Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in ... more Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in tudi letos, ob 103. rojstnem dnevu univerze, so bili predstavljeni najodličnejši raziskovalni dosežki, podeljeni častni nazivi, plakete, nagrade in priznanja vsem, ki so pripomogli, da je Univerza v Ljubljani iz leta v leto boljša. Na Oddelku za lesarstvo Biotehniške fakultete UL smo zelo ponosni, da je na slavnostni seji Senata Univerze v Ljubljani 29. 11. 2022 Zlato plaketo prejel tudi naš sodelavec, prof. dr. Primož Oven, vodja Katedre za kemijo lesa in druge lignocelulozne materiale. Prof. Oven je mednarodno uveljavljen raziskovalec in pedagog na področju proučevanja zvez med funkcijami, strukturami, kemizmom in lastnostmi lesa, biorafinacije ter valorizacije lesne biomase s poudarkom na pridobivanju in uporabi nanoceluloze in lesnih ekstraktivov. V akademskem in gospodarskem okolju promovira trajnostno izrabo lesa v krožnem biogospodarstvu in skrbi za ugled UL doma in v tujini.
The main objective of our study was to investigate the possible differences in the chemical compo... more The main objective of our study was to investigate the possible differences in the chemical composition of extractives from the bark of silver fir (Abies alba) with respect to the location of the bark sample on the tree, viz. differences in extract composition between stem bark and branch bark samples. Extractives in the bark samples from branches, depending on the distance of the sample from the trunk, were also analysed, and the stem bark samples were analysed with respect to their inner and outer parts. The results of the chemical analysis of extractives were supported by information about their antifungal and antioxidant effects. After felling and sampling silver fir trees, the collected bark samples were ground and freeze-dried. Extraction of bark samples was followed by a system of accelerated extraction using only water as a solvent. The extracts were analysed chemically using gravimetry, spectrophotometry and chromatography. Free-radical-scavenging activity was measured usin...
Cilj študije je bil priprava bionanokompozita na osnovi polimlečne kisline (PLA) z dodatkom nanof... more Cilj študije je bil priprava bionanokompozita na osnovi polimlečne kisline (PLA) z dodatkom nanofibrilirane celuloze (NFC) kot ojačitvene komponente. Za izdelavo kompozita smo uporabili nemodificirano in acetilirano NFC (A_NFC). NFC, posušeno z zamrzovanjem, smo acetilirali v heterogenem sistemu z acetanhidridom v dimetilformamidu (DMF) ob prisotnosti piridina kot katalizatorja. Uspešnost acetiliranja smo ugotavljali z infrardečo (FT-IR) spektroskopijo. Pripravili smo PLA filme z 2,5 %, 5 % in 10 % dodatkom nemodificirane oziroma acetilirane NFC. Osredotočili smo se na proučevanje vpliva dodatka NFC na prosojnost bionanokompozita in na njegovo odpornost proti razenju. Prosojnost bionanokompozitnega filma smo merili z UV-Vis spektrofotometrijo, odpornost površine filmov proti razenju pa smo ovrednotili z vzmetnim svinčnikom. Določili smo optimalno količino dodane NFC in A_NFC polimeru PLA za doseganje boljše odpornosti proti razenju. Ugotovili smo, da z dodatkom 2,5 % A_NFC dosežemo ...
Raziskali smo vsebnost in sestavo ekstraktivov v lesnih tkivih in skorji robinije (Robinia pseudo... more Raziskali smo vsebnost in sestavo ekstraktivov v lesnih tkivih in skorji robinije (Robinia pseudoacacia L.). Vzorce njenega lesa in skorje smo ekstrahirali v aparatu Soxhlet z acetonom. Acetonske ekstrakte smo preiskali gravimetrično in s tem izmerili vsebnost skupnih hidrofilnih ekstraktivov. Z UV-Vis spektrofotometrom smo kolorimetrično izmerili vsebnost skupnih fenolov. Ekstrakte lesa in skorje robinije smo nato detajlno preiskali s sistemom za tekočinsko kromatografijo visoke ločljivosti (HPLC). S to tehniko smo v ekstraktih identificirali in kvantitativno ovrednotili dihidrorobinetin. Največje vsebnosti skupnih hidrofilnih ekstraktivov, skupnih fenolov in dihidrorobinetina smo izmerili v vzorcih jedrovine. Značilno manj ekstraktivov je bilo v vzorcih beljave in skorje. Aksialne variabilnosti v vsebnosti topnih komponent za les in skorjo robinije nismo dognali. Ugotovili smo, da je jedrovina robinije bogat vir fenolnih ekstraktivov.The content and composition of extractives in t...
Research Highlights: The antifungal assay confirmed that knotwood extractives of Scots pine inhib... more Research Highlights: The antifungal assay confirmed that knotwood extractives of Scots pine inhibit the growth of wood decay fungi. Heartwood extracts of black locust were found to be much stronger free radical scavengers than the extracts of Scots pine. The extracts were deposited in the lumina and on the wall surface of cells in the impregnated sapwood. Impregnation of the sapwood blocks with Scots pine and black locust extracts reduced the fungal decay of wood. Objectives: Hydrophilic extracts of Scots pine knotwood and black locust heartwood were chemically analyzed, tested for antifungal and antioxidant properties and used for impregnation of beech and Scots pine sapwood. Materials and Methods: Scots pine knotwood and black locust heartwood were extracted, and obtained hydrophilic extractives were chemically analyzed. Extracts were analyzed for antifungal properties with the in vitro well-diffusion method. The free radical scavenging activity of wood extracts was measured color...
Uvod Celuloza je najbolj razširjen biopolimer na planetu. Sestavljena je iz nerazvejanih polimern... more Uvod Celuloza je najbolj razširjen biopolimer na planetu. Sestavljena je iz nerazvejanih polimernih verig, kjer so med seboj povezane D-glukopiranozilne enote preko β (1 → 4) vezi. V lesu in drugih ligno-celuloznih surovinskih virih je celuloza v obliki makroin mikrofibril, ki jih je mogoče izolirati in/ali razgraditi s sodobnimi mehanskimi, kemijskimi ali encimatskimi postopki (Kalia in sod. 2011 ). Produkt, ki pri tem nastane, se najpogosteje označuje z izrazom nanofibrilirana celuloza (NFC), četudi običajno vsebuje različno velike delce, od vlaken in fragmentov vlaken, pa tudi makro in mikrofibrile ter fragmente teh bioloških struktur (glej npr. Chinga-Carrasco 2011). NFC se praviloma nahaja v obliki vodne suspenzije, kar lahko predstavlja resno tehnološko in ekonomsko omejitev. V mnogih tehnoloških procesih je zaželeno, da je NFC popolnoma suha. Proces sušenja NFC je kritična operacija, ker se pri tem tvorijo ireverzibilne vodikove vezi med celuloznimi nanofibrilami, kar vodi do...
The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and b... more The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and branchwood (BW of silver fir (Abies alba Mill.) was analyzed, and their antifungal and antioxidant properties were studied. In addition, the variability of extractives content in a centripetal direction, i.e., from the periphery of the stem towards the pith, was investigated. The extracts were analyzed chemically with gravimetry, spectrophotometry, and chromatography. The antifungal and antioxidative properties of the extracts were evaluated by the agar well diffusion method and the diphenyl picrylhydrazyl radical scavenging method. Average amounts of hydrophilic extractives were higher in KW (up to 210.4 mg/g) and BW (148.6 mg/g) than in HW (34.1 mg/g) and SW (14.8 mg/g). Extractives identified included lignans (isolariciresinol, lariciresinol, secoisolariciresinol, pinoresinol, matairesinol) phenolic acids (homovanillic acid, coumaric acid, ferulic acid), and flavonoids epicatechin, tax...
The aim of the study was to prepare a bionanocomposite based on polylactic acid (PLA) with the ad... more The aim of the study was to prepare a bionanocomposite based on polylactic acid (PLA) with the addition of nanofibrillated cellulose (NFC) as a reinforcement component. For the production of the composite we used unmodified and acetylated NFC (A_NFC). Freeze-dried NFC was acetylated in a heterogeneous system with acetic anhydride in dimethylformamide (DMF) in the presence of pyridine as a catalyst. The success of the acetylation was determined by FT-IR spectroscopy. PLA films were prepared with the addition of 2.5%, 5% and 10% of unmodified and acetylated NFC. The focus of this research was the impact of the NFC additive on the transparency and on the resistance of the bionanocomposite to scratching. The transparency of the bionanocomposite film was measured using UV-Vis spectrophotometry, and the resistance of the films to scratching was evaluated with a scratch test. The optimal amount of NFC and A_NFC added to the polymer PLA to achieve better resistance of the bionanocomposite t...
Namen prispevka temelji na inovativnem postopku izdelave nanokompozitov na osnovi poli(3-hidroksi... more Namen prispevka temelji na inovativnem postopku izdelave nanokompozitov na osnovi poli(3-hidroksibutirata) (PHB) in nanofibrilirane celuloze (NFC). Raziskovalno delo obravnava pripravo koncentratnih me{anic PHB-prahu in NFC v vodni raztopini za tehnologijo ekstruzijskega me{anja. Ekstrudat koncentrirane me{anice PHB/NFC je bil nato uporabljen kot dodatek h granulirani obliki PHB pri pripravi brizganih vzorcev z razli~nimi ute`nimi dele`i NFC. V prispevku so podane dolo~ene omejitve pri predelavi tovrstnih materialov in predlagane uporabne re{itve za njihovo optimiziranje. Morfolo{ke lastnosti nanokompozitnih komponent smo raziskali z elektronsko mikroskopijo (FE-SEM), mehanske lastnosti pa z nateznim preizkusom. Morfolo{ka preiskava koncentratnih me{anic je razkrila prepleteno sestavo celuloznih nanofibril in polimernih kroglic, prĩ emer se posamezne fibrile prepletajo v obliki {ir{ih pramenov in ustvarjajo videz zamre`ene strukture znotraj polimerne komponente. Mikroskopski posnetki nanokompozitnih me{anic in izbolj{ane mehanske lastnosti izhodnih materialov potrjujejo, da je adhezivni stik med matri~no in oja~itveno komponento dose`en, porazdelitev celuloznih nanofibril po polimerni osnovi pa homogena. Nanokompoziti z visokimi ute`nimi dele`i NFC (10 % ute`nega dele`a) dosegajo pomembno ve~je vrednosti modula elasti~nosti (Et = 1720 MPa) in raztezka pri pretrgu (eb = 3,1 %) ter prenesejo vi{je pretr`ne napetosti (sM = 26 MPa) v primerjavi z referen~nim polimernim vzorcem (Et = 1340 MPa; eb = 2,4 %; sM = 20 MPa). Rezultati {tudije dokazujejo, da je ob pravilni predpripravi polimernih me{anic in optimizaciji tehnologije ekstruzijske predelave, mogo~e izdelati trdne in`ilave materiale, pri~emer dele`oja~itvene faze narekuje stopnjo izbolj{ave kon~nih lastnosti biopolimerne osnove. Klju~ne besede: nanofibrilirana celuloza, poli(3-hidroksibutirat), morfologija, mehanske lastnosti, ekstruzija, tehnologija brizganja In this paper a novel processing route for nanocomposites, based on (3-hydroxybutyrate) (PHB) and nanofibrillated cellulose (NFC), is presented. To obtain a uniform dispersion of the reinforcing filler, a PHB powder was first dispersed in water, mixed with an NFC aqueous suspension and then freeze dried to eliminate the water phase from the ensuing system. The dried batch was then extruded and added to the granulated PHB in different weight proportions. Nanocomposites with various NFC contents were subsequently produced with the injection-moulding technology. The processing limits and feasible solutions for their optimization are thoroughly described within this work. Morphological properties were investigated with FE-SEM, while mechanical properties were determined via a tensile test. SEM images showed that the PHB powder can be effectively incorporated into the mesh of cellulose nanofibrils, as clearly evident by the interlaced structure of individual fibrils with the average lateral dimensions of 69±14 nm. Improved mechanical properties and SEM observations confirmed a good interfacial adhesion and uniform distribution of the reinforcing component. Compared to the unfilled matrix (Et = 1340 MPa; sM = 20 MPa; eb = 2.4 %), an escalating trend in Young's modulus (Et = 1720 MPa) and tensile strength (sM = 26 MPa), along with decisively improved values of the elongation at break (eb = 3.1 %), were observed for the nanocomposites with the highest content of NFC. According to the results presented, strong and tough nanocomposites can be produced via extrusion moulding, whereby the proportion of the reinforcing phase dictates the final material performances.
Freeze dried nanofibrils were acetylated in a heterogeneous system with acetic anhydride, pyridin... more Freeze dried nanofibrils were acetylated in a heterogeneous system with acetic anhydride, pyridine, and dimethylformamide and the obtained acetylated cellulose nanofibrils (CNFac) were combined with poly(lactic acid) (PLA) to a composite. CNFac with its partially hydrophobic surface showed a good compatibility with PLA resulting in composite films with improved properties. Tensile strength (TS), modulus of elasticity (MOE), and elongation at break (EB) of PLA/CNF increased significantly when 2–5% of CNFac was added to the PLA matrix, while the addition of 10% and higher amounts CNFac decreased the EB at a higher TS and MOE. Mechanical parameters did not improve in the case of unmodified CNF addition. The addition of CNFac maintained transparency and had absorbance values between those of pure PLA film and PLA film with 2% CNF, while films formed with the addition of 5 and 10% of CNF were less transparent. The addition of CNF did not essentially affect the thermal properties of nanoc...
The most suitable composition of mobile phase for the separation of simple phenolic compounds suc... more The most suitable composition of mobile phase for the separation of simple phenolic compounds such as gallic acid, pyrocatechol, phloroglucinol, resorcinol, vanillin and related compound catechin by the high performance liquid chromatography was investigated. The most appropriate developing mobile system for the separation of these organic compounds was acetonitrile and 2% water solution of formic acid with gradient ratio from 2.98 to 25:75. The best separation of the six organic compounds was achieved using mobile phase with lower content of formic acid. HPLC is a method of choice for qualitative and quantitative analysis compounds in various types of samples in the broad field of forestry-wood-pulp-paper chain.
The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the mor... more The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the morphological, thermal, and structural behaviors of two different nanofibrillated cellulose (NFC) materials were investigated. Field emission scanning electron microscopy (FE-SEM) observations indicated an interlaced network formation of predominantly in-plane fibrillar orientation for air- and oven-dried samples, while freeze and spray drying resulted in the formation of coarse and fine powder fractions. Comparison of redispersed powders obtained by freeze and spray drying indicated that aggregation phenomena are significantly reduced in freeze-dried specimens. Rheological and sedimentation analysis revealed that the freeze-dried NFC powders are more stable than spray-dried NFC powders when redispersed in water. Aggressive dehydration processes, such as freezing or heating, significantly influence the thermal stability of the dried cellulose samples. On the contrary, the crystallinity prop...
The aim of the study was to find appropriate non-chlorinated solvent systems for the extraction a... more The aim of the study was to find appropriate non-chlorinated solvent systems for the extraction and separation of pure pinosylvin (PS) and pinosylvin monomethylether (PSMME) from Scots pine/Norway spruce wood residues. The extraction was performed in a pressurized solvent extractor and the purification and isolation of pure substances was done by flash chromatography. More precisely, pure PS was isolated via sequential flash chromatography in two repetitions in the gradient mode of the mobile phase, with cylcohexane (CX) and ethylacetate (EtOAc), beginning with 100% CX and ending up with 100% EtOAc. The extractives were qualitatively and quantitatively analyzed in terms of PS and PSMME contents by gas chromatography-flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (1H-NMR) spectroscopy.
Different resol phenol-formaldehyde prepolymer resins have been synthesized with different formal... more Different resol phenol-formaldehyde prepolymer resins have been synthesized with different formaldehyde / phenol ratios. The phenolic resin composition depends on monomer ratio, catalyst, reaction conditions, and residual free monomers. Temperature and pH conditions under which reactions of phenols with formaldehyde are carried out have a profound effect on the characteristics of the resulting products. Three reaction sequences must be considered: formaldehyde addition to phenol, chain growth or prepolymer formation and finally the crosslinking or curing reaction. Two prepolymer types are obtained depending on pH, novolacs in an acidic pH region whereas resols by alkaline reaction. Resol resins are synthesized with a molar excess of formaldehyde (1<F/P<3). These are mono-or polynuclear hydroxymethylphenols which are stable at room temperatures, but are transformed into three dimensional, cross linked, insoluble and infusible polymers by the application of heat. An ATR-FTIR spectrometry technique (ReactIR 4000) with light conduit and diamond-composite sensor was used to perform in-line monitoring of phenol-formaldehyde prepolymer synthesis. This technique was found to be ideal for determining residual free phenol and formaldehyde, individual phenol and formaldehyde conversions and prepolymer composition changes as a function of time when the condensation reaction was carried out. The kinetics data obtained through the ReactIR 4000 in-line reaction analysis system agreed well with those determined by the traditional titration method. ReactIR technology replaces time consuming and inaccurate off-line methodology.
Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst a... more Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst at different temperatures. At the highest treatment temperature (150 °C) liquefaction of wood pulp cellulose was achieved and was dependant on cellulose polymerization degree (DP). Furthermore, the rate of amorphous cellulose weight loss was found to increase with cellulose degree of polymerization, while the rate of crystalline cellulose weight loss was reciprocal to the size of the crystallites. The cellulose degradation was studied by monitoring of the molecular mass decrease by size-exclusion chromatography. It was revealed that microcrystalline cellulose degrades via a 'quantum mode' mechanism, while the degradation of Whatman filter paper no 1. and cotton linters proceeded randomly and were partly dependent on the starting polymerization degree, crystallinity, and treatment temperature. The kinetics of cellulose degradation in heterogeneous media was described by means of a one-stage model, characterised by the consumption of glycosidic bonds in amorphous and crystalline cellulose regions until the levelling-off degree of polymerization is reached.
In this study, we investigated the antibacterial modification of polymers with biologically activ... more In this study, we investigated the antibacterial modification of polymers with biologically active substances in essential oils [EOs; linalool, 4-allylanisole (ALY), and trans-anethole]. These compounds were thermoplastically incorporated into a low-density polyethylene matrix via solid inert carriers [wood flour (WF) and talc and molecular sieves] with physically immobilized EOs. The concentrations of the antibacterial modifiers on the carriers and in the resulting composites were determined with three chromatographic techniques (gas chromatography with mass spectrometry, pyrolysis and gas chromatography with mass spectrometry, and high-performance liquid chromatography). The effects of such modifications to the mechanical properties of the prepared composites were studied by stress-strain analysis. Interactions on the polymer matrix carriers were observed by scanning electron microscopy. The prepared composites were also tested for antibacterial activity against both Gram-negative and Gram-positive bacterial strains. The highest efficiency of isothermal immobilization was found for systems consisting of ALY and WF. This finding was in accordance with microbiological studies. The phase of immobilizing the EOs did not influence the mechanical properties of the studied composites. V
The goal of the presented work is to describe the proteinic impurity (as possible residual compon... more The goal of the presented work is to describe the proteinic impurity (as possible residual component from biotechnological lactic acid production from whey) in the reaction mixture with 2-hydroxypropanoic acid (lactic acid) for its direct polycondensation into poly(lactic acid). The impurity presence study was carried out in the range from mass fractions 0 % up to 2 %. For an evaluation of the impurity effect on the values of molecular weight, melting and glass transition temperatures the measurements of intrinsic viscosity, gel permeation chromatography and differential scanning calorimetry were used. Results show slight reduction of molecular weight and increase in polydispersity with rising amount of the impurity. The thermal properties investigation shows noticeable reduction of melting temperature and moderate decrease in glass transition temperature. The results reveal considerable role of lactose on formation of structural irregularities in lactic acid polycondensates.
Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications ... more Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications such as biomedical or smart materials products. In this research, purified pretreated BC was subjected to high intensity ultrasound (HIUS) and was investigated for the development of BC films. The morphological, structural and thermal properties of the obtained films were studied by using FE-SEM, AFM, FT-IR, XRD, TGA and DSC characterizations. Results showed that the most favorable purification treatment was the 0.01 M NaOH at 70°C for 2h under continuous stirring. The most suitable ultrasound operating conditions were found to be, 1cm distance of ultrasonic probe from the bottom of the beaker, submerged in cold water bath cooling around 12 ± 2°C. The power (25 W/cm(2)), time (30 min), BC concentration (0.1%w/w), amplitude (20 μm) and frequency (20 kHz) were maintained constant.
ABSTRACT In this study, we modified melamine-formaldehyde (MF) resin adhesive with liquefied wood... more ABSTRACT In this study, we modified melamine-formaldehyde (MF) resin adhesive with liquefied wood (LW) and determined the properties of MF–LW adhesive mixtures. Furthermore, we produced particleboards using prepared MF–LW mixtures and evaluated their mechanical and physical properties. Results showed that with increasing content of LW in the adhesive mixture gel time and peak temperature increased while reaction enthalpy decreased. With increasing substitution of MF resin adhesive with LW the thermal stability of adhesive mixture reduced, namely thermal degradation started at lower temperature and weight loss increased. Properties of particleboards improved with increasing amount of LW in the adhesive mixture up to 20% and then deteriorated. Nevertheless, the properties of particleboard with 30% LW in the adhesive mixture were comparable to the properties of particleboard without LW while they worsen at greater portion of LW. Consequently, MF resin adhesive with 30% LW substitution could be used to produce particleboards with suitable mechanical properties and reduced formaldehyde release content.
Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in ... more Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in tudi letos, ob 103. rojstnem dnevu univerze, so bili predstavljeni najodličnejši raziskovalni dosežki, podeljeni častni nazivi, plakete, nagrade in priznanja vsem, ki so pripomogli, da je Univerza v Ljubljani iz leta v leto boljša. Na Oddelku za lesarstvo Biotehniške fakultete UL smo zelo ponosni, da je na slavnostni seji Senata Univerze v Ljubljani 29. 11. 2022 Zlato plaketo prejel tudi naš sodelavec, prof. dr. Primož Oven, vodja Katedre za kemijo lesa in druge lignocelulozne materiale. Prof. Oven je mednarodno uveljavljen raziskovalec in pedagog na področju proučevanja zvez med funkcijami, strukturami, kemizmom in lastnostmi lesa, biorafinacije ter valorizacije lesne biomase s poudarkom na pridobivanju in uporabi nanoceluloze in lesnih ekstraktivov. V akademskem in gospodarskem okolju promovira trajnostno izrabo lesa v krožnem biogospodarstvu in skrbi za ugled UL doma in v tujini.
The main objective of our study was to investigate the possible differences in the chemical compo... more The main objective of our study was to investigate the possible differences in the chemical composition of extractives from the bark of silver fir (Abies alba) with respect to the location of the bark sample on the tree, viz. differences in extract composition between stem bark and branch bark samples. Extractives in the bark samples from branches, depending on the distance of the sample from the trunk, were also analysed, and the stem bark samples were analysed with respect to their inner and outer parts. The results of the chemical analysis of extractives were supported by information about their antifungal and antioxidant effects. After felling and sampling silver fir trees, the collected bark samples were ground and freeze-dried. Extraction of bark samples was followed by a system of accelerated extraction using only water as a solvent. The extracts were analysed chemically using gravimetry, spectrophotometry and chromatography. Free-radical-scavenging activity was measured usin...
Cilj študije je bil priprava bionanokompozita na osnovi polimlečne kisline (PLA) z dodatkom nanof... more Cilj študije je bil priprava bionanokompozita na osnovi polimlečne kisline (PLA) z dodatkom nanofibrilirane celuloze (NFC) kot ojačitvene komponente. Za izdelavo kompozita smo uporabili nemodificirano in acetilirano NFC (A_NFC). NFC, posušeno z zamrzovanjem, smo acetilirali v heterogenem sistemu z acetanhidridom v dimetilformamidu (DMF) ob prisotnosti piridina kot katalizatorja. Uspešnost acetiliranja smo ugotavljali z infrardečo (FT-IR) spektroskopijo. Pripravili smo PLA filme z 2,5 %, 5 % in 10 % dodatkom nemodificirane oziroma acetilirane NFC. Osredotočili smo se na proučevanje vpliva dodatka NFC na prosojnost bionanokompozita in na njegovo odpornost proti razenju. Prosojnost bionanokompozitnega filma smo merili z UV-Vis spektrofotometrijo, odpornost površine filmov proti razenju pa smo ovrednotili z vzmetnim svinčnikom. Določili smo optimalno količino dodane NFC in A_NFC polimeru PLA za doseganje boljše odpornosti proti razenju. Ugotovili smo, da z dodatkom 2,5 % A_NFC dosežemo ...
Raziskali smo vsebnost in sestavo ekstraktivov v lesnih tkivih in skorji robinije (Robinia pseudo... more Raziskali smo vsebnost in sestavo ekstraktivov v lesnih tkivih in skorji robinije (Robinia pseudoacacia L.). Vzorce njenega lesa in skorje smo ekstrahirali v aparatu Soxhlet z acetonom. Acetonske ekstrakte smo preiskali gravimetrično in s tem izmerili vsebnost skupnih hidrofilnih ekstraktivov. Z UV-Vis spektrofotometrom smo kolorimetrično izmerili vsebnost skupnih fenolov. Ekstrakte lesa in skorje robinije smo nato detajlno preiskali s sistemom za tekočinsko kromatografijo visoke ločljivosti (HPLC). S to tehniko smo v ekstraktih identificirali in kvantitativno ovrednotili dihidrorobinetin. Največje vsebnosti skupnih hidrofilnih ekstraktivov, skupnih fenolov in dihidrorobinetina smo izmerili v vzorcih jedrovine. Značilno manj ekstraktivov je bilo v vzorcih beljave in skorje. Aksialne variabilnosti v vsebnosti topnih komponent za les in skorjo robinije nismo dognali. Ugotovili smo, da je jedrovina robinije bogat vir fenolnih ekstraktivov.The content and composition of extractives in t...
Research Highlights: The antifungal assay confirmed that knotwood extractives of Scots pine inhib... more Research Highlights: The antifungal assay confirmed that knotwood extractives of Scots pine inhibit the growth of wood decay fungi. Heartwood extracts of black locust were found to be much stronger free radical scavengers than the extracts of Scots pine. The extracts were deposited in the lumina and on the wall surface of cells in the impregnated sapwood. Impregnation of the sapwood blocks with Scots pine and black locust extracts reduced the fungal decay of wood. Objectives: Hydrophilic extracts of Scots pine knotwood and black locust heartwood were chemically analyzed, tested for antifungal and antioxidant properties and used for impregnation of beech and Scots pine sapwood. Materials and Methods: Scots pine knotwood and black locust heartwood were extracted, and obtained hydrophilic extractives were chemically analyzed. Extracts were analyzed for antifungal properties with the in vitro well-diffusion method. The free radical scavenging activity of wood extracts was measured color...
Uvod Celuloza je najbolj razširjen biopolimer na planetu. Sestavljena je iz nerazvejanih polimern... more Uvod Celuloza je najbolj razširjen biopolimer na planetu. Sestavljena je iz nerazvejanih polimernih verig, kjer so med seboj povezane D-glukopiranozilne enote preko β (1 → 4) vezi. V lesu in drugih ligno-celuloznih surovinskih virih je celuloza v obliki makroin mikrofibril, ki jih je mogoče izolirati in/ali razgraditi s sodobnimi mehanskimi, kemijskimi ali encimatskimi postopki (Kalia in sod. 2011 ). Produkt, ki pri tem nastane, se najpogosteje označuje z izrazom nanofibrilirana celuloza (NFC), četudi običajno vsebuje različno velike delce, od vlaken in fragmentov vlaken, pa tudi makro in mikrofibrile ter fragmente teh bioloških struktur (glej npr. Chinga-Carrasco 2011). NFC se praviloma nahaja v obliki vodne suspenzije, kar lahko predstavlja resno tehnološko in ekonomsko omejitev. V mnogih tehnoloških procesih je zaželeno, da je NFC popolnoma suha. Proces sušenja NFC je kritična operacija, ker se pri tem tvorijo ireverzibilne vodikove vezi med celuloznimi nanofibrilami, kar vodi do...
The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and b... more The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and branchwood (BW of silver fir (Abies alba Mill.) was analyzed, and their antifungal and antioxidant properties were studied. In addition, the variability of extractives content in a centripetal direction, i.e., from the periphery of the stem towards the pith, was investigated. The extracts were analyzed chemically with gravimetry, spectrophotometry, and chromatography. The antifungal and antioxidative properties of the extracts were evaluated by the agar well diffusion method and the diphenyl picrylhydrazyl radical scavenging method. Average amounts of hydrophilic extractives were higher in KW (up to 210.4 mg/g) and BW (148.6 mg/g) than in HW (34.1 mg/g) and SW (14.8 mg/g). Extractives identified included lignans (isolariciresinol, lariciresinol, secoisolariciresinol, pinoresinol, matairesinol) phenolic acids (homovanillic acid, coumaric acid, ferulic acid), and flavonoids epicatechin, tax...
The aim of the study was to prepare a bionanocomposite based on polylactic acid (PLA) with the ad... more The aim of the study was to prepare a bionanocomposite based on polylactic acid (PLA) with the addition of nanofibrillated cellulose (NFC) as a reinforcement component. For the production of the composite we used unmodified and acetylated NFC (A_NFC). Freeze-dried NFC was acetylated in a heterogeneous system with acetic anhydride in dimethylformamide (DMF) in the presence of pyridine as a catalyst. The success of the acetylation was determined by FT-IR spectroscopy. PLA films were prepared with the addition of 2.5%, 5% and 10% of unmodified and acetylated NFC. The focus of this research was the impact of the NFC additive on the transparency and on the resistance of the bionanocomposite to scratching. The transparency of the bionanocomposite film was measured using UV-Vis spectrophotometry, and the resistance of the films to scratching was evaluated with a scratch test. The optimal amount of NFC and A_NFC added to the polymer PLA to achieve better resistance of the bionanocomposite t...
Namen prispevka temelji na inovativnem postopku izdelave nanokompozitov na osnovi poli(3-hidroksi... more Namen prispevka temelji na inovativnem postopku izdelave nanokompozitov na osnovi poli(3-hidroksibutirata) (PHB) in nanofibrilirane celuloze (NFC). Raziskovalno delo obravnava pripravo koncentratnih me{anic PHB-prahu in NFC v vodni raztopini za tehnologijo ekstruzijskega me{anja. Ekstrudat koncentrirane me{anice PHB/NFC je bil nato uporabljen kot dodatek h granulirani obliki PHB pri pripravi brizganih vzorcev z razli~nimi ute`nimi dele`i NFC. V prispevku so podane dolo~ene omejitve pri predelavi tovrstnih materialov in predlagane uporabne re{itve za njihovo optimiziranje. Morfolo{ke lastnosti nanokompozitnih komponent smo raziskali z elektronsko mikroskopijo (FE-SEM), mehanske lastnosti pa z nateznim preizkusom. Morfolo{ka preiskava koncentratnih me{anic je razkrila prepleteno sestavo celuloznih nanofibril in polimernih kroglic, prĩ emer se posamezne fibrile prepletajo v obliki {ir{ih pramenov in ustvarjajo videz zamre`ene strukture znotraj polimerne komponente. Mikroskopski posnetki nanokompozitnih me{anic in izbolj{ane mehanske lastnosti izhodnih materialov potrjujejo, da je adhezivni stik med matri~no in oja~itveno komponento dose`en, porazdelitev celuloznih nanofibril po polimerni osnovi pa homogena. Nanokompoziti z visokimi ute`nimi dele`i NFC (10 % ute`nega dele`a) dosegajo pomembno ve~je vrednosti modula elasti~nosti (Et = 1720 MPa) in raztezka pri pretrgu (eb = 3,1 %) ter prenesejo vi{je pretr`ne napetosti (sM = 26 MPa) v primerjavi z referen~nim polimernim vzorcem (Et = 1340 MPa; eb = 2,4 %; sM = 20 MPa). Rezultati {tudije dokazujejo, da je ob pravilni predpripravi polimernih me{anic in optimizaciji tehnologije ekstruzijske predelave, mogo~e izdelati trdne in`ilave materiale, pri~emer dele`oja~itvene faze narekuje stopnjo izbolj{ave kon~nih lastnosti biopolimerne osnove. Klju~ne besede: nanofibrilirana celuloza, poli(3-hidroksibutirat), morfologija, mehanske lastnosti, ekstruzija, tehnologija brizganja In this paper a novel processing route for nanocomposites, based on (3-hydroxybutyrate) (PHB) and nanofibrillated cellulose (NFC), is presented. To obtain a uniform dispersion of the reinforcing filler, a PHB powder was first dispersed in water, mixed with an NFC aqueous suspension and then freeze dried to eliminate the water phase from the ensuing system. The dried batch was then extruded and added to the granulated PHB in different weight proportions. Nanocomposites with various NFC contents were subsequently produced with the injection-moulding technology. The processing limits and feasible solutions for their optimization are thoroughly described within this work. Morphological properties were investigated with FE-SEM, while mechanical properties were determined via a tensile test. SEM images showed that the PHB powder can be effectively incorporated into the mesh of cellulose nanofibrils, as clearly evident by the interlaced structure of individual fibrils with the average lateral dimensions of 69±14 nm. Improved mechanical properties and SEM observations confirmed a good interfacial adhesion and uniform distribution of the reinforcing component. Compared to the unfilled matrix (Et = 1340 MPa; sM = 20 MPa; eb = 2.4 %), an escalating trend in Young's modulus (Et = 1720 MPa) and tensile strength (sM = 26 MPa), along with decisively improved values of the elongation at break (eb = 3.1 %), were observed for the nanocomposites with the highest content of NFC. According to the results presented, strong and tough nanocomposites can be produced via extrusion moulding, whereby the proportion of the reinforcing phase dictates the final material performances.
Freeze dried nanofibrils were acetylated in a heterogeneous system with acetic anhydride, pyridin... more Freeze dried nanofibrils were acetylated in a heterogeneous system with acetic anhydride, pyridine, and dimethylformamide and the obtained acetylated cellulose nanofibrils (CNFac) were combined with poly(lactic acid) (PLA) to a composite. CNFac with its partially hydrophobic surface showed a good compatibility with PLA resulting in composite films with improved properties. Tensile strength (TS), modulus of elasticity (MOE), and elongation at break (EB) of PLA/CNF increased significantly when 2–5% of CNFac was added to the PLA matrix, while the addition of 10% and higher amounts CNFac decreased the EB at a higher TS and MOE. Mechanical parameters did not improve in the case of unmodified CNF addition. The addition of CNFac maintained transparency and had absorbance values between those of pure PLA film and PLA film with 2% CNF, while films formed with the addition of 5 and 10% of CNF were less transparent. The addition of CNF did not essentially affect the thermal properties of nanoc...
The most suitable composition of mobile phase for the separation of simple phenolic compounds suc... more The most suitable composition of mobile phase for the separation of simple phenolic compounds such as gallic acid, pyrocatechol, phloroglucinol, resorcinol, vanillin and related compound catechin by the high performance liquid chromatography was investigated. The most appropriate developing mobile system for the separation of these organic compounds was acetonitrile and 2% water solution of formic acid with gradient ratio from 2.98 to 25:75. The best separation of the six organic compounds was achieved using mobile phase with lower content of formic acid. HPLC is a method of choice for qualitative and quantitative analysis compounds in various types of samples in the broad field of forestry-wood-pulp-paper chain.
The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the mor... more The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the morphological, thermal, and structural behaviors of two different nanofibrillated cellulose (NFC) materials were investigated. Field emission scanning electron microscopy (FE-SEM) observations indicated an interlaced network formation of predominantly in-plane fibrillar orientation for air- and oven-dried samples, while freeze and spray drying resulted in the formation of coarse and fine powder fractions. Comparison of redispersed powders obtained by freeze and spray drying indicated that aggregation phenomena are significantly reduced in freeze-dried specimens. Rheological and sedimentation analysis revealed that the freeze-dried NFC powders are more stable than spray-dried NFC powders when redispersed in water. Aggressive dehydration processes, such as freezing or heating, significantly influence the thermal stability of the dried cellulose samples. On the contrary, the crystallinity prop...
The aim of the study was to find appropriate non-chlorinated solvent systems for the extraction a... more The aim of the study was to find appropriate non-chlorinated solvent systems for the extraction and separation of pure pinosylvin (PS) and pinosylvin monomethylether (PSMME) from Scots pine/Norway spruce wood residues. The extraction was performed in a pressurized solvent extractor and the purification and isolation of pure substances was done by flash chromatography. More precisely, pure PS was isolated via sequential flash chromatography in two repetitions in the gradient mode of the mobile phase, with cylcohexane (CX) and ethylacetate (EtOAc), beginning with 100% CX and ending up with 100% EtOAc. The extractives were qualitatively and quantitatively analyzed in terms of PS and PSMME contents by gas chromatography-flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (1H-NMR) spectroscopy.
Different resol phenol-formaldehyde prepolymer resins have been synthesized with different formal... more Different resol phenol-formaldehyde prepolymer resins have been synthesized with different formaldehyde / phenol ratios. The phenolic resin composition depends on monomer ratio, catalyst, reaction conditions, and residual free monomers. Temperature and pH conditions under which reactions of phenols with formaldehyde are carried out have a profound effect on the characteristics of the resulting products. Three reaction sequences must be considered: formaldehyde addition to phenol, chain growth or prepolymer formation and finally the crosslinking or curing reaction. Two prepolymer types are obtained depending on pH, novolacs in an acidic pH region whereas resols by alkaline reaction. Resol resins are synthesized with a molar excess of formaldehyde (1<F/P<3). These are mono-or polynuclear hydroxymethylphenols which are stable at room temperatures, but are transformed into three dimensional, cross linked, insoluble and infusible polymers by the application of heat. An ATR-FTIR spectrometry technique (ReactIR 4000) with light conduit and diamond-composite sensor was used to perform in-line monitoring of phenol-formaldehyde prepolymer synthesis. This technique was found to be ideal for determining residual free phenol and formaldehyde, individual phenol and formaldehyde conversions and prepolymer composition changes as a function of time when the condensation reaction was carried out. The kinetics data obtained through the ReactIR 4000 in-line reaction analysis system agreed well with those determined by the traditional titration method. ReactIR technology replaces time consuming and inaccurate off-line methodology.
Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst a... more Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst at different temperatures. At the highest treatment temperature (150 °C) liquefaction of wood pulp cellulose was achieved and was dependant on cellulose polymerization degree (DP). Furthermore, the rate of amorphous cellulose weight loss was found to increase with cellulose degree of polymerization, while the rate of crystalline cellulose weight loss was reciprocal to the size of the crystallites. The cellulose degradation was studied by monitoring of the molecular mass decrease by size-exclusion chromatography. It was revealed that microcrystalline cellulose degrades via a 'quantum mode' mechanism, while the degradation of Whatman filter paper no 1. and cotton linters proceeded randomly and were partly dependent on the starting polymerization degree, crystallinity, and treatment temperature. The kinetics of cellulose degradation in heterogeneous media was described by means of a one-stage model, characterised by the consumption of glycosidic bonds in amorphous and crystalline cellulose regions until the levelling-off degree of polymerization is reached.
In this study, we investigated the antibacterial modification of polymers with biologically activ... more In this study, we investigated the antibacterial modification of polymers with biologically active substances in essential oils [EOs; linalool, 4-allylanisole (ALY), and trans-anethole]. These compounds were thermoplastically incorporated into a low-density polyethylene matrix via solid inert carriers [wood flour (WF) and talc and molecular sieves] with physically immobilized EOs. The concentrations of the antibacterial modifiers on the carriers and in the resulting composites were determined with three chromatographic techniques (gas chromatography with mass spectrometry, pyrolysis and gas chromatography with mass spectrometry, and high-performance liquid chromatography). The effects of such modifications to the mechanical properties of the prepared composites were studied by stress-strain analysis. Interactions on the polymer matrix carriers were observed by scanning electron microscopy. The prepared composites were also tested for antibacterial activity against both Gram-negative and Gram-positive bacterial strains. The highest efficiency of isothermal immobilization was found for systems consisting of ALY and WF. This finding was in accordance with microbiological studies. The phase of immobilizing the EOs did not influence the mechanical properties of the studied composites. V
The goal of the presented work is to describe the proteinic impurity (as possible residual compon... more The goal of the presented work is to describe the proteinic impurity (as possible residual component from biotechnological lactic acid production from whey) in the reaction mixture with 2-hydroxypropanoic acid (lactic acid) for its direct polycondensation into poly(lactic acid). The impurity presence study was carried out in the range from mass fractions 0 % up to 2 %. For an evaluation of the impurity effect on the values of molecular weight, melting and glass transition temperatures the measurements of intrinsic viscosity, gel permeation chromatography and differential scanning calorimetry were used. Results show slight reduction of molecular weight and increase in polydispersity with rising amount of the impurity. The thermal properties investigation shows noticeable reduction of melting temperature and moderate decrease in glass transition temperature. The results reveal considerable role of lactose on formation of structural irregularities in lactic acid polycondensates.
Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications ... more Bacterial cellulose (BC) film formation could be a critical issue in nanotechnology applications such as biomedical or smart materials products. In this research, purified pretreated BC was subjected to high intensity ultrasound (HIUS) and was investigated for the development of BC films. The morphological, structural and thermal properties of the obtained films were studied by using FE-SEM, AFM, FT-IR, XRD, TGA and DSC characterizations. Results showed that the most favorable purification treatment was the 0.01 M NaOH at 70°C for 2h under continuous stirring. The most suitable ultrasound operating conditions were found to be, 1cm distance of ultrasonic probe from the bottom of the beaker, submerged in cold water bath cooling around 12 ± 2°C. The power (25 W/cm(2)), time (30 min), BC concentration (0.1%w/w), amplitude (20 μm) and frequency (20 kHz) were maintained constant.
ABSTRACT In this study, we modified melamine-formaldehyde (MF) resin adhesive with liquefied wood... more ABSTRACT In this study, we modified melamine-formaldehyde (MF) resin adhesive with liquefied wood (LW) and determined the properties of MF–LW adhesive mixtures. Furthermore, we produced particleboards using prepared MF–LW mixtures and evaluated their mechanical and physical properties. Results showed that with increasing content of LW in the adhesive mixture gel time and peak temperature increased while reaction enthalpy decreased. With increasing substitution of MF resin adhesive with LW the thermal stability of adhesive mixture reduced, namely thermal degradation started at lower temperature and weight loss increased. Properties of particleboards improved with increasing amount of LW in the adhesive mixture up to 20% and then deteriorated. Nevertheless, the properties of particleboard with 30% LW in the adhesive mixture were comparable to the properties of particleboard without LW while they worsen at greater portion of LW. Consequently, MF resin adhesive with 30% LW substitution could be used to produce particleboards with suitable mechanical properties and reduced formaldehyde release content.
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Papers by Ida Poljansek