PRODUCTS

PHENOLIC RESINS

Phenolic resins are a family of thermosetting binding resins formed as a result of the polycondensation of phenols and aldehydes, most commonly phenol and formaldehyde. It is also called phenol-formaldehyde resins and PF resins in Turkish industrial use. Phenolic resin does not have a single fixed formulation or a single physical form; novolac, rezol and modified phenolic systems show different reaction and curing characteristics.
Novolak resins are two-stage systems that require a separate curer, mostly produced by acidic catalysis and an excess of phenol. Resol resins, on the other hand, are single-stage systems that are mostly produced by basic catalysis and excess of formaldehyde, and can be cross-linked with appropriate heat without requiring additional formaldehyde welding. This distinction is fundamental for resin purchasing and initial formulation development.
CAS No 9003-35-4 is used for general phenol-formaldehyde polymers. However, this CAS does not indicate that every manufacturer's grade has the same chemical composition, free phenol or formaldehyde content, viscosity or curing behavior. The technical data sheet (TDS), safety data sheet (SDS) and certificate of analysis (COA) of the product to be used should be taken as basis.
Phenolic resins are evaluated in applications such as electrical parts, friction materials, abrasives, casting cores and dies, wood board binders, mineral wool, filter impregnation, laminates, composites, refractory systems, and heat-resistant coatings. Cured mesh structures can provide thermal strength, dimensional stability, and charring behavior; however, brittleness, volatiles formation, and susceptibility to process conditions must be considered.

WHAT ARE PHENOLIC RESINS?

Phenolic resin; It is a family of polymeric binding materials based on the reaction of phenol, cresol or other phenolic components with formaldehyde or other aldehydes. Between the ortho and para positions in the phenol ring, mostly methylene (–CH₂–) and ether bridges occur in some systems. As the reaction progresses, a three-dimensional cross-linked structure may form.
Phenolic resins have two basic groups in terms of structure and function: NOVOLAK and REZOL. Novolak is mostly linear/branched pre-polymer and the appropriate crosslinker is required for the final thermoset structure. Remol, on the other hand, can be cured by heating thanks to its reactive hydroxymethyl groups. Therefore, the two resin grades cannot be replaced in the same amount and with the same process.
Phenolic resin expression; It can describe a resin solid, resin solution, powder binder or ready-made molding compound that already contains curer. This form must be clearly stated in the purchase.
Phenolic resin products are also distinguished from each other in terms of the degree of reaction progress. The grade, which is sold as a low molecular weight prepolymer, and the binder with partially advanced and increased viscosity do not have the same processing window. Especially in liquid resol products, the continuation of condensation, albeit slowly, during storage may cause changes in viscosity, pH and gel time. For this reason, the production date and storage history are also important during sale and acceptance.
Some of the resins offered by manufacturers under the same heading are solvent-free powder, some are water or alcohol-based solutions, and some are compounds containing fillers and curers. In recipes prepared with percentages, the dry resin solid should be shown separately as the product was delivered. For example, using 50 kg of liquid resol containing 60% solids means giving 30 kg of polymeric solids and approximately 20 kg of volatile/carrier phase to the system.

COMMON PRODUCT AND CHEMICAL NAMES

Phenolic Resins

Phenol-Formaldehyde Resin

PF Resin

Novolac Phenolic Resin / Novolak Fenolik Reçine

Resole Phenolic Resin / Resol Phenolic Resin

Phenolic Molding Resin

Phenolic Binder / Fenolik Bağlayıcı

Modified Phenolic Resin / Modifiye Fenolik Reçine

CAS 9003-35-4 (general phenol-formaldehyde resin registration)

CAS NO, EC / EINECS NO AND CHEMICAL IDENTIFICATION

Product family: Phenolic resins

General chemical class: Phenolic-aldehyde condensation polymers

Common essential monomers: Phenol and formaldehyde

General phenol-formaldehyde resin CAS No: 9003-35-4

Single molecular formula for all phenolic resins: Not defined

Single exact molecular weight for all grades: Not defined

Novolac structure: Phenolic pre-polymer that often requires additional curing

Resol structure: Reactive phenolic pre-polymer that can be self-cured with heat

Commercial form: Powder, flakes, granules, liquid in solution or dispersion

Important technical parameters: Free phenol, free formaldehyde, solid, viscosity, softening point, gel time, flow, moisture and ash.

CAS 9003-35-4 is the general polymer identifier; it does not prove raw material composition or full regulatory status on its own. The EC number, polymer/regulatory status of the product and the specific scope of registration must be verified through the manufacturer's certificate.
In polymeric materials, the average molecular weight and distribution depend on the synthesis conditions. Instead of writing a specific molecular formula in the formulation or purchase specification, it is more functional to write the characterization method and acceptance range. For example, ring-ball softening point and flow test for solid novolak; Brookfield viscosity, solids percentage, and gel time can be selected for liquid resol.
Free phenol and free formaldehyde refer to low-molecular components that remain in the product that are not attached to the resin chain. These parameters are important for both odor and workplace exposure and volatile emissions, application safety, and regulatory status of the target product. Just because a resin is technically presented under the same CAS does not prove that these impurities are at the same level.

CHEMICAL STRUCTURE AND MOLECULAR PROPERTIES OF PHENOLIC RESINS

The phenol aromatic ring can interact with formaldehyde from the ortho and para positions in electrophilic reactions. Initially, hydroxymethyl phenol intermediates; methylene bridges are formed in subsequent condensations and ether linkages in some conditions. The progression of the reaction raises the polymer molecular weight and converts to an insoluble/non-melting thermoset network under appropriate curing conditions.
In novolax production, the formaldehyde/phenol mole ratio is mostly below one and the environment is acidic. Under these conditions, curers such as hexamethylentetramine (HMTA, hexamine) can be used to cross-link the active positions remaining after the reaction. In the production of resol, excess formaldehyde and base catalysis leave hydroxymethyl functionality in the system, allowing subsequent heat curing.
As the curing intensity increases, temperature strength, hardness, and solvent strength may improve; in turn, impact toughness and ease of processing may decrease. Both types can be adapted with different additives and modifications.
Since the hydroxyl group in the phenolic ring affects the electron distribution, the ortho and para positions are especially important in the addition and condensation reactions with formaldehyde. The methylol/hydroxymethyl groups formed in the first step can enable the formation of bonds between other aromatic rings under subsequent heating and catalysis conditions. Some of the ether bridges may turn into more stable methylene linkages during further condensation; the removal of water and other volatile products is evaluated in the process design.
In the production of novolax, excess phenol and acidic catalysis conditions usually create a resin that does not self-crosslink fast enough. When curers such as HMTA are added later, temperature-reactive intermediate species are formed and the network structure progresses. In resol, synthesis is designed in such a way that a sufficient amount of reactive methylol groups remain on the polymer during the initial reactions. Therefore, Resol may show higher storage reactivity.
In terms of temperature resistance, cross-link density alone is not a sufficient explanation. The amount of aromatic skeleton, the presence of oxygen, the thermal expansion of the filler, the degree of curing and the integrity of the charred layer formed at high temperature are all decisive. The carbonization behavior of the phenolic matrix is also examined, especially in applications such as ablation and friction.

PHYSICAL AND CHEMICAL PROPERTIES OF PHENOLIC RESINS

Appearance: Usually yellowish–brown flakes/powder/solid for Novolak; liquid solution or solid grade for resol
Color: Yellow to dark brown according to synthesis and modification
Density: Depends on resin and solids ratio
Softening point: Varies especially with solid novolac grade
Viscosity: Dependent on temperature, solids and aging in liquid resols and solutions
Behavior with water: Depending on resin form and solvent/alkali content
Solids ratio: Particularly essential for comparing liquid resins
Gel time: The key criterion for comparing curing reactivity
Free phenol and free formaldehyde: Grade-specific quality and safety parameters
Thermal properties: Degree of curing, filler, post-cure and product family dependent
Flame behavior: Phenolic thermosets may have a relatively high charring tendency; application standard testing is required.
It is not correct to give a single melting point or single tensile strength for phenolic resin; cured and uncured products should be specifically separated.
In solid resins, the softening point is not equal to the service temperature of the polymer when fully cured. Uncured resin can soften and flow when heated; after the network structure develops, it acquires a thermosetting character that does not melt again. For this reason, the melting/softening behavior and the final heat deflection temperature should be considered with different experiments.
The viscosity of liquid resins can be very sensitive to measurement temperature. To obtain comparable data, the spindle, rotation speed, temperature, and dwell time must be kept the same. The drying temperature and time selected during solids determination can also advance condensation in some reactive resins; therefore, the test method used should be specified.
A dark color of a product alone is not an indicator of unsuccessful quality. However, it should be evaluated in terms of unexpected darkening, storage reaction or possibility of contamination within the same grade. In the manufacturer's specification, color, free monomer, moisture, ash and gel time should be interpreted together.

HOW DO PHENOLIC RESINS WORK AT THE MOLECULAR LEVEL?

Before curing, the resin works as the binder phase, wetting the fibers/fillers/surfaces and holding them together. When heat and appropriate reaction conditions are provided, the bonds between phenolic groups multiply and a three-dimensional network is formed. In Novolak systems, the addition of HMTA provides formaldehyde-based reactive species that can form cross-links. Resol systems, on the other hand, can proceed through their own reactive functions.
Fluidity is lost by cross-linking; the compound solidifies, gaining mechanical integrity, shape stability to heat, and chemical resistance. The formation of water and other volatiles during curing can create a risk of pores, bubbles, or voids. Controlling the curing rate is therefore critical.
Important control parameters in use are: initial viscosity, filler wetting, open time, temperature-time profile, volatile matter output, gel time and final web density.
During the wetting phase, the resin must be of low viscosity and sufficient fluidity. Dry zones can form when the resin cannot enter the surface cavities of the fiber or mineral filler. On the other hand, excessive resin flow can lead to filler collapse, resin-rich zones, or overflow from the mold. Therefore, the process must allow the resin to flow and wet the surface first, and then gel in a controlled manner.
Gelation and full curing are not the same concept. Continuous network formation begins at the gel point, but chemical transformation, mechanical properties, and volatiles release can continue later. In some applications, the post-cure step is used. Post-curing, when properly programmed, can improve the transformation of the remaining reactive groups; however, excessive temperature and rapid outgassing can cause cracking.
Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), gel behavior with rheometer, and appropriate mechanical tests can be used together for curing monitoring. DSC helps to monitor the exothermic reaction, understand DMA storage module and glass transition behavior. None of these alone guarantee the field performance of the final product.

IN WHICH SECTORS ARE PHENOLIC RESINS USED?

Casting cores and molds

Abrasive discs and abrasives

Brake pads and clutch pads

Electrical-electronic molding parts

Heat-resistant handles and appliance parts

Wood-based boards and plywood

Mineral wool binders

Glass and carbon fiber composites

Laminates and impregnation resins

Refractory binder systems

Special coatings for heat and chemical resistance

Filter paper impregnation

Industrial friction composites

Resin-bonded stone and proppant applications

Resin selection should be made based on the process, curing mechanism, emission conditions and final performance criteria rather than the name of the sector.
Water resistance of the binder and press time in wood composites; hot abrasion, sound and vibration in friction materials; grain adhesion and operating temperature in abrasive discs; dielectric and arc resistance in electrical applications. For this reason, the same phenolic resin should not be considered commercially suitable for all sectors.
In aerospace and applications exposed to high heat flux, the ablation and charring behavior of the phenolic matrix can be evaluated. However, in such specialized applications, fiber texture, porosity, resin distribution, and certification requirements are much more comprehensive than for general industrial resins.

NOVOLAK AND REZOL APPLICATIONS OF PHENOLIC RESINS

Novolaks are generally solid, well-storable two-stage resins. Molding compounds containing HMTA can be evaluated in abrasive and friction composites or binder powder systems. In the formulation of Novolak, the amount of hexamine, filler, and lubricant balance together determine the resin flow and curing behavior.
Resols can often be offered in solution form and can be used in wood adhesives, mineral wool, impregnation, laminate, and various casting binder systems. The ratio of resin solids in solution is important: adding 50% of the 60% resol solution gives the mixture 30% true resin solids. The resin solution and the resin solid should not be mixed.
Novolak + HMTA and Resol should not be considered under one universal process recipe as there are two different curing methods.
When selecting a novolax, the softening point, flow distance, free phenol, and hexamine cure response must be considered together. A resin that gels too quickly during molding can solidify without filling the entire mold. A system that cures too slowly can increase cycle time or lead to inadequate curing of the final part. The amount of HMTA should be optimized according to grade and application; too much does not only mean better mechanical strength.
In rezol systems, pH and the amount of water/solvent affect both shelf stability and surface wetting. Higher solids can provide less evaporation load; however, an increase in viscosity can reduce impregnation quality. Even if the flowability of the more dilute solution is good, its drying energy and volatile output may increase. This balance is the key process decision in applications such as laminate and filter impregnation.

RUBBING, ABRASIVE AND MOLDING APPLICATIONS OF PHENOLIC RESINS

In the brake pad, phenolic resin forms the network that connects the friction components. Resin type; hot friction coefficient can affect wear, mechanical strength, sound and vibration performance. Compatibility with mineral, metallic, organic and graphitic additive packages should be evaluated.
In abrasive products, the phenolic binder provides mechanical integrity by holding the abrasive grains together. In sand/silica casting binders, molding compounds and laminates, the initial wetting ability, flow and final curing behavior of the resin come to the fore.
In molding compounds, the balance of novolac, HMTA, organic or mineral filler, lubricant and pigment is important. In short experiments, changing one variable and keeping the other raw materials constant facilitates grade comparison.
In friction materials, thermal degradation of phenolic binder can affect the formation of a third-body layer on the work surface. Therefore, not only the flexural strength at room temperature, but also the variation in the coefficient of friction with temperature, fade-recovery behavior, wear rate and dust formation should be evaluated. The surface properties of graphite, ceramic fiber, barite and other filler additives can alter the bonding of the resin.
For abrasive wheels, resin is selected based on grain type and grain size. In abrasive or grinder applications, while the binder must hold sufficient grain, a closed and brittle structure that impairs cutting performance may not be desired. Product safety cannot be determined with just an initial percentage recipe, as the curing cycle, wheel geometry and aeration conditions are critical for safety.

COATING, LAMINATE AND COMPOSITE APPLICATIONS OF PHENOLIC RESINS

Phenolic resins can be used in fiber impregnation, composite preform bonding, friction surface coating, and heat-resistant paint systems. Performance goals change with reinforcements such as glass fiber, cellulose, aramid, and carbon fiber. In composites, fiber surface wetting, resin flow, volatiles control, and post-cure integrity are critical parameters.
Phenolic matrices can provide good charring and heat resistance in some applications; however, brittleness and volatile product removal tendencies compared to epoxy systems must be considered in the design. Adherence, flexure, solvent and chemical resistance testing is required in coatings.
In laminate production, the paper or fabric carrier is usually impregnated with a controlled amount of phenolic resin first. The excess volatile phase is then removed and a processable prepreg is obtained through the pre-cure step. In the final hot press cycle, the resin forms bonds between the layers. The amount of impregnation, the volatile matter ratio and the resin flow are the three separate acceptance criteria.
In glass or carbon fiber reinforced compounds, fiber volume ratio and mass ratio should not be confused with each other. Since fiber and resin densities are different, 50% fiber by weight does not mean 50% fiber by volume. In addition, water or solvent in the resin solution is not taken into account as the solid phase of the final cured composite. When designing, the wet mixture recipe and the dry laminate composition should be reported separately.

ARE PHENOLIC RESINS USED IN FOOD, COSMETICS AND PHARMACEUTICAL APPLICATIONS?

General-purpose phenolic resins should not be considered directly as food, cosmetic or pharmaceutical ingredients. Suitable special grades can be used in certain food contact laminate, coating or packaging structures under conditions permitted by legislation. This requires final migration tests and manufacturer conformity certificates.
In a medical or pharmaceutical contact application, extractables, leachables, residual phenol/formaldehyde, biocompatibility, and process residues should be evaluated separately. The general definition of CAS alone does not imply approval for these uses.
Especially in a final product that comes into contact with food, not only the polymer identity of the resin is important, but also the catalysts, fillers, colorants and low-molecular components that remain after curing. Suitability may be limited according to the type of food contacted, temperature, time and local legislation. For the same reason, industrial friction or casting resin and food contact specific grade should not be substituted directly.

INDUSTRIAL APPLICATIONS OF PHENOLIC RESINS

The aim of product development is not only to cure the resin, but also to ensure performance compatible with the target process. Therefore, in the selection of phenolic resin, the type of resin (novolac/rezol), solid, solvent or water content, free phenol and formaldehyde, softening point, gel time, flow amount, viscosity, HMTA amount and target application should be evaluated together.
Filler surface and moisture content in filled compounds; underlay and film thickness in coatings; fiber ratio and impregnation quality in fibrous composites; surface preparation and pressure cycling in adhesives determine performance. The temperature/ventilation capability of the equipment is as important as the formulation.
For quality assurance, it is recommended to link input quality control with final performance tests. For example, when batch viscosity changes, solids and storage age can be examined first; if voids increase are observed in the final composite, moisture, pre-cure level and application thickness are checked. Periodically preparing a control sample with the same standard reference recipe helps to see the difference between producer batches.
Not only the typical value but also specification limits and test methods need to be required from the resin supplier. Two resins with an average viscosity of 500 mPa·s may have a wide acceptance tolerance and the other a narrow acceptance tolerance. In production lines with a narrow process window, this difference can affect cycle consistency.

WHAT PROBLEMS CAN PHENOLIC RESINS HELP SOLVE?

If the binder strength is insufficient at high temperature, the appropriate phenolic thermoset mesh can be evaluated.
If the abrasive or friction material has poor particle adhesion, the grade, ratio and cure profile of the phenolic binder can be examined.
If the molded part is too brittle, different filler, elastomer-modified phenolic resin, or lower web density may be considered.
If curing is too fast, the resin reactivity and temperature schedule can be reviewed.
If there are gaps/bubbles after curing, the volatile component, mold aeration, humidity and heating rate should be investigated.
If the powder resin is not distributed properly, particle distribution, mixing sequence and filler moisture should be checked.
If free phenol or formaldehyde emission is high, appropriate low-free-monomer grade and engineering controls should be preferred.
Not every problem is solved by simply increasing the amount of resin; curing, filling, surface, and process must be optimized together.
If the viscosity of liquid resol rises in the tank, product age, temperature history, pH change, and packaging closure status should be examined. Lowering the viscosity by adding water or solvent is not always the solution; the chemical progression of the resin is irreversible and the solids change.
If surface cracking occurs in the cured part, it is necessary to evaluate the heating rate, gas output, mold design and thermal expansion of the filler together instead of just applying a longer cure. In case of insufficient adherence, surface cleanliness, fiber finishing system, surface tension of the resin and humidity before application are also important variables.
If the high-temperature performance in the brake or abrasive application is lower than expected, the filler mineralogy and binder-filler interface should be investigated as well as the resin grade. Thus, instead of increasing the amount of a single raw material, formulation improvement can be made for the actual failure mechanism.

THINGS TO CONSIDER IN THE USE OF PHENOLIC RESINS

It should be confirmed whether it is novolac or rezol.
It should be determined whether it contains curing agents.
The HMTA ratio of the ready mixture should be examined.
The percentage of the resin solid and the commercial solution should be separated.
Free phenol and free formaldehyde limits should be checked.
Gel time, flow and storage stability should be compared.
Fill moisture and grain distribution should be considered.
Proper ventilation should be provided for volatiles that come off during curing.
Excessive waiting and degradation at high temperature should be avoided.
TDS, SDS and COA should be examined separately for product grade.

Resins, and especially some liquid resols, may contain irritating or hazardous free monomers. The fact that the product exhibits low hazard as a general polymer does not mean that every commercial resin solution is of the same classification.
Especially in novolak mixtures containing HMTA, the ingredients should be prepared in a dry environment and improper heat accumulation should be prevented. Liquid resol products should be stored in appropriate closed packaging at the manufacturer's recommended temperature. If the humidity of the fiber, filler or mineral material with which the resin will be mixed is not controlled, voids may occur during curing.
The safety hazards of phenolic systems cannot be explained by the name of polymers alone. Factors such as the flammability of the water or alcohol-based solution, the amount of free phenol/formaldehyde, co-catalysts and powder treatment determine the risk of exposure. Local suction and manufacturer SDS data should be used during mixture preparation and hot curing.

INITIAL FORMULATION APPROACHES FOR PHENOLIC RESINS

The following compositions are LABORATORY INITIAL APPROACHES prepared for resin raw material selection and initial comparison. It is not a verified commercial recipe, manufacturing instruction or specific standard performance guarantee. All values express a percentage by weight (w/w%) over the feed quantity of commercial raw materials. The solvent/solid in the finished resin is not added separately. Actual curing and emission safety should be determined according to the TDS/SDS of the resin used.
The weight-by-weight percentages given in this section indicate the wet composition at the time of mixture preparation. Especially when liquid resol is used, the mass ratios in the final cured product will change with the evaporation of water. The Novolak-HMTA system may also have a different final mass than the initial weighing composition due to chemical curing and volatile product output.
In order for formulation comparisons to be valid, it is necessary to keep not only the percentage of raw materials; the grade, solids ratio, filler moisture, mixing sequence and test sample sizes of the selected commercial resin constant. Recipes are not commercial production instructions, but starting compositions for initial evaluation.

EXAMPLE 1: NOVOLAK PHENOLIC MOLDING COMPOUND FILLER SCREENING

Purpose: To compare the effect of organic/mineral filler equilibrium on flow, dimensional stability, and mechanical behavior at the same ratio of novolac and HMTA.

Starting ingredients (wt%):

FORMULATION A – CONTROL:

Novolac phenolic resin (cure-free grade): 44.00%

Hexamethylenthetramine (HMTA): 6.00%

Wood flour, dry: 35.00%

Calcium carbonate, dry: 10.00%

Magnesium oxide: 2.00%

Zinc stearate: 1.00%

Pigment: 2.00%

TOTAL: 100.00%

FORMULATION B – MEDIUM MINERAL FILLER:

Novolac phenolic resin (cure-free grade): 44.00%

Hexamethylenthetramine (HMTA): 6.00%

Wood flour, dry: 30.00%

Calcium carbonate, dry: 15.00%

Magnesium oxide: 2.00%

Zinc stearate: 1.00%

Pigment: 2.00%

TOTAL: 100.00%

FORMULATION C – HIGH MINERAL FILLER:

Novolac phenolic resin (cure-free grade): 44.00%

Hexamethylenthetramine (HMTA): 6.00%

Wood flour, dry: 25.00%

Calcium carbonate, dry: 20.00%

Magnesium oxide: 2.00%

Zinc stearate: 1.00%

Pigment: 2.00%

TOTAL: 100.00%

FORMULATION D – HIGHEST MINERAL FILLER:

Novolac phenolic resin (cure-free grade): 44.00%

Hexamethylenthetramine (HMTA): 6.00%

Wood flour, dry: 20.00%

Calcium carbonate, dry: 25.00%

Magnesium oxide: 2.00%

Zinc stearate: 1.00%

Pigment: 2.00%

TOTAL: 100.00%

Application approach:

The ratio of novolac resin and hexamine is kept constant in all samples.

All fillings are prepared in a controlled and comparable dry state.

Mixtures are prepared with the same equipment and the same process history.

Flow, gel time, mold filling, and sample appearance are compared.

Dimensional change, flexural strength, thermal stability and, if necessary, electrical properties are measured.

The curing and hot press cycle is determined solely by the manufacturer's manual of the selected commercial resin.

Proper process aeration is provided for volatile matter and hexamine decomposition products.

The most balanced filling level is taken to further tests.

EXAMPLE 2: REZOL PHENOLIC IMPREGNATION/COATING BINDER SCREENING

Purpose: To evaluate the effect of the addition of short glass fibers with the same commercial Rezol resin feed on the rheology, dispersion, and post-cure integrity of the coating/composite premix.

Starting ingredients (wt%):

FORMULATION A – CONTROL:

Liquid rezol phenolic resin (60% solid): 60.00%

Deionized water: 36.00%

Glass fiber short cut (dry): 0.00%

Wetting agent, nonionic: 1.00%

Mineral filler, fine silica: 2.00%

Defoamer: 0.50%

Rheology modifier: 0.50%

TOTAL: 100.00%

FORMULATION B – 5% GLASS FIBER:

Liquid rezol phenolic resin (60% solid): 60.00%

Deionized water: 31.00%

Glass fiber short cut (dry): 5.00%

Wetting agent, nonionic: 1.00%

Mineral filler, fine silica: 2.00%

Defoamer: 0.50%

Rheology modifier: 0.50%

TOTAL: 100.00%

FORMULATION C – 10% GLASS FIBER:

Liquid rezol phenolic resin (60% solid): 60.00%

Deionized water: 26.00%

Glass fiber short cut (dry): 10.00%

Wetting agent, nonionic: 1.00%

Mineral filler, fine silica: 2.00%

Defoamer: 0.50%

Rheology modifier: 0.50%

TOTAL: 100.00%

FORMULATION D – 15% GLASS FIBER:

Liquid rezol phenolic resin (60% solid): 60.00%

Deionized water: 21.00%

Glass fiber short cut (dry): 15.00%

Wetting agent, nonionic: 1.00%

Mineral filler, fine silica: 2.00%

Defoamer: 0.50%

Rheology modifier: 0.50%

TOTAL: 100.00%

Application approach:

Commercial liquid rezol with 60% solids is accepted as resin for exemplary purposes; formulation is recalculated at other resin concentrations.

In all samples, the amounts of rezol solution, wetting agent, silica, defoamer and rheology modifier are constant; the addition of fiber is deducted from the amount of water and 100% is preserved.

Flow and dispersion are controlled; resin application window and dwell stability are monitored.

Impregnation/coating behavior, drying, gap after curing, and cracking tendency are compared.

Curing conditions are determined according to the manufacturer's recommendations and safety assessment of the selected rezol grade.

Recommended intervals are feasibility screening only; application approval is not given without final performance and emissions testing.

ALTERNATIVES AND COMPARISON OF PHENOLIC RESINS PRODUCT

When choosing an alternative to phenolic resin, not only price and adhesion at room temperature; thermal resistance, toughness, curing mechanism, volatile emissions, chemical resistance and target process should be evaluated together.
When comparing alternatives, the unit performance cost of the final product may be more revealing rather than the cost per binder. If a cheaper resin requires longer hot press time, more scraps, or offers a shorter life at high temperatures, it can increase the actual production cost. The comparison should be made with the same geometry, the same loading, and the same test standard.

PHENOLIC RESINS AND EPOXY RESINS

Epoxy systems can provide high adherence, toughness, and different process options with the appropriate hardener. Phenolic thermosets may excel in some applications with charring and temperature behavior. The curer is not suitable for direct substitution in terms of environment, mechanical targets, and cost.

PHENOLIC RESINS AND UREA-FORMALDEHYDE RESINS

Urea-formaldehyde resins are economical binders, especially in some wood panel applications. Phenolic resins can provide advantages in certain moisture and outdoor resistance targets. Free formaldehyde differs in curing, color, and cost.

PHENOLIC RESINS AND MELAMINE-FORMALDEHYDE RESINS

Melamine-formaldehyde resins can be used for decorative laminate, surface hardness, and different color/finish needs. Phenolic resins perform differently in structural core and heat-resistant binder applications.

PHENOLIC RESINS AND POLYURETHANE RESINS

Flexibility and impact toughness can be adjusted more easily in polyurethanes. In phenolics, cross-linked structure and some temperature performances may be preferred. Isocyanate hazards and phenol/formaldehyde risks should be evaluated separately.

NOVOLAC AND REZOL PHENOLIC RESINS

Novolacs usually require separate curers, while resols can be heat cured with their own reagent groups. It should not be considered the same product on a unit cost or weight basis; gel time, solids, storage behavior and emission are different.

PHENOLIC RESINS AND SILICONE RESINS

Silicone resins can be an alternative in special high-temperature or outdoor applications; elasticity, adherence and cost profile are different from phenolics. Comparative aging is required according to the application.

QUALITY CONTROL AND PURCHASING CRITERIA FOR PHENOLIC RESINS

It should be noted that the resin requested is novolac/remol.
The commercial grade and manufacturer name must be verified.
The solids ratio and solvent type should be specified.
The resin and ready-made HMTA content, if any, should be confirmed.
Free phenol and free formaldehyde measurement limits should be examined.
Viscosity and measurement temperature should be recorded.
Softening point/flow values should be requested for novolax.
PH, gel duration, compatibility with water and storage stability should be determined for Remol.
Curing time and test conditions should be defined.
Filler compliance and target product performance tests should be evaluated.
Storage temperature, shelf life, packaging and batch number should be checked.
TDS, SDS, COA and application standard conformity documents should be requested.

It is not correct to accept two grades as direct equivalents based on a single CAS or resin name.
The purchase specification should include at least the appearance, solids, pH, viscosity and free monomer limits for liquid resol; softening point, flow, free phenol and recommended HMTA requirement for solid novolac. The test standard or in-house method used should also be specified with each parameter. Without this information, the comparison of two numerical values in the catalog is not reliable.
In critical applications, it is recommended that each new batch of resin be tested in a small-scale reference recipe. Even if the input analysis results are within the specification, filler compliance, foam formation or final cure behavior may differ from expected. Material change should not be carried directly to mass production based solely on price advantage.

STORAGE AND HANDLING OF PHENOLIC RESINS

Storage depends on manufacturer grade. Solid novolac should be kept in dry, clean, and sealed packaging; the powder should be protected from moisture, contamination, and high temperature. The viscosity and reactivity of liquid resol systems may change over time in storage. Some resols may require cold storage or limited shelf life.
Whether the resin solution contains solvents, formaldehyde/phenol impurities and other additives may affect the transport classification. A single UN classification should not be given for all phenolic resins. The current SDS Part 14 data of the purchased grade should be taken as basis.
Resealing opened packages, batch tracking, FIFO, and post-wait performance are recommended.
As the storage temperature of the resol rises, it is possible that unwanted condensation will accelerate; therefore, the shelf life depends on the manufacturer's conditions. Some resins may require cold storage, while some powdered novolaks can be stored in normal dry storage. The shelf life of one grade should not be generalized to another phenolic resin.
Whether the liquid product contains water or organic solvents during transportation affects the flammability and transportation classification. For solid resins, dust formation and debris control are important. Up-to-date SDS information of each shipment should be checked.

PHENOLIC RESINS SAFETY INFORMATION

Safety assessment should be made differently for novolac powder, rezol solution and cured phenolic fragment. Products containing free phenol and formaldehyde may pose significant risks to skin/eye health and respiration. Exposure control is important due to the carcinogenic hazard of formaldehyde and the toxic/corrosive effects of phenol.
Formaldehyde, phenol, amine-based products, and other volatiles may be released in curing or superheating. Dust control should be applied in the handling of powdered resins, and local suction should be provided in hot press and reactive binder processes.
Hand and eye protection, appropriate protective clothing, work area ventilation, material labeling, and waste segregation must be determined according to the product SDS. Products must not be considered validated for food/pharmaceutical use. Dry resin and liquid resin solution do not have to have the same hazard classification.
The health hazards of phenol and formaldehyde should not be considered the same as the resin in its fully cured form. Manufacturer classifications regarding inhalation and skin contact are important, especially in the use of liquid/reactive resins containing free formaldehyde or phenol. The fact that formaldehyde is classified as a human carcinogen requires that exposure be controlled by process design. Resin dust, on the other hand, carries the risk of respirable particle exposure and accumulation in the working environment.
Due to the vapors and gases released during hot pressing, SDS descriptions at room temperature should not be relied upon alone. Proper local ventilation and gas emission assessment should be carried out at the process temperature. The safety of the final product should be considered in conjunction with the gas release and exposure controls of the process.

WHAT SHOULD BE CONSIDERED WHEN BUYING PHENOLIC RESINS?

Application: Abrasive, rubbing, casting, veneer, laminate, wood or molding?
Resin type: Novolak, rezol or modified system?
Delivery form: Powder/flakes/pellets/liquid solution?
Solid matter and solvent, if any: How many percentages?
Curing: Does it contain HMTA, do you need additional curer?
Reactivity: What is the gel time and flow target?
What is the free phenol/formaldehyde limit?
What are the storage conditions and temperature constraints?
Is the resin alone or is it a ready-made compound containing filler?
What are the final standards (electrical, fire, mechanical, emission) required?
What are the specific analyses that need to be verified in the COA?

The price is not only based on the price of kilogram resin; the actual resin solid should be compared by considering curing efficiency, wastage, storage life and process cost together.

The initial questions in purchasing should be: is the product novolac or remol, for which process was it developed, what is the delivery form, what is the solids content, and what auxiliary chemical is required for curing? Without answering these questions, an offer that is only given with the name "phenolic resin" is technically incomplete.

In sample comparison, the sample of the same product taken from different packaging may have changed even due to different storage conditions after the package was opened. Therefore, the batch number, sample preparation date and test date should be recorded.

PHENOLIC RESINS SUPPLY FROM ATAMAN KIMYA

Phenolic resins; It is a family of industrial resins that can be evaluated in different novolak and rezol grades for composites, brake friction components, abrasives, casting molds, wood binders, coating, impregnation and molding applications.
Companies that want to get information about the supply of Phenolic Resins from Ataman Kimya can report the target usage area, resin type, form, solid or HMTA content, gel time and viscosity requirement, free phenol/formaldehyde limit, annual usage amount and packaging preference. Current manufacturer, origin, stock, quality certificates, technical suitability and price conditions should be confirmed before ordering.
While preparing the proposal, the temperature limit of the target application, production capacity, existing equipment, desired hardness and mechanical performance, emission limits, if any, and acceptance tests should be specified. Only the total annual consumption amount is not sufficient to determine the appropriate resin grade. If a new grade is to be used instead of the existing resin, technical equivalence should be checked first through the TDS and COA information of the existing product.

FREQUENTLY ASKED QUESTIONS ABOUT PHENOLIC RESINS

What is phenolic resin?

It is a family of polymeric binders formed from the reaction of phenol and mostly formaldehyde.

What is a generic CAS number?

For phenol-formaldehyde resins, general CAS 9003-35-4 is used.

Is phenolic resin one molecule?

No; It is a family of polymers containing different molecular weights and network structures.

What is Novolak?

It is usually a two-stage phenolic pre-polymer that requires separate crosslinker.

What is Resol?

It is usually a single-stage phenolic resin that can be heat cured through its own reagent groups.

How to cure novolax?

Often with the help of suitable curer such as hexamethylentetramine.

What is HMTA?

Hexamethylenetetramine; curing that enables crosslinking in certain novolac resins.

Why is the solids ratio of resin important?

It determines the actual polymer input and the amount of solvent/water.

Is phenolic resin thermoset?

Fully cured phenolic mesh is thermoset; uncured novolak can be processable pre-polymer.

Why is phenolic resin heat resistant?

The aromatic and cross-linked structure can contribute to thermal stability.

Where are phenolic resins used?

In brake pad, abrasive, casting, wood, laminate, veneer and composites.

Are phenolic resins soluble in water?

It depends on the commercial form and type of resin; there is no single universal answer.

Is phenolic resin a substitute for epoxy?

It may be an alternative in some functions, but its curing and mechanical properties are different.

Are phenolic resins flammable?

They are organic materials; fire behavior depends on formulation and test conditions.

Why can phenolic resin be brittle?

High cross-link density may limit deformation ability.

What does the gel duration indicate?

It is the reactivity indicator of the resin to the process of losing its ability to flow at a certain temperature.

Why is free phenol important?

It can have an impact on occupational health, odor, emissions, and product quality.

Why is free formaldehyde important?

It is the critical parameter in terms of health, emissions, regulatory requirement and product performance.

Is there a single melting point for phenolic resin?

No; properties vary according to grade and curing status.

Is liquid rezol and novolac the same?

Nope; their chemistry and curing approach are different.

Are phenolic resins food additives?

No; special grade food contact applications must be documented separately.

How are phenolic resins stored?

According to Grade SDS/TDS conditions, dry/closed and at suitable temperature.

Why do bubbles occur in resin cure?

It can be due to moisture or condensation/volatile products and poor ventilation.

Which quality certificates are required?

TDS, SDS and COA by batch; application conformity certificates if required.

Is Novolak and rezol a one-to-one substitute?

No; curer and process requirements must be re-evaluated.

Why is phenolic resin called thermoset?

Because the cross-linked network is formed during curing, the final material cannot be melted and reshaped like ordinary thermoplastics when heated again.

Can Rezol and novolak be stored in the same way?

Since the reactivity and delivery form may be different, the manufacturer's conditions of each grade must be applied for storage and shelf life.

Why can phenolic resin change color?

The type of synthesis, catalyst, impurities, and chemical reactions that proceed during storage can affect the color. Acceptance evaluation should be made according to the specification of the same grade.

Is the percentage of rosin solid and wet rosin the same?

For example, 10 kg of solution containing 60% solids theoretically contains 6 kg of resin solids. Final composition calculations must take this distinction into account.

How to know if phenolic resin is fully cured?

A single color or hardness observation is not enough. The gel selected for the application is controlled by DSC, DMA, solvent resistance or performance experiments, and the transformation and final properties.

PHENOLIC RESINS – TECHNICAL SUMMARY

Phenolic resins are a family of industrial binder resins obtained from the reaction of phenolic compounds with aldehydes, primarily formaldehyde. The general phenol-formaldehyde polymer registration is CAS 9003-35-4; there is no single exact molecular weight or physical specification for all resin grades.
Novolak systems generally require separate curers, while rezol systems can be self-cured by heat reaction. Both families can be evaluated in friction material, abrasive, wood binder, casting, molding, composite, and special coating applications. Appropriate resin selection should be based on technical properties, reactivity, solids, process, and free monomer content.
Example 1 shows four filler balances in a constant novolac/HMTA ratio; Example 2 shows four glass fiber levels with a constant 60% solids liquid resol feed as 100% complete screening by weight. These formulations are for laboratory evaluation purposes; they are not a substitute for commercial performance, emissions, and product safety approval.
Resin type and grade, free phenol/formaldehyde, gel time, viscosity or softening point, curing conditions and manufacturer TDS/SDS/COA should be evaluated together in the supply.
Technical suitability in phenolic resin projects should be evaluated not on the name of the polymer family, but on the processing properties and final product tests of the selected commercial resin. Novolac resins usually form a network structure with a curer such as HMTA, while rezols form a network structure by condensation of reactive methylol groups. In both systems, volatile matter management, occupational safety and final performance control are critical.