Phenol/formaldehyde resins are strong and durable and relatively inexpensive, but are generally colored resins. Johannes Karl Fink, in Reactive Polymers Fundamentals and Applications (Second Edition), 2013. Copyright © 2020 Elsevier B.V. or its licensors or contributors. At higher temperatures ether bridges can rearrange to methylene bridges. 30 is 1:1.5. 100°C. - Phenol-formaldehyde resin. 28 and 29. The points of double bond are the most reactive and the reaction is started by using an acid or an alkaline catalyst. Phenol-formaldehyde resins make excellent wood adhesives for plywood and particleboard because they form chemical bonds with the phenol-like lignin component of wood. Also known as phenolic resins, phenol-formaldehyde polymers were the first completely synthetic polymers to be commercialized. Another two-phase resin is composed by a highly condensated PF-resin still in an aqueous solution and a PF-dispersion [45]. Mainly for the production of moulding sands used in foundries, for the manufacture of moulding compounds, electric insulation plates used in electronics and varnishes. With the aid of ultramodern methodology, this resin is processed using the best quality chemical compounds by our skilled professionals. PF adhesives for the core layer of panels usually have the highest average molar mass and hence show higher reactivity and quick gelation. A mixture of phenol, formaldehyde, and sulfuric acid—the raw materials for the manufacture of phenol-formaldehyde resin—was discharged onto a roadway four times before the company decided to install a catchpot after the reactor rupture disc. PFs decompose thermally producing several volatile by-products as well as carbonizing glassy carbon. Britannica Kids Holiday Bundle! A cyclic urea prepolymer in phenol/formaldehyde resins acts as a plasticizer for the resin. Modified Resoles Bakelite resole resins can be modified with BPA, styrene, CNSL, DCPD, urea and plasticizers for high performance applications. Used as the basis for Bakelite, PFs were the first commercial synthetic resins. This makes the laminate more post-formable and tougher. Such pH values, however, are obtained in the case of the usual PF-resins at a content of NaOH of 5 to 10 mass%. COVID-19 is an emerging, rapidly evolving situation. Bakelite phenolic novolac resins can be modified to deliver various physical properties and performance characteristics. They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. On the other hand, very high temperatures during stacking might already cause partial deterioration (seen as discoloration) of the wood. Some special resins consist of a two-phase system with a highly condensated and no longer soluble PF-resin and a usual PF-resin [44]. A suitable surfactant to be added to the furan binder compositions is sodium dodecylbenzene sulfonate. This is done by reacting resorcinol with formaldehyde. When an excess of formaldehyde is used under alkaline conditions, the products are resoles that can be self-condensed to thermosets with water as a co-product. The higher the addition of ester, the lower the gel time of the PF-resin [32]. After the fourth incident, they decided that was not enough and they made a change in the design: they installed a catchpot [4]. The resultant polymers—known as phenol-formaldehyde resin, urea-formaldehyde resin, and melamine-formaldehyde resin—are widely used as adhesives in plywood and other structural wood products. Several other attempts, which however failed, have been done by Christiansen [86], incorporating the acid by chemical means into the resin or fixing the hardeners (high molecular polystyrenesulfonic acids) physically within the glue line. Phenol/formaldehyde resins used to manufacture high-pressure laminates are typically produced by reacting phenol and formaldehyde by means of an alkaline catalyst such as sodium hydroxide [10]. A mass molecule of phenol formaldehyde. Phenol-formaldehyde (PF) resins, commonly referred to as phenolic resins, are thermosetting plastics used in a variety of applications. They contain a higher proportion of alkali than face layer resins in order to keep the resin soluble even at higher degrees of condensation. Epichlorohydrin-phenolformaldehyde resin | C10H13ClO3 | CID 132494078 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more. PF core layer resins usually have the highest molar masses and hence show a high reactivity and quick gelation. Phenol-formaldehyde resins make excellent wood adhesives for plywood and particleboard because they form chemical bonds with the phenol-like lignin component of wood. In this study, sodium carbonate (Na 2 CO 3) was used as a catalyst to prepare high‐ortho phenol‐formaldehyde (HOPF) resin, and ester and carbonate curing accelerators were used to increase its curing rate. Although molded products no longer represent their most important application, through their use as adhesives they still represent almost half of the total production of thermosetting polymers.…. A. Pizzi, C.C. There are exactly such pHs, however, which are the ones used for commercial PF resins for wood, with a content of NaOH of 5 to 10% by mass. 229920001568 phenolic resins Polymers 0 claims title 8 EP82100916A 1981-02-25 1982-02-09 Curable phenol-formaldehyde resin with elastic properties after curing Expired EP0058872B1 ( en ) After hot curing the complex that reforms is between the morpholine and the strong acid, almost neutralizing the glue-line and preventing acid deterioration of the wood substrate. The electrochemical properties measurement shows that when used as an anode material for lithium batteries, the porous Li 4 Ti 5 O 12 material obtain both high capacity and good rate performance. Part of the heat of reaction was removed by a cooling jacket and part by condensing the vapor given off during reaction. Feature Unit Value / range 1 Physical state - Liquid 2 Viscosity at 25oC mPas 1000-1450 3 Density at 25oC g/cm3 1,26-1,30 4 Dry matter content % at least 72 5 Phenol content % up to 16 6 Formaldehyde content % up to 0.5 7 Water content % 5,5-9,0 8 pH of aqueous extract - 5,8-6,8 Phenol can react with formaldehyde at the ortho and para positions, generating mono, di, and trimethylolphenol as the reaction products. Also, wood extractives such as flavonoid tannins [1], other wood chemicals [41], and amines [37] have an accelerating effect on the hardening of PF-resins. Ibeh, in Handbook of Thermoset Plastics (Third Edition), 2014. The second discharge occurred because the formaldehyde failed to react, for an unknown reason. Under alkaline conditions, this reaction is kinetically favored over the competing condensation reaction. Phenolics are still very important industrial polymers, though their most common use today is in adhesives for the bonding of plywood and other structural wood products. Furan binders provide many of the advantages of phenolic binders while resulting in substantially reduced VOC emissions. Decreasing the solid content of the resin is limited by a possible too high moisture content of the glued particles. In some cases potash in the form of a 50 mass% solution is added in the core layer resin mix in an amount of approximately 3–5% potash solid based on resin solid content. Introduction. It might be due to the hydrogen carbonate ion formed after hydrolysis of the propylenecarbonate [92], or due to the formation of hydroxybenzyl alcohols and aromatic carbonyl groups in the reaction of the propylene carbonate with the aromatic ring of the phenol [87,88]. In order to improve the properties of boron-containing phenol/formaldehyde resin, a tetrabromobisphenol A-based epoxy resin was used as curing additive., University Federico II of Naples, Italy - What is Chemistry? A further, very effective, and relatively inexpensive manner for accelerating the hardening of PF adhesives is by either partly co-polymerizing them with urea during or after their preparation (see below). Get the latest public health information from CDC: In this video the preparation of a phenol formaldehyde resin is shown. Fig. Phenol-formaldehyde resins were the first completely synthetic polymers to be commercialized. M.J. Mullins, ... H.-J. This polyphenol is subsequently reacted with epichlorohydrin to generate the epoxy resin with high functionality and high cured Tg. In some cases potash in the form of a 50 mass% solution is added to the core layer resin mix in an amount of approximately 3–5% potash solid based on resin solid content. The hardening reaction is only initiated by heat. Phenol Formaldehyde Resin for our esteemed clients. Phenol-formaldehyde thermosets were the first synthetic polymers. They are especially desirable for exterior plywood, owing to their good moisture resistance. Phenol-formaldehyde resin was developed as the first wholly synthetic polymer at the beginning of the 20 th century and was called Bakelite. The failure of the binder is essentially due to the pyrolysis process. Lu and Pizzi [83] showed that lignocellulosic substrates have a distinct influence on the hardening behavior of PF-resins, whereby the activation energy of the hardening process is much lower than for the resin alone [84]. In one method, an excess of formaldehyde is reacted with phenol in the presence of a base catalyst in water solution to yield a low-molecular-weight prepolymer called a resole. Typical mole ratios of formaldehyde to phenol range from 1.2 to 1.9 mol of formaldehyde per mol of phenol. Decreasing the solid content of the resin is limited by a possibly too-high moisture content of the glued particles. This process produces a solid prepolymer called a novolac (or novolak), which resembles the final polymer except that it is of much lower molecular weight and is still thermoplastic (that is, it can be softened by reheating without undergoing chemical decomposition). In this work, GO was incorporated into phenol formaldehyde (PF) resin by in situ polymerization. Phenol/formaldehyde resins are strong and durable and relatively inexpensive, but are generally colored resins. They may be used in this state or an organic solvent such as methanol can be added to reduce the solids concentration and viscosity of the mixture. In order to be cured to a thermosetting resin, novolacs require the addition of more formaldehyde or, more commonly, of compounds that decompose into formaldehyde upon heating. From thermogravimetric analysis three stages can be distinguished with different activation energies, the lowest around 200 kJ mol− 1 and the highest around 300 kJ mol− 1 [9]. Especially with rather acid wood species, the pH of the resin could significantly drop [33], bringing the resin back to the pH of its highest reactivity. By continuing you agree to the use of cookies. The higher the degree of condensation during the production process (the higher the viscosity), the shorter is the gelling time [80]. This is explained due to the stronger bonding between triazine carbons of melamine than those of urea carbons. An in depth investigation of the dependence of the gel time of an alkaline PF–resin from the pH [32] surprisingly found an unexpected lengthening of gel time in the very high pH region (above 10). The chemical composition of phenol and formaldehyde and their combination into networks of permanently interlinked large molecules are explained briefly in the article aldehyde condensation polymer. Phenolic resins are a group of the most versatile polymers yet invented. Phenol-formaldehyde resin, also called phenolic resin, any of a number of synthetic resins made by reacting phenol (an aromatic alcohol derived from benzene) with formaldehyde (a reactive gas derived from methane). Pizzi and Stephanou [81] investigated the dependence of the gel time on the pH of an alkaline PF-resin. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. If that is not possible, we can add on equipment to control it. Catalyst levels range from 0.5% to 3%. This reacts with excess phenol producing diphenyl methane and a molecule of water is split off. Phenolic resins, invariably reinforced with fibres or flakes, are also molded into insulating and heat-resistant objects such as appliance handles, … Bakelite ® Phenolic Resoles Hexion manufactures both modified and unmodified phenolic resole resins with varying properties, to meet customers‘ processing and performance needs. Alkaline PF-resins contain free-reactive methylol groups in sufficient number and can harden even without any further addition of formaldehyde, of a formaldehyde source, or of catalysts. They are used primarily in forest products, and in molding, refractories, friction, abrasive, rubber processing, and other uses. Another way is the addition of esters such as propylene carbonate [81,87–92] or, even better, glycerol triacetate (triacetin) [81,93,94] or guanidine carbonate [94]. Also wood-inherent chemicals might have an accelerating influence on the hardening reactivity of PF-resins [91]. A hard, infusible, and chemically resistant plastic, Bakelite was based on a chemical combination of phenol and formaldehyde (phenol-formaldehyde resin), two … The reason for this is a catalytic activation of PF and other resin condensation by the surface of polymeric wood constituents, in particular carbohydrates like crystalline and amorphous cellulose and hemicellulose. The predominant applications for phenol-formaldehyde thermosets2 are as adhesives for plywood and as binders for similar wood products: oriented strandboard, hardboard, particle board, and molded wood products. After cure, the thermoset has good resistance to water. Phenolic resins are the condensation products of phenol and formaldehyde and are an important class of adhesives. Different from UF-bonded boards, PF-bonded boards should be stacked as hot as possible to guarantee a maximum post-curing effect. Acid-induced gelling reactions of PF resins can cause severe deterioration of the wood substrate and therefore have lost any importance in the wood adhesives field. The physicochemical properties of the prepared resins and the mechanism of curing acceleration were investigated. Novolacs must be cured with a second monomer that reacts with the phenols. The pH of the resin, however, may well change when the resin comes into contact with the acid wood surface. Phenolic resins account for a large portion of phenol production. From the first resins others varieties have been developed and phenol-formaldehyde resins now designates a group of resins with varying properties made from different phenols and aldehydes. Covalent bonding between the PF-resin and the wood, especially lignin, does not play any role [84]. We use cookies to help provide and enhance our service and tailor content and ads. Properties of the Fibers Used in this Study They are noted for their high thermal resistance and strength, and also their fire-resistant properties. Updates? It has also been shown that lignocellulosic substrates have a distinct influence on the hardening behavior of PF-resins [34,35], of all the other formaldehyde-based adhesives, and of other thermosetting wood adhesives (such as isocyanates): the activation energy of the hardening process is much lower than for the resin alone [35]. It may be added in an amount from 0.05% to 1.0%. Opposite to UF-bonded boards, PF-bonded boards should be stacked as hot as possible to guarantee a maximum post-curing effect. Novolak S-120D. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Phenol-formaldehyde resins are heat-resistant and waterproof, though somewhat brittle. M. DUNKY, A. PIZZI, in Adhesion Science and Engineering, 2002. Emulsified furan-based glass fiber binding compositions are advantageous since they allow the use of furan resins that have high molecular weights or the addition of other materials which give rise to the formation of two-phase systems [6]. Phenol and cresol novolacs are another two types of aromatic glycidyl ethers. Table 1. Resoles are cured in a single step by exposure to heat or acids, and develop the high degree of cross linkage responsible for their great stability. Sulfonated melamine/formaldehyde resins exhibit good solubility in water [22]. NOW 50% OFF! The phenol monoalcohol groups may also react together giving diphenyl ether and a molecule of water. The hardening reaction is initiated by heat. Pizzi et al. The company's managers did not ignore the first three incidents. The results showed that, with the addition of Na When a stoichiometric deficiency of formaldehyde is used under acidic conditions, novolac oligomers are produced. Potassium carbonate, sodium carbonate [37,41,42], or sodium and potassium hydrogen carbonates are instead just accelerators of PF resin curing, and don’t contribute to an increase in strength of the hardened network [37]. In experiments, the hydrolytic stability of such a cured resin was measured by the mass loss and the amount of formaldehyde set free after the acid-induced hydrolysis [23]. The ratio of phenol to formaldehyde to form a mass molecule as shown in Fig. 6.4 Properties. In an acidic medium, the reaction between the phenol-hydroxymethyl and the hydrogen atom on the phenol ring is faster than that between the aldehyde and the phenol. Poly vinyl acetate (PVA)/Polyol were blended by weight 3:1. Graphene oxide (GO) has shown great potential to be used as fillers to develop polymer nanocomposites for important applications due to their special 2D geometrical structure as well as their outstanding mechanical, thermal, and electrical properties. The choice of resin depends on the desired properties. Phenol-formaldehyde resins (PF) were the first commercially relevant impregnation resins, made by reacting phenol and formaldehyde, creating a polymer network inside of the wood upon curing. PROPERTIES. For these applications, phenolic resins offer low cost and good compatibility with wood fiber. Phenol formaldehyde (PF) resin, epoxy resin, and unsaturated polyester resin are considered to be the three main thermosetting resin adhesives. They are mainly used in production of circuit boards and molded products–such as laboratory countertops, pool balls, and as adhesives and coatings–friction linings, and oil well proppants. The hot-pressing time in the plywood manufacturing had to be increased by approximately 30% at 150°C for the 50KLPF resin compared with that normally used for PF resin, in order to comply with plywood standard demands. 4 Synthesis of thermoplastic phenolic resin. 4. (Fifth Edition), 2009. We have been engaged in manufacturing, exporting and supplying best in quality Phenolic Resin i.e. The choice of resin depends on the desired properties. Curing can be accomplished by grinding the novolac to a powder, mixing it with fillers such as wood flour, minerals, or glass fibres, and then heating the mixture in a pressurized mold. Since alkaline phenolic resins harden only by heat, post-curing of wood panels during hot stacking is important. The key factors that have made phenolic resin … Covalent bondings between the PF-resin and the wood, especially lignin, do not play any role under the conditions industrially prevalent today for wood adhesives application [35]. Chain products are formed by further addition and condensation with the liberation of water and a mass molecule of phenol formaldehyde resin will form whose structure is shown in Fig. They are formed through the reaction of phenol with formaldehyde, followed by cross-linking of the polymeric chains. The resole, frequently in liquid form or solution, can be cured to a solid thermosetting network polymer by, for instance, sandwiching it between layers of wood veneer and then heating the assembly under pressure to form a plywood. [85] describe a procedure for the neutralization of acid-hardened PF glue lines by partly using as hardener a mix of p-toluene sulfonic acid with a complex of morpholine and a weak acid in order to partly prevent the acid-induced deterioration of the wood substance. Get exclusive access to content from our 1768 First Edition with your subscription. The mechanism of this acceleration, however, is not yet clear. Procedures for the simultaneous neutralization of acid-hardened PF-glue lines during their curing have also been described [36]. They are generally used for products where the color or … 1 The PF resin is a kind of synthetic polymer obtained from the reaction between phenol and formaldehyde. The molar ratio of phenol to formaldehyde is 1: (0.7–0.9). In the first stage, around 300 °C there is a further cross-linking involving the hydroxyl group to form water; the second stage around 500 °C is due to the instability of the methylene bridges. Unlike novolacs, resoles have limited storage stability. The chemicals are reacted with each other to create the resin, which can have varying properties, depending on the ingredients used. They are especially desirable for exterior plywood, owing to their good moisture resistance. This is mixed with different percentages of prepared sulfonated-phenol formaldehyde resin (SPF). 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. The materials are reacted to a suitable endpoint, cooled under vacuum, and usually distilled to remove the water present from the formaldehyde solution as well as the water of condensation from the polymerization reaction. Melamine resins are water clear but are more expensive. These resins are synthetic polymers produced by the reaction of phenol or formaldehyde-substituted phenol. Trevor Kletz, in What Went Wrong? The latter was ineffective, as there was a partial choke in the vapor line where it entered the condenser. Generally, the average molecular weight of the prepolymer is as low as 200–500. Phenoplaste zählen zu den ersten industriell erzeugten Kunststoffen. Although they came into existence at the very start of the age of polymers, they continued to be developed into more and more applications. Der erste im großen Maßstab produzierte Phenoplast ist das 1907 von Leo Hendrik Baekeland erfundene Phenol-Formaldehyd-Kondensationsharz, das unter dem Warenzeichen Bakelitvermarktet und jahrzehntelang in vielen Bereichen eingesetzt wurde. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Sue, in Thermosets, 2012. Phenoplaste sind wegen ihrer Temperaturbeständigkeit, Oberflächenhärte und dem günstigen Preis auch heute die wichtigsten Duroplaste und werden unter anderem zur Herstell… In this last phase the hydroxyl radicals provide an oxidative atmosphere for methylene. Phenolic resins are used as binders with glass and mineral ‘wool’ fibers to make products suitable for thermal and acoustic insulation. Release of water during cure is a manageable problem, and in fact, the resoles typically used are supplied as a solution in water. Water as a significant component can be used. A more effective PF-accelerating system is the addition of esters such as propylene carbonate [32,37–42], or even better, of glycerol triacetate (triacetin) [15,32,43] or guanidine carbonate [43]. The lowest possible temperature for a technically sufficient gelation rate is approximately 100°C. Since phenolic resins harden only thermally, post-curing during hot-stacking is very important. There are other examples of this in Chapter 27. As an important alternative of thermoplastic engineering materials, glass fiber (GF) reinforced phenol formaldehyde resin (GF/PF) composites has many desirable properties for application, such as low specific mass, high rigidity, good corrosion resistance, excellent flame retardation, and less smoke and toxicity when burning [1,2]. Phenolic resins are adaptable to many applications other than ACFs. 1. Diluting the phenol/formaldehyde resin with cyclic urea prepolymer reduces the free phenol and other volatile phenolic moiety levels of the phenol/formaldehyde resin which reduces air pollution. Phenolic resin is also called phenol formaldehyde resin. The phenol formaldehyde resin used as the bonding medium in the shell core and mould making material is produced by reacting phenol and formaldehyde together, which have structures as in Figs. FIG. The reason is a catalytic activation of the PF-condensation by carbohydrates like crystalline and amorphous cellulose and hemicellulose. Especially with rather acidic wood species, the pH of the resin could drop significantly [82]. Our editors will review what you’ve submitted and determine whether to revise the article. The resin consists of an integrated kraft lignin-phenol network. They are produced by combining either phenol or cresol with formaldehyde produces a polyphenol. In industrial practice, there are two basic methods for making the polymer into useful resins. The limits of the increase of the degree of condensation in the production process of the resin is given by (i) the viscosity of the resin (the resin must be able to be pumped to have a certain storage stability as well as a proper distribution of the resin on the particles during blending), and (ii) the flow behavior of the resin under heat, guaranteeing wetting of the unglued second wood surface and a sufficient penetration into the wood surface. When the second addition of catalyst was made, the large excess reacted vigorously. The reaction proceeds in steps, the intermediate product being phenol monoalcohol. Surprisingly they found an increase in the gel time in the region of very high pH values (above 10). Modified resol type phenol formaldehyde resin 1/1 3 2018-03-26 Item no. Phenolic resins are synthesized by adding formaldehyde to phenol, which proceeds via the formation of hydroxymethylphenol, also known as resol (prepolymer). The ratio of formaldehyde to urea and the melamine content governs the hydrolytic stability of a urea/melamine/formaldehyde resin. This study provides direct support for the improvement of the physical and mechanical properties of resin-modified Chinese fir in terms of penetration of the resin into the cell walls. The acid-induced gelling reaction of PF resins can instead cause severe deterioration of wood and therefore has lost more or less completely its importance in the wood panels field. Esters not only accelerate resin curing, but also increase the ultimate strength of the cured resin, indicating that a more cross-linked, hardened network has been obtained. Melamine resins are water clear but are more expensive. They were at one time the primary … The emission of formaldehyde in melamine/urea/formaldehyde resins decreases as the melamine content is increased [21]. In this application phenolic resins are chosen because of their low cost, good thermal resistance (high Tg), relatively good flame resistance, and adhesion to fiber. Because of the plasticizing effect achieved with the cyclic urea prepolymer, higher F/P mole ratio PF resins (traditionally more brittle) can be used, which further reduces the free phenol and volatile phenolic moiety levels. Roberto C. Dante, in Handbook of Friction Materials and their Applications, 2016. Formulations with good flame retardancy have been described. Phenol-formaldehyde resin, novolak-type. The purpose of such special resins is the gluing of wet wood, where the danger of over-penetration of the resin into the wood surface can cause a starved glue line. After treatment with low-molecular weight phenol-formaldehyde resin, the UV absorbance of earlywood tracheid cell walls at different locations did not vary greatly. The lowest possible temperature for a technically sufficient gelling rate is approx. However, oxidation is not responsible for the decomposition of the resin [10]. Phenol/formaldehyde resins and melamine/formaldehyde resins are standard resins used for many products. The curing mechanism, thermal properties, and the fire resistance were investigated by FT-IR spectroscopy, thermogravimetry, torsional braid analysis and by the limiting oxygen index (LOI) method. A.D. SARKAR M.Eng., B.Sc., in Mould & Core Material for the Steel Foundry, 1967. 30. The methylol groups thereby react to methylene and methylene ether bridges. When a hazard is recognized, by experience or in any other way, the most effective action we can take is to remove it. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, Reactive Polymers Fundamentals and Applications (Second Edition), Handbook of Thermoset Plastics (Third Edition), Handbook of Friction Materials and their Applications, Mould & Core Material for the Steel Foundry, International Journal of Adhesion and Adhesives. Emulsified furan resins can be used. Under high temperatures, ether bridges can be retransformed to methylene bridges. Solid; Liquid state at 200⁰C — max 100; Hardening time at 150⁰C — 50-120; Melting point — 50-63 .

phenol formaldehyde resin properties

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