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Polyol resins is the general name for the oligomeric and polymeric raw materials that carry two or more hydroxyl groups (–OH) in the molecule and react with isocyanates to form polyurethane. The term does not describe a single chemical; it covers a broad product family that includes polyether, polyester, acrylic, polycarbonate, polycaprolactone and vegetable oil-based polyols. They are the main component of polyurethane in flexible and rigid foam, paint, adhesive, sealant, elastomer and shoe sole production.
Polyether polyols are obtained by adding propylene oxide and ethylene oxide to initiators such as glycerol, sorbitol, sucrose or amines; with their low glass transition temperatures, resistance to hydrolysis and economical cost, they form the most widely used polyol group in flexible foam, rigid insulation foam and elastomers. About 80 percent of the market value belongs to this group. Their high-functionality grades stand out in sandwich panel and spray insulation.
Polyester polyols are produced by esterifying adipic acid or aromatic acids with glycols and give polyurethane hardness, oil resistance and mechanical strength; they are common in adhesives, footwear, coatings and rigid insulation foam. Acrylic polyols are the basis of two-component polyurethane paints, while polycarbonate and polycaprolactone polyols are the basis of durable coatings and elastomers. These products can be supplied from ATAMAN KİMYA; contacting ATAMAN KİMYA for technical information and requests is recommended.
WHAT ARE POLYOL RESINS?
Polyol resins are oligomeric substances, usually liquid or low-melting, that contain two or more hydroxyl groups in each molecule. They react with isocyanate groups to give urethane bonds and therefore form the alcohol side of polyurethane chemistry.
Many properties of a polyurethane depend on the chemical structure of the polyol used. The chain backbone may be polyether, polyester, polyacrylate, polycarbonate or polycaprolactone; the backbone determines flexibility, hydrolysis resistance, weather resistance and mechanical strength.
Polyols are defined by parameters such as hydroxyl number, functionality, molecular weight, equivalent weight, water content, acid number, viscosity and color. Diols with a functionality of 2 give linear and flexible structures, while those with 3 or more give cross-linked and rigid structures.
Polyethers make up most of the polyols in use; polyesters are the second largest group. Acrylic, polycarbonate and polycaprolactone polyols are chosen for special performance in coatings and elastomers. Polyols obtained from vegetable oils and other renewable raw materials are also increasing their share.
COMMON PRODUCT AND CHEMICAL NAMES OF POLYOL RESINS:
Polyol
Polyol (alternative spelling)
Polyols
Polyols (alternative spelling)
Polyol resin
Polyol resin (alternative spelling)
Polyurethane polyol
Polyurethane raw material polyol
Polyether polyol
Polyether polyol (alternative spelling)
Polypropylene glycol polyol
Polyoxypropylene polyol
Ethylene oxide-capped polyether polyol
Polymer polyol
SAN graft polyol
Polyester polyol
Polyester polyol (alternative spelling)
Aliphatic polyester polyol
Aromatic polyester polyol
Acrylic polyol
Hydroxyl-functional polyacrylate
Polycarbonate diol
Polycaprolactone polyol
Polytetramethylene ether glycol
Vegetable oil-based polyol
Bio-based polyol
Castor oil-based polyol
Rigid foam polyol
Flexible foam polyol
Hydroxyl-terminated oligomer
Diol, triol and tetrol
Polyurethane polyol component
Trade names vary by manufacturer. The Arcol, Voranol, Lupranol and Rokopol series are seen among polyethers, Desmophen and Stepanpol among polyesters, the Setalux and Desmophen A series among acrylic polyols, Polymeg and Terathane for PTMEG, Capa for polycaprolactones, and the Wanol and Puranol series among products of Far Eastern origin.
CAS NO, EC / EINECS NO AND CHEMICAL IDENTIFICATION OF POLYOL RESINS
Product name: Polyol resins
Common abbreviation: POP for polymer polyols; PTMEG for polytetramethylene ether glycol; PCD for polycarbonate diols
Chemical name: Hydroxyl-functional oligomeric and polymeric compounds (polyether, polyester, polyacrylate, polycarbonate, polycaprolactone, etc.)
INCI name: There is no single INCI name for industrial polyurethane polyols; the polypropylene glycols used in cosmetics are registered under separate INCI names in the form PPG-n
CAS No: There is no single number; products carry different numbers depending on their composition, for example 63466-93-3 appears in the safety data sheet of one polyether polyol
EC / EINECS No: Because it is a polymer, no single number is assigned to the polyol itself; the raw materials have separate numbers
Molecular formula: There is no fixed formula; for propylene oxide-based polyethers the general structure is shown as a –[CH2–CH(CH3)–O]n– chain with hydroxyl groups at the ends
Molecular weight: Depends on the product type; in commercial products it ranges, for example, from 260 g/mol to several thousand g/mol, and a range of 300–8,000 g/mol is given for the Capa series
Chemical class: Polymer and oligomer, hydroxyl-functional polyol
Main functions: Polyol component of polyurethane, flexible or rigid segment former, binder
SUB-FAMILIES OF POLYOL RESINS
Polyol resins should be considered not as a single product but as a whole made up of sub-families that differ in chain backbone and field of use. The five main sub-families are summarized below with their chemical structures, typical properties and fields of use.
The values given are example product data published by the manufacturers concerned and general literature ranges. The technical data sheet of each product should be taken as the basis.
1. POLYETHER POLYOLS
Polyether polyols are produced by adding propylene oxide and ethylene oxide to initiators such as glycerol, trimethylolpropane, sorbitol, sucrose or ethylenediamine. The number of hydroxyls on the initiator determines the functionality; it is 2 with glycol and water, 3 with glycerol, 6 with sorbitol and up to 8 with sucrose.
The end groups coming from propylene oxide are mostly secondary hydroxyls and the reaction rate is low. In grades capped with ethylene oxide the proportion of primary hydroxyl rises; these grades react faster with isocyanate and are preferred in flexible foam, elastomers and coatings.
SAN-grafted polymer polyols contain a styrene-acrylonitrile copolymer dispersed as a separate phase within the polyether and give flexible foam hardness and load-bearing capacity. Polytetramethylene ether glycol (PTMEG) is a linear polyether obtained from tetrahydrofuran; it provides hydrolysis resistance and high resilience in elastomers and spandex fiber.
In rigid foam, high-functionality polyethers with sucrose, glycerol, amine or Mannich initiators are used. The hydroxyl number of these grades reaches hundreds of mg KOH/g and they give the foam dimensional stability and flame resistance.
Example manufacturer data, Arcol LG-650 (Covestro, polyether triol): Molecular weight 260; viscosity 820 cps (25 °C); specific gravity 1.09 (20 °C); flash point 198 °C (PMCC); hard coating, potting and thermal barrier applications; shelf life 12 months from delivery.
Example manufacturer data, Arcol LHT-112 and LHT-42 (Covestro, polyether triol): Molecular weight 1,500 and 4,200 respectively; viscosity 280 and 700 cps (25 °C); specific gravity 1.01; flash point 198 and 169 °C; acidified with a low level of phosphoric acid and suitable for isocyanate-terminated prepolymers.
Example manufacturer data, Arcol 11-34 (Covestro, ethylene oxide-capped polyether triol): Molecular weight 4,800; hydroxyl number 33.8–37.2 mg KOH/g; water max. 0.07 percent; acid number max. 0.015 mg KOH/g; color max. 50 Pt·Co; viscosity 820 cps (25 °C); flash point 184 °C.
Example manufacturer data, Voranol 222-029 (Dow, ethylene oxide-capped polyether diol): Nominal molecular weight 4,000; high reactivity and increased hydrophilic character; used in coatings, adhesives, sealants and elastomers.
Example manufacturer data, Lupranol 4002/1 (BASF, SAN-grafted polymer polyol): Solids content about 45 percent; hydroxyl number 29.8 mg KOH/g; viscosity 4,300 mPa·s (25 °C); water 0.05 percent; shelf life at least 6 months from delivery; blended with standard polyethers in flexible slabstock foam.
Example manufacturer data, Polymeg 650, 1000 and 2000 (LyondellBasell, PTMEG): Molecular weight 625–675, 950–1,050 and 1,900–2,100; hydroxyl number 166.2–179.5, 106.9–118.1 and 54.7–57.5 mg KOH/g; viscosity (40 °C) 100–200, 240–360 and 1,180–1,650 cP; water max. 150 ppm.
Example manufacturer data, Desmophen 4050E-LY (Covestro, amine-initiated polyether): Tetrafunctional; hydroxyl number 630 ± 30 mg KOH/g; viscosity 18,500 ± 2,000 mPa·s (25 °C); density about 1.02 g/cm³; continuous lamination and spray applications in rigid foam; 12 months at 10–35 °C.
The propoxylated Mannich polyol Wanol R2470M (Wanhua) is recommended for highly flame-resistant rigid foam, spray foam and building panels; it is stated to improve compatibility in pentane formulations. Voranol RN 411 (Dow) is presented as a general-purpose high-functionality base polyol for continuous lamination, slabstock and pipe insulation.
According to market research, the global polyol market is about USD 40.1 billion in 2024 and about USD 42 billion in 2025. Polyether polyols accounted for about USD 31.9 billion in 2024, roughly 80 percent of the total, and flexible polyurethane foam was the largest application with 39.2 percent.
Main fields of use:
• Flexible slabstock and molded foam, furniture, mattresses and car seats
• Rigid insulation foam, sandwich panels, spray foam and pipe insulation
• Elastomers, spandex fiber, adhesives and sealants
• Water-based adhesives, joint fillers, potting and floor coatings
Strengths:
• Low glass transition temperature and low-temperature flexibility
• Good hydrolysis resistance in alkaline media and low viscosity
• Wide functionality range and economical cost
Limitations:
• Limited resistance to oils, fuels and non-polar solvents
• Mechanical strength of propylene oxide-based grades remains lower than that of polyester and PTMEG
• Need for antioxidants because of susceptibility to thermal and oxidative degradation
2. POLYESTER POLYOLS
Polyester polyols are produced by the polycondensation of aliphatic dicarboxylic acids such as adipic acid or aromatic ones such as phthalic and terephthalic acid with ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol and trimethylolpropane. The water released in the reaction is removed and the acid number is kept low.
Compared with polyethers, polyesters give polyurethane higher hardness, tensile and tear strength, oil and solvent resistance and better thermal oxidation stability. Their resistance to sliding wear and flex fatigue is also high.
The weak point is hydrolytic stability; the ester bond can break over time in hot, humid and especially alkaline conditions. Residual acid and esterification catalyst accelerate this effect. Glycols that carry a side methyl group or are based on neopentyl glycol protect the ester bond sterically and increase resistance.
Branched polyester polyols are used in solvent-borne two-component coatings, while aromatic polyester polyols are used in rigid polyurethane and polyisocyanurate insulation foams. Grades obtained from the glycolysis of recycled PET also belong to this group.
Example manufacturer data, Desmophen 1200 (Covestro, slightly branched polyester): Hydroxyl number 150–174 mg KOH/g (hydroxyl content 4.7–5.3 percent); acid number max. 4; viscosity 16,000–31,000 mPa·s (23 °C); water max. 0.1 percent; color max. 150 Hazen; equivalent weight about 340.
Example manufacturer data, Desmophen 1800 (Covestro, slightly branched polyester): Hydroxyl number 57–63 mg KOH/g (hydroxyl content 1.73–1.91 percent); acid number max. 2; viscosity 19,000–24,000 mPa·s (23 °C); water max. 0.05 percent; equivalent weight about 935; flexible rubber and plastic coatings with Desmodur L.
Example manufacturer data, Desmophen 60WB01 FL (Covestro, flexible slabstock foam polyester): Based on adipic acid, diethylene glycol and trimethylolpropane; hydroxyl number 57–63 mg KOH/g; viscosity 17,400–21,600 mPa·s (25 °C); density 1.19 g/cm³; water max. 0.05 percent; low fogging tendency; 12 months at 20–35 °C.
Desmophen 800 EA (Covestro) is a highly branched, solvent-borne polyester used in fast-drying two-component polyurethane coatings and in the wood and furniture sector. Stepanpol PS-2352 (Stepan) is an aromatic polyester polyol intended for polyisocyanurate board insulation, with high aromatic content, purity and low viscosity.
Desmophen 1200 in this group is generally compatible with most acrylate, polyether, polyester and Desmodur grades; with Desmodur L, HL or IL it gives flexible coatings for metal, wood and plastic. Blend compatibility should be tested before use.
Hydrolysis resistance can be increased through glycol selection. 2-Methyl-1,3-propanediol (MPO) adipate reaches the hydrolysis resistance of neopentyl glycol adipate because the side methyl group protects the ester bond sterically; partially replacing 1,4-butanediol and 1,6-hexanediol with MPO also raises resistance.
Solvent-borne polyesters are thinned with esters, ketones, ether esters and aromatics; the solvents used must be of PU grade and water must be below 0.05 percent. Alcohols react with the polyester and are therefore not used as diluents.
Depending on the intended use, the hydroxyl number is decisive. Linear grades with a low hydroxyl number give flexible, soft films and elastomers, while branched grades with a high hydroxyl number give hard, cross-linked coatings. When the acid number is kept low, stability with isocyanate and hydrolysis resistance increase.
In the European polyol market, the share of polyester polyols in 2025 was reported as about 36.5 percent and that of polyethers as about 63.5 percent.
Main fields of use:
• Solvent-free and solvent-borne polyurethane adhesives, lamination
• Shoe soles, TPU and microcellular elastomers
• Two-component polyurethane coatings, wood and plastic paints
• Rigid PIR board insulation and flexible polyester slabstock foam
Strengths:
• High tensile, tear and abrasion strength
• Good resistance to oils, greases and solvents
• High thermal oxidation stability and wide formulation flexibility
Limitations:
• Sensitivity to hydrolysis in humid and alkaline conditions
• Higher viscosity and melting point than polyethers
• Tendency to stiffen at low temperature
3. ACRYLIC POLYOLS
Acrylic polyols are hydroxyl-functional polyacrylates obtained by free-radical solution copolymerization of hydroxyalkyl (meth)acrylate, alkyl (meth)acrylate and usually less than 20 percent styrene by weight. They are supplied as solutions in solvents such as butyl acetate and xylene.
Hydroxyl content, glass transition temperature and molecular weight are adjusted together. In high-solids grades the hydroxyl number is about 140–175 mg KOH/g, and in medium-solids grades it is in the range of 80–120 mg KOH/g. Keeping the molecular weight below about 2,000 Mn reduces the solvent requirement.
Together with aliphatic polyisocyanates, for example HDI trimer, biuret or IPDI trimer, they give two-component polyurethane paint. The film keeps its gloss, does not yellow in sunlight and resists solvent and gasoline; it stands out in vehicle refinish, industrial furniture and general industrial coatings.
Low-viscosity HDI-based cross-linkers provide fast drying and hard, flexible films. In an acrylic polyol with a high Tg, the theoretical Tg was 75 °C while the measured value was found to be 28 °C; this large difference means high latent hardness and a low solvent requirement.
An acrylic polyol with a low Tg can act like a reactive diluent. In one study, solvent emission was reduced below 1.0 lb/gal (about 120 g/L) with a solvent-free liquid acrylic polyol; the estimated pot life was about 3 hours and the final drying time 135 minutes.
Example manufacturer data, Setalux D A 365 BA/X (allnex): Hydroxyl content 4.5 percent (on non-volatile matter); two-component polyurethane paints with Desmodur N and N 3390; air-drying vehicle refinish paints; shelf life at least 730 days.
Example manufacturer data, Desmophen A 365 BA/X (Covestro, hydroxyl-bearing polyacrylate): Co-reactant in two-component polyurethane paints; good gloss retention, weathering stability, light fastness, chalking resistance and resistance to solvent and gasoline.
Example manufacturer data, Desmophen A 450 BA/X (hydroxyl-functional polyacrylate): Hydroxyl number 33 mg KOH/g (0.8–1.2 percent); acid number 2–6 mg KOH/g; solids 48–52 percent; solvent n-butyl acetate and xylene; viscosity 3,500–5,500 cP (23 °C); fast-drying industrial furniture coating.
In a clearcoat applied at about 66 microns (2.6 mil) over a white automotive basecoat, the solvent-free acrylic polyol system gave weather resistance comparable to the high-VOC commercial reference after 336 hours of accelerated aging and formed a harder film. Under harsh QUV-B conditions without a UV absorber, the commercial system performed better but yellowed more.
VOC limits in environmental regulations are given as between 3.5 and 2.1 lb/gal (about 420 and 250 g/L); high-solids and solvent-free acrylic polyols are therefore gaining importance.
In vehicle paint it can be used blended with other polyacrylate polyols. The amount of polyisocyanate is calculated from the hydroxyl content of the polyol; film properties are sensitive to the NCO/OH ratio, the Tg of the polyol and the curing conditions.
In one-component stoving paints, acrylic polyol is cross-linked with melamine; in water-based systems, water-dispersible grades with neutralized carboxyl groups are used.
Main fields of use:
• Vehicle refinish and automotive clearcoats
• Industrial furniture and wood coatings
• General industrial and metal protection paints
• Plastic surfaces and high-gloss topcoats
Strengths:
• Outstanding outdoor durability and gloss retention
• Fast drying and wide solvent compatibility
• Adjustable Tg and hydroxyl content
Limitations:
• Limited flexibility and impact resistance compared with polyesters
• VOC emission in solvent-borne grades and viscosity increase at high solids
• Limited pot life after the mixture is prepared
4. POLYCARBONATE DIOL AND POLYCAPROLACTONE POLYOLS
Polycarbonate diol is a linear aliphatic polyol that carries carbonate bonds in its main chain. It gives polyurethanes high resistance to hydrolysis, heat, chemicals, weathering and UV light; yellowing is low and gloss is well retained.
Their water absorption is low and their hydrolytic stability is among the highest of the polyol groups. Their performance drops in alkaline media. They are preferred in water-based dispersions, outdoor coatings and thermoplastic polyurethanes.
Polycaprolactone polyols are obtained by ring-opening polymerization of ε-caprolactone. The acid number is low, the molecular weight distribution is narrow and the viscosity is lower than that of adipate-based polyesters. The choice of initiator diol adjusts the final properties.
Compared with adipate polyesters, they resist hydrolysis, weathering and low temperature better; their resistance to oil, fuel and solvents and to cut, tear and flex fatigue is also high.
Example manufacturer data, Desmophen C 1200 (Covestro, linear aliphatic polycarbonate polyester): Hydroxyl content 1.7 ± 0.2 percent (hydroxyl number about 56.1 mg KOH/g); acid number about 0.1; viscosity 16,500 ± 2,500 mPa·s (23 °C); water about 0.05 percent; color max. 120 Hazen; equivalent weight about 1,000.
For Desmophen C 1200, the density is about 1.10 g/ml at 20 °C. The freezing temperature is about 15 °C and it may crystallize at 15 °C and below; the crystals are melted by careful heating to max. 60 °C. It is stored in the original closed container at 0–30 °C, and the manufacturer states specification conformity for 12 months.
The product can be thinned with esters, ketones, aromatic hydrocarbons and ether esters; with polyisocyanates it is used in interior and exterior coatings and sealants, rail vehicle interiors and automotive applications.
Example manufacturer data, Capa series (Perstorp, polycaprolactone): Solvent-free and liquid at room temperature; acid number below 1 mg KOH/g; molecular weight 300–8,000 g/mol; di-, tri- and tetrafunctional. Capa 2043 diol (400 g/mol, hydroxyl number 280, 240 mPa·s); Capa 3050 triol (540 g/mol, 310, 1,190 mPa·s).
Example manufacturer data, Capa 3091 and 4101 (Perstorp): Capa 3091 triol 900 g/mol, hydroxyl number 183, viscosity 1,246 mPa·s; Capa 4101 tetrol 1,000 g/mol, hydroxyl number 218, viscosity 1,850 mPa·s (23 °C). In a manufacturer presentation, adding Capa 3050 is reported to reduce VOC by about 25 g/L at the same application viscosity.
Thanks to their compatibility with acrylics and polyesters, Capa polyols give high gloss and low haze; final hardness, chemical resistance and outdoor durability are good. According to the manufacturer presentation, scratch and abrasion resistance increases in two-component systems and gloss retention under UV-B light improves.
In one-component melamine systems, Capa 2054 (hydroxyl number 204, 550 g/mol) and Capa 2085 (135, 830 g/mol) increase flexibility and impact resistance; the effect depends on both the amount and the chain length. Gloss recovery after scratching is also improved.
Capa 2054 (Ingevity) is a standard low-molecular-weight polycaprolactone diol with primary hydroxyl ends, recommended in water-based, solvent-borne and hot-melt polyurethane adhesives, automotive and footwear.
Main fields of use:
• Exterior and automotive clearcoats
• Water-based polyurethane dispersions
• High-performance TPU and cast elastomers
• Low-VOC two-component coatings and adhesives
Strengths:
• Outstanding resistance to hydrolysis, weathering and UV
• Low yellowing, high gloss retention and scratch resistance
• Low acid number and narrow molecular weight distribution
Limitations:
• Higher cost than standard polyether and adipate polyesters
• Crystallization at low temperature and need for heating before use (in polycarbonate grades)
• Sensitivity to alkaline media in polycarbonate grades
5. VEGETABLE OIL-BASED AND BIO-BASED POLYOLS
Vegetable oil-based polyols are obtained from renewable, readily available and biodegradable raw materials. Castor oil carries hydroxyl naturally; about 87 percent of its fatty acids is ricinoleic acid and its hydroxyl number is about 160 mg KOH/g.
Oils such as soybean, canola and sunflower are chemically converted into polyols. The most common route is epoxidation of the double bonds and ring opening with alcohol, water or acid. Ozonolysis, hydroformylation and reduction, and transesterification with glycerol or pentaerythritol are other routes.
Castor oil can be used directly in some flexible foams; its long side chain provides flexibility and hydrolysis resistance. Epoxidation and ring opening mainly give secondary hydroxyls; through ethoxylation these groups can be converted to primary hydroxyl.
Ozonolysis produces hydroxyl at the ends and lowers the molecular weight, raising Tg and mechanical strength. In transesterification, pentaerythritol is thermally more stable than glycerol and raises the hydroxyl number.
For flexible foam the hydroxyl number is about 28–56 mg KOH/g with a functionality of about 3, and for rigid foam the hydroxyl number is above 200 mg KOH/g with a functionality of 3–6. Published values vary with the oil; soy polyol reaches about 235, palm-based about 102, and some rapeseed polyols 387 mg KOH/g.
The viscosity of soy polyol at 22 °C can be 1.4–3.5 times that of a petroleum-based polyol. This affects mixing and cell structure. Miscibility with petroleum-based polyols and reaction rate are also monitored in the formulation.
In a study from Turkey, polyols were obtained from canola, cotton, sunflower, corn, hazelnut and soybean oil; at the most suitable hydroxyl number, the pores were reported to be homogeneous and open and the cross-link structure strong.
At a low hydroxyl number the pores are closed and soft, and at a high hydroxyl number the material becomes brittle. In camelina and olive oil-based polyols, the cross-link structure, mechanical strength and thermal conductivity were adversely affected.
Phosphorus-modified castor oil polyols increase flame resistance. A thermal conductivity of about 0.045 W/m·K has been reported for a castor oil-based rigid foam. In Europe, sustainability targets are increasing renewable polyol production.
Example manufacturer data, BioPTMG (Mitsubishi Chemical, introduced in 2024): Plant-derived polytetramethylene ether glycol; biomass content above 92 percent. A greenhouse gas emission 20–30 percent lower has been reported for Changhua Chemical's CO₂-based Carnol polyols.
Example manufacturer data, Pluracol 1062 BMBCERT ISCC+ (BASF, polyether polyol): ISCC+ mass balance certified; the safety data sheet states that no classification under GHS is required; flash point above 94 °C; stored at 16–27 °C, protected from moisture.
In rigid foam, full replacement of petroleum-based polyol is limited; pendant oil chains can act as plasticizers. In soy polyol-based foam, thermal conductivity rose from about 24 to 30.5 mW/(m·K) over 150 days.
Main fields of use:
• Flexible foam, furniture, mattresses and car seats
• Rigid insulation foam, roof and refrigerator panels
• Coatings, adhesives and elastomers
• Mass balance products aimed at sustainability
Strengths:
• Renewable raw material and reduced carbon footprint
• Flexibility and hydrophobic character from long side chains
• Blendable with petroleum-based polyols
Limitations:
• Raw material price and supply fluctuation
• High viscosity and limited reactivity
• Risk of decline in long-term insulation performance in rigid foam
CHEMICAL STRUCTURE AND MOLECULAR PROPERTIES OF POLYOL RESINS
The basic functional group of a polyol is the hydroxyl (–OH). The primary hydroxyl (–CH2–OH) at the chain end is more reactive than the secondary hydroxyl (–CH(R)–OH). Ends coming from propylene oxide are secondary, while ends from ethylene oxide capping or from tetrahydrofuran are primary hydroxyl.
The backbone structure determines behavior. The ether bond in a polyether is flexible and resistant to hydrolysis, and the glass transition temperature is low. The ester bond in a polyester is polar, forms hydrogen bonds and gives hardness. Polycarbonate contains the carbonate bond, and polyacrylate has hydroxyalkyl esters hanging from a carbon-carbon backbone.
Functionality is the number of hydroxyls per chain. The hydroxyl number (mg KOH/g) is found from the relation of about 56,100 × functionality ÷ molecular weight; the equivalent weight is 56,100 ÷ hydroxyl number. For example, the equivalent weight of a polyol with a hydroxyl number of 60 is about 935.
Polarity depends on the backbone. As the ethylene oxide proportion rises, a polyether becomes hydrophilic; PTMEG and polyesters are insoluble in water, while acrylic polyols are present as solutions in ester and ketone solvents.
Because hydroxyl and ether oxygens bind water, polyols are hygroscopic. Since water gives carbon dioxide with isocyanate, water content is an important quality parameter. In polyethers, residual base catalyst is neutralized with phosphoric acid.
PHYSICAL AND CHEMICAL PROPERTIES OF POLYOL RESINS
Physical appearance: Polyether polyols are clear and viscous liquids; PTMEG is a white waxy solid at room temperature; polyester polyols are viscous liquids from colorless to pale yellow; acrylic polyols are solvent-borne solutions; polycarbonate diol is a liquid that can crystallize below 15 °C
Chemical character: Hydroxyl-functional, hygroscopic; reacts with isocyanates, melamines and anhydrides; stored closed and dry
Molecular formula: There is no fixed formula; it consists of ether, ester, carbonate or acrylic repeating units depending on the backbone
Molecular weight: Depends on the product type; in example products it varies from 260 g/mol to about 11,000 g/mol
CAS No: There is no single number; it varies with the composition of the product
EC / EINECS No: Because it is a polymer, there is no single number
Hydroxyl number: In example products about 30–630 mg KOH/g for polyethers; 57–174 for polyesters; 135–310 for polycaprolactones; about 56 for polycarbonate diol; 33–175 for acrylic polyols
Functionality: 2–8 for polyethers; 2 and above for polyesters, higher in branched types; di-, tri- and tetrafunctional in the Capa series
Density: In example products about 1.0–1.2 g/cm³; 1.01–1.09 for polyether triols, 1.10–1.19 for polyester and polycarbonate
Viscosity: In example polyether triols 280–820 cps (25 °C); 4,300 mPa·s for the SAN-grafted polymer polyol; 16,000–31,000 mPa·s (23 °C) for polyesters; 3,500–5,500 cP for acrylic polyol solutions
Acid number: Very low in polyethers, max. 0.015 mg KOH/g; about 0.1 in polycarbonate diol; below 1 in polycaprolactones; up to the level of 2–6 in polyester and acrylic polyols
Water content: In polyethers and polyesters, as an example, max. 0.05–0.1 percent; max. 150 ppm in PTMEG
Color: As an example, max. 50 Pt·Co in polyethers; 120–150 Hazen in polyesters and polycarbonate; max. 40 APHA in PTMEG
Solids content: As an example, about 48–52 percent in acrylic polyol solutions; about 100 percent in other polyols
Flash point: 169–198 °C (PMCC) in polyether triols; lower in solvent-borne acrylic and polyester solutions, depending on the solvent
Solubility in water: PTMEG and polyesters are insoluble; polyethers with a high ethylene oxide proportion are compatible with water
Decomposition: Hydrolysis in polyesters, thermal and oxidative degradation in polyethers; in combustion carbon monoxide, carbon dioxide and, in nitrogen-containing products, nitrogen oxides are formed
Reactivity: Reacts with isocyanate; incompatible with acids, oxidizers and isocyanates
Brief Description of Physical Properties
In polyols, the hydroxyl number, functionality, water, acid number, viscosity and color are monitored most. Because these values change with the manufacturer and the batch, the technical data sheet of each product should be taken as the basis.
HOW DO POLYOL RESINS WORK AT THE MOLECULAR LEVEL?
The hydroxyl oxygen of the polyol attacks the carbon atom of the isocyanate group nucleophilically; the urethane bond (–NH–CO–O–) forms through proton transfer. The reaction gives no by-product and links the chains end to end.
The reaction rate is adjusted with tertiary amine and tin catalysts. Because primary hydroxyls react faster, polyethers with ethylene oxide ends give high reactivity.
Functionality determines the network structure. A difunctional polyol and a diisocyanate form a linear chain, while a polyol with a functionality of three or more forms a cross-linked network. The polyol provides the soft segment, and the isocyanate and chain extender provide the hard segment; the two segments give the elastomer its strength through phase separation.
Water remaining in the polyol gives first carbamic acid with the isocyanate, then amine and carbon dioxide. The carbon dioxide inflates the foam, while the amine forms urea with isocyanate. In coatings this reaction causes bubbles, so water content is tightly controlled.
In polyesters, polar ester bonds link the chains through hydrogen bonding; hardness and mechanical strength come from this. Water can split the ester bond into acid and alcohol, and the released acid accelerates degradation. In polyethers, the ether oxygen provides a flexible chain.
In acrylic polyols the hydroxyls are distributed along the chain and a single chain is bound by several isocyanates. With melamine, etherification takes place in the presence of an acid catalyst and methanol is released.
IN WHICH SECTORS ARE POLYOL RESINS USED?
Furniture and mattresses: Flexible slabstock and molded foam, seats and cushions
Insulation, construction and refrigeration: Rigid polyurethane and polyisocyanurate foam, sandwich panels, spray foam, pipe and refrigerator insulation
Automotive: Seat foam, clearcoat, refinish paint, sealants and elastomers
Paint and coating: Two-component polyurethane paints; coatings for wood, metal and plastic surfaces
Adhesives and sealants: Lamination, packaging, footwear and potting applications
Elastomers, footwear and textile: Thermoplastic polyurethane, cast elastomers, shoe soles, synthetic leather and spandex
ARE POLYOL RESINS USED IN COSMETIC, FOOD AND PHARMACEUTICAL APPLICATIONS?
Cosmetics: Industrial polyurethane polyols are not used as cosmetic raw materials. The polypropylene glycols used in cosmetics are special grades registered under separate INCI names in the form PPG-n and should not be confused with industrial polyols.
Food: They are not used directly as food additives. Polyurethane resins and adhesive components in food-contact applications are evaluated in the USA under provisions such as 21 CFR 177.1680 and 175.105; each component must be listed, be GRAS or be approved by notification.
One PTMEG manufacturer states that its product is an acceptable indirect additive under 177.1680, 175.105, 177.1590 and 177.2600; some manufacturers consider food-contact use possible only with written approval. European and Turkish conformity must be verified product by product.
Pharmaceuticals: They are not used as an active ingredient or excipient. If a use such as pharmaceutical packaging, a medical device or an implant is contemplated, product-specific documents, biocompatibility tests and written approval from the manufacturer are required.
INDUSTRIAL APPLICATIONS OF POLYOL RESINS
In flexible foam, a polyether triol of about 3,000–6,000 g/mol is foamed with water, catalyst, silicone surfactant and isocyanate. Polymer polyol provides hardness and load-bearing capacity.
In rigid insulation foam, polyethers with sucrose, sorbitol, amine or Mannich initiators are mixed with aromatic polyesters; the mixture gives low thermal conductivity, dimensional stability and flame resistance.
In coatings, adhesives, sealants and elastomers, acrylic, polyester and polycarbonate polyols are the main component of two-component systems. PTMEG and polyester polyols stand out in cast elastomer and spandex production, and polyester polyols in laminating adhesives.
POINTS TO CONSIDER WHEN USING POLYOL RESINS
• The manufacturer's technical data sheet and safety data sheet should be read before use
• Polyols are hygroscopic; containers should be kept closed, water content should be monitored, and PU-grade solvents with water below 0.05 percent should be used
• The amount of isocyanate should be calculated from the hydroxyl number and water content, and the NCO/OH ratio should be adjusted according to the manufacturer's recommendation
• Reactive substances such as alcohol and water should not be used as diluents; alcohols react with the product in polyester polyols
• Viscosity rises at low temperature; PTMEG and polycarbonate diol should be heated carefully when necessary
• Isocyanate can sensitize the respiratory tract; the work area should be ventilated and personal protective equipment should be used
• Written approval from the manufacturer should be obtained for uses that will contact food, drinking water, cosmetics, medical products and toys
STARTING FORMULATION APPROACHES FOR POLYOL RESINS
The approaches in this section are short starting examples showing how the product family can be evaluated in coating, rigid foam and flexible foam fields. The examples are not verified commercial recipes or final formulas; the proportions are for preliminary laboratory trials and each formulation totals 100%.
Catalyst, water and isocyanate amounts are determined with the manufacturer's recommendation according to the hydroxyl number and water content of the polyol. Since isocyanate can sensitize the respiratory tract, occupational safety and regulatory checks must be made in every application.
EXAMPLE 1: EFFECT OF NCO/OH RATIO ON HARDNESS AND DRYING TIME IN A TWO-COMPONENT ACRYLIC POLYOL COATING
Purpose: To monitor the effect of the NCO/OH ratio on hardness, drying time and solvent resistance in a topcoat made of a hydroxyl-functional acrylic polyol and an aliphatic polyisocyanate.
Starting approach (white topcoat):
Acrylic polyol solution (about 50% solids): about 48.0%
Titanium dioxide: about 22.0%
Solvent blend (butyl acetate and xylene): about 14.5%
Aliphatic polyisocyanate hardener: about 13.0%
UV absorber and light stabilizer additive package: about 1.0%
Flow and surface additive: about 1.0%
Tin catalyst solution: about 0.5%
Application approach:
• The NCO/OH ratio is scanned at about 0.9, 1.0 and 1.1; the hardener is added immediately before use and the paint is applied within the pot life.
• The film cures at constant temperature and humidity; drying time, hardness, gloss and solvent rub resistance are monitored over time.
• Ventilation and eye, hand and respiratory protection are used against solvent and isocyanate vapor.
EXAMPLE 2: EFFECT OF POLYETHER AND AROMATIC POLYESTER POLYOL RATIO ON THERMAL CONDUCTIVITY IN RIGID INSULATION FOAM
Purpose: To monitor the effect of the ratio of high-functionality polyether to aromatic polyester polyol in rigid polyurethane insulation foam on reactivity, cell structure and thermal conductivity.
Starting approach:
Polyol blend (polyether and aromatic polyester): about 36.0%
Flame retardant: about 4.0%
Water: about 0.4%
Amine catalyst: about 0.8%
Silicone surfactant: about 0.8%
Blowing agent (pentane): about 3.5%
Polymeric isocyanate: about 54.5%
Application approach:
• The polyether/polyester ratio is tried at about 70/30, 50/50 and 30/70; the polyol side is premixed and its water content is measured.
• The components are mixed at controlled temperature and poured into a mold; cream, gel and rise times, density and thermal conductivity are monitored.
• Compressive strength, dimensional stability and flame behavior are evaluated; ventilation and protection are provided for the flammable blowing agent and isocyanate.
EXAMPLE 3: EFFECT OF POLYMER POLYOL RATIO ON HARDNESS AND LOAD-BEARING IN FLEXIBLE SLABSTOCK FOAM
Purpose: To monitor the effect of the ratio of polyether polyol to SAN-grafted polymer polyol in flexible polyurethane slabstock foam on hardness, load-bearing and cell openness.
Starting approach:
Polyether triol: about 44.0%
SAN-grafted polymer polyol: about 19.0%
Isocyanate: about 33.5%
Water: about 2.6%
Silicone surfactant: about 0.6%
Amine catalyst: about 0.1%
Tin catalyst: about 0.2%
Application approach:
• The polymer polyol share is tried at about 0%, 30% and 50% of the total polyol; the isocyanate amount is adjusted via the index according to the manufacturer's recommendation.
• The mixture is mixed quickly and poured as free-rise; cream time, rise, collapse and cell openness are monitored.
• Density, hardness and compression set are measured on the cured foam; ventilation is provided against isocyanate vapor.
SIMILAR PRODUCTS AND ALTERNATIVES TO POLYOL RESINS
Polyol types can be alternatives to one another. Polyethers resist hydrolysis and low temperature, while polyesters stand out in mechanical strength and oil resistance. PTMEG gives high resilience and abrasion resistance in elastomers, while polycaprolactone and polycarbonate diol are preferred in demanding outdoor and humid environments.
Amine-terminated polyethers carry amine instead of hydroxyl and react quickly with isocyanate to give polyurea; they are used in spray coating and fast-curing systems.
Polyaspartic esters are products containing secondary amines, such as the Desmophen NH series, and form high-solids, fast-drying coatings with aliphatic isocyanate.
Epoxy resin and hardener systems provide adhesion and chemical resistance but may show a tendency to chalk outdoors. Hydroxyl-functional oil-free polyester resins, bonded with melamine and isocyanate, can be used instead of polyol in coil coating and general industrial paint.
No alternative replaces polyol in every application. Performance, cost, compatibility and regulation should be evaluated together.
QUALITY CONTROL AND PURCHASING CRITERIA FOR POLYOL RESINS
• Hydroxyl number and equivalent weight, for example by ASTM D4274, ISO 14900, ISO 4629-2 or ISO 6796 methods
• Water content (Karl Fischer, DIN 51777) and acid number (ISO 2114)
• Viscosity (ISO 3219, ASTM D4878), density and color (Hazen, APHA)
• Functionality, molecular weight distribution; solids content and dispersion stability in polymer polyols
• Solids content, solvent and hydroxyl content in acrylic polyols; iron and antioxidant level in PTMEG
Typical values of manufacturers are not considered binding specifications unless confirmed in a written contract. A certificate of analysis, safety data sheet and technical data sheet should be requested for every batch.
STORAGE AND TRANSPORT OF POLYOL RESINS
Polyols are stored in the original, tightly closed container in a dry environment; because they are hygroscopic, they are protected from moisture. In example products, storage ranges are given as 0–30 °C, 10–35 °C, 15–60 °C and 20–35 °C; shelf life is generally 9–12 months, and at least 6 months has been stated for one polymer polyol.
At low temperatures viscosity rises markedly. PTMEG is a waxy solid and is heated before use; polycarbonate diol can crystallize at 15 °C and below, and the crystals are melted by careful heating to max. 60 °C. Carbon steel, stainless steel, HDPE, LDPE, tin-plate and glass containers were found suitable in one example safety data sheet.
Transport classification depends on the product. In one example polyether polyol safety data sheet, the product is not considered a dangerous good under USDOT, IMDG and IATA rules. Solvent-borne acrylic and polyester solutions may fall into the flammable liquid class depending on the solvent; section 14 of the safety data sheet of each product should be checked.
SAFETY INFORMATION FOR POLYOL RESINS
Polyether polyols generally have low toxicity and high flash points. One example polyether polyol safety data sheet states that the product is not classified under GHS, the flash point is above 94 °C and there is no known occupational exposure limit.
A PTMEG manufacturer reports that its product is stable and of low toxicity and that slight irritation may be seen on eye and skin contact. In solvent-borne acrylic and polyester solutions, classification is determined by the solvent and mostly includes a flammable liquid hazard.
For personal protection, chemical-resistant gloves, a face shield or goggles where splashing is possible, and a respirator suitable for organic vapor when necessary are used; local exhaust ventilation is recommended.
It is incompatible with acids, oxidizing agents and isocyanates; in the example form, temperatures below 0 °C are to be avoided. In fire, water spray, dry powder, carbon dioxide or foam is used and a water jet is not recommended. In combustion carbon monoxide, carbon dioxide, nitrogen oxides and hydrogen cyanide may form.
Waste is disposed of according to local regulations and must not be discharged into the sewer. Empty drums are not cut or burned. In systems used together with isocyanate, the safety data sheet of the isocyanate should also be taken as the basis.
This section is for general information; it does not replace the safety data sheet.
WHAT SHOULD BE CONSIDERED WHEN BUYING POLYOL RESINS?
• Correct product identity: polyether, polyester, acrylic, polycarbonate, polycaprolactone or vegetable oil-based; diol, triol or higher functionality; ethylene oxide-capped or not; polymer polyol
• Technical specifications: hydroxyl number, functionality, water content, acid number, viscosity, color
• Suitability for the intended use: flexible or rigid foam, coating, adhesive, elastomer; the isocyanate and process to be used
• Packaging, shelf life, batch consistency and certificate of analysis
• The supplier's technical support, regulatory requirements and conformity documents for food-contact uses
• Total cost of supply: cost per hydroxyl number or equivalent weight, isocyanate consumption, waste and storage should be evaluated together
SUPPLY OF POLYOL RESINS FROM ATAMAN KİMYA
Which polyol type, grade and packaging can be supplied varies by product. Product selection is made according to the application, the isocyanate to be used and the desired performance.
For up-to-date information on stock, origin, documents, delivery time and technical support, contacting ATAMAN KİMYA is recommended.
FREQUENTLY ASKED QUESTIONS ABOUT POLYOL RESINS
What are polyol resins?
They are a group of oligomeric and polymeric raw materials that carry two or more hydroxyl groups and form polyurethane with isocyanate.
What does polyol resin mean?
The name comes from the presence of more than one alcohol (hydroxyl) group in the molecule.
What is the CAS number of polyol resins?
There is no single number; it varies with the composition of the product.
What is the EC / EINECS number of polyol resins?
Because they are polymers, there is no single number; the raw materials have separate numbers.
What is the chemical formula of polyol resins?
There is no fixed formula; they consist of ether, ester, carbonate or acrylic repeating units depending on the backbone.
What is the INCI name of polyol resins?
Industrial polyurethane polyols do not have a single INCI name; polypropylene glycols for cosmetic purposes are known by their own INCI names in the form PPG-n.
Are polyol resins used in cosmetics?
Industrial types are not used; only special registered grades for cosmetic purposes are used.
What is the difference between polyether polyols and polyester polyols?
Polyethers are more resistant to hydrolysis and low temperature; polyesters give higher mechanical strength and oil and solvent resistance.
What are polyol resins used for?
They are used as the hydroxyl component in the production of polyurethane foam, coatings, adhesives, sealants and elastomers.
In which sectors are polyol resins used?
They are used in furniture, insulation and construction, automotive, paint, adhesives, footwear, textile and white goods.
How do polyol resins react with isocyanate?
The hydroxyl oxygen attacks the isocyanate carbon and a urethane bond forms; a catalyst accelerates the reaction.
What are polyol resins good for?
They determine the flexible or rigid structure, strength and chemical resistance of the polyurethane.
How do polyol resins work in foam production?
The polyol builds the chain with isocyanate, while water produces carbon dioxide to create foaming.
Are polyol resins soluble in water?
Generally not; polyethers with a high ethylene oxide proportion are compatible with water.
How much polyol is used in foam production?
The amount depends on the application and hydroxyl number; in example starting formulations the polyol is between about one third and two thirds of the total mixture, and the exact proportion is determined with the manufacturer's recommendation.
Are polyol resins a hazardous substance?
GHS classification was not required for the example polyether polyols; solvent-borne types may be flammable and separate precautions are needed when working with isocyanate.
Why is water content important in polyol resins?
Water reacts with isocyanate to form carbon dioxide and urea; this causes bubbles, foaming and unexpected isocyanate consumption.
Are polyol resins registered under REACH?
Polymers are generally exempt from registration; it must be shown that the product meets the polymer definition, and the monomers must be evaluated separately.
What is the physical appearance of polyol resins?
They are mostly clear, viscous liquids; PTMEG is a waxy solid and acrylic polyols are in solution.
What is the UN number of polyol resins?
Since the example polyether polyols are not considered dangerous goods, there is no UN number; for solvent-borne solutions it depends on the solvent.
Why is the hydroxyl number important in polyol resins?
The hydroxyl number determines the required amount of isocyanate and the hardness of the network structure.
What does the price of polyol resin depend on?
It depends on the backbone type, functionality, molecular weight, and crude oil and raw material prices.
Is there an alternative to polyol resins?
Yes; amine-terminated polyethers, polyaspartic esters and epoxy systems can be alternatives in some applications.
How should polyol resins be stored?
In the original closed container, in a dry environment, within the temperature range in the product document and away from moisture.
Which documents should be requested when buying polyol resins?
Safety data sheet, technical data sheet and certificate of analysis.
Which technical properties are important when buying polyol resins?
Polyol type, hydroxyl number, functionality, water content, acid number, viscosity and shelf life.
POLYOL RESINS – TECHNICAL SUMMARY
Chemical name: Polyol (hydroxyl-functional oligomeric and polymeric compounds)
CAS number: There is no single number; it varies with the composition of the product
Chemical class: Polymer and oligomer, hydroxyl-functional polyol
Main functions: Polyol component of polyurethane, flexible or rigid segment former, binder
Important fields of use: Flexible and rigid foam, two-component polyurethane paint, adhesive, sealant, elastomer
Parameters critical for quality control: Hydroxyl number, functionality, water content, acid number, viscosity
Storage: In the original closed container, in a dry environment, within the temperature range in the product document.
