equivalent spherical diameter, was used to estimate the nanofibrils length assuming a cylinder with the same volume and with the diameter (width) assessed by AFM. A simple method is thus proposed to evaluate the cellulose nanofibrils length combining microscopy and light scattering methods.

Reducing the Amount of Catalyst in TEMPO-Oxidized Cellulose Nanofibers: Effect on Properties and Cost

Cellulose nanofibers (CNF) are interesting biopolymers that find numerous applications in different scientific and technological fields. However, manufacturing costs are still one of the main drawbacks for the industrial production of highly fibrillated, transparent CNF suspensions. In the present study, cellulose nanofibers were produced from bleached eucalyptus pulp via TEMPO-mediated oxidation with varying amounts of NaClO and passed through a high-pressure homogenizer. The CNFs were chemically and physically characterized; cellulose nanopapers were also produced to study tensile properties. Production costs were also calculated. Results indicated that CNF properties are strongly dependent on the carboxyl content. Manufacturing costs showed that chemicals, in particular TEMPO catalyst, represent a large part of the final cost of CNFs. In order to solve this problem, a set of samples were prepared where the amount of TEMPO was gradually reduced. Characterization of samples prepared in this way showed that not only were the costs reduced, but also that the final properties of the CNFs were not significantly affected when the amount of TEMPO was reduced to half.

Nanofibrillated cellulose as an additive in papermaking process

During the last two decades, cellulose nanofibers (CNFs) have emerged as a promising, sustainable reinforcement with outstanding potential in material sciences. Though application of CNF in papermaking is recent, it is expected to find implementation in the near future to give a broader commercial market to this type of cellulose. The present chapter highlights recent progress in the field of the application of CNFs as additives in papermaking. The effect of CNF addition on the wet-end process is analyzed. Significant improvement in paper’s overall properties after CNF addition depends not only on the type and amount of CNF applied, but also in the pulp’s origin and treatment. Bulk and surface application of CNF also present significant differences regarding paper’s final properties.

Immobilization of antimicrobial peptides onto cellulose nanopaper

In this work we report the production of cellulose nanopapers modified with alkyl ketene dimer (AKD) in order to allow the immobilization of antimicrobial peptides (AMPs) to produce surfaces with antimicrobial properties. Cellulose nanofibers (CNF) were prepared from softwood bleached pulp via high pressure homogenization after chemical pretreatment of fibers via TEMPO oxidation. Nanopapers were then prepared after a casting technique and functionalized with alkyl ketene dimer before AMPs were immobilized. The immobilization process was performed by submerging the samples into AMP aqueous solutions and then dried at room temperature. Antimicrobial activity was tested against B. subtilis. Results indicated that AMPs were bound onto the nanopaper surface and released when the nanopaper was put in contact with the culture medium, which effectively demonstrates the viability of the immobilization process.