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The results of experimental studies on the modification of the properties of phenol–formaldehyde resin with alkyl aromatic hydrocarbons, which are contained in the light reflux of catalytic cracking, have been presented. The authors propose to use the resulting materials as part of organomineral compositions and film-forming compositions, since they have high strength and dielectric properties. [ABSTRACT FROM AUTHOR]

This research is aimed at analyzing existing plugging compositions and developing a new plugging composition based on phenol-formaldehyde resin. This paper presents the results of studies of a hardening composition based on phenol-formaldehyde resin for repair and insulation work in wells. The plugging composition consists of two parts: Component "A" (resin and additives) and Component "B" (hardener). A resol-type water-soluble phenol-formaldehyde resin was selected for testing. The resin was additionally modified with special additives to improve performance properties. A mixture of acids was chosen as a hardener. Concentrations of resin and hardener were selected to ensure optimal loss of fluidity of the composition for different temperatures. The main physicochemical properties of the plugging composition were determined. The elastic-strength characteristics of the developed composition after curing at various temperatures (Poisson's ratio, Young's modulus, and compressive strength) were assessed. It has been experimentally proven that samples based on phenol-formaldehyde resin do not collapse completely under load but undergo longitudinal and transverse deformations. As the amount of hardener in the system increases, the compressive strength decreases. The presence of the elastic-strength properties of cementing compositions based on synthetic resins distinguishes them favorably from hardening compositions based on cement and microcement. [ABSTRACT FROM AUTHOR]

To realize the effective profile control of a heavy oil reservoir, hydrolyzed polyacrylamide (HPAM) and water-soluble phenol-formaldehyde resin (PR) were chosen to prepare the profile control system, which gelled at medium or low temperatures and existed stably at high temperatures in the meantime. The effects of phenolic ratios, PR concentration, and HPAM concentration on the formation and strength of the gels were systematically studied by the gel-strength code method and rheological measurements. And the microstructure of the gels was investigated by scanning electron microscope measurements. The results showed that the gelling time of the HPAM-PR system was 13 h at 70 °C. The formed gel could stay stable for 90 days at 140 °C. In addition, the gels showed viscoelastic properties, and the viscosity reached 18,000 mPa·s under a 1.5 s−1 shearing rate due to their three-dimensional cellular network structure. The formation of the gels was attributable to the hydroxyl groups of the PR crosslinking agent, which could undergo the dehydration condensation reaction with amide groups under non-acidic conditions and form intermolecular crosslinking with HPAM molecules. And the organic crosslinker gel system could maintain stability at higher temperatures because covalent bonds formed between molecules. [ABSTRACT FROM AUTHOR]

In this study, a phenol–formaldehyde resin–montmorillonite intercalation composite solution was used as a modifier to treat Chinese fir via impregnation and compression. The basic characteristics and wettability of the PF (phenol–formaldehyde)–montmorillonite impregnation solution were analyzed. The effects of the solid content of PF, the quantity of montmorillonite, and the impregnation time on the impregnation weight gain of Chinese fir were studied through orthogonal experiments. The results showed that when the amount of montmorillonite was 1%, the wettability of the PF–montmorillonite impregnation solution performed the best, the curing time was short, and the curing strength was high. The optimal impregnation process consists of a PF solid content of 25%, an impregnation time of 120 min, and a montmorillonite ratio of 1%. Under these conditions, the modified Chinese fir was prepared via hot pressing. The effects of the addition of montmorillonite and different levels of compressibility on the physical and mechanical properties of modified wood were studied. The physical and mechanical properties were found to be better when the compression ratio was 33%: the density increased from 0.33 g/cm3 to 0.58 g/cm3; the surface hardness increased from 33.6 HD to 70.9 HD; the static bending strength increased from 60.4 MPa to 98.7 MPa; and the elastic modulus increased from 6 390 MPa to 11 498 MPa. After 30 days of release, the compression rebound rate was 3.97%. Meanwhile, the micromorphology and heat resistance of the impregnated compressed Chinese fir showed that the PF–montmorillonite impregnation solution entered into the cell cavity and intercellular space of the Chinese fir and formed a good composite, thus improving the water resistance, heat resistance, and physical and mechanical properties. [ABSTRACT FROM AUTHOR]

Phenol-formaldehyde (PF) resins can be impregnated and cured in situ to improve the woods dimensional stability and decay resistance. In search of renewable alternatives, the substitution of phenol by lignin cleavage products (LCP) has been discussed. However, the different chemical nature may affect the performance of the resin against fungal decay, formaldehyde emission, and equilibrium moisture content. In this study, 30 % (w/w) of the phenol in PF resins were substituted by LCP obtained from microwave-assisted pyrolysis. Scots pine sapwood was modified with the resin. The decay resistance against Rhodonia placenta, Gloeophyllum trabeum, and Trametes versicolor was determined. Additionally, effects of specimen organisation within the Petri dish, different substrates, length of leaching, and type of inoculum were studied. Further, the materials water vapor sorption properties and formaldehyde emission were determined. All modifications effectively reduced fungal decay. With 10 % weight percent gain (WPG), initial decay was detected, while 20 % WPG and 30 % WPG provided efficient protection. The substitution of phenol increases the formaldehyde emission. While further reduction in formaldehyde in the resin admixture or formaldehyde scavengers may be required, the method described herein can be used to partly replace fossil-based phenol, while maintaining good fungal resistance. [ABSTRACT FROM AUTHOR]

The phenol–formaldehyde resin (PF) coating regulates Zn ion transfer and interfacial behavior in AZIBs through the dual effect of fast desolvation and ion confinement, thus achieving stable zinc metal anodes. [Display omitted] • PF coating anodes were constructed to regulate the deposition of Zn ions. • Zn@PF anodes has the dual effect of fast desolvation and ion confinement. • Hydroxyl group in PF can promote the desolvation of [Zn(H 2 O) 6 ]2+, thus reducing side reactions. • The pore structure of PF provides ion confinement to uniform ions flux. • Zn@PF||MnO 2 cell can be stably cycled for 1500 cycles at 1.5 A/g. Aqueous Zn ion batteries (AZIBs) are considered to be highly promising rechargeable secondary batteries. However, the growth of zinc dendrites and irreversible side reactions hinder its further application. In this paper, an artificial interfacial protective layer of phenol–formaldehyde resin (PF) was constructed to achieve high-performance zinc anode. There is a strong interaction between hydroxyl groups in PF and Zn ions. This interaction modulates the solvation sheath of Zn ions and promotes the desolvation of [Zn(H 2 O) 6 ]2+, which reduces the side reactions induced by reactive H 2 O. Furthermore, the pore structure of PF provides ion-confinement effect to regulate the Zn ions flux, thus reducing the growth of dendrites caused by inhomogeneous deposition. Thus, the PF coating has the dual effect of fast desolvation and ion confinement, which is beneficial to the uniform Zn ions deposition and achieves highly stable zinc anodes. Consequently, the Zn@PF||MnO 2 full cell can be stably cycled for 1500 cycles at 1.5 A/g and the capacity retention remains 82.4 %. This method provides a convenient and practical approach to tackle the problems of zinc anodes, and establishes the foundation for their further application. [ABSTRACT FROM AUTHOR]

Phenol-formaldehyde resins combined with polymers have a wide range of industrial applications as plugging agents for profile control and enhanced oil recovery. Due to the structural resemblance between lignin and phenol, there are possibilities for environmentally friendly phenol-formaldehyde resin manufacturing. Sulfonated lignin–based phenol-formaldehyde resin was synthesized by partially replacing phenol with lignin, which improved the utilization rate of lignin and achieved the purpose of environmental preservation and resource conservation. Partially hydrolyzed polyacrylamide is the most widely used polymer in chemical methods for enhanced oil recovery. However, the stability of reservoirs with high salt and high temperatures is weak under these conditions. To solve the problem of low oil recovery in high-salt reservoir environments, polymer flooding is adopted, which utilizes high-molecular-weight polymers to raise the viscosity of injected fluids, thereby improving sweep efficiency and altering mobility ratio between oil and injected fluid. We focus on the stability study of different molecular weights partially hydrolyzed polyacrylamide combined with sulfonated lignin – based phenol-formaldehyde resins in metal ions and surfactants. The zeta potential and hydrodynamic diameter of the partially hydrolyzed polyacrylamide – sulfonated lignin – based phenol-formaldehyde resin system in Ca2+ were measured by dynamic light scattering and static light scattering, and the dispersion stability was analyzed. The interfacial energy – modified DLVO theory was introduced to evaluate the stability of its colloidal solution, which made it possible to predict the aggregation behavior of sulfonated lignin – based phenol-formaldehyde resin and the co-migration process of metal cations in real time. [ABSTRACT FROM AUTHOR]

To realize the effective profile control of a heavy oil reservoir, hydrolyzed polyacrylamide (HPAM) and water-soluble phenol-formaldehyde resin (PR) were chosen to prepare the profile control system, which gelled at medium or low temperatures and existed stably at high temperatures in the meantime. The effects of phenolic ratios, PR concentration, and HPAM concentration on the formation and strength of the gels were systematically studied by the gel-strength code method and rheological measurements. And the microstructure of the gels was investigated by scanning electron microscope measurements. The results showed that the gelling time of the HPAM-PR system was 13 h at 70 °C. The formed gel could stay stable for 90 days at 140 °C. In addition, the gels showed viscoelastic properties, and the viscosity reached 18,000 mPa·s under a 1.5 s−1 shearing rate due to their three-dimensional cellular network structure. The formation of the gels was attributable to the hydroxyl groups of the PR crosslinking agent, which could undergo the dehydration condensation reaction with amide groups under non-acidic conditions and form intermolecular crosslinking with HPAM molecules. And the organic crosslinker gel system could maintain stability at higher temperatures because covalent bonds formed between molecules.

In this study, wood of Cryptomeria japonica D. Don (Japanese fir) was liquefied with phenol as a solvent. Phenol‐liquefied wood was mixed with formalin and spherical phenol‐formaldehyde resin (PF) beads were prepared by a two‐stage suspension polymerization reaction. The influence of the kind and dosage of polyvinyl alcohol (PVA) on the particle size distribution, mechanical strength and thermal properties of spherical PF beads were investigated. The results show that PF beads prepared with partially saponified PVA as a granulating agent are smaller than 75 μm, while the PF beads prepared with fully saponified PVA have larger diameters. However, the average diameter of spherical PF beads decreased with the increase of PVA addition. Thermogravimetric analysis (TGA) indicates that the initial thermal degradation temperature of the PF beads is around 150°C, and the main weight loss occurs between 400 and 600°C. Among them, the PF beads with BF‐04 as the granulating agent have the best heat resistance, and have the highest char yield at 800°C. The Brunauer, Emmett and Teller surface adsorption shows that the internal structure of the carbonized spherical PF beads is microporous pores. Carbonized beads prepared with high PVA adding have large absorption volume. [ABSTRACT FROM AUTHOR]

Despite black liquor's (BL) renown as a difficult-to-manage contaminant in the pulp and paper industry, BL has been found as a viable alternative material for adhesive formulation due to its high lignin content. Nevertheless, modification is required to enhance lignin's reactivity, and there is currently a lack of study focusing on this aspect for BL-lignin. This study aims to increase the phenolic hydroxyl content of BL-lignin by phenolation. After being phenolated at lignin to phenol ratio of 1:1, at a temperature of 100°C for 110 minutes, and with the addition of 8% sulfuric acid (H2SO4) as a catalyst, the phenolic hydroxyl content improved by 51.5%. The results of Fourier transform infrared spectroscopy (FTIR), UV/Vis spectrophotometry, proton nuclear magnetic resonance (¹H-NMR), thermogravimetrydifferential scanning calorimetry (TG-DSC), and its differential curve showed that the structural change in phenolated lignin opened up more active sites, implying that this lignin could be a good substitute for phenol in phenol-formaldehyde resin manufacturing. [ABSTRACT FROM AUTHOR]

Wood modification by impregnation and curing inside of the cell wall using phenol–formaldehyde resins (PF resins) is a well-known and commercialized method to improve, amongst others, the dimensional stability and the durability of wood. However, phenol is mainly obtained from non-renewable resources, and the substitution of phenol by renewable resources has been a topic of research interest for years. Due to the high availability of technical lignins, lignin-derived cleavage products are promising candidates. In this study, organic cleavage products obtained from vacuum low-temperature microwave-assisted pyrolysis of softwood kraft lignin were used to substitute up to 45% of phenol in PF resins. The curing behavior and the free formaldehyde content of the resins was studied. Pine sapwood was treated with these resins by a vacuum pressure treatment, and the weight percent gain, leaching, and dimensional stability of the species were examined. Selected samples were analyzed with bright-field microscopy. The results indicate that up to 30% substitution of phenol by lignin-based organic products does not lead to significantly inferior quality of wood modification. Additionally, the amount of formaldehyde added to the resin can be reduced. The method described in this study could be a way to improve the environmental footprint of wood modification by PF resins. [ABSTRACT FROM AUTHOR]

To develop a lower-cost, excellent-performance, and environmentally friendly phenol–formaldehyde (PF) resin, soybean meal was used to modify PF resin, and soybean meal–phenol–formaldehyde (SMPF) resins were prepared. This reveals the effect of soybean meal on the structural, bonding, and curing properties of PF resin, which are very important for its applications in the wood industry. The resins' physicochemical properties and curing performance were investigated, showing that SMPF resins have higher curing temperatures than PF resin. The Fourier transform infrared spectroscopy results indicated that a cross-linking reaction occurred between the amino groups of soybean protein and the hydroxymethyl phenol. Moreover, with the addition of soybean meal, the viscosity of SMPF increased while the gel time decreased. It is worth mentioning that SMPF-2 resin has favorable viscosity, short gel time, low curing temperature (135.78 °C), and high water resistance and bonding strength (1.01 MPa). Finally, all the plywoods bonded with SMPF resins have good water resistance and bonding strength, which could meet the standard (GB/T 17657-2013, type I) for plywood. The optimized SMPF resins showed the potential for application to partially replace PF resin in the wood industry. [ABSTRACT FROM AUTHOR]

This paper considers the use of lignin during the preparation of phenol-formaldehyde resins. The effect of lignin on the properties of phenol-formaldehyde resins and materials based on them is studied. The obtained resins are characterized by differential scanning calorimetry (DSC). The results show that, in the case of increasing the concentration of lignin, the time of the polycondensation reaction, the energy of activation, and the curing time of lignin-containing resins increase. The main parameters of the lignin-containing resins correspond to GOST (State Standard) 20907–2016 except for the concentration of free formaldehyde. The obtained resins are used to obtain a foam composite material—phenolic foam. It is noted that phenolic foams based on resins containing 5–10% lignin in the composition have a higher compression strength in comparison with other samples. At a concentration of lignin in the resin of 20%, the compression strength of the ready-to-use thermal-insulation materials decreases relative to other samples, while it turns out to be impossible to obtain a foam material in the case of using a resin with 30% lignin. The results of the study make it possible to recommend the use of a small amount of lignin (5–10%) in the production of phenol-formaldehyde resins and further production of a thermal-insulation material with an increased compression strength. [ABSTRACT FROM AUTHOR]

Biomaterials have become an integral part of our lives as a result of the current focus on renewable sustainability. In the realm of composites, a diverse variety of polymers coupled with multiple natural fibres enables the achievement of varied functional property criteria. Bio- composite materials have several benefits, in addition to the use of renewables, including minimal impact on the environment, light weight and biodegradability. Here we have isolated nano-silica from rice husk and fabricated woven flax fabric coated with nano-silica and phenol formaldehyde composite with varying weight percentages of nano-silica. The extracted nano-silica was confirmed from XRD, TGA and FESEM. Five types of composites (PF-F, 1 NS, 2 NS, 3 NS, 4 NS) prepared keeping constant weight of PF resin and flax fabric. Mechanical, morphological and electrical behaviour of the prepared composites were examined. From the obtained results, tensile strength was found to be maximum for 1 NS loading. In particular, as compared to neat composites (PF-F), the tensile strength of prepared specimens with nano-silica (1 NS, 2 NS, 3 NS, 4 NS) improved by 93.92%, 99.55%, 49.85% and 26.43% respectively. The FESEM pictures of fracture surfaces demonstrated that the inclusion of nano-silica boosted fibre's interfacial strength, strengthened both fibre and matrix, and improved resin adhesion to fibre, therefore enhancing the composite tensile characteristics. Due to polarisation processes mediated by nano-silica inclusion, the dielectric constant in PF hybrid composites increases as the loading of nano-silica increases. Electronic polarisation causes an increase in AC conductivity at high frequencies (3 NS). The graph shows that as the amount of nano-silica loaded rises, the AC conductivity increases. The dielectric constant values in 2 NS are the highest. [ABSTRACT FROM AUTHOR]

Triple co-oligomers of 4-isopropenylphenol, phenol and formaldehyde were synthesized and used for the first time as precursors in the structuring reaction in the presence of acrylonitrile and the initiator benzoyl peroxide. The yield of cross-linked copolymers is 84% (of theory). The use of hydrolyzed cross-linked copolymers is shown to be effective as sorbents for the extraction of UO22+ ions from model aqueous systems under batch conditions, and the degree of their sorption significantly depends on the medium pH, the initial concentration of UO22+ ions and the exposure time. The best results were achieved at pH 7 and 9, at which the degree of extraction of UO22+ ions from an aqueous solution with their initial concentration of 134 ± 0.5 mg L–1 is ~93.5% (room temperature, 24 h), while the sorption capacity of the cross-linked copolymer is ~210 mg g–1. The highest sorption capacity of the copolymer reaches 300 ± 30 mg g–1. The possibility of regeneration of the sorbent with mineral acid (НNO3, HCl) was revealed; the maximum degree of desorption of UO22+ ions is ~91%. [ABSTRACT FROM AUTHOR]

The stability of phenol–formaldehyde resin (nHAP) in the oil displacement process influences its flooding and profile control capabilities. There aren't many studies that compare how various surfactants affect PFR stability. The surfactants CTAB, Tween 60, and SDS were selected as representative ones. To look at the changes in stability, spectral turbidity and dynamic light scattering experiments were employed. It was found that the cationic surfactant CTAB can connect with the surface of PFR, just as metal cations, lowering electrostatic repulsion and facilitating the aggregation of PFR composite molecules. Anionic and nonionic surfactants both have some degree of system stability stabilizing properties. When Tween 60 and SDS adsorbed on the surface of the PFR molecule formed a hydrogen bond network with the hydroxymethyl or phenolic hydroxyl group, for example by hydrogen bond interaction, the PFR molecule's dispersion stability was increased. The Tween 60 and PFR composite systems have bigger particle sizes in addition to being more stable. Additionally, the energy barrier of the Tween 60/PFR composite system is determined using the modified DLVO theory for Lewis acid–base hydration, and it is discovered to be consistent with the experimental findings. The findings demonstrate that the stability of the composite system can be impacted by changes in the hydrophilicity and hydrophobicity of the composite system. The findings demonstrate that the stability of the composite system can be impacted by changes in the hydrophilicity and hydrophobicity of the composite system. Understanding the co-migration of PFR and surface activity during oil displacement depends heavily on the data. [ABSTRACT FROM AUTHOR]

We present a laboratory study confirming that phenol in phenol–formaldehyde resins can be replaced with deep thermal-processing products of raw wood. Operating conditions of synthesis are described, and a synthetic recipe is given. The synthesized resins were analyzed by physicochemical methods (IR spectroscopy, TGA, and the tensile strength test). The study revealed that such a replacement requires no considerable changes to be made in operating parameters of the current synthetic process for phenol–formaldehyde resins and allows one to obtain a glue based on this resin with a shear strength equal to 1.58 MPa, which meets specifications of the state standard. [ABSTRACT FROM AUTHOR]

The aim of this research is to study the in-plane compressive strength of eleven-layered beech plywood reinforced with non-wood material in its structure. Plywood reinforcement was made by inserting certain numbers of sheets of pre-impregnated cotton fabric (cotton prepreg). Methyl alcoholsoluble phenol-formaldehyde resin was used for fabric pre-impregnation as well as for veneer bonding. The thickness of the veneers used in the plywood structure was between 1.5 and 1.85 mm. Different models of plywood were made by changing the position of cotton prepreg reinforcements in the plywood structure. One control model of plywood without reinforcement was made. The in-plane compressive strength of plywood models was tested in five directions: parallel to the face grain, perpendicular to the face grain, and at angles of 22.5°, 45°, and 67.5° to the face grain of the plywood panel. The obtained results showed that the application of cotton prepreg in plywood structures has an impact on the values of the in-plane compressive strength of plywood. [ABSTRACT FROM AUTHOR]

The melt foaming process has become the most widely used method in closed-cell aluminum foam manufacturing in large dimensions. This process creates pores by adding a foaming agent to the molten metal. Therefore, selecting appropriate foaming agents is vital, and it controls pore sizes and their distribution in producing a homogeneous foam. In the current research, as cost-effective foaming agents, the Bauxite and Phenol-formaldehyde resin (PFR) embedded TiH2 were successfully produced and then investigated by SEM and EDX analysis. It can be concluded that in the presence of the Bauxite ceramic phase and silica gel formation in Bauxite-embedded TiH2 and the formation of a carbon layer due to the burning of resin in PFR-embedded TiH2, heat-resistant protective layers are formed around TiH2 powders, and thus it delays (120 s) the gas release. The delay in the decomposition of H2 gas is equal to/higher than in the literature, and it gives the gas' bubbles enough time to establish pores in the metallic matrix; thus, foams with uniform distribution of pores were produced. A quantitative examination of the cross-section of the produced foams shows that the number of cells with smaller sizes in the foams produced with the modified foaming agent is more, and the distribution of pores or cells is more homogeneous. [ABSTRACT FROM AUTHOR]

This article presents the results of the investigation of the properties of phenol-formaldehyde resin, obtained using the phenol-replacing fraction. A two-step method was developed for phenol-replacing fraction separation from liquid pyrolysis products with a yield up to 15%, and this fraction was used in the phenol-formaldehyde resin synthesis. Then, a work was conducted for the removal of neutrals from the modified phenol-formaldehyde resin with organic solvents, n-hexane and benzene. As a result, benzene was defined as a more efficient solvent because it removed more aromatics, like ethers and substituted phenols, that cannot react and worsen the glue line water resistance. Benzene dissolved 3.2% weight of the resin, and n-hexane dissolved 2.5% weight. The removal of neutrals increased the water resistance coefficient by more than 60%, so neutrals have a considerable effect on the resin properties. The results can be used for production of resin from renewable feedstock with the similar properties with the traditional resin. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effects of four phenol–formaldehyde (PF) resin treatments with different molecular weights at four different concentrations (5, 10, 15, and 20%) in treated beech wood. The mechanical properties of untreated and treated beech wood were evaluated. After impregnation with PF resin, all modified beech wood at all PF resin concentrations exhibited an increase in weight percent gain compared with that in untreated beech samples. PF resins with lower molecular weights more easily penetrate the wood cell wall, leading to increased bulking of the wood structure, which in turn improves the dimensional stability of the wood. The PF resin treatment with a molecular weight of 305 g/mol showed better impregnation ability than that of the other PF resins. The impact bending strength of PF-treated wood was considerably reduced because PF-cured resins formed inside the wood and are rigid and brittle. Additionally, PF resin treatments at all concentrations decreased the modulus of elasticity of the wood. Scanning electron microscopy and light microscopy revealed that the PF resins were comparatively well fixed in the wood samples. The results indicate that the large molecular weight PF resins are more uniformly distributed in the fiber lumens. [ABSTRACT FROM AUTHOR]

The technology of obtaining carbon sorbents from composites based on phenol–formaldehyde resin for the extraction of precious metals from pulp is considered. The process regimes of the carbonization and the subsequent activation of the sorbents by the action of microwave radiation in a steam and inert gas atmosphere are presented. [ABSTRACT FROM AUTHOR]

Sulfonated phenol–formaldehyde (SPF) resin used as a cross-linker for petroleum reservoir conformance control was synthesized under alkaline conditions. The reaction process of SPF resin was evaluated by measuring the solution's viscosity with respect to phenol–formaldehyde (PF) resin. The molecular structure of SPF resin was characterized by both FTIR and HPLC–MS/MS. The influence of the formaldehyde/phenol molar ratio (F/P) and the sodium formaldehyde sulfoxylate/phenol molar ratio (S/P) on the properties of SPF were analyzed in terms of the storage time, coagulation value, molecular size, and zeta potential. The results indicate that the presence of formaldehyde sodium bisulfite could slow down condensation reaction. Phenol rings were connected by methylene bridges in the position of o–p, and sulfonated SPF resin molecules all had one sulfonate group on the oligomer structure. The storage time decreased from 87 to 6 days, and the zeta potential decreased from −3.02 to −7.70 mV with the increase in F/P (1.2–2.0). Meanwhile, the sedimentation value and the diameter increased from 3.291 × 104 to 5.045 × 104 mg/L and from 2.7 to 5.3 nm, respectively. Sulfonation could significantly increase the storage time and dispersion stability. With the increase in S/P (0.1–0.35), the storage time increased from 15 to 86 days, the sedimentation value increased from 1.927 × 104 to 5.269 × 104 mg/L, and the diameter decreased from 6.3 to 3.0 nm. This paper can present new ideas for improving the storage stability and salt tolerance of phenol–formaldehyde resin and further improving the range of its applications, which has essential reference significance. [ABSTRACT FROM AUTHOR]

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Phenol‐formaldehyde resin (PF) is the oldest synthetic resin. Through the design of synthesis conditions, PF resins with different characteristics can be provided, which are widely used in molding materials, adhesives and impregnation. Spherical PF beads are a hardened resin prepared by a special synthesis method. In this study, a mixture of phenol and formaldehyde was added with triethylamine, polyvinyl alcohol (PVA), and hexamethylenetetramine as a catalyst, granulating agent, and hardening agent, respectively. Spherical PF beads were prepared by a three‐stage suspension polymerization in a large‐scale water system, and the effects of PVA addition conditions on the reaction behavior and particle characteristics were discussed. The results show that formalin with a concentration of 14 % can be used as a formaldehyde raw material to prepare spherical PF beads by suspension polymerization. The largest spherical PF beads can be obtained with a reactant‐liquid ratio of 2/1, a stirring speed of 300 rpm, and an addition amount of BF‐04 of 2 %. The particle size of 14–20 mesh accounts for 83.9 % and has the average particle size of 1016 μm. [ABSTRACT FROM AUTHOR]

Toxic formaldehyde emissions, and the necessity to reduce the consumption of petrochemicals, stimulates the development of environmentally friendly adhesives. The aim of this research was to study, for the first time, the possibility of using condensed tannins (CTs)-rich extracts from grey alder (Alnus incana) and black alder (Alnus glutinosa) bark in the production of particleboards and plywood adhesives. The chemical structure, composition, and molecular weight of the CTs were identified by a 13C-NMR and TOF-MS analysis. Three innovative adhesive systems were studied: CTs-phenol-formaldehyde (CTs-PF) resin; a CTs-polyethyleneimine (PEI) adhesive system; and CTs–PEI combined with an ultra-low emitting formaldehyde resin (ULEFR)—CTs–PEI–ULEFR. The results showed that CTs-PF resin has properties close to commercial PF resin, and the formaldehyde emission was twice lower. CTs–PEI bonded particleboards corresponded to the requirements of the EN 312:2010 standard for particleboards in dry conditions (Type P2). CTs–PEI–ULEFR, with a 40–60% substitution of ULEFR by CTs–PEI, had adhesive properties very close to ULEFR; the plywood shear strength fit the requirements of the EN 314-2:1993 standard for application in internal and external system conditions. The introduction of extracted alder bark residues microparticles into the composition of the adhesive system showed their positive potential for application as a filler. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies of thermal conductivity, structure, and physico-chemical properties of samples of polymer composite material based on thermosetting phenol-formaldehyde resin and hexagonal boron nitride. It was found that with an increase in the volume fraction of boron nitride from 5 to 85%, the effective thermal conductivity coefficient at 300 K increased from 0.63 to 18.5 W/m·K. Experimental results were compared with the data calculated using known theoretical models used to describe the process of thermal conductivity in polymer composite materials. [ABSTRACT FROM AUTHOR]

The processing of natural wood into a high‐performance wood‐based composite to broaden the potential applications of wood can be achieved by various techniques using bulk wood as a raw material. However, attention has seldom been paid to the use of wood veneers for preparing high‐performance structural materials. In this study, delignified birch veneers are used as raw materials to fabricate high‐strength delignified wood‐based laminated composites (DWLCs) with phenol‐formaldehyde (PF) resin as adhesive. The DWLCs with a PF resin content of 40% had high mechanical properties and displayed flexural and tensile stress of 405.8 and 324.4 MPa, respectively. The flexural and tensile stress are 1.24 and 1.21 times higher than those of natural wood‐based laminated composites (WLCs). And we confirmed that partial delignification could contribute to enhancing the mechanical properties of high‐strength wood‐based composites. By using scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS), the strengthening mechanisms of the high‐performance DWLCs were investigated. Due to both the surface of the cell lumen and cell walls being filled with PF resin, the wood microstructure was cured under high pressure so that the DWLCs were enhanced. [ABSTRACT FROM AUTHOR]

A novel type of phenol-formaldehyde (PF) resin was prepared by utilizing the liquefaction products liquefied by phenol under acidic conditions and then reacted with formaldehyde under alkaline conditions. The relationship between the liquefaction behavior of cassava starch and the properties of modified PF resin wood adhesive was studied. The effects of the liquid–solid ratio of phenol to cassava starch, sulfuric acid usage, and liquefaction time on the liquefaction residue rate and relative crystallinity of cassava starch were determined. The results showed that the bonding strength of modified PF resin decreased gradually with the decrease of the liquid–solid ratio. It was a great surprise that bonding strength still met the requirement of the national standard of 0.7 MPa when the liquid–solid ratio was 1.0. The detailed contents were analyzed through FT-IR, SEM, and XRD. In terms of the utilization of bio-materials for liquefaction to synthesize wood adhesive, cassava starch may be superior to the others. [ABSTRACT FROM AUTHOR]

This study aimed to propose an alternative technological solution for manufacturing fiberboard panels using a modified hot-pressing regime and hydrolysis lignin as the main binder. The main novelty of the research is the optimized adhesive system composed of unmodified hydrolysis lignin and reduced phenol–formaldehyde (PF) resin content. The fiberboard panels were fabricated in the laboratory with a very low PF resin content, varying from 1% to 3.6%, and hydrolysis lignin addition levels varying from 7% to 10.8% (based on the dry wood fibers). A specific two-stage hot-pressing regime, including initial low pressure of 1.2 MPa and subsequent high pressure of 4 MPa, was applied. The effect of binder content and PF resin content in the adhesive system on the main properties of fiberboards (water absorption, thickness swelling, bending strength, modulus of elasticity, and internal bond strength) was investigated, and appropriate optimization was performed to define the optimal content of PF resin and hydrolysis lignin for complying with European standards. It was concluded that the proposed technology is suitable for manufacturing fiberboard panels fulfilling the strictest EN standard. Markedly, it was shown that for the production of this type of panels, the minimum total content of binders should be 10.6%, and the PF resin content should be at least 14% of the adhesive system. [ABSTRACT FROM AUTHOR]

The bio-oil phenol-formaldehyde (BPF) resin, prepared by using bio-oil as a substitute for phenol, has similar bonding strength but lower price to phenol-formaldehyde (PF) resin. As a common adhesive for outdoor wood, the aging performance of BPF resin is particularly important. The variations in mass, bonding strength, microstructure, atomic composition, and chemical structure of BPF resin under five aging conditions (heat treatment, water immersion, UV exposure, hydrothermal treatment, and weatherometer treatment) were characterized by scanning electron microscope, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, respectively. Compared under five aging conditions, after aging 960 h, the mass loss of plywood and film was largest under hydrothermal treatment; the bonding strength of plywood, the surface roughness, and O/C ratio of the resin film changed most obviously under weatherometer treatment. FT-IR analysis showed that the decreased degree of peak intensity on CH2 and C–O–C characteristic peaks of BPF resin were weaker under water immersion, hydrothermal treatment, and weatherometer treatment than those of PF resin. The comparison of data between BPF and PF resins after aging 960 h showed that adding bio-oil could obviously weaken the aging effect of water but slightly enhance that of heat. The results could provide a basis for the aging resistance modification of BPF resin. [ABSTRACT FROM AUTHOR]

One of the ways to improve the quality of elastomeric materials is to modify them with active compounds. As modifying additives in this work, the systems were considered which are based on sulfur-containing phenol-formaldehyde resins Octofor 10S and 101K together with an amine-containing compound produced by the interaction of ethanol amines with the methyl ester of fatty acids, the raw material being chicken fat. Study was carried out using model polymer compositions based on butadiene and styrene copolymer. Analysis of the complex of properties showed that it is effective to use 3–4 parts by weight of additives at the ratio of components 2:1. Mechanical mixture of components is inferior to the additive produced by the components fusion in this respect. Moreover, the dynamic strength of rubber is significantly increased. A significant reduction in the mechanical loss tangent was established in the composition with the use of Octofor 10S resin. That allows reducing heat formation at dynamic loads and increasing the service life of large articles, such as tyres. The patterns of the influence of modifiers on the complex of properties of elastomeric compositions are useful when choosing the direction of industrial application of the additives under consideration in the composition of rubber compounds. The addition of crushed vulcanizate treated with modifying additives was found to reduce the viscosity of rubber compounds as compared with the use of untreated vulcanizate; this decreases the energy consumption in the manufacture and processing of elastomeric compositions. [ABSTRACT FROM AUTHOR]

The possibility of stabilizing aqueous dispersions of carbon nanotubes (CNTs) using phenol-formaldehyde resin (PFR) and aminocumulene (AC) is shown. The preliminary oxidation of CNTs contributes to their higher solubility in the presence of these stabilizing agents. The concentration of pristine and oxidized CNTs in weakly alkaline solutions containing 2.5 g/L of PFR is 3.0 and 11.4 g/L, respectively. AC promotes the formation of stable dispersions in acidic media with the concentrations of pristine and oxidized CNTs, respectively, 3.3 and 20.4 g/L. A decrease in the effective sizes of agglomerates of both pristine and oxidized CNTs in the presence of PFR and AC has been shown by dynamic light scattering method. According to TG/DSC analysis and Raman spectroscopy data, it was concluded that the oxygen-containing groups of oxidized CNTs interact with the surfactants used. Schemes for the formation of hydrogen and chemical bonds between CNTs and PFR or AС were proposed, which made it possible to explain the effect of dispersion. [ABSTRACT FROM AUTHOR]

In this study different type of composite coatings was obtained by electrodeposition using zinc as matrix and polymeric particles as disperse phase in zinc sulphate electrolyte. The effects of some electrodeposition parameters on the thickness and morphology of obtained composite coatings were analysed by optical microscopy, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) methods. Polymeric particles inclusion into zinc matrix was correlated with imposed electrodeposition parameters. It was observed that the thickness of the coatings is influenced by electrodeposition parameters. From the morphology of the coatings, it could be concluded that pure zinc has a regular surface with hexagonal crystals, while the composite coatings have fine surface structure. Also, the electrodeposition parameters influence the inclusion of the dispersed phase into metallic matrix that will influence further the different properties of the composite materials. [ABSTRACT FROM AUTHOR]

The melt foaming process has become the most widely used method in closed-cell aluminum foam manufacturing in large dimensions. This process creates pores by adding a foaming agent to the molten metal. Therefore, selecting appropriate foaming agents is vital, and it controls pore sizes and their distribution in producing a homogeneous foam. In the current research, as cost-effective foaming agents, the Bauxite and Phenol-formaldehyde resin (PFR) embedded TiH2 were successfully produced and then investigated by SEM and EDX analysis. It can be concluded that in the presence of the Bauxite ceramic phase and silica gel formation in Bauxite-embedded TiH2 and the formation of a carbon layer due to the burning of resin in PFR-embedded TiH2, heat-resistant protective layers are formed around TiH2 powders, and thus it delays (120 s) the gas release. The delay in the decomposition of H2 gas is equal to/higher than in the literature, and it gives the gas’ bubbles enough time to establish pores in the metallic matrix; thus, foams with uniform distribution of pores were produced. A quantitative examination of the cross-section of the produced foams shows that the number of cells with smaller sizes in the foams produced with the modified foaming agent is more, and the distribution of pores or cells is more homogeneous.

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Background: Phenol‐formaldehyde resin 2 (PFR2) has been shown to be a useful marker of contact allergy (CA) to various phenol‐formaldehyde resins. These compounds are used in several industries as solids, powders, or semisolid resins, and are known to be sensitizing agents. Objectives: The aims were to investigate contact allergy to PFR2 in a single tertiary dermatology centre, to examine associated simultaneous allergic reactions, and to identify cases of allergic contact dermatitis (ACD) to PFR2. Methods: A retrospective study was performed of patients patch tested to PFR2 between 1 January 2003 and 17 June 2020. Results: In all, 337 of 7922 patients were tested to PFR2 and 16 (4.7%) reacted. Of those 16 individuals, six (37.5%) had a relevant reaction (1.8% of total). Simultaneous allergic reactions were noted to colophonium in eight (50.0%) patients, Myroxylon pereirae in five (31.3%), and fragrance mix I (FMI) of three cases (18.8%). Conclusion: Contact allergy to PFR2, even in a selected population of patients, is uncommon. However, patients exposed to plastics and glues, or who work with wood products should be routinely patch tested to a plastics and glues series containing PFR2. We recommend that all centres include PFR2 in their plastics and glues series. [ABSTRACT FROM AUTHOR]

Treating wood with water-soluble resins is a well-known and effective method to improve the durability of wood. However, there has been no systematic work to date related to the influence of average molecular size of phenol-formaldehyde (PF) resin on the decay resistance of wood, especially of hardwoods. Therefore, the goal of this study was to investigate the effect of average molecular size of PF resin treatment on the resistance of beech wood against brown- and white-rot fungi. Four different average molecular weights (Mw) of resol type resin oligomers (297, 421, 655 and 854 g/mol) were examined. Different weight percent gains (WPGs) in European beech (Fagus sylvatica) wood blocks (15 × 20 × 50 mm3) were attained through vacuum impregnation using various concentrations of aqueous-PF solutions. Afterwards treated wood blocks passed the leaching and were exposed to brown-rot fungi (Gloeophyllum trabeum; Coniophora puteana) and white-rot fungi (Trametes versicolor) for 16 weeks. No effect of oligomer size on the resistance against G. trabeum decay of wood blocks was observed, resulting in resin loadings of 7–8%. The required WPG for resistance to brown-rot decay by C. puteana increased slightly with increasing oligomer molecular size: 6, 7, 10 and 11% for wood treated with 297, 421, 655 and 854 g/mol, respectively. The extent of white-rot fungal decay resistance of treated wood was affected by the molecular size of oligomers. Resin loadings of 8% and of 17% against T. versicolor were required to attain similar durability levels for beech wood treated with Mw = 297 and 854 g/mol, respectively. [ABSTRACT FROM AUTHOR]

• Bio-derived chemical treated adsorbent for non-radioactive iodine removal. • The separation efficacy of the bio-sorbent for non-radioactive iodine was 3.64 mg/g. • The bio-treated sorbent are efficient in iodine separation both in batch and column mode. Management and separation of radioactive iodine from wastewater of nuclear power plants is time-dependent and needs lot of efforts. Changes of surface chemistry due to radioactive irradiations are the major issue for developing an efficient adsorbent for separation of radionuclei from wastewater. This article presented a promising case of separation of non-radioactive iodine from aqueous solution using neem oil phenolic resin treated lignocellulosic biomass. The resin was prepared with some ingredients with known properties of radiation absorption. The data pointed that the treated biomass has the efficacy of iodine separation from aqueous solution within wide range of pH. The iodine sorption followed the Langmuir isotherm indicating a monolayer surface adsorption reaction. The maximum iodine removal efficacy of the resin treated biomass was 3.64 mg/g. The iodine adsorption was found to follow the pseudo second order reaction. The kinetic analysis also indicated that both surface adsorption and intraparticle diffusion were likely to control the rate of iodine-adsorbent. The treated adsorbent also showed iodine removal efficacy in column mode. The resin used for the treatment of lignocellulosic biomass was prepared using cashew nut shell liquid and phenol-formaldehyde that are known for their radiation adsorption and antioxidant properties. Thus, neem oil cashew nut shell liquid containing phenol formaldehyde resin treated biomass is expected to be stable under radioactive radiation. As radioactive iodine generation is a common phenomenon for nuclear power plant the bio-based chemical modified lignocellulosic adsorbent could be a promising alternative. However, more detail investigations with radioactive iodine containing real wastewater from nuclear power plant is needed for validation of our statement. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymer gel is widely used in oilfield development and has achieved remarkable results in water shutoff and conference control. To comprehensively understand the dynamic gelation of polymer gel, the dynamic gelation of phenol–formaldehyde resin gel is studied under oscillatory shear, which is described by the change in viscosity with shear time. The kinetic formula of the crosslinking reaction of polymer gel under oscillatory shear is fitted by the quantitative relationship between the gelation time and gel strength of dynamic and static gelation. The definition of the critical gelation shear rate is proposed, and that of polymer gel under oscillatory shear is determined. The critical gelation shear rate increases with the increasing mass concentration of the polymer and crosslinker. The viscosity of the process of static gelation after oscillatory shear is analyzed to characterize gel reformation. The shear may have little effect on the viscosity of the static gelation after oscillatory shear in the induction stage but could make the viscosity rapidly decrease in the gelation stage. Viscoelastic experiments show that the phenol–formaldehyde resin gel has a good reformation ability after shear only when the shear rate is less than the critical gelation shear rate. The results provide a theoretical basis for the selection of the appropriate shear rate and shear time in the field application of polymer gel. [ABSTRACT FROM AUTHOR]

The main operational characteristics of adhesive compositions based on phenol–formaldehyde and melamine–carbamide–formaldehyde resins with such modifiers as pectol, technical lignosulfonates, and dolomite powder are investigated. The experiments show that addition of the modifiers improves physicochemical characteristics of the adhesives, increases the strength characteristics of plywood on their basis, and decreases the content of free formaldehyde. It is possible to decrease the assembly time of the products in molding machines when using modified adhesives, which increases the performance of plywood production. [ABSTRACT FROM AUTHOR]

3,13‐Diglycidyloxypropyloctaphenyl double‐decker silsesquioxane (EP‐DDSQ) was synthesized by process of alkaline hydrolysis condensation of phenyltrimethoxysilane and corner capping reaction of methyldichlorosilane, followed by hydrosilylation with allyl glycidyl ether, and the resultant structure was confirmed by fourier transform infrared spectrometer (FTIR) and nuclear magnetic resonance (NMR), respectively. The thermosetting phenol‐formaldehyde (PF) resin was then modified by EP‐DDSQ, and the reactivity of PF resin with EP‐DDSQ and thermal pyrolysis of modified cured resin were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The surface morphologies of modified resins at high temperature were characterized with field emission scanning electron microscope (FESEM), and chemical structure of modified resins was analyzed through X‐ray photoelectron spectrometer (XPS). The results showed that the appropriate addition of EP‐DDSQ did not affect the curing temperature of the PF resin itself, but could improve the heat resistance of the system. When the amount of EP‐DDSQ added was 10%, the initial degradation temperature of PF resin was increased by 49.31°C, and when the amount of EP‐DDSQ added was 16%, the char yield of which was reached up to 61.39%, compared with that of pure PF resin (TGA1,000°C of 57.62%) at Ar atmosphere. More importantly, the modified resin formed a regular and dense layer of SiC and SiOx ceramic on the surface after ablation in the muffle furnace at 800°C air atmosphere, which is very important for ablative resistant materials. [ABSTRACT FROM AUTHOR]

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