16 results on '"Verovkins, Anrijs"'
Search Results
2. POLYELECTROLYTE COMPLEX NANOPARTICLES OF SOLUBLE LIGNIN AND CHITOSAN AS INTERFACIAL MODIFIER
- Author
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Shulga, Galia, Shakels, Vadims, Vitolina, Sanita, Neiberte, Brigita, Verovkins, Anrijs, and This work was carried out due to the financial support of the performed research from the Base Financing provided by the Latvian Ministry of Education and Science.
- Subjects
kraft lignin, chitosan, polyelectrolyte complex, interfacial modifier, oil-in-water emulsion - Abstract
A water-soluble non-stoichiometric polyelectrolyte complex (LCP) was obtained as a result of the interaction of oppositely charged kraft lignin and high molecular chitosan by mixing their dilute water solutions. The sizes of the LCP nanoparticles were characterized by a bimodal distribution at pH 6, and their values were essentially smaller than the sizes of the chitosan particles. It was found that the LCP nanoparticles were characterized by remarkably lower values of surface tension at the air-water and the water-organic liquid interface in comparison with the initial biopolymers. With decreasing pH and increasing concentration of the LCP nanoparticles in the water solution, their adsorption ability at the interfaces was enhanced. The interface tension at the water-heptane interface changed non-linearly with increasing the polyelectrolyte complex concentration that was associated with the “saturation” effect. The dependence of the ability of the LPC nanoparticles to stabilize oil-in-water emulsion on pH values of the water phase was found.
- Published
- 2023
3. Harvesting Mycelial Biomass of Selected Basidiomycetes for Chitosan Biopolymer Extraction.
- Author
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Irbe, Ilze, Andze, Laura, Blumfelde, Mara, Filipova, Inese, Verovkins, Anrijs, and Zoldners, Juris
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CHITOSAN ,HARVESTING ,BASIDIOMYCETES ,DRYING agents ,SOLID-state fermentation ,CULTIVATED mushroom ,EDIBLE coatings ,BIOPOLYMERS - Abstract
This study investigates the mycelial biomass production and chitosan extraction potential of various Basidiomycota strains, including Heterobasidion annosum, Phanerochaete chrysosporium, Pleurotus ostreatus, Trametes versicolor, and Lentinus lepideus. Both submerged fermentation (SF) and solid-state fermentation (SSF) methods were employed. The chitosan yield in basidiocarps of Pleurotus ostreatus, Agaricus bisporus, and Ganoderma applanatum was also evaluated as a reference material. The chitosan extracted from fungal cells was characterized using elemental analyses and FTIR spectroscopy. Among the cultivated strains, P. chrysosporium exhibited the highest mycelial biomass concentration in SF (1.03 g 100 mL
–1 ) after 14 days, while T. versicolor achieved the highest biomass concentration in SSF (3.65 g 100 mL–1 ). The highest chitosan yield was obtained from the mycelium of P. chrysosporium (0.38%) and T. versicolor (0.37%) in shaken SF. Additionally, commercially cultivated A. bisporus demonstrated the highest chitosan yield in fungal fruiting bodies (1.7%). The extracted chitosan holds potential as a functional biopolymer additive for eco-friendly materials, serving as an alternative to synthetic wet and dry strength agents in packaging materials. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
4. Processing and Properties of Woodlastic Composite Containing Alkali-Treated Birch Wood Shavings and Bioadditive Obtained by Biorefinery of Birch Bark.
- Author
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Shulga, Galia, Rizhikovs, Janis, Neiberte, Brigita, Verovkins, Anrijs, Vitolina, Sanita, Betkers, Talrits, and Makars, Raimonds
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WOOD ,BIRCH ,SHAVING ,INJECTION molding ,POLYLACTIC acid ,PACKAGING materials ,PERMANENT magnets - Abstract
In the last two decades, there has been increased interest in research focused on developing innovative polymer composite materials for food packaging, obtained by compounding polymers with organic fillers, intended for the manufacture of food storage containers. Woodplastic composites (WPCs), due to high content of lignocellulosic filler, are consideredbiocomposites and can be used for the fabrication of such types of containers. Their formulations include, along with the matrix and the filler, functional additives. One of the most important considerations while developing a food packaging material is to choose eco-friendly additives. The suberinic acids (SAs), extracted from birch outer bark by hydrolysis in KOH water solution, were examined as lubricants in the formulation of recycled polypropylene/polylactic acid (rPP/PLA) composite filled with the alkali-treated milled birch shaving microparticles and proceeded by extrusion and injection molding. The incorporation of Sas in a birch wood-rPP/PLA composite was performed by treaing the wood microparticles with the SAs water suspension at the defined concentration. Their presence at the optimal content in the composite improved its processing by reducing the extruder rotor torque and injection pressure, which increased the mechanical properties and decreased the wettability of the composite. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
5. Environmental performance of combined treated wood.
- Author
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Kuka, Edgars, Cirule, Dace, Andersone, Ingeborga, Andersons, Bruno, Kurnosova, Nina, Verovkins, Anrijs, and Puke, Maris
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WOOD ,SERVICE life ,COPPER ,WOOD products ,WOOD preservatives - Abstract
Modification can significantly improve the service life of wood products, however, from the environmental perspective, the process has its drawbacks causing excessive influence in some specific impact categories. To reduce the impact that is characteristic of each individual modification process and to gain benefits due to synergy, the potential of using a combined treatment (copper azole impregnation + thermal modification) is evaluated. The results show that a combined treatment can provide enhanced environmental performance over each individual modification. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
6. Lignin-containing Adhesion Enhancer for Wood-plastic Composites.
- Author
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Shulga, Galia, Neiberte, Brigita, Jaunslavietis, Jevgenijs, Verovkins, Anrijs, Vitolina, Sanita, Shakels, Vadims, and Livcha, Sandra
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MECHANICAL ability ,LIGNANS ,CONTACT angle ,FREE groups ,WOOD waste ,COVALENT bonds ,LIGNIN structure ,SORPTION - Abstract
A lignin-containing adhesion enhancer, a water-soluble polyelectrolyte complex (LPEC) composed of soda hardwood lignin (HASL) and polyethylenimine (PEI), and the effect of the treatment of hydrolyzed and ammoxidized aspen sawdust with the LPEC nanoparticles were studied relative to the properties of wood-plastic composites (WPCs) based on recycled polypropylene (rPP). The presence of the excess of free amine groups and salt bonds between PEI and soda lignin, forming hydrophobic sites in the LPEC structure, caused the enhanced surface activity of the LPEC. The treatment with the LPEC nanoparticles increased the content of the fixed nitrogen in the modified sawdust samples and was accompanied by decreasing their water sorption and increasing contact angles that favored the decrease in the polar part of their surface free energy. The decreasing wetting ability enhanced the mechanical and water sorption properties of the obtained WPC samples. The improvement of the interfacial adhesion between the nitrogen-containing groups of the treated sawdust and the oxygen-containing groups of rPP was explained by the formation of both covalent and physicochemical bonds. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
7. Properties of Recycled Polypropylene Based Composites Incorporating Treated Hardwood Sawdust.
- Author
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Shulga, Galia, Jaunslavietis, Jevgenijs, Ozolins, Jurijs, Neiberte, Brigita, Verovkins, Anrijs, Vitolina, Sanita, and Shakels, Vadims
- Subjects
POLYPROPYLENE ,WOOD waste ,THERMOPLASTICS ,PLASTICS ,POLYOLEFINS - Abstract
The effect of different treatment of hardwood sawdust under mild conditions on contact angles, adhesion energy and water sorption was studied. A comparison of these indices for the hardwood treated sawdust and the composites filled with them was performed. The treatment promoted the compatibility between the recycled polypropylene and the hardwood filler. The inclusion of the lignin-based compatibiliser in the composite, containing the ammoxidised wood filler, essentially improved its mechanical properties. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
8. Short Fibre Filler from Wood Residue for Polymeric Composite Materials.
- Author
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SHULGA, Galia, NEIBERTE, Brigita, VEROVKINS, Anrijs, VITOLINA, Sanita, JAUNSLAVIETIS, Jevgenijs, and OZOLINS, Jurijs
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POLYMERIC composites ,WOOD waste ,FILLER materials ,HYDROLYSIS ,ZETA potential ,CONTACT angle ,MECHANICAL behavior of materials - Abstract
A wood residue - sawdust of the mechanical processing of aspen (Populus tremula) wood - was used to obtain a short fibre filler in the form of the modified microparticles < 250 μm for polymeric composite materials. To reduce energy input for wood size reduction and the activation of the lignocellulosic matrix for modification, low temperature acid hydrolysis of the residue under mild conditions was carried out. The effect of the pre-treatment parameters (acid concentration, hydrolysis duration, hydromodulus) on the fractional and chemical composition as well as on the zeta potential and contact angle of the obtained filler were studied. A comparison of the mechanical properties (tensile, bending) of the composites filled with initial sawdust and hydrolysed microparticles modified with a non-stoichiometric polyelectrolyte complex showed a pronounced improvement of the mechanical properties of the composites filled with modified wood microparticles. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
9. Wood processing by-products treated with the lignin-based conditioner as mulch for soil protection.
- Author
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Shulga, Galia, Betkers, Talrits, Vitolina, Sanita, Neiberte, Brigita, Verovkins, Anrijs, Anne, Olga, Ambrazaitienė, Dalia, and Žukauskaitė, Audronė
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WASTE products & the environment ,WOOD products -- Environmental aspects ,HYDROLYSIS ,LIGNINS ,MULCHING -- Environmental aspects ,SOIL conditioners - Abstract
Wood processing by-products such as bark of different wood species and hydrolysis lignin were applied as soil mulch. The lignin-based soil conditioner (LSC) representing a lignin-based polyelectrolyte complex with the different composition (a lignin/polymer mass ratio) was obtained under laboratory conditions and was intended to protect sandy soil from erosion by simultaneous application of a soil conditioner as an adhesive, mulch and plant seeds by hydroseeding. The study revealed the pronounced dependence of the properties of the treated wood-originated mulch on the wood species as well as on the composition, the applied concentration and the application rate of LSC. A comparison of the obtained results showed that the treated hydrolysis lignin was characterised by higher compressive strength, higher water resistance and lower moisture losses from sandy soil for a given LSC composition and application rate than the bark-based mulch. The conditioner concentrations don't have negative impact on the germination of seeds plants of the coastal dune zone. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
10. Characteristics of the Waste Wood Biomass and Its Effect on the Properties of Wood Sanding Dust/Recycled PP Composite.
- Author
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Vitolina, Sanita, Shulga, Galia, Neiberte, Brigita, Jaunslavietis, Jevgenijs, Verovkins, Anrijs, and Betkers, Talrits
- Subjects
WOOD ,HEMICELLULOSE ,BIOMASS ,DUST ,FLOCCULATION ,CLIMATE change - Abstract
To decrease climate changes, more research focuses on decreasing waste wood biomass (WWB) burning and increasing its conversion into value-added products. The WWB was isolated from model wood processing wastewater with a new hybrid coagulant by the coagulation/flocculation method. This study is aimed to characterize the WWB and to investigate its effect in the composition of a hybrid lignocellulosic filler on the properties of recycled polypropylene (rPP)-based wood–plastic composites (WPCs). The waste biomass contained high-molecular lignin and hemicelluloses substances and represented a finely dispersed powder. It was hydrophobic and was characterized by enhanced thermal stability. To minimize the negative effect of polymer wastes on the environment, recycled polypropylene as a polymer matrix was used with the hybrid filler in fabricating WPC samples. The presence of the coagulated WWB in the hybrid filler composition positively affects the mechanical properties, water uptake and dimensional stability of the composite samples. Such a behavior of the waste biomass showed its function as a compatibilizer, which promoted the interfacial adhesion in the composite system. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
11. COMPARISON OF THE PROPERTIES OF WOOD AND PULP FIBERS FROM LODGEPOLE PINE (Pinus contorta) AND SCOTS PINE (Pinus sylvestris).
- Author
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Sable, Inese, Grinfelds, Uldis, Jansons, Aris, Vikele, Laura, Irbe, Ilze, Verovkins, Anrijs, and Treimanis, Arnis
- Subjects
WOOD-pulp ,FIBERS ,LODGEPOLE pine ,SCOTS pine ,COMPARATIVE studies ,WOOD density ,SULFATE pulping process - Abstract
In this study, the relationship between the properties of the wood and kraft pulp fibers as well as paper characteristics of 27-year-old trees, lodgepole pine (Pinus contorta) and Scots pine (Pinus sylvestris), was assessed. All trees had been grown in Latvia, within the same forest type, Myrtillosa. Wood density, year ring width, chemical composition and cross-sectional cell wall dimensions were measured. Fiber characteristics were determined, and handsheets were made for all samples from unbeaten kraft pulp. The results showed that the amount of latewood had a positive correlation with wood density for both species and with further positive impact on the paper burst index. Also, slight differences in cross-sectional dimensions were observed. Lodgepole pine provided paper with higher burst strength than Scots pine. Since the former is of higher density, less wood per volume is needed to produce a ton of pulp, and results showed a higher pulp yield in the case of lodgepole pine. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
12. New Lignin-Based Polymers for Ecological Rehabilitation.
- Author
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Shulga, Galia, Betkers, Talrits, Brovkina, Julia, Neiberte, Brigita, Verovkins, Anrijs, Belous, Olga, Ambrazaitene, Dalia, and Žukauskaite, Audrone
- Subjects
LIGNOSULFONATES ,SOIL conditioners ,MODIFICATIONS ,POLYMERIC composites ,POLYELECTROLYTES ,FLOCCULATION - Abstract
It has been shown that the found regularities of the interaction between lignosulfonate and polymeric cations in aqueous media can serve as a scientific basis for chemical modification of lignin by way of the formation of the interpolyelectrolyte complexes. This energy-saving and non-complicated method of modification was applied for obtaining new lignin-based soil improving agents. Water-soluble polymeric products of the interaction of lignosulfonate with three synthetic polymeric cations have been used in order to study the effect of their adsorption at the clay soil surface on the water stability of the artificially soil aggregates formed by the treatment of soil with lignin-based polyelectrolyte complexes (LPECs). The obtained results are explained from the viewpoint of the complex mechanism of soil structure formation, combining simultaneously the flocculation of soil particles and stabilization of the formed aggregates. The conducted field tests have shown that the application of the lignin-based polyelectrolyte complex as a soil conditioner at a deep loosening of heavy clay soil allows the improvement of the hydrophysical properties and the filtration ability of the soil sublayers and, thereby, to enhance the barley yield. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
13. PENETRATION OF WOOD PRESERVATIVES INTO THERMALLY MODIFIED BIRCH AND PINE WOOD.
- Author
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CIRULE, Dace, KURNOSOVA, Nina, VEROVKINS, Anrijs, KUKA, Edgars, ANTONS, Andis, ANDERSONE, Ingeborga, and ANDERSONS, Bruno
- Subjects
- *
WOOD preservatives , *PINE , *SCOTS pine , *TEMPERATURE effect , *THERMAL analysis - Abstract
The objective of the present study was to investigate the interaction between Cu-containing preservatives and birch (Betula spp.) and pine (Pinus sylvestris L.) wood, modified at a relatively mild temperatures (150 - 180°C). The disposition of wood to absorb water was evaluated by capillary absorption (CA) tests through the specimens' tangential and radial surface. Changes in wood drying characteristics due to thermal modification (TM) were evaluated by monitoring wood moisture dynamics after impregnation. In order to assess the capacity of wood to absorb preservatives, a vacuum/pressure process was used to impregnate small specimens for which uniform saturation into the entire volume can easily be reached. Quantitative determination of copper Cu content in the specimens was performed by using atomic absorption spectroscopy (AAS). The fixation of the absorbed Cu was evaluated by subjecting the specimens to leaching procedures according to EN 84 and assessing the ratio of retained Cu in the specimens. The CA test showed deceleration of capillary absorption in TM birch wood through both surfaces, with similar absorption rates regardless of treatment temperatures. A significant increase in the absorption rate through the tangential surface was recorded for TM pine wood and the increase was greater for specimens treated at higher temperatures. The results of moisture content monitoring showed a similar reduction in the drying rate due to thermal modification regardless of species. Comparing wood of one species with similar densities, less preservative was absorbed by TM wood. However, the results of AAS showed that, in comparison with unmodified wood, 10% (birch) and 25% (pine) more Cu per one gram of wood was introduced during impregnation. Nevertheless, TM also resulted in higher Cu leaching rates for both species. [ABSTRACT FROM AUTHOR]
- Published
- 2018
14. PROPERTIES OF ASPEN AND ASPEN CLONES GROWING IN LATVIA.
- Author
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Grinfelds, Uldis and Verovkins, Anrijs
- Subjects
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ASPEN (Trees) , *PLANT clones , *WOOD - Abstract
The article examines the characteristics of Eurasian aspen and aspen clones grown in Latvia. Results of the study have shown that hybrid aspens have greater annual ring widths compared with Eurasian aspens, leading to a conclusion that the clones or hybrids produce more wood in a span of one year. Young aspen and hybrids were also found to have higher paper mechanical properties compared with older trees. The study asserts that landowners and wood processors will do well to focus on hybrids.
- Published
- 2012
15. Polyurethane rigid foams obtained from polyols containing bio-based and recycled components and functional additives.
- Author
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Gaidukova, Gerda, Ivdre, Aiga, Fridrihsone, Anda, Verovkins, Anrijs, Cabulis, Ugis, and Gaidukovs, Sergejs
- Subjects
- *
RAPESEED oil , *POLYURETHANES , *POLYOLS , *RECYCLED products , *RENEWABLE energy sources - Abstract
We report the preparation of polyurethane (PU) rigid foams from bio-based and recycled components. Rapeseed oil (RO) and recycled polyethylene terephthalate (rPET) were used to synthesize PU polyols. Fifty-five percent of the content of the proposed PU polyols originates from renewable or recycled material. Glycerol (GL) and adipic acid (ADA) were added to improve the final properties of the foams. The GL/ADA content was varied from 1 to 6 wt.%. The hydroxyl value, acid value, water content, and viscosity of the synthesized polyols were measured. Using compression tests on PU rigid foams, we found that for some GL/ADA contents the rigidity increased almost 3-fold; whereas the strength increased almost 2-fold. The water absorption of the foams was below 3 wt.%. Optical microscopy of foam cross-sections revealed a mean cell sizes of 330 μm for PU with GL/ADA, and 420 μm for PU supplemented with GL/ADA and RO. FTIR measurements revealed enhanced hydrogen bond networking due to the incorporation of GL/ADA fragments and RO long aliphatic blocks in the PU chain backbone. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
16. IMPACT OF PROVENANCE ON WOOD AND FIBRES PROPERTIES OF LODGEPOLE PINE, GROWN IN LATVIA.
- Author
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Šāble, Inese, Grīnfelds, Uldis, Sisenis, Linards, Verovkins, Anrijs, and Treimanis, Arnis
- Subjects
- *
LODGEPOLE pine , *BIOCHEMICAL research , *CELLULOSE , *LIGNINS , *WOOD chemistry , *COMPARATIVE studies - Abstract
Lodgepole pine (Pinus contorta) samples from three different provenances in Canada were investigated. All trees were the same age and had been grown in Latvia in similar conditions. Lodgepole pine of Summit Lake provenance had higher wood density (503 kg m-3) and a higher late wood content (46%) in comparison to Fort Nelson and Pink Mountain provenances. Investigation of chemical composition of wood indicated Summit Lake provenance wood as superior in cellulose content (49.7%), but no differences in lignin and extractives content were found between samples. Kraft pulp yield of Summit Lake samples (48%) was the highest, but the handsheet strength properties were relatively higher for pulp from Pink Mountain provenance pine wood. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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