EPOXY RESINS

Epoxy Resins are reactive thermosetting prepolymers that contain epoxide (oxirane) groups and are most commonly made by reacting bisphenol A (BPA) with epichlorohydrin (ECH) in the presence of a base catalyst.
Epoxy Resins range from low-viscosity liquid monomers (BADGE/DGEBA, MW about 340 g/mol) to solid resins above 1,400 g/mol, and they are cured with hardeners into cross-linked networks.
Epoxy Resins are widely used as coatings, adhesives, composite matrices, encapsulants, laminates and construction materials thanks to their mechanical strength, chemical resistance, electrical insulation, thermal stability and adhesion to virtually all substrates.

CAS Number: 25068-38-6 (BPA-epichlorohydrin polymer, average MW 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 uncured prepolymers, so they must react with a hardener such as an amine, anhydride, polyamide, mercaptan or polysulfide to form a three-dimensional cross-linked network.
Epoxy Resins cure with a pot life, cure speed and final mechanical, thermal, chemical and electrical properties that depend on the type and ratio of hardener chosen.

Epoxy Resins use the epoxide equivalent weight (EEW) as the key parameter for calculating the stoichiometric ratio with the hardener.
Epoxy Resins include bisphenol A (most common), bisphenol F, novolac, cycloaliphatic, aliphatic, glycidylamine and bio-based types, each with its own viscosity, functionality and cured glass transition temperature (Tg).

Epoxy Resins are produced by reacting bisphenol A with epichlorohydrin and sodium hydroxide, where a large epichlorohydrin excess gives mainly the BADGE monomer (MW about 340, n≈0) and a higher bisphenol A ratio gives oligomers and solid resins with higher n values.
Epoxy Resins in liquid grades (n=0–1, MW 340–700, EEW 170–280) are the most commercially important grades for coatings and composites.

Epoxy Resins based on bisphenol A have two glycidyl ether groups at the chain ends joined by bisphenol A repeat units, and the epoxide groups open in cross-linking reactions with nucleophilic hardeners.
Epoxy Resins of higher molecular weight carry hydroxyl groups that contribute to adhesion, flexibility and reactivity with isocyanates and anhydrides.

Epoxy Resins of the polymer grade (MW ≤700, CAS 25068-38-6) are classified under GHS as H315 (skin irritation), H317 (may cause an allergic skin reaction), H319 (serious eye irritation) and H411 (toxic to aquatic life with long-lasting effects).
Epoxy Resins have excellent electrical insulation (volume resistivity >10¹⁴ Ω·cm, dielectric constant about 3.5–4.5 at 1 MHz), high adhesive strength to metals (shear strength >20 MPa) and high compressive strength when cured (>100 MPa).

Epoxy Resins reach glass transition temperatures (Tg) from about 60°C for aliphatic amine-cured systems to above 200°C for anhydride-cured aromatic systems.
Epoxy Resins therefore cover applications from flexible coatings to high-temperature composites.

Uses of Epoxy Resins:
Epoxy Resins are the primary binder in protective coatings for metals, concrete and other substrates, including marine coatings, automotive primers, industrial maintenance coatings, pipeline coatings, tank linings, floor coatings and anti-corrosion paints.
Epoxy Resins give such coatings superior adhesion, chemical resistance, abrasion resistance and barrier properties compared with conventional alkyd and polyurethane coatings.

Epoxy Resins are used as structural adhesives in aerospace, automotive, electronics, construction and marine applications to bond dissimilar substrates such as metals, composites, ceramics and glass.
Epoxy Resins adhesives give high lap shear strength, toughness, fatigue resistance and durability under extreme temperature and environmental conditions, and they are available as one-component (1K) heat-cure and two-component (2K) room-temperature-cure systems.

Epoxy Resins are the matrix resin in fiber-reinforced polymer (FRP) composites reinforced with carbon, glass or aramid fiber for aerospace structures (fuselage panels, wings, nacelles), wind turbine blades, pressure vessels, automotive body panels, sporting goods and civil infrastructure reinforcement.
Epoxy Resins provide the strength, stiffness, fatigue resistance and temperature performance required for high-performance structural applications.

Epoxy Resins are used in the electronics and electrical industries to encapsulate and pot semiconductors, integrated circuits, transformers, capacitors and printed circuit boards (PCBs), including copper-clad glass fiber FR-4 laminates.
Epoxy Resins give these parts electrical insulation, moisture protection, mechanical support and thermal dissipation.

Epoxy Resins are used in civil engineering and construction for 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.
Epoxy Resins give these systems high adhesion to concrete, low shrinkage and compressive strengths of 70–100 MPa and more.

Epoxy Resins are used as tooling resins for molds, jigs, fixtures, patterns and master models in aerospace, automotive and composite manufacturing.
Epoxy Resins give such tooling low shrinkage on cure, dimensional stability and machinability, which produce accurate, durable and thermally stable tooling surfaces.

Epoxy Resins in solid grades (EEW 650–3,000) are used in powder coatings for appliances, automotive components, pipelines, furniture and architectural metalwork.
Epoxy Resins are melt-mixed with solid amine or anhydride hardeners, extruded into a powder and applied electrostatically before oven curing to give a smooth, durable, 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.
Epoxy Resins linings have been joined by BPA-free alternative lining chemistries because of BPA migration concerns.

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.
Epoxy Resins give these parts corrosion resistance, light weight and design flexibility compared with steel and other fiberglass alternatives.

Epoxy Resins are used in semiconductor and microelectronics manufacturing as underfill materials, die attach adhesives and molding compounds.
Epoxy Resins offer low coefficient of thermal expansion (CTE), high purity, low ionic impurity levels and electrical insulation, which are critical for reliable long-term performance of electronic assemblies.

Epoxy Resins are used to make electrical laminates (prepregs) for multilayer PCBs and high-frequency circuit boards.
Epoxy Resins are also used in epoxy-based encapsulants and conformal coatings that protect 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 give optically clear, durable, glossy surfaces.
Epoxy Resins give such surfaces excellent UV stability when formulated with appropriate photoinitiators and UV absorbers.

Epoxy Resins are used as binders for solid rocket propellants and as matrix resins for ablative heat shields and thermal protection systems in aerospace.
Epoxy Resins are also used as sealants for pressure vessels, hydraulic systems and fuel tanks in defense and aerospace applications.

Epoxy Resins are used in electrically conductive adhesives containing silver or carbon fillers and in thermally conductive compounds containing aluminum oxide or boron nitride fillers.
Epoxy Resins are used in magnetic compounds for assembling electronic components, bonding 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.
Epoxy Resins form strong, durable bonds that resist peeling, delamination and environmental attack across a wide temperature range.

Epoxy Resins show very low shrinkage on cure (typically 1–4% by volume) compared with polyesters (6–8%) and other thermosetting systems.
Epoxy Resins therefore give better dimensional accuracy, lower residual stress, less microcracking and a better fit and finish in composite and tooling applications.

Epoxy Resins are highly versatile in formulation, since viscosity can be adjusted from very low to paste or solid, pot life from minutes to hours, and cure temperature from ambient to 180°C and above.
Epoxy Resins cured properties can be tailored from flexible rubbers to rigid, high-Tg thermosets through the choice of resin grade and curing agent.

Epoxy Resins have excellent chemical resistance to acids, alkalis, solvents, fuels and hydraulic fluids when fully cured.
Epoxy Resins therefore suit 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.
Epoxy Resins can thus be formulated into systems tailored precisely to application-specific performance requirements.

Epoxy Resins have a long history of use in demanding structural applications, with well-understood structure-property relationships and extensive design databases.
Epoxy Resins are supported by established industry standards (ISO, ASTM, EN) for 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) and light-yellow to tan solids (MW >1,400, EEW 450–3,000+) at ambient temperature.
Epoxy Resins in liquid grades have a density of approximately 1.15–1.20 g/cm³.

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).
Epoxy Resins mixing ratios are calculated from the resin EEW and the active hydrogen equivalent weight (AHEW) or anhydride equivalent weight of the curing agent, and thorough mixing is 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, and have low flammability in the cured state (LOI about 22–28%).
Epoxy Resins 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 can sensitize the skin on repeated contact because of the low-MW BADGE monomer, so all direct skin contact should be avoided.
Epoxy Resins that are fully cured 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 (epoxide) groups.
Epoxy Resins have an average number of repeat units n that sets 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) of the curing agent.
Epoxy Resins can also cure by ring-opening homopolymerization initiated by Lewis acids, Lewis bases or photoinitiators.

Epoxy Resins form a cured network that is an amorphous thermoset whose Tg is set by cross-link density, backbone rigidity and curing agent type.
Epoxy Resins are incompatible with strong oxidizing agents, strong bases, strong acids and reactive compounds that can open the epoxide group prematurely.

Epoxy Resins in liquid grades are combustible (flash point about 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.

Epoxy Resins in the uncured state are susceptible to photodegradation of the glycidyl ether linkage under UV irradiation.
Epoxy Resins for outdoor use should therefore be UV-stabilized or topcoated with UV-resistant coatings.

Production of Epoxy Resins:
Epoxy Resins are produced commercially by reacting bisphenol A with a molar excess of epichlorohydrin in the presence of sodium hydroxide catalyst.
Epoxy Resins form through glycidylation, in which the phenolic hydroxyl groups of bisphenol A react with epichlorohydrin to give chlorohydrin intermediates that cyclize to epoxide groups.

Epoxy Resins in liquid grades (n≈0, MW about 340–380) require a large excess of epichlorohydrin.
Epoxy Resins in 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 from bisphenol F (lower viscosity, higher chemical resistance), novolac phenols (higher functionality, higher Tg) and aliphatic diols and polyols (lower-viscosity reactive diluents).
Epoxy Resins can likewise be made from cycloaliphatic alcohols (outdoor durability), glycidylamines (very high-Tg aerospace grades) and bio-based phenols (sustainably sourced alternatives).

Epoxy Resins quality is characterized by epoxide equivalent weight (EEW, g/eq), viscosity (mPa·s at 25°C), color (Gardner or Hazen), hydrolyzable chlorine (ppm), total chlorine (ppm) and density.
Epoxy Resins are supplied as single-component resins or as pre-formulated two-component kits, with liquid grades typically packed in 200 kg steel drums or 1,000 kg IBCs and solid grades in 25 kg paper or PE bags or as flakes.

SDS of Epoxy Resins:

Stability and Reactivity of Epoxy Resins:

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

Reactivity:
Epoxy Resins react exothermically with amine, anhydride, mercaptan and other curing agents, and 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:
Epoxy Resins should not be stored above 60°C, which accelerates viscosity increase and premature gelation.
Epoxy Resins in liquid grades should not be frozen, since freezing may cause permanent cloudiness or phase separation.
Epoxy Resins should be kept away from strong acids, strong alkalis and oxidizing agents.
Epoxy Resins in large unmixed batches at elevated temperatures carry an exotherm risk, and prolonged skin contact with uncured liquid resin should be avoided.

Incompatible materials:
Epoxy Resins react on contact with curing agents (amines, anhydrides, mercaptans).
Epoxy Resins are incompatible with strong oxidizing agents, strong acids and strong bases.

Hazardous decomposition products:
Epoxy Resins may release carbon monoxide (CO) and carbon dioxide (CO2).
Epoxy Resins may release phenol vapors, bisphenol A, epichlorohydrin (on thermal decomposition) and irritating organic fumes.

Handling and Storage of Epoxy Resins:

Handling:
Epoxy Resins should be handled according to good industrial hygiene practice and the applicable Safety Data Sheet.
Epoxy Resins handling calls for chemical-resistant gloves (nitrile ≥0.4 mm or butyl rubber) at all times with uncured resin, which is the critical PPE requirement.
Epoxy Resins handling calls for local exhaust ventilation where vapors or aerosols may be generated, particularly during spraying, heating or sanding.
Epoxy Resins should be kept off the skin and eyes, with safety glasses or goggles worn.
Epoxy Resins handling should be followed by thorough hand washing, and contaminated clothing should be removed immediately and laundered before reuse.
Epoxy Resins aerosols should be prevented, and they should not be sprayed in enclosed spaces without suitable respiratory protection.
Epoxy Resins should be kept away from heat sources, sparks and open flames.

Storage:
Epoxy Resins should be stored in original sealed containers in a cool, dry, well-ventilated area at 15–25°C.
Epoxy Resins in liquid grades should be protected from freezing and from temperatures above 50–60°C.
Epoxy Resins should be kept away from curing agents, strong oxidizers, acids and alkalis.
Epoxy Resins have a typical storage stability of 12–24 months for liquid grades and 24 months for solid grades in original sealed containers.

First Aid Measures of Epoxy Resins:

Inhalation:
After inhalation of Epoxy Resins vapor or aerosol, move the person to fresh air and ensure ventilation.
Epoxy Resins vapor or aerosol that causes respiratory irritation, coughing or asthma-like symptoms calls for medical attention, since sensitized persons may react to very low concentrations.

Skin contact:
After skin contact with Epoxy Resins, remove contaminated clothing immediately and wash the skin thoroughly with soap and plenty of water.
Epoxy Resins skin contact that leads to redness, itching, rash or allergic reaction calls for medical advice, since repeated exposure to uncured resin may cause skin sensitization.

Eye contact:
After eye contact with Epoxy Resins, rinse cautiously with clean water for at least 15 minutes while holding the eyelids open.
Epoxy Resins eye contact calls for removal of contact lenses if present and easy to do, and for medical attention if irritation, redness or pain persists.

Ingestion:
After ingestion of Epoxy Resins, rinse the mouth with water and do not induce vomiting unless instructed by medical personnel.
Epoxy Resins ingestion calls for medical advice, although the oral LD50 of BPA epoxy resin in rats is >5,000–11,400 mg/kg, indicating a low acute oral hazard.

Firefighting Measures of Epoxy Resins:

Suitable extinguishing media:
Epoxy Resins fires can be fought with foam, dry chemical powder, carbon dioxide or water spray.

Specific hazards:
Epoxy Resins in liquid grades are combustible with flash points typically above 160°C, while cured resins are not readily flammable.
Epoxy Resins may produce carbon monoxide, carbon dioxide, phenol vapors and irritating organic fumes on thermal decomposition or combustion.

Protective equipment for firefighters:
Epoxy Resins fires require firefighters to wear self-contained breathing apparatus (SCBA) and full chemical protective clothing.

Firefighting instructions:
Epoxy Resins containers exposed to fire should be cooled with water spray.
Epoxy Resins firefighting run-off should be kept out of drains and waterways.

Accidental Release Measures of Epoxy Resins:

Personal precautions:
Skin contact with spilled uncured Epoxy Resins should be avoided, with gloves and eye protection put on immediately.
Spilled liquid Epoxy Resins create a severe slipping hazard and should be contained and absorbed at once.

Environmental precautions:
Epoxy Resins must be kept out of drains, sewers, soil and waterways, since they are classified as an aquatic hazard (H411).

Methods for cleaning up:
Epoxy Resins liquid spills should be absorbed with sand, vermiculite or another inert absorbent and collected into labeled waste containers.
Epoxy Resins spills should not be absorbed with sawdust or other combustible absorbents, and the waste should be disposed of according to local regulations.

Exposure Controls / Personal Protective Equipment of Epoxy Resins:

Engineering controls:
Epoxy Resins operations should have local exhaust ventilation at all points of vapor or aerosol generation, and closed systems for large-scale handling where possible.
Epoxy Resins handling areas should have emergency eyewash stations and safety showers nearby.

Eye protection:
Epoxy Resins handling calls for safety glasses with side shields or chemical splash goggles where splashing is possible.

Hand protection:
Epoxy Resins handling calls for nitrile rubber gloves ≥0.4 mm for short-term or splash contact and butyl rubber gloves ≥0.7 mm for prolonged contact.
Epoxy Resins barrier creams may supplement but do not replace gloves.

Skin and body protection:
Epoxy Resins handling calls for a chemical-resistant apron and long-sleeved work clothing, with contaminated clothing removed immediately.

Respiratory protection:
Epoxy Resins in liquid grades normally need no respiratory protection under ambient conditions.
Epoxy Resins spraying, or sanding of cured material, calls for an organic vapor and particulate respirator.

Hygiene measures:
Epoxy Resins handling should be followed by thorough washing of hands and forearms, and the face should not be touched with contaminated gloves.
Epoxy Resins work should end with a change of contaminated clothing before leaving the workplace.

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 (polymer grade, MW ≤700)

Specifications of Epoxy Resins (typical standard liquid BPA epoxy resin):
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