EPOXY RESINS

Epoxy Resins are a class of reactive thermosetting polymers containing epoxide (oxirane) functional groups, most commonly produced by the polycondensation reaction of bisphenol A (BPA) with epichlorohydrin (ECH) in the presence of a base catalyst, yielding a range of products from low-viscosity liquid monomers (BADGE/DGEBA, MW ~340 g/mol) to high-molecular-weight solid resins (MW >1,400 g/mol), widely used as coatings, adhesives, composite matrices, encapsulants, laminates, and construction materials due to their outstanding mechanical strength, chemical resistance, electrical insulation, thermal stability, and adhesion to virtually all substrates.
Epoxy Resins are uncured prepolymers that require reaction with a hardener (curing agent) such as amines, anhydrides, polyamides, mercaptans, or polysulfides to form a three-dimensional cross-linked thermoset network; the type and ratio of curing agent selected determines the pot life, cure speed, and the mechanical, thermal, chemical, and electrical properties of the cured system, and the epoxide equivalent weight (EEW) of the Epoxy Resins is the key parameter used to calculate the stoichiometric ratio with the curing agent.
Epoxy Resins encompass a broad family of chemistries including bisphenol A type (most common), bisphenol F type, novolac epoxy, cycloaliphatic epoxy, aliphatic epoxy, glycidylamine epoxy, and bio-based epoxy types, each offering distinct viscosity profiles, functionality levels, cured glass transition temperatures (Tg), and performance profiles suited to specific high-performance applications including aerospace composites, electronics packaging, civil engineering reinforcement, wind energy, automotive, marine, and protective coatings.

CAS Number: 25068-38-6 (BPA-epichlorohydrin polymer, MW avg. 700); 1675-54-3 (BADGE/DGEBA monomer)
EC Number: 500-033-5 (polymer); 216-823-5 (BADGE monomer)
Molecular Formula: C₁₈H₂₁ClO₃ (representative unit); C₂₁H₂₄O₄ (BADGE monomer)
Molecular Weight: Variable (340 g/mol for BADGE monomer; 700–10,000+ g/mol for oligomers and polymers)

Synonyms: Epoxy Resin, Epoxide Resin, Polyepoxide, Bisphenol A Epoxy Resin, BPA Epoxy Resin, Bisphenol A Diglycidyl Ether (BADGE), DGEBA, Bisphenol A-Epichlorohydrin Copolymer, Poly(bisphenol-A-co-epichlorohydrin), Reaction Product of Bisphenol A and Epichlorohydrin, Epon 828, Epon 1001, Epon 1002, Epon 1004, Araldite GY 250, Araldite GY 783, D.E.R. 330, D.E.R. 331, D.E.R. 332, D.E.R. 337, D.E.R. 661, D.E.R. 664, ERL 2795, Epikote 828, Epikote 1001, Epiclon 840, Epiclon 850, CAS 25068-38-6, CAS 1675-54-3

Epoxy Resins are produced by the reaction of bisphenol A with excess epichlorohydrin in the presence of sodium hydroxide catalyst; when epichlorohydrin is used in large excess relative to bisphenol A, the product is predominantly the low-MW BADGE monomer (MW ~340, n≈0); as the ratio of bisphenol A to epichlorohydrin increases, higher-molecular-weight oligomers and solid resins with increasing n values are produced, with liquid resins (n=0–1, MW 340–700, EEW 170–280) being the most commercially significant grades for coatings and composites.
Epoxy Resins based on bisphenol A contain a characteristic structural motif of two glycidyl ether groups at the chain termini connected through bisphenol A repeat units, with the epoxide groups available for ring-opening cross-linking reactions with nucleophilic curing agents; the hydroxyl groups on higher-MW oligomers contribute to adhesion, flexibility, and reactivity with isocyanates and anhydrides.

Epoxy Resins are classified under GHS with Hazard Statements H315 (skin irritation), H317 (may cause allergic skin reaction), H319 (causes serious eye irritation), and H411 (toxic to aquatic life with long-lasting effects) for the polymer grade (MW ≤700, CAS 25068-38-6); the BADGE monomer (CAS 1675-54-3) carries additional classification as H361 (suspected of damaging fertility or the unborn child) and is listed on the ECHA SVHC Candidate List as a substance of very high concern due to reproductive properties.
Epoxy Resins have excellent electrical insulating properties (volume resistivity >10¹⁴ Ω·cm, dielectric constant ~3.5–4.5 at 1 MHz), high adhesive strength to metals (shear strength >20 MPa), high compressive strength of cured systems (>100 MPa), and glass transition temperatures (Tg) ranging from approximately 60°C for aliphatic amine-cured systems to greater than 200°C for anhydride-cured aromatic systems.

Uses of Epoxy Resins:
Epoxy Resins are used as the primary binder in protective coatings for metals, concrete, and other substrates in applications including marine coatings, automotive primers, industrial maintenance coatings, pipeline coatings, tank linings, floor coatings, and anti-corrosion paints, providing superior adhesion, chemical resistance, abrasion resistance, and barrier properties compared to conventional alkyd and polyurethane coatings.
Epoxy Resins are used as structural adhesives in aerospace, automotive, electronics, construction, and marine applications to bond dissimilar substrates including metals, composites, ceramics, and glass, providing high lap shear strength, toughness, fatigue resistance, and durability under extreme temperature and environmental conditions; commercial one-component (1K) heat-cure and two-component (2K) room-temperature-cure systems are available.

Epoxy Resins are used as the matrix resin in fiber-reinforced polymer (FRP) composite materials reinforced with carbon fiber, glass fiber, and aramid fiber for aerospace structures (fuselage panels, wings, nacelles), wind turbine blades, pressure vessels, automotive body panels, sporting goods, and civil infrastructure reinforcement, providing the strength, stiffness, fatigue resistance, and temperature performance required for high-performance structural applications.
Epoxy Resins are used in the electronics and electrical industries for the encapsulation and potting of semiconductors, integrated circuits, transformers, capacitors, and printed circuit boards (PCBs, including copper-clad glass fiber laminates using FR-4 laminate), providing electrical insulation, moisture protection, mechanical support, and thermal dissipation.

Epoxy Resins are used in civil engineering and construction applications including grouting, anchoring, crack injection, concrete repair, carbon fiber reinforced polymer (CFRP) strengthening of bridges and buildings, precast concrete bonding, floor coatings and self-leveling terrazzo, and tunnel lining systems, providing high adhesion to concrete, low shrinkage, and compressive strengths exceeding 70–100 MPa.
Epoxy Resins are used as tooling resins in the production of molds, jigs, fixtures, patterns, and master models for aerospace, automotive, and composite manufacturing, where their low shrinkage on cure, dimensional stability, and machinability produce accurate, durable, and thermally stable tooling surfaces.

Epoxy Resins are used in the formulation of powder coatings for appliances, automotive components, pipelines, furniture, and architectural metalwork, where solid epoxy resin grades (EEW 650–3,000) are melt-mixed with solid amine or anhydride curing agents, extruded into a powder, and electrostatically applied before oven curing to produce a smooth, durable, and solvent-free coating.
Epoxy Resins are used as can and container linings for food and beverage packaging including metal cans, drums, and caps to prevent corrosion, contamination, and metallic taste, although BPA migration concerns have led to the development of BPA-free alternative lining chemistries.

Epoxy Resins are used as the resin matrix in glass fiber-reinforced pipes, tanks, vessels, and ducts for chemical processing, water and wastewater treatment, desalination, and oil and gas applications, providing corrosion resistance, light weight, and design flexibility compared to steel and fiberglass alternatives.
Epoxy Resins are used in semiconductor and microelectronics manufacturing as underfill materials, die attach adhesives, and molding compounds, where their low coefficient of thermal expansion (CTE), high purity, low ionic impurity levels, and electrical insulation are critical for reliable long-term performance of electronic assemblies.

Epoxy Resins are used in the production of electrical laminates (prepregs) for multilayer PCBs and high-frequency circuit boards, and in the formulation of epoxy-based encapsulants and conformal coatings for protection of electronic assemblies against moisture, dust, chemical attack, and mechanical vibration.
Epoxy Resins are used in art and crafts (epoxy resin art, jewelry casting, river tables, woodworking) as casting and coating resins that produce optically clear, durable, glossy surfaces with excellent UV stability when formulated with appropriate photoinitiators and UV absorbers.

Epoxy Resins are used as binders for solid rocket propellants, as matrix resins for ablative heat shields and thermal protection systems in aerospace, and as sealants for pressure vessels, hydraulic systems, and fuel tanks in defense and aerospace applications.
Epoxy Resins are used in the formulation of electrically conductive adhesives containing silver or carbon fillers, thermally conductive compounds containing aluminum oxide or boron nitride fillers, and magnetic compounds for assembly of electronic components, bonding of magnets, and thermal management in LED lighting and power electronics.

Benefits or Advantages of Epoxy Resins:
Epoxy Resins provide outstanding adhesion to virtually all substrates including metals, ceramics, glass, wood, concrete, and most plastics without the need for primers, forming strong, durable bonds that resist peeling, delamination, and environmental attack across a wide temperature range.
Epoxy Resins exhibit very low shrinkage on cure (typically 1–4% volume) compared to polyesters (6–8%) and other thermosetting systems, resulting in better dimensional accuracy, lower residual stress, reduced microcracking, and improved fit and finish in composite and tooling applications.

Epoxy Resins are highly versatile in their formulation — viscosity can be adjusted from very low (reactive diluents) to paste or solid, pot life can range from minutes to hours, cure temperature can range from ambient to 180°C+, and cured properties can be tailored from flexible rubbers to rigid high-Tg thermosets — through selection of resin grade and curing agent system.
Epoxy Resins have excellent chemical resistance to acids, alkalis, solvents, fuels, and hydraulic fluids when fully cured, making them suitable for demanding corrosion protection, chemical plant, and marine applications where other coating and adhesive systems would fail.

Epoxy Resins are compatible with a wide range of fillers, pigments, tougheners (rubber particles, core-shell particles), reactive diluents, accelerators, flame retardants, and specialty additives, enabling formulation of systems precisely tailored to application-specific performance requirements.
Epoxy Resins have a long history of use in demanding structural applications with well-understood structure-property relationships, extensive design databases, and established industry standards (ISO, ASTM, EN) supporting their use in certified aerospace, civil engineering, and electrical applications.

Features of Epoxy Resins:
Epoxy Resins range from clear, pale-yellow, low-viscosity liquids (liquid BPA epoxy, EEW 170–280 g/eq, viscosity 5,000–15,000 mPa·s at 25°C) to amber semi-solids (MW 900–1,400) to light yellow to tan solids (MW >1,400, EEW 450–3,000+) at ambient temperature, with density approximately 1.15–1.20 g/cm³ for liquid grades.
Epoxy Resins are supplied as Part A (resin) in a two-component system and must be combined with a stoichiometric or near-stoichiometric quantity of Part B (curing agent/hardener) calculated from the EEW of the resin and the active hydrogen equivalent weight (AHEW) or anhydride equivalent weight of the curing agent, with thorough mixing essential for complete cure and optimal properties.

Epoxy Resins are thermally stable up to approximately 150–200°C when cured with high-performance hardeners (depending on Tg), have low flammability in the cured state (LOI ~22–28%), and can be further flame-retarded with halogenated, phosphorus, or nitrogen-based flame retardants for electronics and construction applications requiring UL94 V-0 classification.
Epoxy Resins in the uncured liquid state are potentially sensitizing to skin upon repeated contact due to the low-MW BADGE monomer, and all direct skin contact should be avoided; once fully cured, epoxy systems are inert and non-sensitizing.

Chemical Properties of Epoxy Resins:
Epoxy Resins based on bisphenol A consist of the repeating unit [–O–C₆H₄–C(CH₃)₂–C₆H₄–O–CH₂–CH(OH)–CH₂–]n with terminal glycidyl ether groups –O–CH₂–CH–CH₂ (epoxide), where n is the average number of repeat units determining molecular weight, viscosity, EEW, and physical state (liquid for n<2, solid for n>2).
Epoxy Resins cure by ring-opening polyaddition of the epoxide groups with active hydrogen groups (–NH₂, –NH, –OH, –COOH, –SH) on the curing agent, or by ring-opening homopolymerization initiated by Lewis acids, Lewis bases, or photoinitiators; the cured network is an amorphous thermoset with Tg determined by crosslink density, backbone rigidity, and curing agent type.

Epoxy Resins are incompatible with strong oxidizing agents, strong bases, strong acids, and reactive compounds capable of ring-opening the epoxide group prematurely; liquid grades are flammable (flash point ~160–200°C for unmodified liquid BPA epoxy), and all grades should be kept away from heat, sparks, and ignition sources during storage and processing.
Epoxy Resins hydrolyze slowly under strongly acidic or alkaline aqueous conditions, and the glycidyl ether linkage is susceptible to photodegradation under UV irradiation in the uncured state; UV-stabilized grades or topcoating with UV-resistant coatings is recommended for outdoor applications.

Production of Epoxy Resins:
Epoxy Resins are produced commercially by the reaction of bisphenol A with a molar excess of epichlorohydrin in the presence of sodium hydroxide catalyst, proceeding through a glycidylation mechanism in which the phenolic hydroxyl groups of bisphenol A react with epichlorohydrin to form chlorohydrin intermediates that cyclize to epoxide groups; liquid grades (n≈0, MW ~340–380) require a large excess of epichlorohydrin, while solid grades (n=2–25+) are produced by advancing the liquid resin with additional bisphenol A using a triphenylphosphine or other catalyst.
Epoxy Resins are also produced by specialty chemistries including glycidylation of bisphenol F (lower viscosity, higher chemical resistance), novolac phenols (higher functionality, higher Tg), aliphatic diols and polyols (lower viscosity reactive diluents), cycloaliphatic alcohols (outdoor durability), glycidylamines (very high Tg aerospace grades), and bio-based phenols (sustainably sourced alternatives), expanding the family to cover the full spectrum of performance requirements.

Epoxy Resins quality is characterized by epoxide equivalent weight (EEW, g/eq), viscosity (mPa·s at 25°C), color (Gardner or Hazen), hydrolyzable chlorine content (ppm), total chlorine content (ppm), and density; major global producers include Huntsman (Araldite), Olin (D.E.R./Epon), Hexion (Epikote/Epon), DIC (Epiclon), Nan Ya Plastics, and Kukdo Chemical.
Epoxy Resins are supplied as single-component resins or as pre-formulated two-component kits in metal cans, pails, drums, and bulk containers; liquid grades are typically packed in 200 kg steel drums or 1,000 kg IBCs; solid grades in 25 kg paper or PE bags or flake form.

Material Safety Data Sheet (MSDS) of Epoxy Resins:

Handling of Epoxy Resins:
Epoxy Resins should be handled in accordance with good industrial hygiene practices and in compliance with the applicable Safety Data Sheet; the primary hazard in handling uncured Epoxy Resins is skin sensitization from repeated dermal contact with the low-MW BADGE monomer, which requires wearing chemical-resistant protective gloves at all times.
Epoxy Resins handling requires adequate local exhaust ventilation to control vapor and aerosol exposure, particularly during spraying, heating, or sanding operations; contaminated work clothing must not leave the workplace and must be laundered before reuse.

SDS of Epoxy Resins:

Stability and Reactivity of Epoxy Resins:

Chemical stability:
Epoxy Resins are stable under recommended storage conditions; liquid grades should be protected from excessive heat and freezing; solid grades from moisture.

Reactivity:
Epoxy Resins react exothermically with amine, anhydride, mercaptan, and other curing agents; the reaction rate and exotherm increase with temperature and batch size.
Epoxy Resins may react with strong acids, strong alkalis, and strong oxidizing agents.

Conditions to avoid:
Excessive heat above 60°C during storage (accelerates viscosity increase and premature gelation).
Freezing of liquid grades (may cause permanent cloudiness or phase separation).
Contact with strong acids, strong alkalis, and oxidizing agents.
Large unmixed batches at elevated temperatures (exotherm risk).
Prolonged skin contact with uncured liquid resin.

Incompatible materials:
Curing agents (amines, anhydrides, mercaptans) — react on contact.
Strong oxidizing agents.
Strong acids.
Strong bases.

Hazardous decomposition products:
Carbon monoxide (CO).
Carbon dioxide (CO2).
Phenol vapors and bisphenol A.
Epichlorohydrin (thermal decomposition).
Irritating organic fumes.

Handling and Storage of Epoxy Resins:

Handling:
Wear chemical-resistant gloves (nitrile ≥0.4 mm or butyl rubber) at all times when handling uncured Epoxy Resins; this is the critical PPE requirement.
Use local exhaust ventilation where vapors or aerosols may be generated.
Avoid skin and eye contact; wear safety glasses or goggles.
Wash hands thoroughly after handling; remove contaminated clothing immediately.
Prevent formation of aerosols; do not spray in enclosed spaces without appropriate respiratory protection.
Keep away from heat sources, sparks, and open flames.

Storage:
Store in original sealed containers in a cool, dry, well-ventilated area at 15–25°C.
Protect liquid grades from freezing and from temperatures above 50–60°C.
Keep away from curing agents, strong oxidizers, acids, and alkalis.
Storage stability: typically 12–24 months for liquid grades, 24 months for solid grades in original sealed containers.

First Aid Measures of Epoxy Resins:

Inhalation:
Remove affected person to fresh air; provide fresh air and ventilation.
If vapor or aerosol causes respiratory irritation, coughing, or asthma-like symptoms, seek medical attention; sensitized persons may react to very low vapor concentrations.

Skin contact:
Remove contaminated clothing immediately; wash affected skin thoroughly with soap and large quantities of water.
Seek medical advice if redness, itching, rash, or allergic reaction develops — skin sensitization may occur from repeated exposure to uncured Epoxy Resins.

Eye contact:
Rinse cautiously with clean water for at least 15 minutes while holding eyelids open.
Remove contact lenses if present and easy to do.
Seek medical attention if irritation, redness, or pain persists.

Ingestion:
Rinse mouth with water; do not induce vomiting unless instructed by medical personnel.
Seek medical advice; oral LD50 of BPA epoxy resin is >5,000–11,400 mg/kg in rats, indicating low acute oral hazard.

Firefighting Measures of Epoxy Resins:

Suitable extinguishing media:
Foam, dry chemical powder, carbon dioxide, or water spray.

Specific hazards:
Liquid Epoxy Resins are combustible with flash points typically >160°C; cured resins are not readily flammable.
Thermal decomposition or combustion of Epoxy Resins may produce carbon monoxide, carbon dioxide, phenol vapors, and irritating organic fumes.

Protective equipment for firefighters:
Wear self-contained breathing apparatus (SCBA) and full chemical protective clothing.

Firefighting instructions:
Cool exposed containers with water spray; prevent contaminated firefighting water from entering drains or waterways.

Accidental Release Measures of Epoxy Resins:

Personal precautions:
Avoid skin contact with spilled uncured Epoxy Resins; wear gloves and eye protection immediately.
Spilled liquid Epoxy Resins create a severe slipping hazard; contain and absorb immediately.

Environmental precautions:
Prevent Epoxy Resins from entering drains, sewers, soil, or waterways; they are classified as aquatic hazard (H411 — toxic to aquatic life with long lasting effects).

Methods for cleaning up:
Absorb liquid spill with sand, vermiculite, or other inert absorbent; collect into labeled waste containers.
Do not use sawdust or other combustible absorbents.
Dispose of waste in accordance with local regulations.

Exposure Controls / Personal Protective Equipment of Epoxy Resins:

Engineering controls:
Provide local exhaust ventilation at all points of vapor or aerosol generation; use closed systems for large-scale handling where possible.
Install emergency eyewash stations and safety showers near handling areas.

Eye protection:
Wear safety glasses with side shields or chemical splash goggles where splashing is possible.

Hand protection:
Wear nitrile rubber gloves ≥0.4 mm for short-term/splash; butyl rubber ≥0.7 mm for prolonged contact; barrier creams may supplement but do not replace gloves.

Skin and body protection:
Wear chemical-resistant apron and long-sleeved work clothing; remove contaminated clothing immediately.

Respiratory protection:
Normally not required under ambient conditions for liquid resins; use organic vapor and particulate respirator when spraying or sanding cured material.

Hygiene measures:
Wash hands and forearms thoroughly after handling Epoxy Resins; do not touch face with contaminated gloves; change contaminated clothing before leaving the workplace.

Identifiers of Epoxy Resins:
CAS Number: 25068-38-6 (BPA epoxy polymer, MW avg. 700); 1675-54-3 (BADGE monomer)
EC Number: 500-033-5 (polymer, NLP); 216-823-5 (BADGE monomer)
ECHA InfoCard: 100.015.294 (BADGE); polymer grades registered under REACH
IUPAC Name (BADGE): 5,5-Dimethyl-3,7-dioxa-1,9(2)-bis(oxirana)-4,6(2,4)-dibenzenanonaphane
Molecular Formula: C₁₈H₂₁ClO₃ (representative unit); C₂₁H₂₄O₄ (BADGE monomer)
Molecular Weight: 340 g/mol (BADGE); variable (polymer)
PubChem CID: 2286 (BADGE monomer)
InChIKey (BADGE): LCFVJGUPQDGYKZ-UHFFFAOYSA-N
GHS Signal Word: Warning
GHS Hazard Statements: H315 (skin irritation), H317 (may cause allergic skin reaction), H319 (serious eye irritation), H411 (aquatic chronic 2)
SVHC: BADGE monomer (CAS 1675-54-3) — H361, reproductive concern
Key Parameters: EEW (g/eq), Viscosity (mPa·s at 25°C), Gardner Color, Hydrolyzable Chlorine (ppm)

Properties of Epoxy Resins:
Physical state: Liquid (low-MW grades); semi-solid or solid (high-MW grades)
Appearance: Clear to pale yellow liquid or amber to yellow solid
Odor: Very mild, slightly phenolic
Density (liquid grades): ~1.15–1.20 g/cm³ at 25°C
Viscosity (liquid BPA epoxy, EEW 185): ~12,000–15,000 mPa·s at 25°C
EEW range: 170–280 g/eq (liquid); 300–3,000+ g/eq (solid)
Flash point (liquid grades): ~160–200°C (closed cup)
Tg (cured, amine-cured liquid grade): ~100–140°C
Tg (cured, anhydride-cured): ~120–180°C
Volume resistivity (cured): >10¹⁴ Ω·cm
Dielectric constant (cured, 1 MHz): ~3.5–4.5
Solubility in water: Insoluble (liquid grades slightly dispersible)
Solubility in organic solvents: Soluble in ketones, esters, aromatic solvents, chlorinated solvents
GHS Classification: Warning; H315, H317, H319, H411

Specifications of Epoxy Resins:
Key specifications for standard liquid BPA epoxy resin (e.g., D.E.R. 331/Araldite GY 250/Epikote 828 equivalent):
EEW (Epoxide Equivalent Weight): 182–192 g/eq
Viscosity (25°C): 11,000–14,000 mPa·s
Color (Gardner): ≤1
Hydrolyzable chlorine: ≤0.10%
Total chlorine: ≤0.50%
Density (25°C): ~1.16 g/cm³
Flash point (CC): >160°C
Moisture: ≤0.10%
Available grades: Liquid (EEW 170–280); Semi-solid (EEW 300–500); Solid (EEW 450–3,000+)
Packaging: 200 kg steel drum; 1,000 kg IBC; bulk; 25 kg bag (solid grades)
Storage: 15–25°C; protect from freezing (liquid) and moisture (solid); 12–24 months

Names of Epoxy Resins:
Epoxy Resins
Epoxide Resin
Polyepoxide
Bisphenol A Epoxy Resin
BPA Epoxy Resin
Bisphenol A Diglycidyl Ether (BADGE)
DGEBA
Bisphenol A-Epichlorohydrin Copolymer
Poly(bisphenol-A-co-epichlorohydrin)
Reaction Product of Bisphenol A and Epichlorohydrin
Epon 828 / Epon 1001 / Epon 1004
Araldite GY 250 / Araldite GY 783
D.E.R. 330 / D.E.R. 331 / D.E.R. 332 / D.E.R. 661 / D.E.R. 664
Epikote 828 / Epikote 1001
Epiclon 840 / Epiclon 850
ERL 2795
CAS 25068-38-6
CAS 1675-54-3