Search Results (174)

To address the issues of traditional gels in high-temperature reservoir leakage plugging, such as injection–retention imbalance, poor high-temperature stability, and insufficient thixotropy, this study developed a thixotropic polymer gel system via molecular design and component optimization, aiming to achieve excellent thixotropy, high strength, and wide temperature adaptability (80–140 °C) while clarifying its gelation mechanism. First, the optimal polymer was selected by comparing the high-temperature stability and crosslinking activity of AM/AMPS copolymer (J-2), low-molecular-weight acrylamide polymers (J-3, J-4), and AM/AMPS/NVP terpolymer (J-1). Then, the phenolic crosslinking system was optimized: hexamethylenetetramine (HMTA) was chosen for controlled aldehyde release (avoiding poor stability/dehydration) and catechol for high crosslinking efficiency (enhancing strength via dense crosslinking sites). Urea–formaldehyde resin (UF) was introduced to form a “polymer-resin double network,” improving high-temperature compression resistance and long-term stability. Cyclic shear rheological tests showed the gel system had a larger hysteresis area than the polymer solution, indicating excellent thixotropy before gelation. It gelled completely at 80–140 °C (gelation time shortened with temperature). At 120 °C, its viscosity was 7500 mPa·s, storage modulus (G′) 51 Pa, and loss modulus (G″) 6 Pa, demonstrating good shear thixotropy. The final system (1% J-1, 0.3% catechol, 0.6% HMTA, 15% UF) is suitable for high-temperature reservoir leakage plugging. Full article

This study investigated the potential of hazelnut wood (Corylus avellana L.) as an alternative raw material in the production of single-layer structural particleboards. Boards with a target density of 700 kg m⁻³ and thickness of 13 mm were manufactured using varying substitution levels (5%, 10%, 25%, 50% and 100%) of hazel wood particles relative to industrial pine (Pinus sylvestris L.) particles. Phenol-formaldehyde (PF) resin was used as the adhesive at a 15% resination rate. Mechanical and physical properties, including modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), screw withdrawal resistance (SWR), water absorption (WA), and thickness swelling (TS), were evaluated according to relevant European standards. Density profiles (DP) were also assessed. The results showed that while higher hazel content reduced bending strength (from 23.3 N mm⁻² for reference to 18.7 N mm⁻² for 100% hazel wood board) and stiffness (from 3515 N mm⁻² for reference to 2520 N mm⁻² for 100% hazel wood board), most boards met standard mechanical requirements of EN 312 for P3 and P5 boards. Notably, IB strength improved significantly at higher hazel content, with the 100% variant (2.07 N mm⁻²) exceeding the reference board (1.57 N mm⁻²). Screw withdrawal resistance also increased with hazel wood addition (from 235 N mm⁻¹ for reference to 262 N mm⁻¹ for 100% hazel wood board), linked to its higher density. However, water resistance and dimensional stability worsened with increasing hazel content, particularly in bark-containing particles, leading to excessive thickness swelling after prolonged water exposure. Thickness swelling after 24 h of soaking rose from 16.36% for the reference board to 20.13% for the 100% hazel wood board. Density profiles revealed a more uniform internal structure in boards with higher hazel content. Overall, hazelnut wood shows promise as a partial substitute for pine in particleboard production, especially at moderate substitution levels, though limitations in moisture resistance must be addressed for broader industrial application. Full article

Resol phenol–formaldehyde (PF) resin was modified with 2.5 and 5.0 wt% polymethylhydrosiloxane (PMHS). This study characterizes the modified resin and its subsequently fabricated glass fiber (GF)-reinforced composites (30–60 wt% GF). Formation of an organic–inorganic hybrid network, via reaction between Si-H groups of PMHS and hydroxyl (-OH) groups of the resol resin, was confirmed by FTIR and ¹H NMR. DSC and TGA/DTG revealed enhanced thermal stability for PMHS-modified resin: the decomposition temperature of Resol–PMHS 5.0% increased to 483 °C (neat resin: 438 °C), and char yield at 800 °C rose to 57% (neat resin: 38%). The 60 wt% GF-reinforced Resol–PMHS 5.0% composite exhibited tensile, flexural, and impact strengths of 145 ± 7 MPa, 160 ± 7 MPa, and 71 ± 5 kJ/m², respectively, superior to the unmodified resin composite (136 ± 6 MPa, 112 ± 6 MPa, and 51 ± 5 kJ/m²). SEM observations indicated improved fiber–matrix interfacial adhesion and reduced delamination. These results demonstrate that PMHS modification effectively enhances the thermo-mechanical properties of the PF resin and its composites, highlighting potential for industrial applications. Full article

Lignin, an abundant and renewable biopolymer, has gained significant attention as a sustainable modifier and building block in polymeric materials. Recent advancements highlight its potential to tailor mechanical, thermal, and barrier properties of polymers while offering a greener alternative to petroleum-based additives. This review provides an updated perspective on the incorporation of lignin into various polymer matrices, focusing on lignin modification techniques, structure–property relationships, and emerging applications. Special emphasis is given to recent innovations in lignin functionalization and its role in developing high-performance, biodegradable, and recyclable materials such as polyurethanes, epoxy resins, phenol-formaldehyde resins, lignin-modified composites, and lignin-based films, coatings, elastomers, and adhesives. These lignin-based materials are gaining attention for potential applications in construction, automated industries, packaging, textiles, wastewater treatment, footwear, supporting goods, automobiles, printing rollers, sealants, and binders. Full article

Using a relatively inexpensive method, phenol–cresol–formaldehyde resin (PhCR-F) was produced utilizing the byproducts of coal coking. It is shown that petroleum road bitumens, to which 1.0 wt.% PhCR-F is added, in terms of basic physical and mechanical parameters, comply with the requirements of the regulatory document for bitumens modified with adhesive additives. Research on the operational properties of these modified bitumens as a binding material for asphalt concrete is described. It has been proven that modified bitumen can store stable properties during its application (resistance to aging). The interaction of bitumens modified by PhCR-F with the surfaces of mineral materials, which occurs during the creation of asphalt concrete coatings, was studied. It was shown that adding 1.0 wt.% PhCR-F to road bitumen significantly improves the adhesion of the binder to the mineral material and increases the hydrophobicity of such a coating. The production of effective bitumen modifiers from non-target coking products of coal will not only make it possible to use new resources in road construction but will also increase the depth of decarbonization of the coking industry. Full article

This study investigates the use of carbonized hemp fiber (CHF) as a reinforcement for phenol resorcinol formaldehyde (PRF)-based fiber composites. The hemp fiber was carbonized slowly up to 1000 °C under N₂ with a yield of 18%. Compression-molded composites were prepared with CHF and then compared to hemp (HF) and wood fiber (WF) at 0 to 50% loading with PRF resin. The flow characteristics of the uncured composites were determined by dynamic rheology and showed pseudoplastic behavior; the composites show promise as extrudable materials. The flexural strength of the HF composites (69 MPa for 40% HF) was higher than the CHF composites. The thermal stability of the composites was determined by thermogravimetric analysis (TGA), and the CHF composites were more stable than the HF and WF composites. Carbonization was shown to enhance both the thermal stability and the hydrophobicity of the composites, which is expected to lead to less susceptibility to weathering and biological attack. Formulations of 50% WF, 50% CHF, and 30% HF fiber loadings with PRF were able to be extruded into rods. Extruded CHF composites showed better mechanical properties than the HF and WF composites. Full article

Passenger car tires (PCTs) usually consist of a silica/silane-filled Butadiene Rubber (BR) or Solution Styrene Butadiene (SSBR) tread compound. This system is widely used due to improvements observed in rolling resistance (RR) as well as wet grip compared to carbon black-filled compounds. However, the covalent bond that couples silica via silane with the rubber increases the challenge of recycling these products. Furthermore, this strong covalent bond is unable to reform once it is broken, leading to a deterioration in tire properties. This work aims to improve these negative aspects of silica-filled compounds by developing a novel coupling system based on non-covalent interactions, which exhibit a reversible feature. The formation of this new coupling was accomplished by reacting silica with silane and a phenolic resin in order to obtain simultaneous π–π interactions and hydrogen bonding. The reaction was performed using two different silanes (amino and epoxy silane) and an alkyl phenol–formaldehyde resin. The implementation of the new coupling resulted in improved crosslink density, better mechanical performance, superior fatigue behavior, and a similar rolling resistance indicator. Full article

This study addresses the need for thermomechanically robust materials for high-temperature environments by investigating fabric-reinforced composites produced through polymer infiltration and thermal pressing using phenol-formaldehyde (PF) and epoxy (ER) resins. Experimental validation was required due to the lack of comparative data across different textile reinforcements under identical conditions. Seven technical fabrics—carbon, aramid, basalt, silica, fiberglass, asbestos, and a carbon/aramid hybrid—were used as reinforcements. Mechanical testing revealed that carbon- and hybrid fiber composites exhibited the highest tensile (up to 465 MPa) and compressive strengths (up to 301 MPa), particularly when combined with ER. Conversely, the use of PF generally resulted in a 30–50% reduction in mechanical strength. However, PF-based composites demonstrated superior thermal resistance, with the silica/PF combination showing the lowest back-face temperature (401 °C), up to 37% lower than other pairings. Thermal conductivity ranged from 0.041 to 0.51 W/m·K, with PF-based systems offering 6–12% lower values on average compared to ER-based analogs. Morphological analysis confirmed better interfacial bonding in ER composites, while PF systems showed higher structural integrity under thermal loading. Overall, the results emphasize the trade-offs between mechanical strength and thermal protection depending on the fabric–resin combination. Among all variants, the silica fabric with PF demonstrated the most balanced performance, making it a promising candidate for thermomechanical applications. Full article

With the concept of sustainable development gaining increasing traction, the high-value utilization of forest biomass has received growing attention. In this study, an acorn-based wood adhesive was developed using Quercus fagaceae, offering a sustainable alternative that not only supports the multifunctional use of acorn shell resources, but also reduces dependence on fossil-based materials in traditional wood adhesives, a development of significant importance to the wood industry. The effects of various crosslinking agents and phenolic resin (PF) additions on the performance of the acorn-based adhesive (AS) were investigated. Among the crosslinking agents tested, isocyanate (MDI), epoxy resin E51, and trimethylolpropane diglycidyl ether (TTE), PF demonstrated the best bonding performance. The modified AS adhesive with a 30% PF addition showed the highest bonding strength (0.93 MPa) and superior water resistance. These improvements are attributed to the formation of a stable, multi-dimensional crosslinked network structure resulting from the interaction between gelatinized starch molecules and PF resin. Moreover, the AS-PF adhesive exhibited a remarkably low formaldehyde emission of 0.14 mg/L, representing a 90.67% reduction compared to the national E1 standard. The incorporation of PF also enhanced the adhesive’s mildew resistance and toughness. These findings highlight the potential of acorn-based adhesives as a sustainable alternative for applications in the wood and bamboo industries. Full article

A sustainable and efficient approach for converting carbohydrates into 5-hydroxymethylfurfural (HMF) via heterogeneous catalysis is crucial for effectively utilizing biomass. In this study, we synthesized a series of CrX-polyphenol-formaldehyde resin (PTF) catalysts, which are composites of Cr-doped phenolic-resin-based hydrothermal carbon, using a chelation-assisted multicomponent co-assembly strategy. The performance of the synthesized catalysts was assessed through various analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, pyrolysis–Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller analysis. Cr incorporation into the catalysts enhanced the total and Lewis acidities. Notably, the optimized catalyst, designated as Cr0.6-PTF, achieved an effective glucose conversion into HMF, yielding a maximum of 69.5% at 180 °C for 180 min in a saturated NaCl solution (NaClaq)/dimethyl sulfoxide (2: 18) solvent system. Furthermore, Cr0.6-PTF maintained excellent catalytic activity and a stable chemical structure after nine cyclic reactions, resulting in a 63.8% HMF yield from glucose. This study revealed an innovative approach for utilizing metal-doped phenolic resin hydrothermal carbon to transform glucose into platform chemicals. Full article

The traditional preparation of polyvinyl alcohol (PVA) grinding wheels typically involves hazardous chemicals such as formaldehyde and hydrochloric acid, posing significant health risks to operators and contributing to environmental pollution. In this study, we utilized the freeze-drying method to fabricate PVA grinding wheels, optimizing both the manufacturing process and the structure of the porous composite materials. The results demonstrate that phenolic resin (PF) participates in constructing a hydrogen-bonded network with PVA and pure terephthalic acid (PTA), which synergistically enhances the esterification efficiency between PTA and PVA. Furthermore, the incorporation of PTA as a crosslinking agent led to a more concentrated pore distribution, reducing the average pore size while enhancing mechanical strength. The freeze-drying duration of 42 h and 10% solid content of the PVA solution yields the favorable comprehensive porosity and mechanical performance of the grinding wheel with a unique bimodal pore structure and porosity exceeding 50%. The maximum grinding ratio was achieved at 0.81, while the surface roughness (Sa) was 0.308 μm. The freeze-drying approach significantly enhances pore uniformity and adjustability, producing grinding wheels with superior mechanical properties and performance consistency. This study presents a novel and environmentally friendly alternative to traditional PVA grinding wheel fabrication methods. Full article

The study of pore structure regulation methods has always been a central focus in enhancing the capacitance performance of porous carbon electrodes in lithium-ion capacitors (LICs). This study proposes a novel approach for the synergistic regulation of the pore structure in porous carbon using phenol-formaldehyde (PF) resin and boric acid (BA). PF and BA are initially dissolved and adsorbed onto porous carbon, followed by hydrothermal treatment and subsequent heat treatment in a N₂ atmosphere to obtain the porous carbon materials. The results reveal that adding BA alone has almost no influence on the pore structure, whereas adding PF alone significantly increases the micropores. Furthermore, the simultaneous addition of PF and BA demonstrates a clear synergistic effect. The CO₂ and H₂O released during the PF pyrolysis contribute to the development of ultramicropores. At the same time, BA facilitates the N₂ activation reaction of carbon, enlarging the small mesopores and aiding their transformation into bottlenecked structures. The resulting porous carbon demonstrates an impressive capacitance of 144 F·g⁻¹ at 1 A·g⁻¹ and a capacity retention of 19.44% at 20 A·g⁻¹. This mechanism of B-catalyzed N₂-enhanced mesopore formation provides a new avenue for preparing porous carbon materials. This type of porous carbon exhibits promising potential for applications in Li-S battery cathode materials and as catalyst supports. Full article

Phenolic compounds are an extensive group of natural and anthropogenic organic substances of the aromatic series containing one or more hydroxyl groups. The main sources of phenols entering the environment are waste from metallurgy and coke plants, enterprises of the leather, furniture, and pulp and paper industries, as well as wastewater from the production of phenol–formaldehyde resins, adhesives, plastics, and pesticides. Among this group of compounds, phenol is the most common environmental pollutant. One of the cheapest and most effective ways to combat phenol pollution is biological purification. However, the inability of bacteria to decompose high concentrations of phenol is a significant limitation. Due to the uncoupling of oxidative phosphorylation, phenol concentrations above 1 g/L are toxic and inhibit cell growth. This article presents data on the biodegradative potential of Rhodococcus opacus strain 3D. This strain is capable of decomposing a wide range of toxicants, including phenol. In the present study, cell growth with phenol, growth after rest, growth of immobilized cells before and after rest, phase contrast, and scanning microscopy of immobilized cells on fiber were studied in detail. The free-living and immobilized cells can decompose phenol concentrations up to 1.5 g/L and 2.5 g/L, respectively. The decomposition of the toxicant was catalyzed by the enzymes catechol 1,2-dioxygenase and cis,cis-muconate cycloisomerase. The role of protocatechuate 3,4-dioxygenase in biodegradative processes is discussed. In this work, it is shown that the immobilized cells can be stored for a long time (up to 2 years) without significant loss of their degradation activity. An assessment of the induction of genes potentially involved in this process was taken. Based on our investigation, we can conclude that this strain can be considered an effective destructor that is capable of degrading phenol at high concentrations, increases its biodegradative potential during immobilization, and retains this ability for a long storage time. Therefore, the strain can be used in biotechnology for the purification of aqueous samples at high concentrations from phenolic contamination. Full article

In this paper, alumina-modified wood liquefaction (AL-WP) was prepared by blending nano-alumina (Al₂O₃) into wood liquefaction phenolic resin (WP) using a co-blending method. Alumina-modified wood liquefaction protofilament fiber (AL-WPF) was obtained by melt-spinning, curing, and thermo-curing processes, which were followed by carbonization to obtain alumina-modified wood liquefaction carbon fiber (AL-WCF). This paper focuses on the enhancement effect of nano-alumina doping on the mechanical properties and heat resistance of wood liquefaction carbon fiber (WCF), explores the evolution of graphite microcrystalline structure during the high-temperature carbonization process, and optimizes the curing conditions of AL-WPF. The results showed that the introduction of Al₂O₃ significantly improved the mechanical properties and heat resistance of carbon fibers. When 1.5% Al₂O₃ was doped and carbonized at 1000 °C, the tensile strength of AL-WCF was increased from 33.78 MPa to 95.74 MPa, there was an enhancement of 183%, its residual carbon rate could reach 79.2%, which was better than that of the undoped wood liquefaction (WCF), and it exhibited a more substantial heat-resistant property. In addition, the best curing process for alumina nanoparticle wood liquefiers was obtained by optimizing the curing conditions: hydrochloric acid concentration of 16%, formaldehyde concentration of 18.5%, temperature increase rate of 15 °C/min, holding time of 3 h, and holding temperature of 100 °C. These studies provide a theoretical basis and technical support for developing and applying carbon fibers from alumina-modified wood liquefiers. Full article

This study aimed to evaluate the bondability of beech and alder wood modified through styrene polymerization within the wood lumen. Unmodified wood samples served as the reference material. Bondability was tested using four adhesive types commonly used in wood technology: polyvinyl acetate (PVAc), urea-formaldehyde (UF), phenol-resorcinol-formaldehyde (PRF), and epoxy resin. In addition to shear strength measurements, the adhesive density profile was also assessed. Results indicated that styrene modification generally reduced wood bondability, with reductions in shear strength ranging from 8% to 23% for beech wood and 1.6% to 29% for alder wood, depending on the adhesive type. The only exception was observed with the epoxy adhesive, which showed a 13% improvement in bonding quality for modified wood. These findings suggest that while styrene modification may enhance specific properties of wood, it can adversely affect its adhesion performance with some adhesive systems, except epoxy, which displayed improved compatibility with styrene-modified wood. The study offers insights for selecting suitable adhesives when using modified wood in structural applications. Full article