Resol Resin Research Articles

Preparation of hierarchically porous carbon nanosheets by carbonizing resol resin for supercapacitors

Hierarchically porous carbon nanosheets were synthesized by using homogeneous mixture of soluble phenolic resin and KOH activator, which was carbonized and activated through one step. Structural characterization revealed that the as-prepared carbon materials consisted of abundant macropores, mesopores and micropores from the carbonization of the resin and activation of KOH. With the appropriate ratio of KOH to resol resin, hierarchically porous carbon nanosheets with specific surface area beyond 3000 m2g−1 and average pore size of up to 3.44 nm were achieved, which exhibited a high specific capacitance of 365.6 F g−1 at 0.5 A g−1, excellent cycle life with 98.7% specific capacitance retained after 10,000 cycles, and high energy density of 12.7 Wh Kg−1 when measured as an electrode in a coin type symmetric supercapacitor in 6 M KOH electrolyte, indicating a promising electrode material for real energy storage in supercapacitors.

Tailoring Properties of Resol Resin-Derived Spherical Carbons for Adsorption of Phenol from Aqueous Solution.

The polycondensation of resorcinol and formaldehyde in a water–ethanol mixture using the adapted Stöber method was used to obtain resol resins. An optimization of synthesis conditions and the use of an appropriate stabilizer (e.g., poly(vinyl alcohol)) resulted in spherical grains. The resins were carbonized in the temperature range of 600–1050 °C and then chemically activated in an aqueous HNO3 solution, gaseous ammonia, or by an oxidation–reduction cycle (soaking in a HNO3 solution followed by treatment with NH3). The obtained carbons were characterized by XRD, the low-temperature adsorption of nitrogen, SEM, TGA, and XPS in order to determine degree of graphitization, porosity, shape and size of particles, and surface composition, respectively. Finally, the materials were tested in phenol adsorption. The pseudo-second order model perfectly described the adsorption kinetics. A clear correlation between the micropore volume and the adsorption capacity was found. The content of graphite domains also had a positive effect on the adsorption properties. On the other hand, the presence of heteroatoms, especially oxygen groups, resulted in the clogging of the pores and a decrease in the amount of adsorbed phenol.

Yolk-shell silicon/carbon composites prepared from aluminum-silicon alloy as anode materials for lithium-ion batteries

Silicon is an attractive anode material for lithium-ion batteries due to its ultrahigh theoretical specific capacity. However, its commercial application is largely limited by the poor cycling stability due to its huge volume change during lithiation and delithiation. A low-cost method is developed to prepare yolk-shell silicon@void@carbon composite particles in this study. The synthetic phenol-formaldehyde resole resin was used to bind the graphite to the surfaces of the aluminum-silicon alloy particles, and then was thermal cross-linked and carbonized; aluminum was gently dissolved into ferric chloride etchant, leaving void space between the carbon shell and silicon core. Owing to the presence of the robust carbon shell and internal void space, the yolk-shell composites exhibited significantly better cycling stability than the powder mixture of silicon and graphite. The capacity retention of the silicon component in the powder mixture dropped below 60% after only one cycle, whereas silicon in the composite still has about 70% remaining capacity after 100 cycles.

Rheological Studies of Phenolic Resole Resin Incorporated with Modified Graphite Additives

AbstractAn understanding of rheology is vital in polymer processing as it depicts the complex molecular structures, viscoelastic nature, and dynamic mechanical properties of these macromolecules. In this study, graphite powder subjected to different steps of modification like H2SO4 intercalation, silanization, and finally Fe3O4 and BaFe12O19 grafting was used. Changes in viscous behavior were obvious from the flow characteristics and dynamic mechanical properties of the composites. Viscoelastic experiments illustrated the effects of interfacial bonding of polymer and additives on the viscoelastic moduli. Different regression models were applied to the data points, and information regarding regression parameters like the power law exponent and the relaxation time was obtained.

Modified resol type phenolic resin nanocomposites as surface metal coatings

AbstractNanocomposites based on resol resin as a matrix and prepared organoclay, from Egyptian bentonite clay, as reinforcement material were synthesized. The effect of organoclay content (i.e., 0.5, 1.0, 1.5, 2.0, and 2.5 phr) on the properties of the prepared samples with respect to the prepared composites and resol resin with no clay was investigated. The prepared samples with higher organoclay content (i.e., 2.0 phr) were modified with epoxy or/and urethane resin and characterized using transmission electron microscope (TEM), X‐ray diffraction (XRD), and Fourier transform infrared measurements (FTIR). TEM showed uniform dispersion of the clay while XRD showed exfoliated structures. FTIR measurements confirmed the bond formation between epoxy or/and diisocynate with phenolic hydroxyl groups of resol resin. Mechanical properties, chemical resistance, thermal properties, and electrical volume resistivity were studied. Results showed that epoxy modified resol resin film samples with 2.0 phr organoclay exhibited higher adhesion and scratch hardness values, higher chemical resistance, thermal stability, and lower electrical conductivity compared with mixed epoxy/urethane and urethane samples as well as unmodified resol resin nanocomposite film samples. The samples could be useful as surface metal coatings.

Sustainable phenolic thermosets coatings derived from urushiol

AbstractThe over‐exploitation of finite fossil resources and/or the increased environmental and sustainable awareness inspire scientists and technologists to search for inexpensive alternatives from renewable chemicals. Phenol formaldehyde (PF) resins, the oldest type of synthetic polymers with good mechanical properties and heat resistance, are widely used in the production of coatings, laminates, molding compositions, and glues. Here, biobased urushiol‐derived PF resins were synthesized from the alkali‐catalyzed reaction between urushiol and formaldehyde. The chemical compositions and molecular structures of resole resins were characterized by carbon‐13 nuclear magnetic resonance and Fourier transform infrared spectroscopy, and their curing behaviors were studied by differential scanning calorimetry. The as‐prepared urushiol‐derived resole resins had methylol (Ph−CH2OH), ortho‐ and para‐hemiformal groups (Ph−CH2OCH2OH), and the para−para/ortho−para/ortho−ortho links of methylene groups (Ph−CH2−Ph), whereas the resole resins had low curing temperatures at about 100–113°C. Additionally, given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol‐derived resole resins had low glass transition temperatures of 132 ± 2°C. Furthermore, the as‐prepared urushiol‐derived coatings exhibited excellent physical and mechanical properties.

Study of the open porosity of carbon materials using thermoporometry

Thermoporometry is a calorimetric method for characterizing pore structure from the melting or freezing point depression of a liquid confined in a pore, by the reason of the added contribution of surface curvature to the phase-transition free energy. Porous materials are widely used in the production of noise and vibration-absorbing coatings, thermal insulation, filters, etc. We present the results of studying the porous structure using thermoporometry, a method based on lowering the melting point of the working substance (penetrant) which previously filled micro- and mesopores of the sample under study. The open porosity of carbon materials based on phenol-formaldehyde resins and a pore former obtained after pyrolysis under different conditions of microphase separation induced by polymerization is analyzed. The tests were carried out using a differential scanning calorimeter. Bidistilled water, which has a relatively high value of the enthalpy change upon melting of the crystalline phase is used as a penetrant to lower the error of measurements. Differential and integral curves of the size distribution of micro- and mesopores are presented. It is shown that an increase in the microphase separation temperature entails an increase in the total porosity. Moreover, an increase in the polymerization rate of phenol-formaldehyde resin due to resin modification with m-cresol also facilitated an increase in the cumulative volume of micro- and mesopores. It is shown that replacement of phenol with paracresol leads to an increase in the total porosity even under a significant decrease in resole resin polycondensation rate. The results obtained can be used in the development of carbon matrices with controlled parameters of the mass transfer.

Synthesis, characterization and properties of phthalonitrile-etherified resole resin

Abstract A new type of phthalonitrile-etherified resole resin (PNR) was synthesized from resole resin and 4-nitrophthalonitrile. The differential scanning calorimetry results showed that the curing temperature of PNR is lower than that of phthalonitrile resin. Excellent thermal stability and bonding properties were obtained after curing at 220°C. TGA showed that in air, the temperature of 5% weight loss (T 5%) of the cured PNR was 446°C, approximately 41°C higher than that of resole resin (RS), and the char yield at 800°C increased from 4% for RS to 33% for PNR. The shear strengths of PNR at room temperature and high temperature were increased by 8% and 133%, respectively, over those of RS, and after aging at 350°C for 2 h, these values were increased by 262% and 198%, respectively, over those of RS. Its excellent curing behavior, heat resistance and high bonding strength show that PNR can be used as a high temperature-resistant adhesive.

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 carbon matrix with tunable carbide formation ability for reactive infiltration techniques

The reactive melt infiltration (RMI) is a cost- and time-efficient technique to produce ceramic matrix composites with low porosity. In the case of carbide-forming infiltrating agent, the carbon matrix should have sufficient open porosity, wettability, and controlled reactivity. A synthetic approach towards carbon matrices with tunable reactivity and mass transport properties is proposed. The approach is based on resol resin/ethylene glycol systems and variable conditions of polymerization-induced phase separation (PIPS). It is shown that increasing the polymerization rate in the PIPS step by raising the temperature or by modifying the resol resin, for example, by partial replacement of phenol with meta-cresol, results in higher segregation intensity and higher capillary pressure during RMI. The mobile pore-forming agent (ethylene glycol) results in the formation of a less defective carbon matrix after pyrolysis in comparison with corresponding thermosetting resol component. The PIPS step and partial replacement of phenol by meta-cresol increase the reactivity of carbon matrix towards carbide-forming infiltrating agent.

Enhancement in electrical conductivity and dynamic mechanical properties of resole resin with ZnO-RGO as nanofiller

The present study aimed at investigating the influence of ZnO-RGO nanofiller on the electrical and dynamic mechanical properties of phenol formaldehyde (PF) resin. The nanocomposites were prepared by solution mixing method followed by compression molding and nanofillers were synthesized by refluxing graphene oxide with zinc acetate dihydrate in DMF. The maximum value of the dielectric constant is observed for composites with 1 wt% ZnO-RGO content. A comparative study on the experimental and theoretical values of effective dielectric constant was done by Maxwell Garnet equation. The theoretical modeling of DC conductivity of the nanocomposites was done by the Bueche, Scarisbrick, and Rahaman modeling. The effect of ZnO-RGO on the viscoelastic properties of PF was analyzed with DMA. About 28% increase in storage modulus is observed with the addition of 0.12 wt% ZnO-RGO. The degree of entanglement, reinforcement efficiency factor, and cross-link density were calculated from DMA analysis to understand the interaction between PF and ZnO-RGO. The nature of the drawn Cole-Cole plot shows the existence of heterogeneity in PF/ZnO-RGO nanocomposites.

In Situ Generation of Ammonia: an Efficient Catalyst for the Synthesis of Phenol-Aniline-Formaldehyde Resol Resin

A novel method developed for the synthesis of resol based phenol-aniline-formaldehyde (PAF) resins by in situ generation of ammonia using magnesium hydroxide and ammonium chloride as reagents in the presence of phenol, aniline and formaldehyde. The synthesized PAF resol resins were characterized by IR, NMR spectroscopic methods, thermal stability by thermogravimetric analysis (TGA) and thermal properties by differential scanning colorimerty (DSC). Free phenol and free aniline of PAF resins were determined using gas chromatography and also these resins characterized for elemental analysis, inherent viscosity, molecular weight and gel time. DSC results illustrated that the glass transition temperatures of PAF resins exhibited in the range of 72-110 °C, whereas TGA results depicted that the thermal stability of the PAF resins revealed in the range of 516-548 °C. In situ generation of ammonia showed higher thermal stability and lower content of free phenol and free aniline in PAF resin.

Structural Characterization of Cure Bio-based Phenol Formaldehyde Wood Adhesive

Bio-phenol formaldehyde (BPF) resole resins were characterized by liquid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy. The liquid 13C NMR analysis indicated that the condensation reactions between the bark phenolic compounds and the formaldehyde occurred during the synthesis of the resins. Methylene ether bridges in the resins were more pronounced in the BPF resin when compared to the PF resin system. The liquid-state 13C NMR study revealed significant differences in the resins structures induced by the inclusion of bark-phenolic components. The bark-phenolic components favored the formation of para-ortho methylene linkages in the BPF resins and also enhanced the cure rate of the BPF resin system.

Effect of thermal conductivity of ceramic compact on the porous structures of foamed bodies via direct-foaming method

ABSTRACTThe effect of the thermal conductivity of ceramic compact on the porous structure of a foamed body formed by the direct foaming process was investigated. In order to change the thermal conductivity of the ceramic compact, three types of ceramic powder (alumina, mullite, and cordierite) with different particle sizes were used. These ceramic powders were mixed with powdered resol resin, which is a foamable thermoset resin used as both a foaming agent and binder for the ceramic powders. Ceramic compacts were prepared from the mixed starting ceramic and resol powders by press molding, and then characterized by thermal conductivity. The foamed bodies were produced from the ceramic compacts by heating to the resol foaming temperature to produce porous structures. The pore structures of the foamed bodies were strongly affected by differences in thermal conductivity in the ceramic compacts.

Synthesis and thermal properties of some phenolic resins

Introduction: Phenolic resins have been in use since the early twentieth century and are considered the first class of synthetic polymers to achieve commercial success, moreover phenolic resins continue to succeed and attract special interest in a large range of industrial applications such as adhesives, paints, and composites; because of their unique physical and chemical properties. Materials and Methods: Prepolymers resol resins (RR, RH, RP, and RC) were synthesized by the reaction of phenolic compounds (resorcinol, hydroquinone, phloroglucinol, and catechol) respectively, with formaldehyde at molar ratio phenol/ formaldehyde 1/1.5, using sodium hydroxide as a catalyst. These resins were characterized by FTIR. The curing reaction of these resins was evaluated using differential scanning calorimetry (DSC), while the thermal stability study was evaluated using thermogravimetric analysis (TGA). Results and Discussion:From the results showing that these prepolymers have different curing temperatures and curing energy, while the TGA study showed that the cured resins have decomposition temperature more than 300 ºC, and char residue at 650 ºC more than 60%. Conclusions: These resol resins have different gel times (8-55) min, and viscosities (435-350) mpa.s. The curing temperature of these resin obtained from DSC curves was (120, 129, 105 and 127 °C), while the thermal behavior of the cured resins obtained from TGA curves showed that these cured resin have two decomposition temperatures and the rate of decomposition in the order of RC < RR< .

Mechanical, thermal, and rheological studies of phenolic resin modified with intercalated graphite prepared via liquid phase intercalation

Abstract In this study, phenolic resole resin was modified at polymeric level with a particulate additive (intercalated graphite (IG)), and its effect on mechanical, thermal and rheological properties was studied. Intercalated graphite was prepared via liquid phase intercalation method using H2SO4 as the intercalant species and KMnO4 as the oxidizer. X-Ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) image and Fourier Transform Infra-Red (FTIR) spectrum confirmed the formation of intercalated species. Composites with three different IG concentrations were prepared using tetrahydrofuran (THF) as the solvent. Thermogravimetric analysis (TGA) of the composites showed improvement in degradation temperature and char yield even at 1% IG concentration. The mechanical and ageing properties were evaluated using Universal Testing Machine (UTM) as per ASTM standards. Visible enhancement in properties (about 25% rise in tensile strength) for the composites was observed in the studies. The addition of intercalated graphite also enhanced the shelf life. Moreover, phenolic resin – IG composites showed superior properties than composites with natural graphite as a modifier due to better dispersion. Rheological characterizations were also done to study the flow behavior of resin systems.

Fabrication and microstructural characterization of the diamond@amorphous carbon nanocomposite core/shell structure via in-situ polymerization

A novel diamond@carbon core/shell structure, constituting diamond as a hard core and carbon as a soft shell, was synthesized from resole resin and nanodiamond as the starting materials via in-situ polymerization and subsequently high-temperature carbonization. The diamond@carbon nanocomposite was characterized using field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and Fourier transform infrared spectroscopy (FT-IR). The results indicated that the shell material are comprised of amorphous carbon. The thickness of carbon shell was controlled from 502.5 nm to 27 nm by adjusting the concentration of the nanodiamond. As confirmed by TEM, FT-IR and XPS, the diamond@carbon nanocomposite revealed a stable structure, due to the formation of the chemical bonding between diamond and carbon shell after calcination process. Overall, the diamond@carbon nanocomposite abrasives could lead to a reducted surface roughness and damage of SiC wafer comparing with the nanodiamond abrasives, due to the spring-like effect coming from the elastic component of the amorphous carbon shell. Moreover, the as-prepared nanoparticles exhibited better dispersion stability than the pure diamond in the pH range from 8 to 11. • Core/shell structured diamond@carbon, was synthesized via in-situ polymerization then high-temperature carbonization. • Core/shell structured diamond@carbon comprises of nanodiamond as a hard core and carbon as a soft shell. • The thickness of carbon shell was controlled from 502.5 to 27 nm by adjusting the concentration of the nanodiamond. • The composite abrasives led in a decreased surface roughness and surface damage compared with nanodiamond.

Thermal Kinetics and Post Curing Thermal Stability of Bio-Based Phenol Formaldehyde Resins for Its Potential in Particleboard Production

The thermal degradation kinetics and post curing behavior of phenol-formaldehyde and Bio-phenol formaldehyde (BPF) resole resins were investigated with thermogravimetry analysis at four different heating rates (5, 10, 15 and 20°C/min) from 25 to 700°C. The curing reaction for all the resole resins proved to be approximately 1st order, and the activation energies of the BPF resins at 25 wt% and 50 wt% bio-phenol replacement were 132.2 kJ/mol and 131.6 kJ/mol. These were comparable to that of the laboratory synthesized pure PF resin 131.0 kJ/mol but also remarkably lower than the commercial PF resin (138.1 kJ/mol) respectively. The result of the thermal degradation kinetics showed that the post-curing thermal stability of the 25 and 50 wt% BPF resins were similar to that of the commercial and laboratory synthesized pure PF resin but, that of 75 wt% differed from the commercial or laboratory synthesized PF resin.

The using of thermal analysis methods for study of pore formation in the system resol phenol-formaldehyde resin – Ethylene glycol – p-toluenesulfonyl chloride

The pore formation in the system resol resin – ethylene glycol – p-toluenesulfonyl chloride based on polymerization induced phase separation (PIPS), post-curing and pyrolysis techniques are studied by thermal analysis methods, pyrolysis gas chromatography mass spectrometry and electron microscopy. The presence of p-toluenesulfonyl chloride leads to accelerating of curing reaction and reaction order increasing. It was shown that PIPS step determines the texture and morphology of final carbon matrix precursors. The increasing of PIPS step temperature results in decreasing of the segregation scale and increasing of segregation intensity of phase separation. The decreasing of PIPS step temperature leads to increasing of macropores sizes, but decreasing of mesopores cumulative volumes. The increased mesopores content at high PIPS temperature is supposed to be resulted and from the oligoethylene glycol formation. Insufficient PIPS step time leads to partial collapsing of formed porous structure during pyrolysis.

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.