Introduction to Expanded Polypropylene

Expanded Polypropylene (EPP) is an innovative and versatile material that has gained significant recognition for its remarkable properties and diverse applications. EPP is a type of foam made from expanded polypropylene beads, resulting in a lightweight and resilient material with exceptional energy absorption capabilities. Its unique combination of strength, durability, and thermal insulation makes it a popular choice across various industries, ranging from automotive and packaging to sports and leisure.

In this article, we mainly introduce this excellent material from four aspects: its definition, type, characteristics, and uses. The picture to the left is some examples of what is possible with our EPP products. Send your 3D files and we can provide processing services for you.

What is Expanded Polypropylene (EPP)?

Expanded Polypropylene (EPP) is a highly versatile closed-cell foam material known for its exceptional energy absorption, impact resistance, thermal insulation, buoyancy, and recyclability, making it a preferred choice across various industries. With its lightweight yet durable nature, EPP offers a wide range of applications, from protective packaging and automotive components to thermal containers and buoyancy aids, providing reliable performance and sustainability.

What Is the History of Expanded Polypropylene?

Expanded Polypropylene (EPP) has a history dating back to the 1970s when it was first developed by JSP, a company engaged in researching new forms of polypropylene. Initially used in automotive products in Japan in 1982, EPP gained popularity due to its ability to improve energy management while reducing weight and providing environmental benefits. Since then, EPP has found extensive use in automotive applications, including energy-absorbing components in bumper systems, seating, and interior components. Its demand has grown globally, and it continues to be utilized in various industries.

What Is the Other Term for Expanded Polypropylene?

Another term for Expanded Polypropylene (EPP) is “expanded PP.”

How Is Expanded Polypropylene Made?

Expanded Polypropylene (EPP) is made through a molding process that involves expanding and fusing polypropylene beads. The beads are pre-expanded using steam and then placed into a mold where they are subjected to heat and pressure, resulting in the fusion of individual beads and the formation of a solid, lightweight foam structure with closed cells. The molding process allows for the creation of various shapes and densities of EPP products. Let’s delve deeper into the processing of Expanded Polypropylene (EPP):

1. Pre-Expansion

The EPP manufacturing process begins with the pre-expansion of polypropylene (PP) beads. These beads are pre-expanded using steam or a physical blowing agent to achieve a specific density and expand their volume.

2. Molding

Once the pre-expansion is complete, the expanded beads are transferred to a mold cavity designed to create the desired shape of the final EPP product. The mold can be made of various materials, such as aluminum, steel, or composite.

3. Steam Chest Molding

The molding technique primarily used for EPP is called steam chest molding. During this process, the mold cavity is closed, and steam is injected into a steam chest surrounding the mold. The steam softens the expanded beads and causes them to expand further within the mold cavity.

4. Fusion and Shape Formation

As the steam continues to heat the beads, they begin to fuse. The pressure inside the mold helps shape the beads and create a solid foam structure. The duration of the molding process depends on factors such as the desired thickness, density, and complexity of the product.

5. Cooling and Demolding

After achieving the desired shape and density, the mold is cooled to solidify the fused beads. Cooling can be performed by circulating cool air or water through the mold. Once the EPP part has cooled and hardened, it is removed from the mold.

6. Trimming and Finishing

Trimming and finishing processes may be employed to remove any excess material or imperfections from the EPP part. This ensures the final product meets the required specifications and aesthetic standards.

7. Additional Processing

Depending on the intended application, further secondary operations may be performed on the EPP parts. These can include cutting, shaping, laminating, painting, printing, or assembling the parts with other components.

What Color Is Expanded Polypropylene?

Expanded Polypropylene (EPP) is typically available in a variety of colors. The color of EPP can vary based on the specific manufacturing process and the addition of colorants during production. It is commonly seen in shades of white, gray, or black. The picture below is an example of EPP raw materials:


What Does Expanded Polypropylene Look Like?

Expanded Polypropylene (EPP) has a distinct appearance characterized by its foam-like structure. It consists of interconnected cells, forming a lightweight and porous material. The surface of EPP typically has a textured or slightly rough texture. The foam structure of EPP gives it a unique and recognizable visual appeal. The specific appearance of EPP can vary based on factors such as the density, molding process, and any additional treatment or finishes applied to the surface. The picture below is an example of EPP parts:


What Are the Different Types of Expanded Polypropylene?

Expanded Polypropylene (EPP) can be categorized into different types based on its physical properties and intended applications. Here are some common types:

1. Automotive Grade EPP

This type of EPP is specifically designed for automotive applications, including energy-absorbing components, interior parts, and structural reinforcements in vehicles.

2. Packaging Grade EPP

EPP is widely used in packaging applications due to its cushioning and protective properties. Packaging grade EPP is utilized in cases, inserts, and trays to safeguard delicate and fragile items during transportation.

3. Thermal Insulation Grade EPP

EPP with enhanced thermal insulation properties is utilized in applications where heat or cold insulation is required. It can be found in building construction, HVAC systems, and temperature-controlled packaging.

4. Marine Grade EPP

EPP with excellent buoyancy and water resistance is suitable for marine applications such as floats, buoys, and marine safety equipment.

5. Sports and Recreation Grade EPP

EPP is utilized in sports and recreational equipment, such as helmets, protective gear, padding, and lightweight components for various sporting goods.

6. Industrial Grade EPP

EPP with high strength and durability is used in industrial applications, including material handling, load-bearing components, and equipment protection.

7. Customized EPP

Ruitai can purchase customized EPP raw materials for you or provide customized EPP raw materials yourself to meet the specific requirements of aerospace, electronics, healthcare, and other industries.

What Are the Characteristics of Expanded Polypropylene?

Expanded Polypropylene (EPP) possesses several characteristic properties that make it a sought-after material for various applications. Here are some key characteristics of EPP:

1. Lightweight: EPP is exceptionally lightweight, which allows for the creation of lightweight end products while maintaining structural integrity.

2. High Energy Absorption: EPP exhibits excellent energy absorption properties, making it ideal for impact-resistant applications. It can absorb and dissipate energy during impacts, providing enhanced safety and protection.

3. Excellent Cushioning: EPP has outstanding cushioning properties, making it an ideal material for packaging and protective applications. It can effectively absorb shocks and vibrations, safeguarding delicate and fragile items.

4. Thermal Insulation: EPP offers good thermal insulation properties, making it suitable for applications where temperature control is required, such as in building insulation or temperature-controlled packaging.

5. Chemical Resistance: EPP is resistant to most chemicals, oils, and solvents, which contributes to its durability and suitability for a wide range of environments.

6. Recyclable: EPP is a recyclable material, allowing for sustainable and environmentally friendly practices. It can be recycled and reused in various applications, reducing waste and promoting circular economy principles.

7. Versatile Processing: EPP can be easily molded into complex shapes and sizes, enabling the production of customized components for different industries. It can be molded with different densities and thicknesses to meet specific requirements.

8. Low Water Absorption: EPP has low water absorption properties, ensuring its dimensional stability and preventing degradation when exposed to moisture.

9. UV Resistance: EPP is resistant to ultraviolet (UV) radiation, making it suitable for outdoor applications where prolonged exposure to sunlight is expected.

What Are the Properties of Expanded Polypropylene?

In the table below, we summarize some common general properties of epp material :

What Are the Physical Properties of Expanded Polypropylene?

The table below lists some physical properties of epp:

EPP Material Physical Properties Table
Physical PropertyDescription
DensityLow to high density range depending on application
Cell StructureClosed-cell foam structure
FlexibilityHighly flexible and resilient
Compressive StrengthHigh compressive strength
Tensile StrengthGood tensile strength
Impact ResistanceExcellent impact resistance
Thermal ConductivityLow thermal conductivity
Thermal ExpansionLow coefficient of thermal expansion
Water AbsorptionLow water absorption
RecyclabilityFully recyclable and environmentally friendly
Sound AbsorptionGood sound absorption properties
BuoyancyExcellent buoyancy in water
Operating TemperatureTypically -40°C to +100°C (-40°F to +212°F)
Color OptionsAvailable in various colors

What Are the Chemical Properties of Expanded Polypropylene?

The table below lists some chemical epp:

EPP Material Chemical Properties Table
Chemical PropertyDescription
Chemical ResistanceResistant to most chemicals and solvents
Water AbsorptionLow water absorption
Biological ResistanceResistant to biological degradation
Oxidation ResistanceResistant to oxidation
Acid ResistanceResistant to mild acids
Alkali ResistanceResistant to mild alkalis
UV ResistanceGood resistance to UV radiation
FlammabilitySelf-extinguishing, low flammability

What Are the Mechanical Properties of Expanded Polypropylene?

The table below lists some mechanical properties of epp:

EPP Material Mechanical Properties Table
Mechanical PropertyDescription
Flexural StrengthGood flexural strength
Tensile StrengthGood tensile strength
Compressive StrengthHigh compressive strength
Impact ResistanceExcellent impact resistance
ElasticityHighly elastic and resilient
HardnessTypically medium hardness
Fatigue ResistanceGood resistance to fatigue
Creep ResistanceLow creep tendency
StiffnessGenerally high stiffness
Fracture ToughnessHigh fracture toughness
Shear StrengthGood shear strength
Modulus of ElasticityTypically high modulus of elasticity
Poisson's RatioTypically low Poisson's ratio

How to Compare the Main EPP Types?

The following is a comparison of several common epp materials:

EPP Material Comparison Table
PropertyExpanded Polypropylene (EPP)Automotive Grade EPPPackaging Grade EPPThermal Insulation Grade EPPMarine Grade EPPSports and Recreation Grade EPPIndustrial Grade EPP
Density, g/cm³0.018-0.040.02-0.030.018-0.0220.03-0.040.025-0.0350.018-0.030.022-0.04
Shore Hardness (D)20-5030-4520-4020-3530-5030-4520-50
Stress at Yield, MPa0.5-3.51.5-2.50.8-1.50.5-1.51.0-2.01.0-2.50.5-3.0
Elongation at Break, %15-10030-6020-4015-3020-5030-7015-80
Tensile Modulus, GPa0.1-0.60.3-0.50.2-0.40.1-0.30.2-0.50.3-0.60.1-0.7
Notched Impact Strength ASTM D256, J/m20-20050-15030-10020-8040-12050-18020-150
HDT A(1.8 MPa), °C70-10080-9570-9070-8575-9580-10070-100
Minimum Service Temperature, °C-40 to -10-30 to -10-40 to -20-40 to -20-30 to -10-30 to -10-40 to -10
UL94 Fire RatingHB, V-0HB, V-0HB, V-0HB, V-0HB, V-0HB, V-0HB, V-0

What Are the Advantages of Expanded Polypropylene?

Expanded Polypropylene (EPP) offers several advantages that contribute to its popularity and wide range of applications. Here are some of the key advantages of EPP:

1. Lightweight: EPP is incredibly lightweight, allowing for the production of lightweight end products. This property is particularly beneficial in applications where weight reduction is critical, such as automotive and aerospace industries, as it can contribute to fuel efficiency and improved performance.

2. Excellent Impact Resistance: EPP exhibits exceptional impact resistance, making it ideal for applications that require protection against impacts, vibrations, and shocks. It can effectively absorb and dissipate energy, providing enhanced safety and durability.

3. Energy Absorption: EPP has outstanding energy absorption properties, making it highly suitable for applications that require cushioning and protection. It can absorb and distribute impact forces, reducing the risk of damage to fragile or sensitive components.

4. Thermal Insulation: EPP offers good thermal insulation properties, making it valuable in applications that require temperature control and energy efficiency. It helps to minimize heat transfer, providing insulation against both hot and cold temperatures.

5. Chemical Resistance: EPP is resistant to most chemicals, oils, and solvents. This property ensures its durability and suitability for a wide range of environments, including those exposed to harsh chemicals or corrosive substances.

6. Recyclability: EPP is fully recyclable, allowing for sustainable and environmentally friendly practices. It can be recycled and reused in various applications, promoting waste reduction and resource conservation.

7. Design Flexibility: EPP can be easily molded into complex shapes and sizes, offering design flexibility and customization options. It can be molded with different densities, thicknesses, and colors to meet specific requirements and aesthetic preferences.

8. Buoyancy: EPP exhibits excellent buoyancy in water, making it suitable for marine and water-related applications. It is widely used in floats, buoys, and water sports equipment.

9. Sound Absorption: EPP has good sound absorption properties, making it useful in applications that require noise reduction. It can help to dampen and absorb sound waves, contributing to a quieter environment.

What Are the Disadvantages of Expanded Polypropylene?

While Expanded Polypropylene (EPP) offers numerous advantages, it’s important to consider some of its potential disadvantages. Here are a few notable disadvantages of EPP:

1. Limited Temperature Resistance

EPP has a relatively limited temperature resistance compared to some other materials. It may deform or lose its mechanical properties when exposed to high temperatures above its recommended operating temperature range.

2. Limited UV Resistance

EPP may experience some degradation or color fading when exposed to prolonged ultraviolet (UV) radiation. To mitigate this, additional UV stabilizers or protective coatings may be required for outdoor applications.

3. Cost

EPP can be more expensive compared to other foam materials, such as Expanded Polystyrene (EPS). The cost of production and processing, as well as the customization options, can contribute to the higher overall cost of EPP products.

4. Limited Availability of Recycling Facilities

While EPP is recyclable, the availability of recycling facilities for EPP may be limited in certain regions. This can pose challenges for proper disposal and recycling practices.

5. Flammability

EPP is combustible and can burn when exposed to a flame. However, it generally exhibits self-extinguishing properties and low flammability.

6. Surface Finish

The surface of EPP may have a textured, porous, or matte appearance, which may not be suitable for applications that require a smooth or glossy finish. Additional surface treatments or coatings may be required to achieve the desired aesthetic qualities.

7. Limited Chemical Resistance

While EPP is generally resistant to most chemicals and solvents, it may have limitations in handling certain aggressive chemicals or solvents.

What Processes Are Expanded Polypropylene Suitable for Processing?

Expanded Polypropylene (EPP) is a versatile material that can be processed using various manufacturing techniques. Here are some common processes suitable for processing EPP:

1. Injection Molding: EPP can be injection molded to produce complex shapes and intricate designs. The process involves injecting molten EPP into a mold, which then cools and solidifies to form the desired product.

2. Thermoforming: EPP sheets can be heated and formed into specific shapes using thermoforming processes. This method is commonly used for producing EPP packaging trays, automotive components, and protective casings.

3. Compression Molding: EPP can be compression molded by applying heat and pressure to pre-cut or pre-expanded EPP beads. The beads fuse to form a solid molded part. Compression molding is often used for larger, thicker EPP parts.

4. Cutting and Fabrication: EPP can be easily cut and fabricated into desired shapes using various cutting techniques such as die cutting, waterjet cutting, or CNC milling. This allows for the production of custom EPP components with precise dimensions.

5. Lamination: EPP can be laminated with other materials, such as fabrics or films, to enhance its properties or create composite structures. Lamination can improve the aesthetics, strength, or barrier properties of EPP products.

6. Welding: EPP can be welded together using techniques like hot plate welding or ultrasonic welding. Welding is often employed to join EPP parts, creating strong and durable bonds.

7. Foam-in-Place: EPP can be used in foam-in-place processes, where the molten EPP is injected into a mold or cavity and expands to fill the space, conforming to the shape of the mold. This method is commonly used for producing custom-fitted packaging or cushioning solutions.

8. Coating and Bonding: EPP surfaces can be coated or bonded with other materials, such as adhesives or coatings, to enhance their properties or achieve specific requirements like moisture resistance or improved surface finish.

What Is Expanded Polypropylene Used for?

Expanded Polypropylene (EPP) is a versatile material with a wide range of applications across various industries. Here are some common uses of EPP:

1. Packaging

EPP is widely used in packaging applications due to its excellent cushioning and impact resistance properties. It is commonly used for protective packaging of fragile and sensitive products, such as electronics, appliances, automotive parts, and medical equipment.

2. Automotive Industry

EPP is extensively used in the automotive industry for various applications. It is utilized in interior components like door panels, instrument panels, headliners, and seat cores. EPP is also employed in bumper cores, energy absorbers, and crash pads due to its exceptional impact resistance and energy absorption capabilities.

3. Sports and Recreation

EPP is used in the manufacturing of sports and recreational equipment. It can be found in helmets, padding for sports gear, protective gear, flotation devices, and insulation for water sports equipment.

4. Construction and Building

EPP is utilized in the construction and building industry for insulation purposes. It is commonly used in insulation panels, roofing insulation, and concrete void forms. EPP’s thermal insulation properties, lightweight nature, and energy-efficient characteristics make it suitable for these applications.

5. Furniture

EPP is employed in the production of furniture for its lightweight, durable, and comfortable properties. It is used in seating cushions, backrests, armrests, and padding for various types of furniture.

6. Electronics

EPP is utilized in the electronics industry for the packaging and protection of electronic components. It provides cushioning and shock absorption, safeguarding delicate electronic devices during transportation and handling.

7. Medical and Healthcare

EPP is used in the medical and healthcare sectors for various applications. It is employed in medical packaging, transport trays, and protective casings for medical devices. EPP’s hygienic properties, resistance to chemicals, and ability to withstand sterilization processes make it suitable for medical applications.

8. Industrial Applications

EPP finds applications in various industrial sectors. It is used in industrial packaging, material handling trays, dunnage, and pallets. EPP’s lightweight nature, durability, and stackability make it suitable for these industrial applications.

What is the difference between EPP and EPS material?

Expanded Polypropylene (EPP) and Expanded Polystyrene (EPS) are both foam materials commonly used in various industries, but they have some key differences. Here are the main differences between EPP and EPS:

1. Material Composition: EPP is made from expanded polypropylene beads, while EPS is made from expanded polystyrene beads. The primary difference lies in the base polymer used for each material.

2. Mechanical Properties: EPP exhibits superior mechanical properties compared to EPS. EPP has higher impact resistance, flexural strength, and elasticity, making it more resilient and durable. EPS, on the other hand, is more rigid and brittle, with lower impact resistance.

3. Density: EPP has a higher density compared to EPS. The density of EPP typically ranges from 20 to 180 kg/m³, while EPS has a density ranging from 10 to 50 kg/m³. The higher density of EPP contributes to its enhanced mechanical properties.

4. Thermal Properties: EPP has better thermal insulation properties compared to EPS. EPP offers higher resistance to heat transfer, making it more suitable for applications that require temperature control or insulation.

5. Processing Methods: EPP and EPS are processed using different manufacturing techniques. EPP can be easily molded, thermoformed, and welded, allowing for greater design flexibility. EPS is commonly molded through steam molding or block molding processes.

6. Applications: EPP and EPS find applications in different areas. EPP is commonly used in automotive components, protective packaging, sports equipment, and insulation panels. EPS is widely used in packaging, construction insulation, and disposable food containers.

7. Environmental Impact: EPP and EPS have different environmental characteristics. EPP is recyclable and can be reused, whereas EPS recycling is more challenging due to its lower recycling rates and limited recycling infrastructure.


This article serves as an introduction to expanded polypropylene (EPP), a versatile material. It provides a definition, explores its properties, and highlights its diverse applications. We have also included commonly asked questions to enhance your knowledge of EPP. If you need further information, please don’t hesitate to reach out to our team.

Ruitai specializes in manufacturing prototype parts and offers a wide range of manufacturing services to meet various prototyping and production requirements. We are available to provide you with a complimentary quote at your convenience. Feel free to contact us.


Please be aware that the content provided in this article is for reference purposes only. Ruitai Mould assumes no responsibility for the completeness, accuracy, or validity of the information presented, whether expressed or implied.

Addressing Common Expanded Polypropylene Questions:

Q1: Is EPP environmentally friendly?
A1: Yes, EPP is considered environmentally friendly as it is recyclable and offers potential for reuse.

Q2: Can EPP withstand high temperatures?
A2: EPP has good heat resistance and can typically withstand temperatures up to around 110-120°C (230-248°F).

Q3: Is EPP water-resistant?
A3: EPP has inherent water resistance, making it suitable for applications where exposure to moisture is a concern.

Q4: How does EPP compare to other foam materials in terms of strength?
A4: EPP is known for its exceptional strength-to-weight ratio, surpassing many other foam materials.

Q5: Can EPP be easily molded into complex shapes?
A5: Yes, EPP can be molded into intricate and complex shapes using techniques like injection molding or thermoforming.

Q6: Is EPP chemically resistant?
A6: EPP exhibits good resistance to chemicals, oils, and solvents, making it suitable for various industrial applications.

Q7: Can EPP be used for food packaging?
A7: Yes, EPP is commonly used for food packaging due to its hygienic properties and suitability for contact with food.

Q8: Does EPP provide sound insulation?
A8: Yes, EPP’s closed-cell structure makes it an effective material for sound insulation and vibration dampening.

Q9: Can EPP be painted or coated?
A9: Yes, EPP can be painted or coated with appropriate surface treatments to enhance aesthetics or improve performance.

Q10: Is EPP resistant to UV radiation?
A10: EPP can be formulated with additives to enhance its resistance to UV radiation, increasing its outdoor durability.

Q11: What are the advantages of using EPP in automotive applications?
A11: EPP offers lightweight construction, energy absorption, impact resistance, and design flexibility in automotive components.

Q12: Can EPP be used for medical applications?
A12: Yes, EPP is suitable for medical applications such as packaging, transport trays, and protective casings due to its cleanliness and sterilizability.

Q13: Does EPP have any electrical insulating properties?
A13: EPP has inherent electrical insulating properties, making it suitable for certain electrical and electronic applications.

Q14: Can EPP be recycled?
A14: Yes, EPP is recyclable and can be processed into new EPP products or used as a raw material for other plastic products.

Q15: How does the cost of EPP compare to other foam materials?
A15: EPP generally falls in the mid to higher range in terms of cost compared to other foam materials, reflecting its superior properties and performance.