Novolac Resin Research Articles

Bio‐based novolac resins from cashew nut processing waste: Alternative resource for the development of high‐value sustainable products

AbstractIn the last decades, there is an increasing trend for replacing petro‐based adhesives with sustainable and eco‐friendly alternatives, especially in the wood industry. In this work it was developed and characterized novolac‐type phenolic resins from the full use of the cashew nut shell liquid (CNSL), an agro‐industrial residue and a rich source of phenolic compounds, sustainable alternative to petroleum‐derived chemicals, to develop bio‐based polymers. CNSL and paraformaldehyde were reacted, using oxalic acid as a catalyst, under a solvent‐free methodology. A dark and viscous resin of high molar mass and thermally stable was obtained. The development of highly bio‐based adhesives was proposed by combining CNSL‐based novolac resin (CNSL‐nov) with commercial epoxy resin (DGEBA), as an alternative to conventional hardeners. The use of the epoxy‐novolac system proved to be efficient and promising in obtaining new highly cross‐linked polymers with excellent thermal performance and with potential for wood industry, improving the bio‐based content of high‐performance adhesive.

Epoxy phenol novolac resin: A novel precursor to construct high performance hard carbon anode toward enhanced sodium-ion batteries

Although hard carbon has been considered as one of the most promising anodes for sodium-ion batteries, however, the poor performance and ambiguous sodium storage mechanism limit the further development. Herein, a novel epoxy phenol novolac resin is used as precursor for the first time to construct excellent electrochemical performance anode by pyrolyze it at different temperature. The results demonstrate that the plateau region in discharge curve of hard carbon is ascribed to Na insertion into the long-range ordered carbon structure. Improving ordering degree with suitable interlayer distance can both enhance the plateau capacity and total capacity. With the increasing of pyrolysis temperature, the graphitization degree of hard carbon is gradually enhanced. The cured epoxy phenol novolac resin pyrolyzed at 1800 °C delivers the reversible capacity of 480.3 mAh g−1 at 50 mA g−1, high initial coulombic efficiency of 84.6%, and capacity retention of 92% after 1000 cycles at 500 mA g−1. The “adsorption-intercalation mechanism” for Na storage in EPNHC-1800 is verified by in-situ Raman spectroscopy analysis. We believe that the sodium storage mechanism of hard carbon is “adsorption-intercalation-filling”, namely, the adsorption of Na-ions on the surface of carbon layers providing the slope capacity, the intercalation of Na-ions between carbon layers and filling in the nanopores providing the plateau capacity. This study offers a novel precursor to synthesize low cost and high-performance hard carbon anode material for sodium-ion batteries, delivering great opportunity for the commercialization of anode.

Влияние количества стадий импрегнации на макроструктурные и прочностные характеристики стеклоуглеродных пен

The template synthesis of glassy carbon foams was used in the work and the influence of the initial template cell size, the concentration of the solution, and the number of impregnation stages on the macrostructural and strength characteristics of the obtained materials was studied. As a carbon precursor was used the solution of Novolac resin grade SFP-012A2, the coke residue of which is more than 57 wt. %. It was shown that increasing the number of impregnation stages makes it possible to improve strength characteristics while maintaining open porosity at the level of 90 %, while glassy carbon foam based on a polyurethane template with a porosity of 60 pores per inch and 4 stages of impregnation with a solution with a concentration of 30 wt. % has the best set of properties due to the uniform wall thickening in the material volume. The value of compressive strength was 1.12 MPa, which is 2 times higher than the value of foreign analogues, while the open porosity was 91 %. It has been established that a decrease in the size of the cells of the initial template can lead to embrittlement of the material due to the formation of a cluster of overlapped cells. Increasing the mechanical strength of glassy carbon foams while maintaining an open-cell structure expands the field of application of this class of materials.

Synthesis of Cardanol-Based Acetaldehyde Novolac Resin from Cashew Nut Shell Liquid (CNSL)

Polymers are currently in the limelight. Phenolic resin is one of the polymer products obtained from the polymerization process, either from natural or synthetic sources. One of the natural compounds that can be applied to polymers is cardanol. This study aimed to synthesize cardanol-based acetaldehyde novolac resin from Cashew Nut Shell Liquid (CNSL). Isolation of cardanol from CNSL was done by liquid-liquid extraction method with acetone and purified by gravity column chromatography in a mixture of n-hexane and ethyl acetate in a ratio of 9:1. HPLC analysis showed that cardanol compounds had aliphatic chains with different levels of saturation and the yield was 18.48%. The cardanol-acetaldehyde novolac resin was synthesized through a condensation polymerization reaction with a cardanol-acetaldehyde mole ratio (1:0.5), using HCl as a catalyst. FTIR and 1H-NMR analysis were employed to identify the novolac resin structure. The product was a brownish-orange solid with a yield of 12.80 mg (40%) and followed ortho-ortho substitution. Cardanol is one of the natural phenol sources that might be utilized to manufacture novolac resins.

Functionalized carbon nanotube and carbon nanodot modified multiblock poly(arylene ether ketone sulfone) copolymer as proton exchange composite membranes for fuel cell applications

AbstractThe present study describes the successful synthesis of –COOH functionalized carbon nanodots (f‐CNDs) via pyrolysis of citric acid and 4,4′‐bis(4‐hydroxyphenyl)valeric acid (DPA‐OH, Sigma Aldrich, St. Louis, Missouri, United States) based hydrophilic oligomer at 250 °C. The multiblock copolymers were prepared by a coupling reaction between phenoxide terminated valeric acid based poly(arylene ether ketone) (DPA‐OH) hydrophilic oligomer and decafluorobiphenyl (DFBP, Alfa Aesar, Haverhill, Massachusetts, United States) end‐capped poly(arylene ether sulfone) (BP‐X‐F) hydrophobic oligomers (where X is 6, 9 and 12). Multiblock poly(arylene ether ketone sulfone) copolymer crosslinked membranes were prepared using 6F‐bisphenol‐A based novolac epoxy resin (EFN) and –COOH functionalized multiwalled carbon nanotubes/functionalized carbon nanodots (f‐MWCNTs/f‐CNDs, Nanoshell company, Utah, U. S) were used for the preparation of acid doped composite membranes for fuel cell applications. From high resolution TEM images, the average size of the prepared f‐CNDs found to be ca 10–12 nm. The N1 multiblock copolymer membrane with loading of 0.9 wt% ratio of CNTs showed better proton exchange membrane related properties such as proton conductivity (0.136 S cm−1), ion exchange capacity (1.18 meq g−1) and selectivity ratio (0.17) compared to the prepared pristine, crosslinked and CND based composite membranes. The overall results revealed that the composite membranes with loading of 0.9 wt% of CNTs and CNDs exhibited a superior combination of fuel cell related properties such as higher proton conductivity, high dimensional and oxidative stability and low methanol permeability and also showed better fuel cell performance compared to the respective pristine and EFN crosslinked membranes. © 2022 Society of Industrial Chemistry.

Fast curing phthalonitrile modified novolac resin: Synthesis, curing study and preparation of carbon and glass fibric composites

Phthalonitrile modified novolac (PNN) was synthesized in aim to develop a fast-curing resin for hot-pressing processing and characterized by NMR to confirm a full substitution of hydroxyl groups with phthalonitrile. PNN blended with high amounts (10–50 wt%) of the amine curing agents have been investigated by DSC, FT-IR spectroscopy and TGA, which revealed T5% = 420 °C. Curing times for the compositions were 4–16 min at 240 °C. The 50 min post-curing cycle for FRPs was selected based on DMA. Composites were fabricated via hot-pressing of prepregs including post-curing at 280 °C (providing Tg > 340 °C) in total of 60 min, which is the fastest curing cycle for thermosetting resins developed for applications up to 300 °C. Carbon and glass fabric reinforced polymers (CFRP and GFRP) were obtained by the developed program yielding integral composites with high mechanical properties and great heat resistance. Interlaminar shear strengths of the CFRP were up to 31 MPa and up to 70 MPa for GFRP. The latter which demonstrated retention of 75% of initial ILLS values after dwelling for 200 h at 300 °C. Thus, a new fast-processing phthalonitrile resin was developed for application in electric transport, aerospace and heat-resistant insulation.

Investigation of electrical resistivity and electrostatic discharge sensitivity of Mg/ Ba(NO3)2/novolac resin composite

Each composite energetic material (CEM) has specific electrical resistivity (ER) and electrostatic discharge (ESD) sensitivity. These parameters depend on the concentration of composite ingredients. The effect of different mole ratios of ingredients on the ER and ESD sensitivity of Mg/Ba(NO3)2/novolac resin composite was modeled by response surface methodology (RSM) and central composite design (CCD). Nonlinear regression analysis and analysis of variance (ANOVA) indicated that the predicted responses were in good agreement with the experimental results. The results showed an inversely proportional correlation between increasing the mole ratio of Mg with ER and the minimum ignition energy (MIE) of ESD ignition. Similarly, there is a directly proportional correlation between increasing the mole ratio of Ba(NO3)2 and the novolac resin with increasing ER and MIE. A composite with low ER will conduct electrical energy and accumulate joule heating to begin ESD ignition. Therefore, increasing the conductive Mg ratio in the composite decreases joule heating. Thus, the MIE decreases with an increase in the Mg concentration. Similarly, increasing the concentration of electrical insulated novolac resin or Ba(NO3)2 in the composite increases the joule heating and the MIE. Therefore, a correlation was made to predict the ESD sensitivity of composites with different mole ratios of ingredients according to the values obtained from their ER measurements.

Novolac-based microcapsules containing isocyanate reagents for self-healing applications

Microcapsules (MCs) containing isocyanate compounds for use as self-healing materials in waterborne polyurethane coatings have been synthesized, in the presence of modified Novolac resins. With modification of Novolac resin, it is succeeded partial or total protection (Benzylation and Acetylation) of its hydroxyl groups. The idea here is to use a protected Novolac resin as the organic substrate for the encapsulation of the less reactive Isophorone isocyanate (IPDI) while the more reactive one, Methylene diphenyl diisocyanate (MDI), is used for the shell formation. Based on that strategy microcapsules of different morphologies and sizes were obtained, depending on the agitation conditions, as revealed using SEM and optical microscopy. Selective extraction was performed to determine the amount of the less reactive isocyanate (IPDI) stored inside the capsules through FTIR-ATR spectroscopy and isocyanate titration as well as the stability of IPDI inside the capsules over time. As determined, microcapsules based on Acetyl-modified Novolac resin encapsulated 96 wt% of IPDI monomer; this amount is about five and ten times higher than that encapsulated in MCs based on by Benzyl-modified Novolac resin or unprotected Novolac resin, respectively. At the same time, MCs based on Acetyl-modified Novolac resin were stable, maintaining approximately 80 % of the initial isocyanate content after two months of storage under inert conditions. Finally, the self-healing ability of the microcapsules was tested by adding selected IPDI-loaded microcapsules in waterborne polyurethane dispersions. It was proven that the Acetyl-modified Novolac-based MCs showed efficient healing behavior, in the absence of any catalyst, on the polyurethanes’ surfaces when scratched artificially.

Effect of Ingredients Ratio on the Friction Sensitivity and Burning Performances of Mg/Ba(NO3)2/Novolac Resin Pyrotechnic Compositions

AbstractEach pyrotechnic composition has specific sensitivity such as electrostatic discharge (ESD) sensitivity and friction sensitivity (FS), and it also has specific ignition performance, including luminous intensity (LI) and burning rate (BR). These parameters depend on the concentration of pyrotechnic composition ingredients. In this study, Mg/Ba(NO3)2/novolac resin compositions were prepared using different weight ratios (wt.%) of Mg, Ba(NO3)2, and novolac resin. Then, they were investigated by their FS, LI, and BR. The results showed that by increasing Ba(NO3)2 concentration from 33.76 to 84.54 wt.% Ba(NO3)2, the FS increases from 343 N to 65.5 N. However, the LI and BR of this composition increased by increasing Ba(NO3)2 concentration until a 3/1 stoichiometric ratio of Mg/Ba(NO3)2 (from 13086 to 20588 cd (candela) and 11.25 to 13.71 cm/s, respectively for 33.76 to 64.92 wt.% Ba(NO3)2) and decreased afterward (from 20488 to 53.24 cd and 13.71 to 6.45 cm/s, respectively). For Mg/Ba(NO3)2/novolac resin containing 3 to 12 wt.% novolac resin FS increased from 56 to above 360 N. LI and BR decreased from 20057 to 1203 cd and 17.3 to 1.2 cm/s, respectively. The stoichiometric ratio of Mg/Ba(NO3)2 has the highest enthalpy of reaction. Therefore, it can be concluded that it has the highest LI and BR.

Synthesis and property study of novel maleimide‐cardanol based modifiers for epoxy resins

AbstractThe biomass‐based chemicals from renewable resources are countermeasures to ease the problem of fossil fuel shortage. This work is to develop a biobased functional reactive modifier for thermosetting epoxy resins appropriate for excellent overall performance. The novel maleimide‐cardanol modifiers (CA‐HPM) is synthesized from natural extract cardanol (CA) and N‐(4‐hydroxyphenyl) maleimide (HPM), which is then mixed with phenolic epoxy resin and linear phenolic novolac resin systems. CA‐HPM plays a versatile role in tuning the comprehensive properties of epoxy such as thermal property, adhesive property, and thermo‐mechanical property. Systems with CA‐HPM show slightly lower curing activity and distinct decreased single glass transition temperature (Tg). Besides, the crosslinking density of the cured resin increases, meanwhile the thermal stability keeps at high level, which is due to the rigid five‐membered ring structure of maleimide. Metal lap shear test results manifest that the adhesion between epoxy resin and metal interface augments. With 10% CA‐1HPM, the cured resin exhibits lower equilibrium water sorption (1.88%) and diffusion coefficient (2.94 × 10−8 s−1 cm2). This biobased functional reactive modifier has provided balanced overall performance and would pave the way to a wide range of possible “eco‐friendly” applications.

The effect of DOPO concentration and epoxy amine stoichiometry on the rheological, thermal, mechanical and fire‐retardant properties of crosslinked networks

AbstractPresented here is an investigation into the effect of a phosphorus‐based fire retardant on the thermal, rheological and mechanical properties and flammability of an epoxyamine network prepared using stoichiometric and off‐stoichiometric epoxyamine compositions. The flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was reactively incorporated into a blend of a bisphenol‐F diglycidyl ether epoxy resin and a polyfunctional epoxidized phenol Novolac resin, then cured with diethyltoluenediamine and accelerated using imidazole. Increased DOPO concentration improved fire retardancy, but reduced reactivity and thermal and mechanical properties. An increasing amino excess stoichiometry, however, comparatively increased reactivity and improved thermal and mechanical properties. Despite evidence of an earlier onset of degradation and higher char yield, enhanced graphitisation and reduced volatile emissions for the off‐stoichiometric networks, no significant improvements in fire resistance as a function of stoichiometry were observed using UL‐94 and limiting oxygen index measurements. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Evaluation of the effect of the novolac resin ratio on the high temperature performance of the brake pads

The resin is a widely used binder in the brake pads. Determining the optimum, resin ratio is important for the brake pad to show the best wear and braking performance. In this article, the impression of the novolac resin ratio (15% and 30%) on the perfor-mance of the brake pads at high temperatures was studied. Friction experiments of the brake pads were performed according to ASTM G99–95a test standard in Pin-on disc test device at 350 °C. The average friction coefficients obtained in the friction tests of 15% and 30% novolac resin samples at 500 rpm rotation speed, 350 C temperature, and 10 N load were 0.151 and 0.308, respectively. With the increase in the novolac res-in ratio, the hardness, density, and thermal conductivity of the brake pads have in-creased.

Healable ablative composites from synergistically crosslinked phenolic resin

Due to the excellent processability and high char yield, phenolic resin plays a pivotal role in ablative thermal protection systems for the aerospace industry. However, internal defects in conventional phenolic resin matrix composites could potentially scrap the entire thermal protection system and cause devastating safety hazards to the spacecraft. Herein, hexamethylenetetramine (HMTA) and phenylboronic acid are applied as the co-curing agents of novolac resin. With the HMTA amount below 2.5 phr, a series of synergistically crosslinked phenolic resin (HPNR), which consist of both traditional methylene linkages and dynamic boronic ester linkages, are successfully synthesized. By tuning the ratio of the traditional/dynamic bonds, the HPNR demonstrates high char yield and controlled plasticity. Compared with its conventional counterparts, the carbon fabric reinforced HPNR matrix composites show healing capability and superior mechanical properties and ablation resistance, with an interlayer shear strength and mass ablation rate of 37.0 MPa and 0.055 g/s, respectively. The synergistic crosslinking strategy provides a promising pathway for designing and preparing healable ablative thermal protection system materials.

THE PREPARATION AND CHARACTERIZATION OF THE RED FLAME COMPOSITION BASED ON STRONTIUM NITRATE, MAGNESIUM, AND POLYVINYL CHLORIDE

This paper presents the influence of oxidizer/fuel ratios on several energetic characteristics (the heat of combustion, gaseous volume, burning rate) of the red flame pyrotechnic containing strontium nitrate, magnesium, polyvinyl chloride, and novolac resin. Based on the received experimental data and theoretical calculation results, the reasonable strontium nitrate/magnesium ratio of 58/15 is determined. The pyrotechnic mixture has the heat of combustion of 921 cal/g, a gaseous volume of 260 ml/g, a burning rate of 2.02 mm/s at a pressed density of 1.60 g/cm3, a color purity of 89%, a decomposition temperature of 481.5oC, and less sensitive to friction and impact.

Synthesis of Boron-Doped Phenolic Porous Carbon As Efficient Catalyst for the Dehydration of Fructose into 5-Hydroxymethylfurfural

Porous carbon materials are widely used in adsorption, supercapacitors, catalytic reactions, electrochemistry, and so on. However, the need to develop porous carbon materials with easy template removal and controllable pore size is urgent. This study provides an efficient strategy for the preparation of boron-doped phenolic porous carbon through in situ pyrolysis to form a template. Phenylboronic acid is used to cross-link novolac resin. The optimization of the pyrolysis conditions reveals that boron oxide (B2O3) is formed at 400 °C. The porous carbon material with a high specific surface area is obtained utilizing the hydrolysis characteristics of B2O3. After loading titanate, 5-hydroxymethylfurfural with a high yield (92%) is achieved at 20 °C in ethanol. The catalytic activity showed no significant decrease after utilization six times. The method is simple and easy to implement, providing an efficient catalyst for the conversion of biomass materials into biofuels.

Synthesis of self-healing inhibitor releasing nanocapsules blended phenol novolac resin for high performance anticorrosion coating

The present work intended to synthesize a composite material exhibiting self-healing and enhanced anticorrosion properties. In this context, MWCNT incorporated nanocapsule (NC) filler material was synthesized, then it is blended with phenol novolac resin (PNR). The surface characterization studies of MWCNT/NC-PNR composite material signify the nano-size, spherical, and multiwalled structures of NC and CNT. The composite materials consisting of different weight percentages of MWCNT inserted NC were coated on the mild steel (MS) surface by the doctor blade method. The 0.3 wt% MWCNT/NC blended PNR showed significantly enhanced hydrophobicity of the coating which is evidenced by the high value of water contact angle (98.2°) amongst the coating materials prepared. Further, electrochemical impedance spectroscopy (EIS) tests of the coating confirm a high impedance value of 3.039× 107 ohm cm2 at the low frequency region for 50 days of immersion in 3.5 wt% NaCl solution. Thus, it was found that 0.3 wt% MWCNT incorporated NC filler increased the corrosion protection efficiency of NC/PNR coating by 32.61%. Therefore, the results show that the MWCNT/NC-PNR composite coating exhibits significantly elevated corrosion resistance, and can be used as a self-healing inhibitor coating material for long-term anti-corrosion shield.

Synthesis and characterization of phenolic resins based on pyrolysis bio-oil separated by fractional condensation and water extraction

The combination of fractional condensation and water extraction methods is proposed to produce phenol rich beech wood pyrolysis bio-oil fractions, which have great potential to replace petroleum-based phenol in polymerization of novolac resin. The polymerization of model phenol acetaldehyde (MPA) resins, mimic acetaldehyde (mimic) resin which base on the composition of phenol compounds in bio-oil, and bio-oil acetaldehyde (BOA) resins were studied. MPA and mimic resins were used to compare with the BOA resins to determine the feasibility of using bio-oil. Bisphenol A type epoxy resin (DGEBA) was used, for the first time, as a formaldehyde-free cross-linker for bio-oil based novolac resins. The kinetic parameters of the curing reaction with model-free methods were obtained using data from a differential scanning calorimeter (DSC). The BOA resin showed curing activation energy was close to that of the phenol-acetaldehyde (PA) resin (95.5 and 94.9 kJ/mol by Kissinger method). The physicochemical and thermal properties of the novolac resins before and after curing are compared, and the potential of treated bio-oil products to effectively replace commercial phenols is demonstrated.

Hybrid In Situ Reinforcement of EPDM Rubber Compounds Based on Phenolic Novolac Resin and Ionic Coagent

For the design of stretchable and flexible high-performing materials, the reinforcement of elastomeric grades plays a crucial role. State-of-the-art fillers such as carbon black benefit from a high reinforcement but often negatively affect the processing and mixing properties of rubber compounds. To overcome this drawback, the synergistic properties of hybrid in situ filler systems are studied for EPDM compounds comprising a phenol novolac resin and ionic coagents such as zinc (meth)acrylates (ZD(M)A. With the help of a combined novolac/ZD(M)A system, the compounds could be tailored in a unique way towards higher toughness and enhanced cross-link density. Further, the fracture surface of the EPDM–novolac compounds was analyzed by scanning electron microscopy, revealing a significant change of the morphology from rough and disordered to smooth and homogenous for samples with coagents. In addition, the results clearly showed that the introduction of ionic coagents is able to compensate shares of carbon black filler in the EPDM compound. The toughening of samples with zinc (meth)acrylates is attributed to the synergistic formation of an interpenetrating polymer-filler network by simultaneous covalent and ionic cross-linking.

Anionic Polymerization of Para-Diethynylbenzene: Synthesis of a Strictly Linear Polymer.

Anionic homo- and copolymerization of p-diethynylbenzene in the presence of n-BuLi in polar solvents was carried out. The use of hexamethylphosphortriamide (HMPA) makes it possible to synthesize a completely linear soluble polymer that does not have branching and phenylene fragments. A copolymer of p-diethynylbenzene with diphenyldiacetylene was synthesized. Homo- and copolymers of p-diethynylbenzene have high thermo- and thermo-oxidative stability. By the interaction of side reactive ethynylphenylene groups with various reagents, it is proposed to synthesize clusters along the conducting chain of poly-p-diethynylbenzene. Due to presenting C≡CH side groups, boron, copper, and cobalt derivatives were synthesized. It is shown that not all theoretically possible stereoisomers can be formed as a result of the polymerization. The application of p-diethynylbenzene polymers for the modification of industrial samples of epoxy novolac resin, oligoester acrylates, and carbon fibers has been demonstrated.

New hydrophilic carbon molecular sieve membranes for bioethanol dehydration via pervaporation

Tubular supported carbon molecular sieve membranes (CMSMs) with high hydrophilicity and perm-selectivities for water suitable for ethanol dehydration were developed from a Novolac oligomer phenolic resin as precursor. Alpha alumina supported CMSMs resulted in 1.69 times higher surface roughness than zirconia supports. The higher surface roughness resulted in 48% higher selective layer thickness. According to pervaporation results, water permeance decreased by the increase in selective layer thickness and mole based selectivity of water- ethanol was enhanced. The oligomer with 3982 g/mol molecular weight enabled membrane to reach high selectivity with one-layer coating. Performance of the membranes are compared with literature data in terms of mole-based selectivity vs. water permeance. CMSMs could be a potential substitution for traditional ethanol dehydration methods with offering higher performance and as a result reducing the final price of bioethanol to be used as a sustainable energy source.