Synthesis Of Phenol Formaldehyde Resin Research Articles

Synthesis of phenol formaldehyde resin (PFR) based fluorescence resonance energy transfer (FRET) composites for double channel detection of latent fingerprints.

A reversible two-channel fluorescent nanocomposite with fluorescence resonance energy transfer (FRET) effect was designed for the development, analysis, and characterization of latent fingerprints (LFPs). For the construction of the FRET probe, a core of mesoporous silicas (MSNs) were used to encapsulate the organic dye rhodamine 6G (RhD-6) as an acceptor, while green-emitting monodisperse phenolic resin nanoparticles (PFR NPs) were selected as a donor. The up-conversion material (UC) of NaYF4:Yb,Er was synthesized using a simple hydrothermal method, and the MSNs-RhD-6/PFR (PRM) was electrostatically adsorbed onto the UC nanoparticles using a layer-by-layer method to obtain MSNs-RhD-6/PFR-UC (PMU). Compared to ordinary single-channel materials, PMU can be excited by different light sources (365 nm UV/980 nm laser) and its fluorescence can be reversibly switched between yellow and green, demonstrating excellent light reversibility. The PMU composites were successfully used to visualize and detect LFPs on various substrate surfaces using a simple powder coating method. Due to the existing FRET effect and dual-channel characteristics, this composite material displays excellent contrast, outperforming commercially available products for wider applicability. Even on complex backgrounds and after aging or washing treatments, it still clearly recognizes fingerprints in first-, second-, and third-level details, showing its great potential in latent fingerprint detection.

Bio-Based Alternatives to Phenol and Formaldehyde for the Production of Resins.

Phenol–formaldehyde (PF) resin continues to dominate the resin industry more than 100 years after its first synthesis. Its versatile properties such as thermal stability, chemical resistance, fire resistance, and dimensional stability make it a suitable material for a wide range of applications. PF resins have been used in the wood industry as adhesives, in paints and coatings, and in the aerospace, construction, and building industries as composites and foams. Currently, petroleum is the key source of raw materials used in manufacturing PF resin. However, increasing environmental pollution and fossil fuel depletion have driven industries to seek sustainable alternatives to petroleum based raw materials. Over the past decade, researchers have replaced phenol and formaldehyde with sustainable materials such as lignin, tannin, cardanol, hydroxymethylfurfural, and glyoxal to produce bio-based PF resin. Several synthesis modifications are currently under investigation towards improving the properties of bio-based phenolic resin. This review discusses recent developments in the synthesis of PF resins, particularly those created from sustainable raw material substitutes, and modifications applied to the synthetic route in order to improve the mechanical properties.

Neutrals influence on the water resistance coefficient of phenol-formaldehyde resin modified by wood pyrolysis liquid products

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.

Phenolformaldehyde Resins: Properties, Fields of Application and Methods of Synthesis

The review considers the current situation in the market of phenolformaldehyde resins, which form the basis for a wide spectrum of binding compositions with variable properties, which allow obtaining various materials for particular technological purposes. Properties, types and application fields of phenolformaldehyde resins are characterized, their advantages and drawbacks are discussed, and possible more promising analogs are considered. The development of new and modification of existing processes for the synthesis of phenolformaldehyde resins by varying the process conditions and selecting the optimal catalyst were shown to be topical.

Rheological Study of Phenol Formaldehyde Resole Resin Synthesized for Laminate Application.

Heat explosions are sometimes observed during the synthesis of phenol formaldehyde (PF) resin. This scenario can be attributed to the high latent heat that was released and not dissipated leading to the occurrence of a runaway reaction. The synthesis temperature and time played important roles in controlling the heat release, hence preventing the resin from hardening during the synthesis process. This study aims to assess the rheological and viscoelasticity behaviors of the PF resin prepared using paraformaldehyde. The prepared PF resin was designed for laminate applications. The rheological behavior of the PF resin was assessed based on the different molar ratios of phenol to paraformaldehyde (P:F) mixed in the formulation. The molar ratios were set at 1.00:1.25, 1.00:1.50 and 1.00:1.75 of P to F, respectively. The rheological study was focused at specific synthesis temperatures, namely 40, 60, 80 and 100 °C. The synthesis time was observed for 240 min; changes in physical structure and viscosity of the PF resins were noted. It was observed that the viscosity values of the PF resins prepared were directly proportional to the synthesis temperature and the formaldehyde content. The PF resin also exhibited shear thickening behavior for all samples synthesized at 60 °C and above. For all PF resin samples synthesized at 60 °C and above, their viscoelasticity results indicated that the storage modulus (G′), loss modulus(G″) and tan δ are proportionally dependent on both the synthesis temperature and the formaldehyde content. Heat explosions were observed during the synthesis of PF resin at the synthesis temperature of 100 °C. This scenario can lead to possible runaway reaction which can also compromise the safety of the operators.

Synthesis of Phenol Formaldehyde Resin with Paraformaldehyde and Formalin

Phenol and formaldehyde are the well-known raw materials used in synthesizing Phenol Formaldehyde (PF) resin. PF resin has been used extensively in various applications including molding and composite laminate industries. This study focused on the synthesizing PF resin using formalin and/or paraformaldehyde for laminate application and assess the physical properties, mechanical properties and fracture toughness of the resins. The density, dynamic viscosity, solid content, gel time, flexural properties, tensile properties and fracture toughness of the synthesized resins were evaluated upon varying the formalin content from 0% to 40% (w/w) in the synthesis process. The result shows that addition of 40% w/w formalin in the PF resin synthesis had increased the fracture toughness and decreased the flexural strength and modulus properties of PF by 97.14% and 97.60% respectively. The tensile stress value was also reduced by 67.80% when the 40% w/w of formalin was added. However, the PF resins that produced by adding formalin up to 20% w/w in the PF resin synthesis, still maintained their flexural and tensile properties within the acceptable range required by EN438 standard for decorative high-pressure laminate (HPL) application. This work shows that paraformaldehyde enhanced the mechanical properties of PF laminate resin compared to formalin.

The simultaneous preparation of nano cupric oxide (CuO) and phenol formaldehyde (PF) resin in one system: aimed to apply as wood adhesives

To reduce the cost of nano copper oxide (CuO) modified phenol-formaldehyde (PF) resin, the PF resin synthesis and the preparation of the nano CuO were carried out simultaneously in one system. The modified PF resins were evaluated via X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDXS), and thermogravimetry (TG). Physical and mechanical properties of oriented strand board (OSB) prepared using these modified PF resins were also evaluated. XPS results proved that nano CuO was present in the modified PF resin. XRD data showed that the derived nano CuO has a face-centered cubic structure. The minimum particle size of nano CuO was below 10 nm and the distribution of CuO was uniform as seen in TEM and EDXS images. TG analysis illustrated that the main degradation peak of the modified PF resins narrowed and shifted to a lower temperature by introducing nano CuO. Though the physical and mechanical properties of OSB decreased slightly, values were still within the requirements set by the appropriate Chinese Standard; this means that the modified PF resin has potential to be applied in engineered wood composites manufacturing.

Suitability of a lignin-derived mono-phenol mimic to replace phenol in phenol-formaldehyde resin for use in wood treatment

Abstract The goal of this study was to assess the suitability of a single mono-aromatic for substitution of petroleum-based phenol for phenol-formaldehyde (PF) resin synthesis and the usage of a new resin for wood treatment. After proper thermal decomposition of wood-based lignin, pyrolysis oil can be obtained. Due to the heterogeneity of the lignin macromolecule, oil contains large variety of organic-based compounds, mainly mono-aromatics, which are proposed to be used for replacement of phenol during PF resin synthesis. Therefore, for this purpose, nine of the most abundant mono-aromatic compounds in bio-oil were selected: ortho-, meta-, para-cresol, guaiacol, catechol, 4-methylcatechol, resorcinol, syringol, 4-ethylphenol and resol-type resin from each mono-aromatic were synthesized. Relevant features of the resin such as pH, viscosity, average molecular weight and curing behavior of resins using differential scanning calorimetry (DSC) were analyzed. Scots pine (Pinus sylvestris L.) sapwood samples were used to evaluate the suitability of resin for wood treatment in terms of dimensional stability and were compared with the PF resin-treated wood. From all tested resins, those made of guaiacol or ortho-, or meta-, or para-cresol and/or 4-ethylphenol proved to be suitable for wood treatment, whereas resins made of catechol or 4-methylguaiacol and syringol did not. Suitability of mono-aromatics for synthesis of resol-type resin depends on chemical structure, where the reactivity of the mono-aromatic (derivative of hydroxybenzene) is defined by the type, location and number of substituents.

Fabrication of nano-cupric oxide in phenol–formaldehyde resin adhesive: synthesis, curing characteristics, and morphology

To explore the possibilities of reducing the costs of nano-copper oxide (CuO)-modified phenol–formaldehyde (PF) resin, PF resin synthesis and nano-CuO preparation utilizing different copper salts were carried out simultaneously in one system. The curing kinetics, morphology, as well as physical and mechanical properties of modified PF resins-bonded oriented strand boards (OSB) were evaluated. Nano-CuO showed a positive effect on the curing reaction of the PF resin, characterized by a significant decrease in the activation energy of the reaction. X-ray diffraction and transmission electron microscopy tests showed that the derived nano-CuO was in nano- and microscale. Four different types of crystal structure of the nano-CuO, varied according to their copper salts, were observed in scanning electron microscopy images. The water resistance and bonding strength of glued OSB prepared with these resin samples indicated that the influence of nano-CuO on the mechanical properties of the boards was positive. This system has the potential to be applied to the engineered wood-based composites manufacturing.

Studies on Synthesis, Characterization of Modified Phenol Formaldehyde Resin and Metal Adsorption of Modified Resin Derived From Lignin Biomass

This study was related to development of economically viable method of extraction of lignin from saw dust in order to produce lignin modified phenolic resin and ecofriendly adhesives (bio-based resin). This study cover to improve the mechanical properties by modification of phenol formaldehyde resole resin using some additives such as boric acid, sulfuric acid and lignin biomass. The synthesis and metal adsorption capacity of resin derived from lignin biomass were explored. Lignin sample was extracted from sawdust of Acacia sp. collected from Batticaloa region by alkali extraction method called delignification process. Qualitative tests were carried out on the extracted alkali lignin and it was used to prepare modified resin. Resin synthesized by using lignin substitution phenol and allowed to condensation reaction in the presence of sodium hydroxide. Boron-modified phenol formaldehyde resin was prepared by using boric acid with formalim method. The above reaction was performed for four hours by refluxing with toluene. Which was produced a high viscous massive resin with 90% yield. The absorbtion peak of B-O bond at 1362cm-1 was observed at IR spectra. Rise in solid mass content leads to produce smooth resin surface without causing cracks and bubbling. Phenol formaldehyde resin was modified into their sulfonated forms to increase their ion exchange capacity, since the ion exchange capacity of virgin resin was found to be zero. Conductivity property shown by sulfonated resin(121mS/cm). The synthesized Lignin based PF resin was used to study the metal adsorption capacity of Cd2+ in aqueous solution. The adsorption capacity of heavy metal Cd2+ ion shown by lignin modified resin (55%) and lignin (86%). In this study sawdust lignin could be best substitution for phenol in synthesis of Phenol-Formaldehyde resin. It’s better due to their sustainability, environmental control, low production cost and their ability to adsorb heavy metals. Phenolic resin was modified with boric acid to improve thermal resistance property and to get smooth resin surface.

Processing Variable Optimization of Plywood Hot Pressed with Ba2+-Modified Phenol-Formaldehyde Resin by a Response Surface Method

Abstract Ba(OH)2 was added in the synthesis of phenol-formaldehyde resin to realize a low-temperature and fast-bonding process for plywood production. Plywood bonding was investigated by studying a number of parameters, such as the glue spread, the amount of curing agent, and the temperature and duration of the hot-pressing process. The plywood bonding strength was characterized by the shear strength of the adhesive layer, and a mathematical model describing the process and the response was developed using a central composite design and response surface methods. The variance analysis revealed that the newly developed model was reliable, with a high signal-to-noise ratio. All the factors and their interactions were analyzed to optimize the bonding process. Thus, seven optimized processes were obtained from the model, and the optimal process conditions were revealed (glue spread: 277.8 g/m2; amount of curing agent: 3.5%; hot-pressing temperature: 108°C; and hot-pressing duration: 34.99 s/mm). The results from repeated average shear strength experiments of five veneer testing samples (1.64 MPa) verified the reliability of the optimized technics.

Catalytic and ortho-directing effect of Zn2+, Mg2+, Ba2+, and Ca2+ metal hydroxides on the preparation of phenolic-formaldehyde resin

A one step method was employed to prepare PF (phenol-formaldehyde) resin adhesive from phenol and formaldehyde with Zn2+, Mg2+, Ba2+, and Ca2+ hydroxides as catalysts, and the physicochemical properties of the resulting polymeric material were analyzed. The viscosity of the liquid adhesive decreased at intermediate catalyst concentrations, while the polymerization rate decreased at the highest concentrations; no clear pattern could be observed between catalyst concentration and solid content. Differential scanning calorimetry (DSC) performed on the PF resin catalyzed by Ba2+ showed that the polymer had a curing exothermic peak at around 110 °C, while the initial curing temperatures of PF resins were affected by the type of metal hydroxide used, and were in the order Ca2+ < Mg2+ <control sample. FTIR spectroscopy was used to monitor the degree of ortho/para substitution during the synthesis of PF resin with Ba2+, Ca2+, and Mg2+ hydroxides. The highest ortho/para ratio was achieved with Ba2+ at a concentration of 0.45 wt.%, which also resulted in the most significant increase in the polymerization rate for the formation of PF resin.

The similar in-situ polymerization of nano cupric oxide preparation and phenol formaldehyde resin synthesis: The process and mechanism

The process and mechanism of phenol-formaldehyde (PF) resin synthesis and nano copper oxide (CuO) preparation simultaneously in the same reaction vessel were studied in this paper. Curing kinetics, molecular structure changes as well as the bonding performance of the modified PF resin was investigated. The results indicated that loading levels of the derived nano CuO at 4% and 8% reduced the apparent activation energy of the PF resin and accelerated both the addition and condensation reactions, while changes of reaction enthalpy were consistent of these results. With the introduction of the derived nano CuO, the chemical shifts of all samples were generally offset to the low field for the solvent effect. A complexation reaction between copper ions and oxygen on the phenolic hydroxyl groups had an influence on phenoxy carbons as shown by NMR. Quantitative analysis indicated that nano CuO had a positive effect on para substituted reaction and thus enhanced both the addition and the condensation reactions. Though the shear strength under several test conditions decreased slightly, values were within the requirements set by the appropriate Chinese Standard.

Transformation of lignin from bioethanol production for phenol substitution in resins

The main objective of biorefineries is the efficient conversion of lignocellulosic materials into valuable products. Lignin, a major abundant polymer not sufficiently exploited, is considered to be a promising substitute of phenol in phenol–formaldehyde resin synthesis. In this study, a lignin sample from a bioethanol production plant was modified under different experimental conditions by a depolymerisation treatment. The modification was intended to enhance the reactivity of lignin by increasing its functionality. The structural changes were studied with several characterisation techniques including size exclusion chromatography, Fourier transform infrared spectroscopy and nuclear magnetic resonance. The lignin reactivity towards formaldehyde was determined with a formaldehyde reactivity test. From the characterisation results of the reacted lignins, it was concluded that increasing the severity of the depolymerisation treatment (i.e. higher temperature, reaction time and catalyst content) resulted in an increase in active functional groups. Consequently, lignins depolymerised at more severe conditions were more reactive towards formaldehyde reaction. Due to their improved reactivity, the treated lignins could be successfully used as substitutes of phenol, converting them into a highly value-added product. An estimation of the cost of the proposed process is provided.

Exploring the potential of high resolution mass spectrometry for the investigation of lignin-derived phenol substitutes in phenolic resin syntheses.

Chemical degradation is an efficient method to obtain bio-oils and other compounds from lignin. Lignin bio-oils are potential substitutes for the phenol component of phenol formaldehyde (PF) resins. Here, we developed an analytical method based on high resolution mass spectrometry that provided structural information for the synthesized lignin-derived resins and supported the prediction of their properties. Different model resins based on typical lignin degradation products were analyzed by electrospray ionization in negative ionization mode. Utilizing enhanced mass defect filter techniques provided detailed structural information of the lignin-based model resins and readily complemented the analytical data from differential scanning calorimetry and thermogravimetric analysis. Relative reactivity and chemical diversity of the phenol substitutes were significant determinants of the outcome of the PF resin synthesis and thus controlled the areas of application of the resulting polymers. Graphical abstract ᅟ.

Theoretical Confirmation of the Quinone Methide Hypothesis for the Condensation Reactions in Phenol-Formaldehyde Resin Synthesis.

The mechanisms for the base-catalyzed condensation reactions in phenol-formaldehyde resin synthesis were investigated by using the density functional theory method. The structures of the intermediates and transition states, as well as the potential energy barriers of the involved reactions, were obtained. The hypothesis of quinine methide (QM) formation was theoretically confirmed. Two mechanisms were identified for QM formation, namely E1cb (elimination unimolecular conjugate base) and water-aided intra-molecular water elimination. The latter is energetically more favorable and is proposed for the first time in this work. Based on the QM mechanism, the condensation should be a unimolecular reaction because the following condensation between an ionized species (dissociated phenol or hydroxymethylphenol) with QM is much faster. The previously proposed SN2 condensation mechanism was found to be not competitive over the QM mechanism due to a much higher energy barrier. The condensation reaction between neutral phenol or hydroxymethylphenol and QM was also found to be possible. The energy barrier of this reaction is close to or higher than that of QM formation. Therefore, the overall condensation reaction may appear to be bimolecular if such a reaction is incorporated. The theoretical calculations in this work rationalized the discrepant results reported in previous kinetics studies well.

Liquefaction of lignin in hot-compressed water to phenolic feedstock for the synthesis of phenol-formaldehyde resins

Abstract The corn stalk lignin was liquefied in hot-compressed water without any other additives to obtain the degraded liquids (DL) with liquefaction yields of 45.9–61.4 wt%, under 3.4 MPa and 260 °C. The degradation liquids, mainly composed of small molecular phenols as high as 84.6 wt%, were put to use as substitutes for phenol to modify phenol-formaldehyde resin. The degradation liquids modified phenol-formaldehyde resins (DLPFs) possessed the highest adhesive strength (1.32 ± 0.10 MPa) than the lignin-phenol-formaldehyde resin (LPF, 0.72 ± 0.20 MPa) and typical phenol-formaldehyde resin (PF, 0.77 ± 0.26 MPa). The free formaldehyde contents of the DLPFs were all lower than the requirement of the corresponding standard (≤0.3 wt%), even when 60% of phenol was replaced by DL (0.232 wt%). The curing behavior analysis showed that the introducing of DL notably decreased the curing activation energy. The results demonstrated that the DLs were very suitable substitution for phenol in preparation of DLPFs. The adhesive strengths of DLPFs were considerably improved compared with typical PF. The thermal curing kinetic analysis revealed that the values of activation energy were decreased obviously with the introduction of DL.

Optimization of the acetosolv extraction of lignin from sugarcane bagasse for phenolic resin production

The experimental central composite design 22 was applied to optimize the acetosolv process for lignin extraction from sugarcane bagasse, with an aim to replace the petroleum-derived phenols conventionally used for resin production. The highest acetosolv extraction yield (55%±4.5%) was achieved with an acetic acid concentration of 95% (w/w), containing 0.1% (v/v) HCl, at 187°C for 40min. Other optimal conditions for extraction, such as 187°C, 15min (OC187;15) and 205°C, 15min (OC205;15), were calculated from statistical models. The optimized acetosolv lignins were characterized by thermal analysis (TGA and DSC), size exclusion chromatography, and spectroscopic methods (FT-IR and HSQC-NMR). Compared to Kraft lignin, they exhibited higher thermal stability, low molar mass, p-hydroxyphenyl units as their major constituent, higher relative phenolic and total hydroxyl contents, and lower relative methoxyl group content. Accordingly, optimized acetosolv lignins seem to have structural features suitable for phenol-formaldehyde resin synthesis.

Synthesis and Mechanism of Metal-Mediated Polymerization of Phenolic Resins.

Phenol-formaldehyde (PF) resin is a high performance adhesive, but has not been widely developed due to its slow curing rate and high curing temperature. To accelerate the curing rate and to lower the curing temperature of PF resin, four types of metal-mediated catalysts were employed in the synthesis of PF resin; namely, barium hydroxide (Ba(OH)2), sodium carbonate (Na2CO3), lithium hydroxide (LiOH), and zinc acetate ((CH3COO)2Zn). The cure-acceleration effects of these catalysts on the properties of PF resins were measured, and the chemical structures of the PF resins accelerated with the catalysts were investigated by using Fourier transform infrared (FT-IR) spectroscopy and quantitative liquid carbon-13 nuclear magnetic resonance (13C NMR). The results showed that the accelerated efficiency of these catalysts to PF resin could be ordered in the following sequence: Na2CO3 > (CH3COO)2Zn > Ba(OH)2 > LiOH. The catalysts (CH3COO)2Zn and Na2CO3 increased the reaction activity of the phenol ortho position and the condensation reaction of ortho methylol. The accelerating mechanism of (CH3COO)2Zn on PF resin is probably different from that of Na2CO3, which can be confirmed by the differences in the differential thermogravimetric (DTG) curve and thermogravimetric (TG) data. Compared to the Na2CO3-accelerated PF resin, the (CH3COO)2Zn-accelerated PF resin showed different peaks in the DTG curve and higher weight residues. In the synthesis process, the catalyst (CH3COO)2Zn may form chelating compounds (containing a metal-ligand bond), which can promote the linkage of formaldehyde to the phenolic hydroxyl ortho position.

Preparation of lignin nanoparticles by chemical modification

Lignin is the main natural aromatic polymer and consists of about a quarter of lignocellulosic biomass. That is why products obtained from lignin are very attractive research topics, but it is also a very complex issue due to its complicated structure which depends on the separation method and plant species. To become a widely used raw material, the basic characteristics and structure-dependent properties must be elucidated, initially. For this reason, it is necessary to obtain lignin with superior properties, to be able to compete with fossil resources. This paper presents a chemical method to modify lignin by hydroxymethylation to obtain nanoparticles. Nanotechnology allows using chemical, physical and biological effects that do not occur outside the nanoscale world. To find the best conditions (from the average particle size distribution point of view), three reaction parameters were varied: ratio of lignin/aldehyde, pH and temperature. The following output value has been the average particle size distribution. The obtained data were processed with software in demo version (Modde 9) and resulted regression equation allows us to establish the optimum conditions. At the same time, the reaction products thus synthesized were characterized by FTIR spectroscopy, GPC, and 31PNMR spectroscopy. The results confirm that using this reaction, it is possible to synthesize nanoparticles from hydroxymethylated lignin. Lignin derivatives containing high hydroxyl group content have a potential utilization as phenol substitute in the phenol formaldehyde resin synthesis, composites, biocides, etc.