Liquefied Wood Research Articles

Enhancement of thermal conductivity and abrasion resistance of woody carbon fiber composites via boride catalysis

In order to investigate the effect of boron element on liquefied wood carbon fibers and their composites, boric acid and boron carbide were utilized to modify liquefied wood resin through copolymerization and blending methods respectively. Then boric acid-modified liquefied wood carbon fiber (BA-WCF) and boron carbide-modified liquefied wood carbon fiber (BC-WCF) were produced via melt spinning, curing, and carbonization treatments. As expected, this modification approach effectively prevents the formation of skin-core structures and accelerates the evolution of a graphite microcrystalline structure, thereby enhancing the mechanical properties of the carbon fibers. Particularly, the tensile strength and elongation at break of BA-WCF increased to 331.57 MPa and 7.57 % respectively, representing increments of 117 % and 86 % compared to the conventional fibers. Furthermore, the as-fabricated carbon fiber/resin composites (CFPRs), composing of BA-WCF or BC-WCF as fillers and liquefied wood resin as matrix, exhibited excellent interlaminar shear strength, outstanding abrasion resistance, and well thermal conductivity, as well as electrical performance, significantly outperforming the conventional carbon fiber/phenolic resin composites. The friction rate of BC-WP/BA-WCF/CF was 2.37 %, while its thermal conductivity could reach 1.927 W/(m·K). These promising attributes lay the groundwork for the development of high-performance carbon fiber-based materials, fostering their widespread utilization across various industries.

Worm‐like ordered mesoporous carbon from liquefied wood: Morphological manipulation by varying hydrothermal temperature

AbstractThe hydrothermal/soft templating method is an effective way to synthesize ordered mesoporous carbon (OMC), yet the mechanism of this strategy is not well illustrated. Herein, a hydrothermal temperature‐controlled approach is developed to precisely synthesize OMCs with well‐defined morphologies from liquefied wood (LW). As the hydrothermal temperature increases from 130 to 210°C, the hydrophilicity of the hydrophilic blocks decreases accompanied by the increase of the relative volume of the hydrophobic block, resulting in the packing parameter p of micelles changing from p ≤ 1/3 to 1/3 < p < 1/2, which transforms the micelle's structure from spherical to cylindrical. Additionally, accelerated nucleation occurred with the increased hydrothermal temperature. When the rate of nucleation is matched to the self‐assembly of the composite micelles, the composite micelles grow into worm‐like morphology and an ordered p6m mesostructure. This hydrothermal temperature‐controlled strategy provides a straightforward and effective approach for synthesizing OMCs with various morphologies from LW, addressing the previously insufficiently elucidated micelle formation mechanism in the hydrothermal/soft templating method.

NiS Nanosheets Decorated on Hollow Carbon Spheres from Liquefied Wood for Supercapacitors

Carbon-based supercapacitors with high performance have a wide foreground among various energy storage devices. In this work, wood-based hollow carbon spheres (WHCS) were prepared from liquefied wood through the processes of emulsification, curing, carbonization, and activation. Then, the hydrodeposition method was used to introduce nickel sulfide (NiS) to the surface of the microspheres, obtaining NiS/WHCS as the supercapacitor electrode. The results show that NiS/WHCS microspheres exhibited a core-shell structure and flower-like morphology with a specific surface (307.55 m2 g-1) and a large total pore volume (0.14 cm3 g-1). Also, the capacitance could be up to 1533.6 F g-1 at a current density of 1 A g-1. In addition, after 1000 charge/discharge cycles, the specific capacitance remained at 72.8% at the initial current density of 5 A g-1. Hence, NiS/WHCS with excellent durability and high specific capacitance is a potential candidate for electrode materials.

Polypyrrole-decorated hierarchical carbon aerogel from liquefied wood enabling high energy density and capacitance supercapacitor

Carbon aerogels (CAs) from biomass have low energy density and specific capacitance due to underutilized structure, severely hindering their application in high-performance supercapacitors. Herein, we address this issue through a binary composite in which psudocapacitive polypyrrole (PPy) microparticles are in situ grown on the surfaces of hierarchical porous liquefied wood carbon aerogels (LWCA). The deposited pseudocapacitive PPy microparticles contributes to the high energy density and specific capacitance. The hierarchical structure of LWCA prevents aggregation of PPy microparticles and ensures rapid transfer of electrolyte ions. In three electrodes system, the optimized hybride capacitive LWCA-PPy-65 composite exhibites excellent capacitive performance of 421.45 F g−1 and cycle stability with 82.9% after 5000 cycles. In KOH electrolyte, the hybrid supercapacitor from LWCA-PPy-65 demonstrates a high energy density of 52.0 Wh kg−1 with a power density of 2012.8 W kg−1, and excellent cyclic performance of 92.81% retention after 5000 cycles at 5 A g−1. In H2SO4 electrolyte, the fabricated solid state supercapacitor displays prominent cyclic performance of 92.81% retention after 5000 cycles at 5 A g−1. Such three-dimensional biomass-based composite aerogels with high energy density and capacitance demonstrated a promising application prospect in energy storage devices.

Characterization of Curing and Bonding of Wood with Adhesive Mixtures of Liquefied Wood and Hexamethylenediamine

Various crosslinking agents can be added to the formulations of natural-based adhesives for wood bonding in order to achieve better durability and higher strength of the formed joints. In the present study, the effect of hexamethylenediamine (HMDA) addition on the performance of liquefied wood (LW) adhesive for wood bonding is investigated. Differential scanning calorimetry showed the improved thermal stability and crosslinking of the LW adhesive with HMDA. The intensified presence of amide linkages (C–N bonds) was found in LW+HMDA with attenuated total reflection Fourier transform infrared spectroscopy. Analysis of the bonded joints using an automated bonding evaluation system showed that a higher press temperature resulted in stronger bonds for both types of adhesives. Moreover, the addition of HMDA to LW adhesive improved the bond strength of the joints and accelerated the crosslinking of the adhesive. However, with a tensile shear strength of (6.76 ± 2.16) N × mm−2 (for LW) and (6.89 ± 2.10) N × mm−2 (for LW+HMDA), both adhesives were found to be unsuitable for interior non-structural use. In addition, the acidity of LW resulted in relatively high wood failure (70%) in the adhesive joints tested. Improved crosslinking of LW with HMDA was reflected in improved resistance of LW+HMDA adhesive joints to water degradation. In conclusion, HMDA is a promising additive for improving the adhesive performance of LW adhesives.

Studies on the reactivity of epoxy/polyol/isocyanate blend resins and the properties of epoxy/polyurethane composites

AbstractEpoxy resin (ER) is one of the most widely used synthetic resins, and the improvement of its toughness is an important issue. In this study, Epon 828 is used as ER resin, polytetramethylene ether glycol (PTMG) and liquefied wood (LW) are used as polyol, and IPDI, H12‐MDI, Desmodur N, and Desmodur L are used as isocyanate. The influence of polyurethane resin (PU) composition on the reactivity of ER/polyol/isocyanate blended resin and the properties of ER/PU composite are investigated. The results show that the mixture of ER/PTMG/IPDI has greater reactivity, followed by ER/PTMG/Desmodur N, while ER/PTMG/Desmodur L has lower reactivity. In the structure of ER/PU blended resin composites, ER and PU resins not only form a physical interpenetrating structure, but also undergo a copolymerization crosslinking reaction. The modulus of elasticity of ER/PU composites prepared with trifunctional Desmodur L and Desmodur N is greater than that of bifunctional IPDI and H12‐MDI, while those with LW as polyol is greater than that of PTMG as the raw material.

Ordered mesoporous carbons from liquefied wood: Morphological effects of nucleation and growth processes

A HCl concentration-controlled hydrothermal/soft-templating strategy is proposed to prepare ordered mesoporous carbons (OMCs) with diverse morphologies from flakes to gyroids then to spheres by using liquefied wood as a carbon precursor. The effect of nucleation and growth process on morphology change was systematically studied. Results showed that an accelerated nucleation rate and a transformation of self-assembly pattern from slow and weak aggregates to fast and strong assembly are achieved in accordance with increasing HCl concentration. Detailed mechanism studies reveal that a reaction solution without seed nuclei formed at the initial stage of the hydrothermal process under low HCl concentration will lead the micelles to slowly self-assemble into microscale flakes, whereas a high HCl concentration will make the micelles rapidly self-assemble into rodlike micelles and further grow along the surface of the initially formed seed nuclei to produce nanoscale products with an annular structure. The OMCs with highly ordered p6mm mesostructure synthesized at a proper HCl concentration of 1.61 M exhibit higher electrochemical performance than the less ordered OMCs. The detailed study of nucleation and growth mechanism provides new understanding of controllable design and synthesis of OMCs with desired morphology.

Performance and emissions of liquefied wood as fuel for a small scale gas turbine

This study investigates for the first time the combustion in a micro gas turbine (MGT) of a new bioliquid, a viscous biocrude, which is a liquefied wood (LW) produced via solvolysis of lignocellulosic biomass in acidified glycols. The test rig includes a modified fuel injection line, a re-designed combustion chamber and revised fuel injection positions. The main novelties of this work are: (1) producing of liquefied wood with pure ethylene glycol as a solvent, and methanesulfonic acid as a catalyst, to obtain a bio-crude with lower viscosity and higher lignocellulosics content than previous tested formulations; (2) upgrading raw liquefied wood by blending it with ethanol to further reduce the viscosity of the mixture; (3) utilizing a commercially available MGT Auxiliary Power Unit (APU) of 25 kW electrical power output, with notably reduced extent of adaptations to use the newly obtained fuel mixture. Fuel properties, and their impact on combustion performance using liquefied wood, are investigated by analyzing MGT performance and emissions response at different load and blend ratios. Emissions revealed that the presence of LW in the blends significantly affects CO and NOX concentrations compared to conventional fuels. CO roughly increased from 600 ppm (pure ethanol as fuel) to 1500 ppm (at 20 kW electrical power). The experimental study reveals that it is possible to achieve efficient MGT operation while utilizing high biocrude to ethanol ratios, but a number of adaptations are necessary. The achieved maximum share of liquefied wood in the fuel blend is 47.2% at 25 kW power output. Main barriers to the use of higher share of liquefied wood in these type of systems are also summarized.

Effect of containing polyhydric alcohol liquefied wood on the properties of thermoplastic polyurethane resins

Polyurethane (PU) is one of the most important synthetic resins which have been widely used in various industries. Most of the PU resins are prepared by reacting isocyanate with polyols. Polyhydric alcohol liquefied biomasses are rich in hydroxyl groups and are considered having the potential to be a raw material for preparing PU resins. In this study, wood of Japanese cedar (Cryptomeria japonica) was liquefied in polyethylene glycol/glycerol co-solvent with H2SO4 as a catalyst at 150 °C for 60 min. After being cooled, the liquefied product was diluted, neutralized, filtered and vacuum distilled to obtain the liquefied wood (LW). Thermoplastic PU resin (TPU) containing LW was prepared by reacting a mixture of polytetramethylene ether glycol (PTMG) and LW with different OH/OH molar ratios with 1,6-hexamethylene diisocyanate (HDI), using 1,4-butanediol as a chain extender. The influence of the amount of LW on the molecular structure, mechanical and thermal properties of TPU was investigated. FTIR analysis shows that LW-containing TPU, referred to as LWTPU, has more hydrogen bonding than neat TPU. Resin films made from LW-TPU prepared with a mixture of PTMG/LW with an OH/OH molar ratio of 80/20 and 65/35 have higher tensile strength and less breaking elongation than that of neat TPU. DMA results show introducing LW leads to TPU films being more rigid. TGA results show the thermal stability of TPU films can be enhanced by LW before the temperature reaches 350 °C.

Curing behavior and bonding strength of two-component fast-setting adhesives prepared with phenol-liquefied Cryptomeria japonica wood

Honeymoon adhesive is a special adhesive system that contains two components which are applied onto two substrates separately for glulam manufacturing to provide a fast-setting capability. It has been confirmed that phenol-liquefied wood can be used as a raw material for preparing phenolic resins. In this study, liquefied wood (LW) was obtained by liquefying Cryptomeria japonica wood in phenol with sulfuric acid as a catalyst. Resorcinol–formaldehyde resin (RF), phenol-resorcinol–formaldehyde resins (PRF), LW–PF and LW–PRF (synthesized using LW as a raw material), and RF/LW and RF/LW–PF (blended RF with LW and LW–PF) were prepared. The properties such as non-volatile content, pH, viscosity gelation time and DSC curing behavior of these resins were measured. The results show all resins can be cured at room temperature when paraformaldehyde is added as a hardener, except for the LW–PF. The honeymoon adhesive was prepared by using RF and PRF that contains 10% paraformaldehyde as the A-component and LW–PRF, RF/LW and RF/LW–PF without paraformaldehyde as the B-component. After mixing the A-component and B-component, the gelation time of RF and PRF can be shortened. The glued lumber was prepared by separately applying the A-component and B-component on the surface of two wood strips and combining them. The result shows using RF/LW–PF as the B-component has faster bonding strength development than others. When PRF and RF are used as the A-component, they have a bonding strength of over 5.4 MPa, the requirement of CNS 11031 standard for the glued lumber of C. japonica, at pressing times of 2 and 4 h, respectively.

Emissions and Combustion Performance of a Micro Gas Turbine Powered with Liquefied Wood and its Blends

The combustion of a viscous biofuel, liquefied wood (LW) produced via solvolysis of lignocellulosic biomass in acidified glycols, has been studied in a small gas turbine rig. The test rig includes a modified injection line which is compatible with acidic, viscous biofuels allowing fuel preheating and two pilot injectors, and a re-designed combustion chamber. The link between fuel properties and combustion performance of liquefied wood is investigated by burning the biofuel at different blending ratios with ethanol. Exhaust emissions have been compared to reference measurements with diesel fuel and ethanol. Combustion analysis is supported by the investigation of the engine operating parameters and the main emission species at different electrical loads. The experimental study reveals that it is possible to establish efficient operation of the micro gas turbine while utilizing liquefied wood-ethanol blends with high share of liquefied wood.

Exploitation of liquefied wood waste for binding recycled wood particleboards

Abstract Four types of industrial waste from wood processing, namely a mixed hardwood-softwood powder, pine and beech sawdust, and bark were liquefied and tested as binders for particleboards (PB) made of recycled wood. The liquefaction reaction was carried out at elevated temperature with a mixture of solvents from polyhydroxyl alcohols such as glycerine and propylene glycol, and p-toluenesulfonic acid as a catalyst. Then the liquefied woods (LWs) were characterized in terms of their suitability for PB production as a partial substitute for synthetic urea-formaldehyde (UF) resin. The standard properties of PBs such as tensile strength, bending strength and modulus of elasticity, density, moisture content, swelling after 24 h, water absorption, and formaldehyde content were measured. All tests were performed in comparison to a standard PB bonded by UF resin. It was demonstrated that the substitution of UF resin up to 20% of LW did not have a significant effect on the mechanical properties. PB made of recycled wood produced with LW possessed good mechanical properties that meet the European standard quality demands for PBs.

Preparation and characterisation of carbon fibre-reinforced laminated woodceramics

To improve the structure and basic performance, carbon fibre-reinforced woodceramics with a laminated structure were prepared by using liquefied wood and carbon powder as matrix materials and carbon fibre as a reinforcing material through structure and process designs with the establishment of a unit structure model thereof. Basic performance tests indicated that the sintering temperature and content of liquefied wood played important roles. The apparent density first reduced, later increased and then decreased with increasing sintering temperature; the apparent porosity decreased with increasing liquefied wood content. Scanning electron microscopy showed that the woodceramics presented a clear laminated structure and tight joints between glassy carbon (GC) and the embedded carbon fibres. There was an interface layer found between the amorphous carbon and GC. Meanwhile, it still partially retained the natural structural characteristics of wood. Raman spectrum detection verified that raising the sintering temperature could increase the number of graphite crystallites and the orderliness of their arrangement. Transmission electron microscopy showed that the specimens formed at higher temperatures presented clear lattice fringes. In addition, the laminated structure and the application of reinforced carbon fibre greatly enhanced the bending strength, elastic modulus, and fracture toughness.

Preparation of Nanofibres from Phenol Liquefied Wood by Electrospinning

To prepare electrospun fibres from phenol liquefied wood (LW), polyvinyl pyrrolidone (PVP) with an average molecular weight of 1,300,000 g/mol was considered as an additive to synthesize the electr...

Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates.

Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester’s material quality; Cupriavidus necator was applied as microbial production strain. For proof of concept, pre-experiments were carried out on a shake flask scale using different mixtures of glucose and LW as carbon source. The results indicate that LW definitely acts as a 3HV precursor, but, at the same time, displays toxic effects on C. necator at concentrations exceeding 10 g/L. Based on these findings, PHA biosynthesis under controlled conditions was performed using a fed-batch feeding regime on a bioreactor scale. As major outcome, a poly(3HB-co-0.8%-3HV) copolyester was obtained displaying a desired high molar mass of Mw = 5.39 × 105 g/mol at low molar-mass dispersity (ĐM of 1.53), a degree of crystallinity (Xc) of 62.1%, and melting temperature Tm (176.3 °C) slightly lower than values reported for poly([R]-3-hydroxybutyrate) (PHB) homopolyester produced by C. necator; thus, the produced biopolyester is expected to be more suitable for polymer processing purposes.

Properties of liquefied wood modified melamine-formaldehyde (MF) resin adhesive and its application for bonding particleboards

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.

Preparation of Two-Component Polyurethane Coatings from Bleached Liquefied Wood

Liquefied wood-based polyurethane wood coatings of an aesthetically acceptable light colour were prepared and characterised. Liquefied black poplar wood was obtained by solvolysis in a polyethylene glycol/glycerol mixture, and it was bleached with hydrogen peroxide. The bleaching treatment converted liquefied wood from a dark brown to a yellowish product. Polyurethane films were prepared by the curing of liquefied wood with polymeric diphenylmethane diisocyanate or trimethylolpropane toluene diisocyanate prepolymer (TMP/TDI) isocyanate-type hardeners. It was found that the selected properties of the films prepared from the bleached liquefied wood were, in general, equivalent to those prepared from unbleached liquefied wood. The mechanical properties of the films obtained with the TMP/TDI curing agent were acceptable for wood coating applications. The initial poor resistance of the films to water and ethanol was substantially improved by the addition of n-octyltriethoxysilane to the liquefied wood prior to the preparation of the polyurethane coatings; the hardness of the films also increased.

Properties of polyurethane (PUR) films prepared from liquefied wood (LW) and ethylene glycol (EG)

Abstract The wood of Cryptomeria japonica D. Don was liquefied in ethylene glycol (EG) with sulfuric acid (H2SO4) as a catalyst at 150°C for 60 min. The liquefied wood (LW)- and EG-based polyester polyols (EG-Polyest.-ol) were synthesized by reacting LW and EG with adipic acid (AA), respectively. Polyurethane (PUR) resins were made by mixing Polyest.-ol with isocyanate. The results show that LW-Polyest.-ol is a suitable raw material for PUR. The PUR films prepared with LW-Polyest.-ol have higher tensile strength with less elongation at breaking point than that with EG-Polyest.-ol. According to dynamic thermomechanical analysis, the PUR films prepared with EG-Polyest.-ol have a homogeneous molecular structure, whereas a phase separation has been found for those made with LW-Polyest.-ol. Thermal gravimetric analysis showed that the thermal degradation of LW-PUR films only starts at higher temperature than that of EG-PUR.

Microturbine combustion and emission characterisation of waste polymer-derived fuels

The work presented here characterises the influences of different waste-derived fuels on the combustion process in a microturbine. The two most common types of solid waste are converted into liquids by liquefaction in polyhydric alcohols and by pyrolysis to produce the novel fuels LW (liquefied wood) and TPO (tire pyrolysis oil). Baseline results were obtained with diesel fuel and with raw polyhydric alcohols otherwise used in wood liquefaction process. The original contribution of this analysis is the in-depth comparison of the combustion and emission phenomena of LW and TPO under different operating conditions. The results revealed significantly higher CO (carbon monoxide) and THC (total hydrocarbons) emissions for LW due to its reduced atomisation ability and increased spray penetration in line with the physical and chemical properties of the fuel. The combustion properties of TPO resembled those of diesel fuel in terms of CO and THC. NOx (nitrous oxides) emissions reflected the elemental composition of the fuels. In addition, pronounced soot formation is observed when utilizing TPO, whereas for LW, the opacity measurements are surprisingly low. These results indicate that TPO can be exploited directly in gas turbines, whereas LW requires adaptations in the fuel supply system and a narrower range of operating conditions.

Microscopic analysis of the wood bond line using liquefied wood as adhesive

The bonding of beech (Fagus sylvatica L.) with liquefied wood (LW) causes deterioration of the wood surface, resulting in a high percentage of wood failure at a relatively low bond shear strength. Light microscopy, scanning electron microscopy, FT-IR micro-spectroscopy and elemental carbon, nitrogen and sulphur (CNS) analysis techniques were used to investigate the formation of such bonds. It was assumed that the degradation of lignin, hemicelluloses and parts of the cellulose occurred in the cells of the wood surface where the LW had been applied. At the elevated temperatures occurring during the bonding process, the deteriorated cells were carbonised to some extent. The weak boundary layer of the bond was determined to be a layer of delignified cells located between the zone of partly carbonised cells on the one side and the cells of the undamaged wood of the adherend on the other side. The bonds which formed during the bonding of wood with LW were found to be very untypical compared to bonds formed by synthetic wood adhesives. No adhesive film was formed, the adhesive-adherend interface was not clear and the cells of the adherend subsurface were damaged.