Bio-based Phenolic Resin Research Articles

Valorizing cashew nutshell residue for sustainable lignocellulosic panels using a bio-based phenolic resin as a circular economy solution

The motivation for this study stems from the significant annual amount of cashew nutshells produced worldwide, which has raised growing concerns about proper environmental disposal. One alternative is to utilize the nutshells to produce particleboards and eco-friendly resin, thereby contributing to the circular economy. The present study proposes an innovation by providing the first insights into particleboard production, utilizing pressed cashew nutshell and a phenolic resin derived from the reaction of cashew nutshell liquid (CNSL) with formaldehyde. The mass proportions of CNSL to formaldehyde were varied at 1:0.25, 1:0.5, and 1:0.75 (w/w) without the necessity for isolating chemical compounds at 105 °C. The resin was characterized using rheology, DSC, FTIR, HPLC, and NMR techniques. The mechanical properties of the particleboard were evaluated through density, tensile, flexural, water absorption, and thickness swelling tests. The formaldehyde emission and biodegradability content of the particleboards were also evaluated. Eco-friendly phenol-formaldehyde resin promoted the modulus of elasticity (MOE) from 707 to 1866 MPa and the modulus of rupture (MOR) from 6.4 to 14.3 MPa. In addition, using adhesive with CNSL to formaldehyde mass ratios of 1:0.25 and 1:0.50 resulted in particleboards of class E1 in terms of formaldehyde emissions. The biodegradability of panels PB25, PB50 and PB75 was 30%, 21% and 20%, respectively, in 30 days. These findings demonstrate the potential of cashew nutshell biomass and eco-friendly resin as an adhesive in the particleboard industry.

Novel hydrophobic butyl rubber damping composites modified with bio-based PF/DBA via the construction of a three-dimensional network

It is of interest to develop wide-temperature domain damped hydrophobic materials. In this paper, we designed incorporating bio-based phenolic resin into the IIR matrix and introducing dibenzyl fork acetone (DBA) into the main chain structure with sodium hydroxide activation to construct three-dimensional network. In this paper, we designed incorporating bio-based phenolic resin into the IIR matrix and introducing dibenzyl fork acetone (DBA) into the main chain structure with sodium hydroxide activation to construct three-dimensional network. The added bio-based phenolic resin has reticulated structure blended with butyl rubber, combined with sodium hydride activation-modified IIR. The results show that sodium hydride activated modification of DBA is introduced into the main chain structure of IIR by infrared and 1H NMR analysis. The material hydrophobic is realized by the introduction of DBA with static water contact angle of 103.5°. The addition of 10phr lignin-based phenolic resin (LPF) is compatible with IIR, and the torque can reach 7.0 N-m. The tensile elongation of the modified butyl rubber composite can reach 2400% with tensile strength up to 11.43 MPa, while the damping factor can reach 0.37 even at 70 °C. The thermal stability of the composites is enhanced with mass retention rate of 28%. The bio-based PF/NaH activation-modified butyl rubber damping material has potential applications in damping hydrophobicity with wide temperature range.

Elucidating the Role of Lignin Type and Functionality in the Development of High-Performance Biobased Phenolic Thermoset Resins.

In this work, a series of biobased phenolic resins were developed starting from kraft and soda lignin, suitably functionalized through esterification by means of succinic anhydride. As a result of an extensive optimization study of the functionalization and curing reactions, clear correlations between lignin type and chemical-physical characteristics and the properties of the resulting phenolic resin systems were described. In particular, the esterification reaction through succinic anhydride was found to play a key role in enhancing the chemical reactivity and in facilitating the successful incorporation of lignin into the resin formulations. The obtained high-lignin-content thermoset materials were shown to exhibit tunable chemical (functionality, gel content, and cross-linking density), thermal (glass transition temperature and thermo-oxidative stability), and mechanical (surface hardness, indentation modulus, and creep behavior) characteristics, which could outperform those of fully oil-based reference phenolic resins by judicious control of lignin concentration and chemical characteristics. In particular, succinylated kraft lignin was found to enable more efficient incorporation into the cured systems. This work provides the first demonstration of the incorporation of succinic-anhydride-modified-lignin in the formulation of high-performance phenolic resins, ultimately contributing to the definition of structure-property-performance correlations for rational biobased material design in the context of advanced and sustainable manufacturing.

Electrospun porous carbon nanofibers derived from bio-based phenolic resins as free-standing electrodes for high-performance supercapacitors

Electrospun porous carbon nanofibers derived from bio-based phenolic resins as free-standing electrodes for high-performance supercapacitors

Liquefied wheat straw as phenols for bio-based phenolic resins: Reaction parameters optimization and chemical routes

The value-added conversion of biomass materials is accepted as a promising approach to alleviate the energy crisis and promote green chemistry. This work aims to investigate the conversion process and chemical routes from liquefied wheat straw (LWS) to bio-based phenolic resins (BPFRs) and their potential opportunity as an alternative to petroleum-based asphalt binders. Response surface methodology (RSM) was introduced for the optimization of synthesis conditions, while the Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) were used to explore the chemical reactions during the conversion process and the morphological characteristics of resins. The feasibility of BPFRs application in asphalt binders was investigated based on rheological tests. The results demonstrate that the LWS is rich in phenolic compounds with reactive sites in para or ortho positions, which can replace petroleum-based phenol in the reaction with formaldehyde. Further, the produced intermediates, methylolphenols and bisphenol F, are subject to the condensation reaction to form BPFR molecules with about five phenolic nuclei. The connection between phenolic nuclei is dominated by para-methylene bridges (about 70%). The synthesis is suggested to be carried out at a molar ratio of phenol-to-formaldehyde of 0.75 without additional sulfuric acid , and the preferred polymerization temperature and time are 95 °C and 120 min. It should be noted that the reactivity of LWS is lower than that of petroleum-based phenol and may be accompanied by self-curing effects. Noticeable folds are observed on the surface of BPFRs. Encouragingly, acceptable compatibility and rutting resistance in the BPFR-asphalt system are identified. • Liquefied wheat straw can replace phenol in the synthesis of BPFRs. • The impact of F/P ratio, H 2 SO 4 dosage, temperature, and time is investigated. • Reaction parameters are optimized by response surface methodology. • The phenolic nuclei in BPFRs are mainly connected by para-methylene bridges. • The BPFR-asphalt system shows acceptable compatibility and rutting resistance.

Facile and scalable preparation of cage-like mesoporous carbon from lignin-based phenolic resin and its application in supercapacitor electrodes

Due to the similarity in chemical structure, lignin has presented great potential in the synthesis of bio-based phenolic resin. Herein, a facile and scalable synthesis strategy for a novel cage-like lignin-based phenolic resin was proposed through direct spray drying of the mixture of phenolic resin and unmodified lignin. The as-prepared lignin-based phenolic resin was pre-carbonized and carbonized using KOH to produce mesoporous carbon materials (LPRAC) that were further employed as supercapacitor electrodes. The results revealed that the lignin addition led to the noticeable change of the resin shape from perfect sphere to cage-like structure owing to the surfactivity and hydrophilicity of lignin. The cage-like structure promoted the KOH-activated pore generation and expansion in the carbonization process, resulting in the significantly increased specific surface area of the phenolic carbon and the intensified mesoporous formation. The electrochemical performance determination indicated that the specific capacitance of LPRAC-20% (20% lignin addition) was 217.3 F/g at 0.5 A/g, which was considerably higher than that of the lignin-free phenolic carbon (122.6 F/g). Moreover, the LPRAC-20% also exhibited preferable capacitance retention and excellent cycling stability. Accordingly, the present work offers a simple and scalable approach to prepare cage-like mesoporous carbon with excellent electrochemical performance from lignin-based phenolic resin and thus provides a promising route for lignin valorization in energy storage materials.

Structural and thermal behavior of lignin-based formaldehyde-free phenolic resin

Phenolic resin has been widely used in various field applications and is a crucial resin in daily life. However, the raw materials used for producing phenolic resin are quite costly and harmful to the consumer. Therefore, the production of bio-based phenolic resins has attracted considerable scientific and industrial interest. The utilization of bio-based substituents for phenol and formaldehyde as phenolic resin raw materials is described in this paper. The structural properties of the prepared bio-based phenolic resin are established by FTIR and NMR, and the thermal stability is determined by DSC and TGA. The presence of the methylene bridge functional group at around 1460 cm−1 confirms the formation of phenolic resins. The resins have a decomposition temperature of about 300 °C and exhibit good thermal stability. This confirmed structure and thermally stable resins could be used to substitute the current commercialized phenolic resins.

A review on sources and extraction of phenolic compounds as precursors for bio-based phenolic resins

Residues from biomass processing/harvesting (e.g., straw, saw chips, bark) contain value-added chemicals for multiple applications. Biomass residues can be converted to chemicals and fuels, unlike other renewable sources such as wind and hydro, with the added benefit of reducing economic and environmental costs associated with residue disposal. Pyrolysis, the thermal degradation of the biomass, can convert these low-value residues to high-value energy or chemicals. The pyrolysis oils derived from lignocellulosic biomass are of particular interest as potential sources of bio-phenols. This review is focused on the extraction and recovery of phenolic compounds from bio-oil produced during the pyrolysis of various biomass residues with a particular focus on the potential of hemp residues (hurds and straw) as a source of phenolic compounds. Considerable progress has been made toward producing cost-effective renewable phenolic resins. New and advance technologies and materials are being used for the production of bio-based resins. However, further investigation is required on the optimization of pre-treatment, extraction, and analytical techniques to meet the challenges of satisfactory quality and low cost of renewable resins.

Wood Fireproofing Coatings Based on Biobased Phenolic Resins

Different formulations of phenolic resins based on two natural products, namely, lignin and tannins, were implemented as biobased fireproofing coatings for wood. Moreover, inorganic nanoparticles were included as additives for improving the thermal resistance of the coatings. The biobased coating formulations were first characterized for their structure and thermal properties via Fourier transformed infrared (FTIR) and thermogravimetric analyses (TGA). Then, their fireproofing performance was assessed over a softwood and a hardwood species. Various parameters were studied, such as the heat released during combustion, the integrity of the samples, and the flames’ propagation. Furthermore, their performance regarding the mentioned parameters was evaluated with respect to two different commercial formulations (top-ranked fireproofing coatings). It was confirmed that the risks derived from the exposure of wood to fire were significantly reduced after the application of the biobased coatings: the heat release during combustion was reduced, a protective effect was achieved concerning wood integrity, and the propagation of the flames was significantly delayed. Besides, these parameters displayed a better performance on beechwood compared to maritime pinewood. Finally, it was observed that the results obtained by the biobased coating formulations RA and RB were comparable to those achieved with the used commercial fireproofing coatings.

Preparation of high molecular weight thermoplastic bio-based phenolic resin and fiber based on lignin liquefaction

In order to improve the application range of lignin phenolic resin, lignin thermoplastic phenolic resin was prepared by controlling the molar ratio (formaldehyde: phenol) with liquefied lignin, phenol and formaldehyde as raw materials, and thermoplastic phenolic fiber was obtained by melt spinning. The effects of different curing bath acid proportion (40%, 50%, 60%) on the mechanical property, thermal property and morphology of the fiber were investigated, and the curing behavior of lignin phenolic fiber was studied. The structure and properties of the resin and fiber were characterized by FT-IR, NMR, GPC, TG, DSC, XRD, SEM and fiber strength testing. The results showed that when the molar ratio was 0.7:1, the resin had the best performance, the O/P value was 1.75, Mw was 8298, and PDI was 2.92. After curing, the fiber continued cross-linking reaction, and the diameter of the cured fiber was thicker than that of the original fiber. The most suitable curing process for the original fiber was that formaldehyde and hydrochloric acid were prepared into curing bath according to the mass ratio of 1:1, the heating rate was 20 ℃ h−1, the curing termination temperature was 170 ℃. The tensile strength of the fibers reached 176.64 MPa and the elongation at break was 1.48%, and finally the carbon yield at 800 ℃ was 37.2%.

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.

Evaluation of synthetic bio-phenol resins derived from biomass gasification in bio-adhesive formulation

Bio-phenol formaldehyde adhesives formulated from sustainable biomass sources is an excellent alternative to phenolic petroleum-based adhesives with lower pollution level. This study aimed to formulate bio-adhesive from two types of biomass namely palm kernel shell (PKS) and Leucaena sp. Wood. The intention was to find the best process condition which results in maximum content of bio-phenol in the product. The bio-based phenolic resins (bio-oils) were produced from gasification process and their physical and chemical properties were determined. Both produced bio-oils were involved in formulation of bio-based phenol formaldehyde adhesives (resinification) at different operating conditions (temperature, time and catalyst loading). The chemical functional groups and individual compounds of the phenol resins and bio-adhesive samples were identified by GC-MS. The results indicated that temperature has persistent increasing effect on phenol percent of the bio-oil from Leucaena sp. wood however for the bio-oil from PKS the increase of phenol was until the temperature of 85 °C. Reaction time and catalyst loading were observed to have similar effects on resinification of both bio-oil samples. The bio-adhesive produced under best operating condition has the highest amount of bio-phenol and therefore is considered an environmental friendly adhesive with lower cost and pollution than the petroleum-based types.

Synthesis of biobased phenolic resins using catalytic pyrolysis oil and its effect on oriented strand board performance

ABSTRACTThe aim of this work is to investigate the chemical, physical, thermal and mechanical properties of bio-oil-phenol–formaldehyde (BPF) resin synthesized with catalytic pyrolysis oil. In this way, catalysed and uncatalysed pyrolysis processes were carried out in a vacuum pyrolysis reactor at the temperature of 500°C. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) were used as catalysts in the catalysed pyrolysis processes. The BPF resins were synthesized using the bio-oil at 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% phenol replacement levels. The chemical composition of the bio-oil was analyzed by GC/MS analysis. The thermal characteristics and chemical structures of the resins were characterized by TGA and FT-IR analysis, respectively. Physical properties including pH, viscosity, solid content and gel time of the resins were determined. Oriented Strand Board (OSB) were manufactured to evaluate the mechanical performances of modified resins. The BPF resins were successfully synthesized with phenol, bio-oil and formaldehyde. BPF resins synthesized with catalytic bio-oils showed better thermal stability than BPF resin synthesized with non-catalytic bio-oil. The mechanical test results showed that the IB strengths of OSBs made with BPF resins synthesized by use of NaOH exhibited better performance than OSBs commercial PF made.

Alkali lignin depolymerization under eco-friendly and cost-effective NaOH/urea aqueous solution for fast curing bio-based phenolic resin

It is still a challenge to use lignin without any pretreatment due to its high molecular weight, strong steric hindrance, and low reactivity. To prepare value-added low molecular weight aromatic compounds for preparation of lignin-based phenolic resins, alkali lignin (AL) was depolymerized under low cost and environmental-friendly NaOH/urea aqueous solution at low temperature in this paper. The molecular structure changes of the depolymerized AL (DAL) products were characterized by MALDI-TOF-MS, 1H NMR, and FT-IR spectrophotometers. Low molecular weight aromatic compounds mainly composed of phenyl-propane trimers were prepared after depolymerization. The active proton content at C5 position increased from 0.03 mmol/g to 0.26 mmol/g, and the phenolic hydroxyl group content increased from 0.07 mmol/g to 0.12 mmol/g. Moreover, a depolymerization mechanism was proposed to explicate the depolymerization process. AL and DAL products were used for the preparation of lignin-based phenolic resins. The chemical properties of lignin-based phenolic resins were studied by liquid-state 13C NMR and FT-IR spectroscopy, and its physical properties were also investigated. The results indicated that the depolymerized alkali lignin-phenol-formaldehyde (DALPF) resins exhibited enhanced properties, such as faster curing rate, lower formaldehyde emission, and higher bonding strength, compared to alkali lignin-phenol-formaldehyde (ALPF) resins.

Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition.

Demethylation technique has been used to enhance lignin reactivity for preparation of phenolic resins. However, the demethylation efficiency and the demethylated lignin (DL) reactivity were still unsatisfactory. To improve the demethylation efficiency, alkali lignin was demethylated under different mild conditions using sodium sulfite as a catalyst. Lignin and DL were characterized by 1H-NMR (nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy to determine the demethylation mechanism. With the demethylation of lignin, the methoxyl group content decreased from 1.93 m mol/g to 1.09 m mol/g, and the phenolic hydroxyl group content increased from 0.56 m mol/g to 0.82 m mol/g. These results revealed that methoxyl groups were attacked by SO32−, and some methoxyl groups were converted to phenolic hydroxyl groups by a nucleophilic substitution reaction, generating DL with high reactivity. The chemical properties of lignin-based phenolic resins were studied by 13C-NMR and FT-IR spectroscopy, and their physical properties were also investigated. The results indicated that lignin-based phenolic resins exhibited faster curing rate and shorter gel time. In addition, the bonding strength increased from 0.92 MPa to 1.07 MPa, and the formaldehyde emission decreased from 0.58 mg/L to 0.22 mg/L after lignin demethylated at the optimum condition.

Preparation and characterization of lignin demethylated at atmospheric pressure and its application in fast curing biobased phenolic resins

Agricultural crop-based lignin was utilized to modify phenol-formaldehyde (PF) resin to prepare fast curing biobased phenolic resins by copolymerization.

New method for the synthesis of formaldehyde-free phenolic resins from lignin-based aldehyde precursors

Phenolic resins are mainly obtained from phenol and the highly toxic and volatile formaldehyde. In order to synthesize new formaldehyde substituents for the synthesis of resol-type phenolic resins, we designed a method to functionalize phenolic compounds with aliphatic aldehydes by a two-steps reaction: the functionalization of an acetal group on aromatic hydroxyl functions and the subsequent deprotection of theses acetal groups into aliphatic aldehyde groups. This method was used on the lignin-based aromatic aldehyde precursors i.e. 4-hydroxybenzaldehyde and vanillin to turn them into reactive and difunctional biobased aromatic aldehyde precursors. Those precursors proved to lead to formaldehyde-free and biobased phenolic resins with competitive thermal properties compared to the usual formaldehyde resins.

Preparation and characterization of novolac phenol–formaldehyde resins with enzymatic hydrolysis lignin

Enzymatic hydrolysis lignin (EHL) derived from bio-ethanol production is attracting increased attention for use as a substitute for petroleum-based phenol in phenolic resins. In this work, EHL was successfully liquefied into small phenolic compounds catalyzed by oxalic acid in the presence of phenol. Experiments were designed to determine the effects of different replacement percentages of phenol by EHL on the residue content (RC) and the combined phenol (CP). Up to a 55% weight of phenol was substituted by liquefied EHL to formulate a novolac bio-based phenolic resin (EHL–PF). The differences between EHL and liquefied EHL, PF and EHL–PF were studied by Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC), 1H NMR spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). RC was found to increase with the increasing replacement percentage, while CP was found to increase at a lower replacement percentage and decrease at a higher replacement percentage. EHL–PF possessed comparable properties to those of commercial products.

Pyrolysis kinetics of tannin–phenol–formaldehyde resin by non-isothermal thermogravimetric analysis

The interest of using tannin–phenol–formaldehyde (TPF) resin as adhesive for industrial and building material application is growing fast. Because of copolymerization among tannin, phenol, and formaldehyde molecules, TPF resin has better thermal stability than phenolic resin. The goal of this paper is to investigate the thermal degradation behavior of TPF resin by thermogravimetric analysis and to summarize and verify the favorable pyrolysis kinetics model corresponding to bio-based phenolic resin. For this purpose, a comprehensive study was conducted to reveal the thermal behavior of TPF resin. Firstly, a model containing three pseudo-components was used to describe the overall pyrolysis process performed at three constant heating rates. Then, bi-Gauss method, an asymmetric multi-peak fitting function was applied to separate the overlapping peaks. Kinetic parameters and kinetic mechanism of each separated peak were determined by model-free isoconversional method and y(α) and z(α) master plots, respectively. Finally, the pyrolysis kinetics model was validated to prove its prediction ability. With results of the apparent activation energies, pre-exponential factors, and the most probable kinetic mechanism functions, the simulated data of reaction model agreed with experimental data well. Therefore, these procedures and results can help improve the industrial performance of TPF resin.

Production of bio-based phenolic resin and activated carbon from bio-oil and biochar derived from fast pyrolysis of palm kernel shells

A fraction of palm kernel shells (PKS) was pyrolyzed in a fluidized bed reactor. The experiments were performed in a temperature range of 479–555°C to produce bio-oil, biochar, and gas. All the bio-oils were analyzed quantitatively and qualitatively by GC-FID and GC–MS. The maximum content of phenolic compounds in the bio-oil was 24.8wt.% at ∼500°C. The maximum phenol content in the bio-oil, as determined by the external standard method, was 8.1wt.%. A bio-oil derived from the pyrolysis of PKS was used in the synthesis of phenolic resin, showing that the bio-oil could substitute for fossil phenol up to 25wt.%. The biochar was activated using CO2 at a final activation temperature of 900°C with different activation time (1–3h) to produce activated carbon. Activated carbons produced were microporous, and the maximum surface area of the activated carbons produced was 807m2/g.