Laura Vikele

Preparation of Nanocellulose Using Ammonium Persulfate and Method’s Comparison with other Techniques

Cellulose nanocrystals (CNCs) have generated increasing attention in the past few years as potential sources of innovative bionanomaterials. This study focuses on an alternative method of nanocellulose particle preparation, using ammonium persulfate, and compares this to existing techniques. Nanoparticles were prepared using 4 different methods: thermocatalytic method, TEMPO oxidation, the acid hydrolysis and oxidation with ammonium persulfate. With the ammonium persulfate method, the grinding time of the oxidised cellulose is reduced drastically to only 0.5h, and results in an average nanoparticles size of 404.5 nm, zeta potential of -26.4 and crystallinity degree of 80%. Based on comparison of these parameters to results from existing techniques, oxidising cellulose using ammonium persulfate appears to be a promising alternative.

Wood-Based Biocomposites: Mechanical Processing, Physical and Biological Properties

Wood-based nanoparticles fabricated by different optimized methods – acid hydrolysis, thermocatalytic destruction and TEMPO catalysed oxidation – show the potential to improve the physical-mechanical and biological properties of polymer-matrix biocomposites. In this work, the influence of obtained nanoparticles on physical-mechanical and biological properties of chitosan-matrix biocomposite was investigated. The results showed that wood-based nanoparticles are promising constituents of polymer-matrix biocomposites.

Micro-nanoparticle gels obtained from bark for their use alone and with chitosan and Na-CMC in paper coatings

Abstract The effect of coatings on paper sheets has been studied. For this purpose gels were prepared from unextracted and extracted bark. The gels represented dispersions of micro- and nanoparticles. The coatings were also prepared from mixtures of gels with chitosan solutions in 1% acetic acid and aqueous Na-carboxymethylcellulose (Na-CMC) solutions. The properties – Gurley air resistance, water vapour sorption, and mechanical properties of paper sheets – were tested. For obtaining the gels, the bark was destructed by a thermocatalytic method and then dispersed in water in a ball mill. The gels contained mainly nanoparticles with an average size of about 300 nm. Paper sheets produced by the Ligatne Paper Mill (Latvia) were coated on both sides. Gurley air resistance increases with increasing thickness of the coatings and with increasing gel concentration. At a gel concentration of 10% and a coating thickness of 35 μm, air resistance increases by 57% (gel from unextracted bark) and 72% (gel from extracted bark) compared to uncoated paper sheets. The coatings from bark gels in combination with Na-CMC and chitosan solutions increase further the air resistance. The coatings at gel concentrations up to 6% elevate the burst strength and tensile strength in a dry state. The coatings from mixtures of bark gel and chitosan and Na-CMC heighten further the mechanical properties and elevate the water vapour sorption of paper sheets.

Chemical composition and fiber properties of fast-growing species in Latvia and its potential for forest bioindustry

Abstract Bioenergy, including energy from wood, currently provides about 9–13% of the total global energy supply. Every fibre of fast-growing wood has a value for its potential use as a material in both pulp and paper and wood chemical industries. The aim of this study was to assess the chemical composition and fibre’s properties of fast-growing species in Latvia – aspen, hybrid aspen, lodgepole pine, poplar and willow. Results showed a variation of cellulose, lignin, extractives and ash contents among the species. Kraft pulp yield and amount of residual lignin were measured and properties of pulp fibres determined. Form factor and fine content in pulp were measured. Poplar and aspen wood had the highest content of cellulose, while lodgepole pine had the highest lignin content in wood and the longest kraft pulp fibres. Willow had 20% of fines in pulp. Individual results suggest the most suitable application of each species.

Nanoparticle fillers obtained from wood processing wastes for reinforcing of paper

Paper sheets were produced from bleached kraft pulp, and office and newsprint waste paper. Nanoparticles from black alder bark, grey alder bark and pine bark as well as birch sawdust were obtained for using them as reinforcing fillers in paper. Non-extracted bark and that extracted in biorefinery were used. For producing nanoparticles, the materials were destructed using the thermocatalytic destruction method and then dispersed in water medium in a ball mill. At a sufficient concentration, gel-like dispersions were obtained, which contained nanoparticles with the size ~300 nm. The dispersions were introduced in paper furnish in different amounts. It has been established that all the nanoparticle fillers increase the tensile index and burst index in dry and wet states. The nanoparticle fillers from extracted bark increase the mechanical indices to a higher extent. At 20% filler content, tensile index in a dry state increases in the case of non-extracted grey alder bark, black alder bark and pine bark by 28...

Bio-Based Nanomaterials - Versatile Materials for Industrial and Biomedical Applications

In this work, unmodified bacterial cellulose pellicles, biosynthesized by the bacterium Komagataeibacter rhaeticus, bleached birch Kraft pulp (Sodra Cell AB, Sweden) and birch bark supplied by the plywood industry (JSC Latvijas Finieris, Latvia), were used to obtain the nanoparticles. The results showed that cellulose nanoparticles fabricated by the ammonium persulfate oxidation method, an alternative method developed at the Latvian State Institute of Wood Chemistry, are promising constituents for producing nanopaper. Cellulose and birch bark nanofillers show the potential to improve the physical-mechanical and biological properties of chitosan-matrix films.

Improvement of Paper Hydrophobic Properties by Using Biodegradable Natural Polymer – Chitosan

The aim of the present study was to improve the paper handsheets parameters by adding biodegradable natural polymer – chitosan. The addition of chitosan in the amount of 2-4% improved tensile strength of the handsheets by up to 20% in dry condition and by up 5 times in wet state. Addition of chitosan increases the hydrophobic properties of paper as it was revealed by contact angle and water penetration dynamic measurements.