Resol Type Research Articles

Environmentally Friendly o-Cresol-Furfural-Formaldehyde Resin as an Alternative to Traditional Phenol-Formaldehyde Resins for Paint Industry.

This paper describes studies on the preparation of an o-cresol-furfural-formaldehyde resin in the presence of an alkaline catalyst and its modification with n-butanol or 2-ethylhexanol. The novelty of this research is to obtain a furfural-based resin of the resole type and its etherification. Such resins are not described in the literature and also are not available on the market. The obtained resin based on furfural, which can be obtained from agricultural waste, had a low minimum content of free o-cresol < 1 wt.%, furfural < 0.1 wt.%, and formaldehyde < 0.1 wt.%. The resin structure was characterized by mass spectrometry (ESI-MS), FT-IR, and NMR spectroscopy, which showed the presence of hydroxymethylene groups in the resin before modification and alkyl groups derived from n-butanol and 2-ethylhexanol after modification. The etherified resins had a lower viscosity and were more flexible (DSC) than the resin before modification and they can be used as an environmentally friendly, safe, and sustainable alternative to traditional phenol-formaldehyde resins in the paint industry. They demonstrate the ability to create a protective coating with good adherence to metal substrates and an excellent balance of flexibility and hardness.

Antifrictional composites based on a two-component modified phenol-formaldehyde binder

In this paper, new polymer composite materials (PCM) based on a mixture of the resole type phenol-formaldehyde and phthalide-containing phenol-formaldehyde binders, reinforced with polyoxadiazole fiber, were obtained, and their tribological properties were studied. The influence of the content of phthalide-containing phenol-formaldehyde polymer in a two-component mixture of binders on the hardness of the surface layer, tribological and thermofrictional properties of PCM in various units of dry friction on steel has been studied. It is shown that the resulting PCM are superior to PCM based on phenol-formaldehyde or phthalide-containing phenol-formaldehyde binders of the resole type in terms of tribological and thermal friction properties.

Production of pyrolytic lignin for the phenolic resin synthesis via fast pyrolysis

Recycling of waste wood into resol type phenol-formaldehyde (PF) resins via fast pyrolysis was demonstrated. Waste wood collected from the building demolition site in Finland was pyrolyzed with 20 kg/h circulating fluidized bed pyrolysis pilot unit. Pilot was operated with high organic liquid yield (60 wt% on average) and the produced fast pyrolysis bio-oil was fractionated by water addition into aqueous phase and water insoluble phase. The obtained fractions were characterized, and the water-insoluble viscous lignin fraction was used in the synthesis of PF-resins. Commercial phenol was successfully replaced by pyrolytic lignin fraction at 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% producing resins of low in free formaldehyde content, but resins with high replacement ratio exhibited higher viscosities. The use of H2O/n-butanol mixture as solvent at a ratio 70:30 wt/wt% proved capable to prolong the storage time of the resin and helped to maintain the viscosity at acceptable values for at least 2 weeks before their use in the targeted application. Finally, the gluing performance of the resins was evaluated by measuring the tensile shear strength of lap joints formed by gluing 5 mm thick beech wood veneers. All the produced resins fulfilled a dry strength limit of ≥ 10 N/mm2. Wet strength limit ≥ 7 N/mm2 was fulfilled by the resins with the replacement ratio up 40 wt%, but resins with replacement ratio of 50 wt% had somewhat reduced wet strength. These results confirm a promising protentional application of pyrolysis derived lignin fraction in phenolic wood adhesives, at least in dry conditions.

Sustainable Chitosan/Polybenzoxazine Films: Synergistically Improved Thermal, Mechanical, and Antimicrobial Properties.

Polybenzoxazines (Pbzs) are considered as an advanced class of thermosetting phenolic resins as they overcome the shortcomings associated with novolac and resole type phenolic resins. Several advantages of these materials include curing without the use of catalysts, release of non-toxic by-products during curing, molecular design flexibility, near-zero shrinkage of the cured materials, low water absorption and so on. In spite of all these advantages, the brittleness of Pbz is a knotty problem that could be solved by blending with other polymers. Chitosan (Ch), has been extensively investigated in this context, but its thermal and mechanical properties rule out its practical applications. The purpose of this work is to fabricate an entirely bio-based Pbz films by blending chitosan with benzoxazine (Bzo), which is synthesized from curcumin and furfuryl amine (curcumin-furfurylamine-based Bzo, C-fu), by making use of a benign Schiff base chemistry. FT-IR and 1H-NMR spectroscopy were used to confirm the structure of C-fu. The impact of chitosan on benzoxazine polymerization was examined using FT-IR and DSC analyses. Further evidence for synergistic interactions was provided by DSC, SEM, TGA, and tensile testing. By incorporating C-fu into Ch, Ch-grafted-poly(C-fu) films were obtained with enhanced chemical resistance and tensile strength. The bio-based polymer films produced inhibited the growth of Staphylococcus aureus and Escherichia coli, by reversible labile linkages, expanding Ch galleries, and releasing phenolic species, which was 125 times stronger than bare Ch. In addition, synthesized polybenzoxazine films [Ch/Poly(C-fu)] showed significant dose-dependent antibiofilm activity against S. aureus and E. coli as determined by confirmed by confocal laser scanning microscopy (CLSM). This study suggests that bio-based Ch-graft-polymer material provide improved anti-bacterial property and characteristics that may be considered as a possibility in the near future for wound healing and implant applications.

Properties of fiber-filled molding material based on viscose carbon fiber and phenolformaldehyde resin of various types

A comparative study of the characteristics of two fiber-filled molding materials, which include a discrete carbon viscose fiber as a filler and phenol-formaldehyde resins of the novolac or resol type as a binder, is given. The DTA-DTG characteristics of the initial resins and the physico-mechanical properties of carbon fiber blanks obtained from fiber-filled molding materials of these types by hot compression molding were determined. It has been established that, regardless of the type of phenol-formaldehyde resin, the density, strength characteristics, toughness and thermal conductivity of carbon fiber plastics based on various resins are practically the same. A comparison of the microstructure of the obtained carbon fiber plastics based on various resins showed that in the case of using phenol-formaldehyde resin of the novolac type, a higher degree of orientation of the fiber filaments parallel to the pressing plane is achieved, which is associated with greater fluidity of the initial fiber-filled molding material. In the direction perpendicular to the pressing axis, the chaotic orientation of the fiber filaments is realized.

Study on the feasibility of alternatives for phenolic resins used in sand casting

ABSTRACT Phenolic resins are in-organic polymers with properties that make them high-strength binders with great potential for modification. The base-catalyzed phenol-formaldehyde resins provide the desired hardness to the core avoiding sand slipping on the surface. A modified resol type phenolic resin is developed for this study with minimum ingredients to compare it with existing recipes in the literature. A batch of cores was prepared with the standard 1-inch cross-section briquettes (dog-bone) with modified resol and cured through hot-curing process. Hardness and ultimate tensile strength values of these cores were compared with previous data present in literature. The average hardness as well the tensile strength from modified resol was higher than the cores from previous hot coating resol recipes and the gas-set cores present in the literature. Furthermore, the surface roughness of the cores was examined through Atomic Force Microscopy (AFM), and the ten-point height (Rz) value was lower than existing recipes.

Synthesis and characterization of resol type phenol-formaldehyde resin improved by SiO2-Np

Synthesis and characterization of resol type phenol-formaldehyde resin improved by SiO2-Np

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.

Effect of phenol-formaldehyde (PF) resin oligomer size on the decay resistance of beech wood

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

Adhesive hybrid nanocomposites for potential applications in moulding sands technology

Abstract The results of investigations concerning the production of nanocomposite based on phenol-formaldehyde resin, resol type, with organophilic montmorillonite MMT Na (ogranophilic MMT Na), for applications in the moulding sands technology, are presented in the hereby paper. This composite with mass fractions of: 0.75; 1.5 or 3 mas.% of nanofiller constituted the point of departure for investigating: X-Ray diffraction (XRD), microstructure by transmission electron microscopy (TEM), physical-chemical properties (η viscosity), strength (tensile strength Rmu; flexural strength Rg) and abrasive wear investigations of moulding sands. The performed investigations indicate that the produced nanocomposite has an intercalated structure and its viscosity increases with an increase of the nanofiller fraction. The optimal nanofiller fraction in a binder, above which mechanical properties in the system binder-mineral matrix are getting worse, was found. Thermal degradation behavior cured binder used in foundry process were studied using a convectional dynamic thermogravimetric analysis (TG) and (differential scanning calorimetry) DSC.

Studies on thermal decomposition of phenol binder using TG/DTG/DTA and FTIR-DRIFTS techniques in temperature range 20–500 °C

This paper presents results of thermoanalytical and structural research on phenolic binder used in foundry for the preparation of moulding sand. The binder has been prepared based on resole type phenolic resin with the addition of ester hardener. The aim of the study was to determine the structural changes taking place in the phenolic binder under the influence of temperature. Results show that in the investigated range of temperatures, phenolic binder exhibits three exothermic thermal effects accompanying the decomposition process. The test results using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) technique show that the addition of a hardener stabilizes the binder structure within methylene bridges. The reduction in the reaction rate observed in the DTA curve at about 330 °C can be associated with the formation of gaseous products by decomposition of the binder or, as suggested by the literature data, the formation of triple bonds and CN-HCN groups.

Studies on solvent based phenolic pre-pregs with various reinforcements

The Glass, rayon based carbon, PAN based carbon and high silica fabric reinforcements were impregnated with standard resole type phenolic resin in a vertical impregnating plant. The heating zones of prepreg plant converts resin impregnated fabric into partially polymerized state is called B-stage. The required volatile content and chang’s index are achieved by adjusting plant parameter based on online testing of prepreg, and it was noticed resin content varying depend on reinforcement used. The rayon carbon/phenolic prepregs had high wet resin content and glass/phenolic prepregs had low wet resin content

Innovative ablative fire resistant composites based on phenolic resins modified with mesoporous silica particles

Mesoporous silica particles were used as reinforcement of a phenolic resin to develop new ablative materials. A resol type phenolic resin was filled with mesoporous silica particles synthesized from tetraethyl orthosilicate (TEOS). Samples of neat phenolic resin, phenolic resin reinforced with carbon black and with mesoporous silica particles (5 and 20 wt %), were obtained. The ablative properties of the materials were studied by the oxyacetylene torch test and the ablated samples were observed by scanning electron microscopy (SEM). The composites were also characterized by dynamic mechanical analysis and transmission electron microscopy (TEM). Results showed a stronger chemical interaction between silica particles and the phenolic resin, than carbon black, thus increasing the glass transition temperature and mechanical properties of the silica/resin composites. In addition, the samples with mesoporous silica particles achieved lower erosion rates and back-face temperatures than the others, becoming promising thermal protection materials for the aerospace industry.

High temperature ablation and thermo-physical properties improvement of carbon fiber reinforced composite using graphene oxide nanopowder

Ablative nanocomposites were prepared by incorporating graphene oxide (GO) nanosheets into resole type phenolic resin and then impregnating them into rayon-based carbon fabric. GO were dispersed into phenolic resin at 0.25, 0.75, and 1.25wt.% loadings using high shear mixing to insure uniform GO dispersion. The morphology and structure of graphene oxide nanosheets (synthesized by a Hummers method) and the structural, thermal and ablative properties of the samples were characterized using Fourier Transform Infrared spectroscopy(FTIR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), oxyacetylene flame test, and Thermo-Gravimetric Analysis (TGA) methods. It was found that the thermal stability and ablative properties of the GO/phenolic resin/carbon fiber composites were greatly enhanced due to the well dispersion of GO sheets in polymer matrix and the strong interfacial interaction between the GO sheets and phenolic matrix as well as layered carbon structure after pyrolysis. The specimen with 1.25wt.% GO showed the best results in the rate of ablation, thermal diffusivity and thermal stability compared to other samples. This laminate had constant thermal diffusivity at different temperatures, and improved char yield and ablation rate to about 10% and 51%, respectively.

Design and properties of a series of high‐temperature thermoplastic elastomeric blends from polyamides and functionalized rubbers

ABSTRACTA series of high‐temperature thermoplastic elastomers (TPEs) and thermoplastic vulcanisates (TPVs) were successfully developed based on two different types of heat resistant polyamide (PA) (25 parts by weight)—PA‐12 and PA‐6, in combination with three different functionalized rubbers (75 parts by weight) of varying polarity, e.g., maleic anhydride grafted ethylene propylene diene terpolymer (MA‐g‐EPDM), sulphonated ethylene propylene diene terpolymer, and carboxylated acrylonitrile butadiene rubber, by melt mixing method. These rubbers have low level of unsaturation in its backbone, and the plastics showed high melting range. Thus, the developed TPEs and TPVs were expected to be high temperature resistant. Resol type resin was used for dynamic vulcanization to further increase the high temperature properties of these blends. Interestingly, initial degradation temperature of the prepared blends was much higher (421 °C for MA‐g‐EPDM/PA‐12) than the other reported conventional TPEs and TPVs. Fourier transform infrared analysis described the interactive nature of the TPEs and TPVs, which is responsible for their superior properties. The maximum tensile strength with lowest tension set was observed for the carboxylated acrylonitrile butadiene rubber/PA‐12 TPV. Mild increase in mechanical properties without any degradation was observed after recycling. Dynamic mechanical analysis results showed two distinct glass transition temperatures and indicated the biphasic morphology of the blends, as evident from the scanning electron microscopy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45353.

Phenolic Polymer Solvation in Water and Ethylene Glycol, I: Molecular Dynamics Simulations.

Interactions between pre-cured phenolic polymer chains and a solvent have a significant impact on the structure and properties of the final postcured phenolic resin. Developing an understanding of the nature of these interactions is important and will aid in the selection of the proper solvent that will lead to the desired final product. Here, we investigate the role of the phenolic chain structure and the solvent type on the overall solvation performance of the system through molecular dynamics simulations. Two types of solvents are considered: ethylene glycol (EGL) and H2O. In addition, three phenolic chain structures are considered, including two novolac-type chains with either an ortho-ortho (OON) or an ortho-para (OPN) backbone network and a resole-type (RES) chain with an ortho-ortho network. Each system is characterized through a structural analysis of the solvation shell and the hydrogen-bonding environment as well as through a quantification of the solvation free energy along with partitioned interaction energies between specific molecular species. The combination of simulations and the analyses indicate that EGL provides a higher solvation free energy than H2O due to more energetically favorable hydrophilic interactions as well as favorable hydrophobic interactions between CH element groups. In addition, the phenolic chain structure significantly affects the solvation performance, with OON having limited intermolecular hydrogen-bond formations, while OPN and RES interact more favorably with the solvent molecules. The results suggest that a resole-type phenolic chain with an ortho-para network should have the best solvation performance in EGL, H2O, and other similar solvents.

Thermal Study of Gels Obtained From Resol Type Phenolic Resins Modified With Lignin

SummaryGels were obtained from resol type phenolic resins, with resorcinol, formaldehyde and lignin as precursors. Thermal response was evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and curing kinetics were determined from the SDTA curves using Flynn–Wall–Ozawa and Friedman iso‐conversional models. Additionally, it was used Fourier transform infrared spectroscopy (FTIR) to evaluate the progress of the curing reaction. These analyzes were performed for two gels, one of them prepared with lignin (lignin resin), and a reference (resorcinol resin). Lignin resins tend to be more thermally stable than resorcinol resins. Average values found for activation energy of the curing processes are 55.07 kJ mol−1 and 60.60 kJ mol−1 for resorcinol resin and lignin resins respectively using Flynn–Wall–Ozawa method; values of 51.94 kJ mol−1 and 53.14 kJ mol−1 were obtained using Friedman method. It was possible to conclude that the lignin affects positively the thermal stability of the resin; the curing reaction takes place in the first six hours and the Flynn–Wall–Ozawa model fits better.

Thermal decomposition of foundry resins: A determination of organic products by thermogravimetry–gas chromatography–mass spectrometry (TG–GC–MS)

The article presents the results of research on thermal decomposition of Ester-Cured Alkaline Phenolic No-Bake (ALPHASET) binders used in molding technology. In the ALPHASET system phenol-formaldehyde resin of resole type is cured with a liquid mixture of esters. Under the influence of the molten metal the thermal decomposition of the binder follows, resulting in the evolution of gases, often harmful, e.g. from benzene, toluene, ethylbenzene and xylenes (BTEX) or Polycyclic Aromatic Hydrocarbon (PAH) groups. The identification of gases evolved during the pyrolysis of the binders was carried out and their decomposition temperatures were determined using the Thermogravimetry–Gas Chromatography–Mass Spectrometry (TG–GC–MS) technique. The tests were subjected to two types of binders from different manufacturers. Among the products of pyrolysis there have been identified mainly benzene and its derivatives, and phenol and its derivatives. Compounds identified in pyrolytic gas are largely considered to be harmful to humans and the environment (some of the compounds are carcinogenic and mutagenic). The presented results of the TG–GC–MS measurements show that the applied analytic methods are feasible to perform a qualitative and also quantitative characterization of the binder samples.

Retraction Note to: Effect of dynamic cross-linking on melt rheological properties of isotactic polypropylene (iPP)/ethylene–propylene diene rubber (EPDM)/nitrile rubber (NBR) elastomeric blends

An attempt has been made to study the melt rheological properties of uncross-linked and dynamically cross-linked isotactic polypropylene (iPP)/ethylene-propylene-diene rubber (EPDM)/Nitrile rubber (NBR) elastomeric blends, at blending ratios 10–40 wt.%, EPDM/NBR are reported. Blends were prepared by melt blending in an internal mixture at 190 °C and various rheological parameters have been evaluated at 220 °C by single screw capillary rheometer. Cross-linking was performed with resole type dimethylol phenolic resin. The effects of (i) blends composition (ii) shear stress/shear rate on melt viscosity (iii) flow characteristics and shear sensitivity at processing (iv) melt elasticity of the extrudate and (v) dynamic vulcanization effect on the processing characteristics were studied. It was found that the melt viscosity increases with the increasing EPDM/NBR concentration and decrease with increasing intensity of the shear mixing of all the blend compositions. As compared to the uncross-linked blends, dynamically cross-linked blends displayed high pseudoplastic behavior and provides unique processing characteristics that enable to perform well in both injection molding and extrusion process. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enabling low injection pressure and less injection time. Also the low die-swell characteristics of cross-linked blends also gave high precision for dimensional control during processing (extrusion).

Synthesis of microporous carbon nanofibers with high specific surface using tetraethyl orthosilicate template for supercapacitors

Microporous carbon nanofibers (CNFs) with a high specific surface area were prepared by sol–gel, electrospun, carbonization and pickling processes. Resol type phenolic resin (PF) acted as carbon source, tetraethyl orthosilicate (TEOS) worked as template and polyvinyl-pyrrolidone worked as spinning additives. The specific surface area and total pore volume of the CNFs were increased obviously with the increased amount of TEOS. A high specific area of 2164 m2 g−1, high microporosity and relatively narrow pore size distribution were achieved. The electrochemical performance was evaluated in 6 M KOH aqueous solution. The microporous CNFs exhibited outstanding electrochemical performance as binder-free electrode of supercapacitors, including a high specific capacitance (316 F g−1 at 0.2 A g−1), considerable rate performance (210 F g−1 at 20 A g−1) and good cycle stability (95% after cycling 1000 times). The microporous CNFs were promising electrode materials for high-performanced supercapacitors.