Epoxy resin is a type of reactive polymer material made from an epoxy resin component and a curing agent, or hardener.
Many common epoxy resins are manufactured using chemical building blocks such as epichlorohydrin and bisphenol A (BPA) to produce an epoxy resin containing reactive epoxide groups. The resin is then combined with a compatible curing agent—often an amine, amide, anhydride or another chemistry—to form a cross-linked solid.
The exact formulation varies depending on the intended application. Epoxy products used for garage floors, industrial coatings, adhesives, electronics and composite materials can contain different resins, curing agents, pigments, fillers, modifiers and additives.
So, in simple terms:
Epoxy resin + curing agent → chemical reaction → cured epoxy material
The chemistry is what gives cured epoxy its combination of adhesion, hardness, chemical resistance and durability.
What Is Epoxy Resin?
Epoxy resin is a reactive polymer system that contains epoxide groups capable of reacting with a curing agent.
Unlike a thermoplastic that can simply be melted and reshaped, a thermosetting epoxy undergoes an irreversible chemical reaction during curing. The molecules link together to form a three-dimensional network.
Before curing, the resin component is usually a viscous liquid. After the curing reaction is sufficiently complete, it becomes a solid material with properties that depend on the formulation and curing conditions.
Epoxy resins are used in:
- Floor coatings
- Protective coatings
- Adhesives
- Electrical and electronic components
- Composite materials
- Marine applications
- Construction products
- Art and decorative applications
What Is Epoxy Resin Made Of?
Most epoxy systems have two primary components:
- Epoxy resin
- Curing agent or hardener
However, commercial epoxy formulations can contain additional ingredients to achieve specific performance characteristics.
1. Epoxy Resin
The resin component contains molecules with reactive epoxide groups.
A common family of epoxy resins is based on reactions involving:
- Epichlorohydrin
- Bisphenol A (BPA)
These materials are chemically processed to produce epoxy resin molecules with reactive epoxide groups.
Other epoxy chemistries also exist. Depending on the application, manufacturers can use different chemical building blocks to create resins with specific properties such as improved flexibility, heat resistance, chemical resistance or lower viscosity.
What is epichlorohydrin?
Epichlorohydrin is a reactive chemical building block used in the production of many epoxy resins.
It is not simply “epoxy” by itself. Rather, it is one of the raw materials used to manufacture certain epoxy resin systems.
What is bisphenol A?
Bisphenol A, commonly abbreviated as BPA, is another important building block used in the manufacture of many conventional epoxy resins.
When epoxy resin is properly formulated and cured, the BPA-based starting material is incorporated into the polymer network rather than remaining as the original starting chemical.
2. Curing Agent or Hardener
The second major component is the curing agent, often called the hardener.
The hardener reacts with the reactive groups in the epoxy resin and causes the material to cross-link.
Common curing-agent chemistries include:
- Amines
- Amides and polyamides
- Anhydrides
- Other specialized curing agents
Different curing agents affect properties such as:
- Cure speed
- Hardness
- Flexibility
- Chemical resistance
- Heat resistance
- Adhesion
- Working time
This is why you cannot assume that every epoxy product has the same chemical composition or performance.
What Happens When Epoxy Resin and Hardener Are Mixed?
When the resin and curing agent are combined in the correct proportions, a chemical curing reaction begins.
The reactive epoxide groups in the resin react with functional groups in the curing agent.
As the reaction progresses, individual molecules become connected through chemical bonds.
This process is called cross-linking.
The result is a three-dimensional polymer network.
In simple terms:
Liquid resin + liquid/solid curing agent
↓
Chemical reaction
↓
Cross-linked polymer network
↓
Hard, durable cured epoxy
The curing reaction can also release heat, meaning it is generally exothermic.
The exact curing time depends on the product formulation and environmental conditions such as temperature, humidity, mix ratio and application thickness.
Why Does Epoxy Become Hard?
Epoxy doesn’t become hard simply because it “dries.”
That’s an important distinction.
Water-based coatings can primarily harden as water evaporates. Epoxy systems primarily become solid through a chemical reaction between the resin and curing agent.
As cross-linking progresses, the material changes from a liquid or viscous mixture into a solid network.
This chemical structure contributes to epoxy’s:
- Hardness
- Adhesion
- Chemical resistance
- Abrasion resistance
- Dimensional stability
- Mechanical strength
What Gives Epoxy Its Strength?
The strength and performance of cured epoxy come from its cross-linked molecular structure.
When properly formulated and cured, epoxy can provide strong adhesion and resistance to many forms of wear.
Depending on the formulation, cured epoxy can resist:
- Abrasion
- Impact
- Oils
- Grease
- Many chemicals
- Moisture
- Everyday wear
However, epoxy isn’t universally resistant to every chemical or environmental condition.
Performance depends on the specific formulation and application.
What Other Ingredients Are Added to Epoxy?
Commercial epoxy products are often more complex than simply “resin + hardener.”
Manufacturers can add other ingredients to modify performance or appearance.
These may include:
Pigments
Used to create different colours and finishes.
Fillers
Used to modify physical properties, viscosity or cost.
Reactive diluents
Used in some formulations to adjust viscosity and processing characteristics.
Toughening agents
Used to modify flexibility and impact performance.
Flow and leveling additives
Used to improve application and surface appearance.
UV stabilizers and other additives
Used in some formulations to improve resistance to environmental exposure.
The exact ingredients vary significantly between manufacturers and applications.
Is All Epoxy Resin Made From BPA?
No.
Many widely used epoxy resins are based on BPA-derived chemistry, but epoxy resin is a broader category of materials.
There are different types of epoxy resins designed for different applications.
Examples include:
- Bisphenol A-based epoxies
- Bisphenol F-based epoxies
- Novolac epoxies
- Aliphatic epoxy systems
- Glycidyl ester epoxies
- Other specialized epoxy chemistries
Therefore, saying “epoxy resin is made from BPA” is an oversimplification.
A more accurate statement is:
Many common epoxy resins are manufactured using BPA-derived chemistry, but epoxy resin is a broad class of materials with multiple formulations.
This distinction is worth adding because it makes the article considerably more authoritative.
What Is Epoxy Flooring Made Of?
Epoxy flooring is not simply a layer of pure epoxy resin.
A professional epoxy flooring system can contain several components, depending on the system design.
A typical system may include:
- Prepared concrete substrate
- Primer or penetrating base layer, where specified
- Epoxy base coat
- Decorative flakes or broadcast aggregate, if selected
- Additional coating layer
- Protective topcoat
The actual products and number of layers vary by application.
For a garage floor, the coating system may be engineered to provide a combination of:
- Adhesion
- Durability
- Chemical resistance
- Abrasion resistance
- Decorative appearance
- Easier cleaning
This is why “epoxy resin” and “epoxy flooring” should not be treated as exactly the same thing.
Epoxy resin is the chemistry; epoxy flooring is an installed coating system.
How Is Epoxy Resin Used on Concrete Floors?
When properly formulated epoxy is applied to appropriately prepared concrete, it can form a durable protective coating.
Depending on the system, epoxy flooring can help:
- Protect concrete from staining
- Resist oil and automotive fluids
- Reduce concrete dusting
- Improve cleanability
- Improve the appearance of the floor
- Provide a durable finished surface
However, surface preparation is critical.
The concrete must be suitable for the selected coating system, and contaminants, weak surface material and problematic moisture conditions may need to be addressed before installation.
See our guide on whether epoxy can be applied over old concrete.
Why Is Epoxy Used for Garage Floors?
Garage floors experience conditions that can be difficult for untreated concrete.
These include:
- Vehicle traffic
- Tire abrasion
- Oil and grease
- Road salt
- Water
- Dirt
- Dropped tools
- Automotive chemicals
A properly selected and installed epoxy flooring system can provide a finished surface that is easier to clean and more resistant to many common garage contaminants.
Decorative epoxy systems can also dramatically change the appearance of an ordinary concrete garage.
For homeowners comparing epoxy and polyaspartic systems, see our guide to epoxy vs. polyaspartic garage flooring.
What Are the Main Properties of Epoxy?
Epoxy is used across many industries because different formulations can provide a useful combination of properties.
Strong adhesion
Epoxy can bond strongly to properly prepared substrates.
Chemical resistance
Many cured epoxy systems provide good resistance to oils, solvents and other chemicals, although resistance varies by formulation.
Abrasion resistance
Properly formulated coatings can withstand significant everyday wear.
Hardness
Cured epoxy can form a hard surface suitable for many demanding applications.
Electrical insulation
Certain epoxy formulations are used for electrical insulation and encapsulation.
Design flexibility
Pigments, aggregates and other additives can produce a wide variety of colours, textures and finishes.
Where Is Epoxy Resin Used?
Epoxy is used far beyond garage flooring.
Construction
Epoxy is used in coatings, adhesives, repair materials and composite applications.
Automotive
Epoxy-based products can be used for coatings, adhesives and composite components.
Electronics
Epoxy materials are used for encapsulation, insulation and protection of electronic components.
Marine
Epoxy is widely used in certain marine repair, bonding and composite applications.
Aerospace
Specialized epoxy systems are used in composite materials and structural applications.
Art and crafts
Clear epoxy systems can be used for casting, decorative objects, artwork and furniture.
Industrial flooring
Epoxy coatings are used in warehouses, manufacturing facilities, commercial buildings and other demanding environments.
Is Epoxy Resin Toxic?
Uncured epoxy components should be handled carefully.
The hazards depend on the specific resin, hardener and formulation.
Before curing, some epoxy components can cause:
- Skin irritation
- Eye irritation
- Skin sensitization
- Respiratory irritation
Once fully cured, epoxy is generally much less reactive than its uncured components, but the exact safety profile depends on the formulation.
For that reason, anyone working with epoxy should follow the manufacturer’s Safety Data Sheet (SDS) and product instructions.
Basic precautions include:
- Use appropriate gloves
- Protect your eyes
- Provide adequate ventilation
- Avoid skin contact
- Follow the manufacturer’s mixing ratio
- Use appropriate respiratory protection when required by the product’s SDS
- Store components safely
- Dispose of materials according to applicable requirements
Don’t assume that all epoxy products have identical hazards.
Does Epoxy Contain BPA?
Some epoxy resins are manufactured using bisphenol A (BPA) as a starting material.
However, the presence of BPA in the manufacturing chemistry does not mean that a finished cured epoxy coating is simply “BPA.”
The chemistry changes during resin manufacture and curing, and the properties of the finished material depend on the specific formulation.
If BPA exposure is a concern for a particular application, the appropriate approach is to consult the manufacturer’s technical documentation and SDS rather than making assumptions based solely on the word “epoxy.”
Epoxy Resin vs. Epoxy Coating
These terms are related but shouldn’t be used interchangeably.
| Epoxy Resin | Epoxy Coating |
|---|---|
| Chemical resin component | Finished coating system |
| Usually combined with a curing agent | Formulated for a specific application |
| Can be used in many industries | Designed to protect/decorate a substrate |
| May contain reactive components | Applied and cured as a complete system |
| One component of many coating systems | Can include multiple layers and additives |
For example, a garage floor may use an epoxy coating as one part of a multi-layer system.
Epoxy Resin vs. Polyaspartic Coatings
Epoxy and polyaspartic are both used in professional flooring systems, but they are different chemistries.
| Feature | Epoxy | Polyaspartic |
|---|---|---|
| Chemistry | Epoxy resin + curing agent | Polyaspartic/polyurea-related chemistry |
| Adhesion | Excellent when properly prepared | Excellent when properly prepared |
| Cure speed | Generally slower | Generally faster |
| UV resistance | Formulation-dependent | Generally excellent |
| Garage flooring | Common | Common |
| Decorative options | Excellent | Excellent |
If you’re choosing a garage floor coating, the chemistry is only one consideration. Concrete preparation, system design, application and topcoat selection also affect performance.
How Long Does Epoxy Take to Cure?
Epoxy doesn’t have one universal cure time.
The curing process depends on:
- Product formulation
- Resin-to-hardener ratio
- Temperature
- Humidity
- Coating thickness
- Substrate temperature
- Ventilation
- Manufacturer specifications
Some epoxy products can become tack-free relatively quickly, while full mechanical or chemical cure can take considerably longer.
Always follow the specific manufacturer’s technical data sheet rather than relying on a generic cure time.
Why Is Epoxy Popular for Garage Floors?
Epoxy has become popular for garage flooring because it can combine:
Durability + chemical resistance + cleanability + appearance
A properly installed system can transform unfinished concrete into a more functional and visually finished surface.
Decorative flake systems are particularly popular for residential garages because they can provide texture, colour variation and a finished appearance while helping disguise minor visual imperfections.
Learn more about epoxy flake flooring.
Final Answer: What Is Epoxy Resin Made Of?
Epoxy resin is a class of reactive polymer materials. Many common epoxy resins are manufactured from chemical building blocks such as epichlorohydrin and bisphenol A, although other epoxy chemistries also exist.
To create a cured epoxy material, the resin is combined with a compatible curing agent or hardener. The two components undergo a chemical reaction that cross-links the molecules into a three-dimensional polymer network.
Commercial epoxy formulations may also contain pigments, fillers, modifiers and other additives designed for a specific application.
That’s what allows epoxy to be formulated for everything from garage floors and industrial coatings to adhesives, electronics, composites and decorative applications.
Frequently Asked Questions
What are the two main ingredients in epoxy resin?
The two primary components of a two-part epoxy system are epoxy resin and a curing agent (hardener). The exact chemical composition varies between products.
Is epoxy resin made from plastic?
Epoxy is a type of thermosetting polymer. It starts as reactive resin components and becomes a cross-linked solid during curing.
Is epoxy resin made from BPA?
Many conventional epoxy resins use BPA-derived chemistry, but not all epoxy resins are identical or necessarily based on BPA.
What is the hardener in epoxy resin?
The hardener is a curing agent that reacts chemically with the epoxy resin. Common curing-agent families include amines, amides/polyamides and anhydrides.
What happens when epoxy resin and hardener are mixed?
They undergo a chemical reaction called curing. The reaction cross-links the resin molecules and converts the mixture from a liquid or viscous material into a solid polymer network.
Is epoxy resin waterproof?
A cured epoxy coating can provide strong resistance to water and moisture, but “waterproof” should not be treated as an absolute claim for every epoxy formulation or installation.
For flooring applications, moisture can also come from the concrete substrate itself, which is why substrate assessment is important.
Is epoxy resin safe after it cures?
Fully cured epoxy is generally much less reactive than uncured resin and hardener, but safety depends on the particular formulation. Always follow the manufacturer’s SDS and technical documentation.
Is epoxy resin the same as epoxy flooring?
No. Epoxy resin is a material chemistry; epoxy flooring is a complete installed coating system that may contain epoxy resin along with curing agents, pigments, aggregates, additives and other layers.
Why is epoxy used for garage floors?
Epoxy can provide a durable, easy-to-clean surface with good resistance to many common garage contaminants. Its performance depends heavily on proper concrete preparation and installation.
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