EPDM Injection Molding: Custom EPDM Rubber Parts

custom rubber parts, rubber injection molding

injIn daily life, we always uses the EPDM rubber products. As a a versatile synthetic rubber high-quality material, it is already one of the most worthy choices in the industry. EPDM injection molding refers to using EPDM to custom EPDM rubber parts through various processing methods under high pressure, and combing with various spare parts of different materials and functions. Finally, get the end products we want and need. At Sungplastic, we are dedicated to offering the highest quality EPDM  injection molding products. We are a one stop EPDM injection molding shop for manufacturing, sourcing, packaging and shipping parts on time, every time, even in an emergency. Next, let us know more about this material and EPDM injection molding.
WordPress website

Introduction of EPDM

Ethylene Propylene Diene Monomer, commonly known as EPDM, is a versatile synthetic rubber material that exhibits excellent resistance to weathering, ozone, heat, and UV radiation. EPDM is a copolymer of ethylene, propylene, and a diene monomer, which imparts its unique properties, making it suitable for a wide range of applications. This elastomeric material is widely used in automotive, construction, electrical, and industrial sectors due to its outstanding performance characteristics and cost-effectiveness. EPDM is available in a range of colors, including black, white, and gray, and can be formulated with various additives to enhance its performance for specific applications. As a highly versatile material, EPDM is often used in the injection molding process to produce a wide variety of rubber products and parts. Some examples of the types of parts that can be produced using EPDM include grommets, gaskets, drain tubes, formed hoses, spacers, dampers, vibration isolators, O-rings, covers, diaphragms, and bellows.
WordPress website

Properties of EPDM

EPDM exhibits a range of remarkable properties that contribute to its widespread use in various industries. Some of the key properties of EPDM are:

  • 1. Excellent weather resistance:
    EPDM can withstand exposure to extreme weather conditions, including sunlight, rain, and snow, without degradation or loss of physical properties.
  • 2. High thermal stability:
    EPDM maintains its mechanical properties at elevated temperatures, making it suitable for applications with demanding thermal environments.
  • 3. Good chemical resistance:
    EPDM is resistant to a wide range of chemicals, including acids, alkalis, and polar solvents, making it ideal for sealing and gasket applications.
  • 4. Exceptional electrical insulation:
    EPDM possesses excellent electrical insulation properties, making it suitable for use in electrical components and cable insulation.
  • 5. High elasticity and flexibility:
    EPDM is highly elastic and flexible, allowing it to recover its original shape after deformation, making it ideal for sealing applications.
  • 6. Low temperature flexibility:
    EPDM retains its flexibility even at low temperatures, enabling its use in cold climate conditions.
  • 7. Good tear and abrasion resistance:
    EPDM offers good resistance to tearing and abrasion, enhancing its durability in demanding applications.

Introduction of EPDM Injection Molding

EPDM injection molding is a specialized process of manufacturing components and products using EPDM as the raw material. Injection molding is a popular method to shape and form EPDM injection molding parts due to its efficiency, high production rate, and ability to create complex geometries with precision. The process involves injecting molten EPDM into a closed mold under high pressure, where it solidifies and takes the shape of the mold cavity. This technology offers various advantages, making it a preferred choice for manufacturing EPDM injection molding parts.

YouTube video

Conditions of EPDM Injection Molding Process

The successful EPDM injection molding process relies on maintaining specific conditions to achieve high-quality and consistent parts. Some critical process conditions include:

  • 1. Injection Temperature:
    The temperature at which the EPDM material is melted and injected into the mold is crucial for the molding process. The temperature should be controlled within the recommended range specified by the material manufacturer to ensure proper flow and fill of the mold cavity.
  • 2. Mold Temperature:
    The temperature of the mold plays a significant role in the cooling and solidification of the EPDM material. Proper mold temperature control is essential to achieve uniform part dimensions, prevent warping, and reduce cycle times.
  • 3. Injection Pressure:
    The injection pressure determines how the molten EPDM material is forced into the mold cavity. The pressure needs to be optimized to ensure complete mold filling and avoid voids or defects in the final product.
  • 4. Injection Speed:
    The injection speed refers to the rate at which the molten EPDM material is injected into the mold. Controlling the injection speed helps prevent material degradation, reduce stress on the mold, and improve part quality.
  • 5. Cooling Time:
    The cooling time is the duration during which the molded EPDM part remains in the mold to solidify and cool down. The cooling time is influenced by the part’s thickness, complexity, and material properties. Proper cooling time is critical to achieving dimensional stability and preventing part distortion.
  • 6. Mold Venting:
    Adequate venting is essential to allow air and gases to escape from the mold cavity during injection. Proper venting prevents trapped air pockets or voids in the molded part and helps maintain part integrity.
  • 7. Part Design:
    The design of the EPDM part is critical for a successful injection molding process. Proper consideration should be given to wall thickness, draft angles, and fillet radii to ensure easy mold filling and part ejection.
  • 8. Material Drying:
    EPDM is hygroscopic, meaning it can absorb moisture from the environment. Before injection, the EPDM material should be properly dried to minimize moisture content, which can lead to defects in the molded part.
  • 9. Post-Curing (Optional):
    In some cases, post-curing the EPDM part after molding may be necessary to further improve its properties, such as tensile strength, elongation, and heat resistance.
  • 10. Injection Molding Machine Capacity:
    Selecting the appropriate injection molding machine with the right clamping force and shot size is crucial to accommodate the size and complexity of the EPDM part.
  • 11. Mold Material:
    The mold material should be chosen carefully to withstand the elevated temperatures and pressures of the injection molding process. Steel molds are commonly used for EPDM injection molding due to their durability and longevity.
  • 12. Quality Control:
    Implementing a robust quality control process is essential to inspect and test the molded EPDM parts for dimensional accuracy, surface finish, and material properties.

Carefully controlling these process conditions and optimizing the EPDM injection molding parameters can ensure the production of high-quality, durable, and reliable EPDM parts for various applications.

EPDM Injection Molding Process: To Mold Custom EPDM Rubber Parts

The EPDM injection molding process involves several essential steps to transform raw EPDM material into a finished product with the desired shape and properties. Each step requires careful attention to detail and precise control to ensure the production of high-quality EPDM parts. Below, we will delve into the detailed steps of EPDM injection molding:

  • 1. Material Preparation:
    The first step in the EPDM injection molding process is material preparation. EPDM, which stands for Ethylene Propylene Diene Monomer, is a synthetic rubber with excellent properties such as weather resistance, heat resistance, and flexibility. EPDM is supplied in various forms, including pellets, granules, or pre-formed sheets. Before injection, the EPDM material needs to be properly dried to eliminate any moisture content, as moisture can negatively affect the material’s properties and cause defects in the molded parts. Drying is typically done in a hopper dryer or desiccant dryer.
  • 2. Melting and Mixing:
    Once the EPDM material is dried, it is fed into the injection molding machine’s hopper, which leads to the heating barrel. Inside the barrel, the EPDM pellets are heated to their melting point and then mixed to ensure uniform distribution of any additives or fillers. During the melting and mixing process, the EPDM material undergoes a transformation from solid pellets to a molten state.
  • 3. Injection:
    After melting and mixing, the molten EPDM material is injected into the mold cavity. The injection molding machine consists of a reciprocating screw, which moves forward to inject the molten material into the mold and then retracts to prepare for the next shot. The injection pressure and speed are carefully controlled to ensure complete mold filling and to avoid any air pockets or voids in the molded part.
  • 4. Mold Filling and Cooling:
    During the injection phase, the molten EPDM material flows into the mold cavity, taking on the shape of the part. The cooling phase immediately follows, during which the mold is kept at a controlled temperature to solidify the EPDM material. The cooling time depends on the part’s thickness and complexity and is crucial for achieving dimensional stability and preventing part distortion.
  • 5. Part Ejection:
    Once the EPDM injection molding part has solidified and cooled sufficiently, it is ready for ejection from the mold. The mold opens, and ejector pins or rods are used to push the part out of the mold cavity. Proper design of the mold and part features, such as draft angles and ejector pins, is essential to ensure smooth and easy part ejection without causing any damage to the finished product.
  • 6. Trimming and Deflashing:
    After ejection, the EPDM parts may require trimming or deflashing to remove any excess material or flash along the parting line. Flash is a thin excess of material that forms at the mold parting line during the injection process. Trimming and deflashing processes ensure that the final EPDM parts meet the required specifications and have a clean appearance.
  • 7. Post-Curing (Optional):
    In some cases, especially for parts that require enhanced material properties, a post-curing step may be necessary. Post-curing involves subjecting the EPDM parts to elevated temperatures for a specific duration to further cross-link the polymer chains, improving properties such as tensile strength, elongation, and heat resistance.
  • 8. Quality Inspection:
    After the molding and post-curing (if applicable) steps, the EPDM parts undergo a comprehensive quality inspection. This inspection may include dimensional measurements, visual inspection for any defects or surface imperfections, and testing for material properties such as hardness, tensile strength, elongation, and compression set. The parts that pass the quality inspection are then ready for assembly or distribution.
  • 9. Recycling and Waste Management:
    During the EPDM injection molding process, there may be some scrap or waste material generated. Proper recycling and waste management practices are essential to minimize material wastage and environmental impact. EPDM material can often be recycled and reused in future molding processes, reducing the overall material cost and environmental footprint.

Advantages of EPDM Injection Molding

EPDM injection molding offers several advantages, making it a preferred choice for manufacturing EPDM parts:

  • 1. Cost-effective production:
    EPDM Injection molding allows for high-volume production, reducing per-unit costs and making it economically viable for large-scale manufacturing.
  • 2. Complex part geometries:
    The EPDM injection molding process enables the production of intricate and complex part designs with high accuracy and repeatability.
  • 3. Fast production cycle:
    EPDM injection molding has a short production cycle, resulting in quicker turnaround times and faster product delivery.
  • 4. Minimal material wastage:
    The use of precise molds and automated processes reduces material wastage, making EPDM injection molding a cost-efficient and environmentally friendly option.
  • 5. Wide range of applications:
    EPDM injection molding can produce parts with diverse applications, including automotive seals, weatherstripping, gaskets, O-rings, electrical insulators, and more.
  • 6. Excellent material properties:
    The inherent properties of EPDM, such as weather resistance, thermal stability, and chemical resistance, make it suitable for various challenging environments.
  • 7. Excellent resistance to ozone:
    EPDM rubber is highly resistant to ozone, which is a common environmental factor that can cause rubber to degrade over time. This makes EPDM rubber a great choice for use in applications where it will be exposed to ozone, such as outdoor seals and gaskets.
  • 8. Resistance to water and detergents:
    EPDM rubber is highly resistant to water and detergents, which makes it suitable for use in applications such as hoses and seals that may be exposed to these substances.
  • 9. Resistance to greases:
    EPDM rubber is also resistant to greases, which makes it a great choice for use in automotive parts and machinery that experience exposure to grease.
  • 10. Resistance to mild acids and silicone oils:
    EPDM rubber has good resistance to mild acids and silicone oils, which makes it a versatile material for a wide range of applications.
  • 11. Easy to process:
    EPDM rubber is easy to process using a variety of techniques, such as extrusion and molding, which makes EPDM injection molding a popular choice for manufacturers.
  • 12. Common and readily available:
    EPDM rubber is a widely used material, and as such it is readily available from many suppliers, which makes it easy to source for manufacturing purposes.

Disadvantages of EPDM Injection Molding

Despite its numerous advantages, EPDM injection molding has some limitations and considerations that need to be addressed:

  • 1. Not suitable for all materials:
    EPDM injection molding is specifically designed for EPDM rubber, and it may not be compatible with other materials, limiting its material flexibility.
  • 2. Initial setup cost:
    The initial setup cost for EPDM injection molding can be higher due to the need for precision molds and equipment. However, this cost is often offset by the benefits of high-volume production.
  • 3. Limited color options:
    EPDM is generally available in a limited range of colors, which may require additional post-processing if specific color requirements are essential.
  • 4. Limited resistance to petroleum oils and fuel:
    EPDM rubber is not recommended for use in applications where it will be exposed to petroleum oils or fuel. These substances can cause the rubber to swell, soften, or deteriorate over time, which can reduce its effectiveness and lifespan.
  • 5. Limited resistance to mineral oils:
    Similar to petroleum oils and fuel, EPDM rubber also has limited resistance to mineral oils. Exposure to these oils can cause the rubber to degrade, which can compromise its performance and durability.
  • 6. Limited resistance to petroleum-based lubricants:
    EPDM rubber is not recommended for use in applications where it will be exposed to petroleum-based lubricants. These lubricants can cause the rubber to swell, which can lead to leaks or other failures in the system.
  • 7. Temperature range limitations:
    While EPDM rubber has a wide temperature range compared to some other materials, it does have some limitations. EPDM rubber can become brittle at low temperatures, which can cause it to crack or fail. At high temperatures, EPDM rubber can lose its elasticity and become less effective.

Applications of EPDM Injection Molding Parts

EPDM (Ethylene Propylene Diene Monomer) injection molding parts find wide-ranging applications across various industries due to their exceptional properties and performance characteristics. EPDM is a synthetic rubber known for its excellent weather resistance, heat resistance, and flexibility, making it an ideal choice for applications that require reliable sealing, gasketing, and vibration dampening. Below are some of the key applications of EPDM injection molding parts:

  • 1. Automotive Industry:
    Seals and Gaskets: EPDM injection molding parts are commonly used as seals and gaskets in automotive applications. They provide a reliable barrier against water, dust, and noise, making them suitable for door seals, window seals, and trunk seals.


    Weatherstripping: EPDM weatherstripping is used to seal gaps between automotive body panels and doors, windows, and hoods. It ensures a tight and weather-resistant fit, enhancing the vehicle’s overall comfort and energy efficiency.

    Engine Components: EPDM gaskets and seals are employed in various engine components to prevent leaks, resist high temperatures, and ensure the efficient functioning of the engine.

  • 2. Construction Industry:
    Window and Door Seals: EPDM injection molding parts are widely used as weather seals for windows and doors. They provide effective insulation against drafts, moisture, and noise, contributing to energy-efficient building designs.


    Roofing Membranes: EPDM roofing membranes are highly durable and weather-resistant, making them a popular choice for flat and low-slope roofing applications.

  • 3. Electrical Industry:
    Cable and Wire Insulation: EPDM injection molding parts are used as insulation for electrical cables and wires. They offer excellent electrical insulating properties and resistance to moisture, ensuring the safety and reliability of electrical systems.


    Electrical Grommets: EPDM grommets are employed to protect electrical wires and cables as they pass through holes in panels and enclosures. They provide strain relief and prevent damage to the cables.

  • 4. Marine Industry:
    Marine Seals: EPDM injection molding seals are utilized in marine applications, such as boat hatches, windows, and portholes, to provide water-tight and weather-resistant seals.
  • 5. Appliances and HVAC:
    Refrigerator and Freezer Seals: EPDM seals are commonly used in refrigerators and freezers to maintain a proper seal and prevent temperature leakage.


    HVAC Gaskets: EPDM gaskets are used in heating, ventilation, and air conditioning systems to ensure air-tight seals, reducing energy consumption and enhancing system efficiency.

  • 6. Industrial Equipment:
    Vibration Isolators: EPDM parts are used as vibration isolators and dampeners in industrial equipment to reduce vibration and noise, extending the equipment’s lifespan and improving worker safety.


    Conveyor Belts: EPDM belts are employed in conveyor systems, providing durability and resistance to wear and tear.

  • 7. Consumer Goods:
    Household Appliances: EPDM injection-molded parts find applications in various household appliances, including washing machines, dishwashers, and microwave ovens.


    Gardening Equipment: EPDM components are used in gardening tools and equipment, providing weather resistance and durability.

  • 8. Medical Industry:
    Medical Seals and Gaskets: EPDM injection molding parts are utilized in medical devices and equipment that require biocompatibility, chemical resistance, and durability.
  • 9. Aerospace and Defense:
    EPDM injection molding parts are used in aerospace and defense applications, such as aircraft seals, gaskets, and vibration dampening components.

Rubber Injection Molding Materials We Specialize in

Rubber Molding Materials as followed:

  • EPDM Rubber: Ideal for outdoor applications
  • Butyl Rubber: Lower resilience rubber
  • Natural Rubber (NR): An elastomer with incredible resilience
  • Neoprene Rubber / Chloroprene Rubber: Resistant to oils
  • Nitrile Rubber/NBR Rubber: Exceptional chemical resistance against oils and gasoline
  • Synthetic Rubber: A versatile elastomer with lower overall cost
  • Thermoplastic Elastomers (TPE): High resistance to flame and ozone
  • Fluoroelastomer/Viton Rubber(FKM/Viton): Resistance to fuel at at extreme temperatures and chemical
  • Silicone Rubber(VMQ): High heat resistance
  • Styrene-Butadiene Rubber(SBR): Good abrasion resistance with high resilience
  • Polyurethane (PU): Excellent wear resistance, high load-bearing capabilities, and good tear strength
  • Liquid Silicone Rubber (LSR): Excellent bio-compatibility
  • Ethylene Propylene Rubber (EPR): Good resistance to weather, ozone, and UV exposure

Partner With a Trusted Custom Rubber Parts Supplier For Your Molding Needs

With many years of experience, Sungplastic is a reliable choice for businesses of EPDM injection molding to custom rubber molded parts. Our expertise can provide custom EPDM injection molding solutions that cater to your specific performance requirements. By working with Sungplastic, you can invest in high-quality, cost-effective EPDM Injection molding rubber parts for your applications. Of course, any materials we provide you can choose. Contact us to discuss your needs and get a quote for your project.

FAQs about EPDM Injection Molding

  • Q1: How can EPDM injection molding help in reducing production costs?
    Enhanced part design flexibility, enabling the integration of multiple features into a single injection-molded component.
    Long-lasting EPDM parts that require less frequent replacement, reducing maintenance and downtime costs.
  • Q2: Can EPDM injection molding be used for custom color-matching?
    Yes, EPDM injection molding allows for custom color-matching capabilities. Manufacturers can use colorants and pigments during the injection process to achieve specific colors required by customers or to match existing components in assemblies. This flexibility in color selection ensures that EPDM parts seamlessly integrate into the overall product design.
  • Q3: Are There Different Types of EPDM?
    EPDM is a term that refers to a variety of formulations made by mixing an EPDM polymer with additives and curing it. There are many different formulations available with slightly different properties depending on the additives used. Common additives include carbon black, antioxidants, and zinc oxide, which can improve the material’s performance for specific applications. The catalyst for vulcanization is usually sulfur, but peroxide-cured EPDM is also available, although it’s more expensive. Sulfur-cured EPDM is cheaper, more common, and easier to work with.
  • Q4: How Long Does EPDM Rubber Last?
    EPDM rubber lasts longer than most other polymers and elastomers when exposed to sunlight, ozone and other weather conditions, but specific estimates depend on the environment in which it will stay. An EPDM part that is constantly exposed to sunlight and ozone generally lasts 15 to 20 years. But a grommet or small part enclosed indoors in a cabinet can last for decades, up to 40 years, before it may need replacement.
  • Q5: How Do You Bond EPDM Rubber to Metal?
    Bonding EPDM rubber to metal is similar to bonding other types of rubber. There are three main methods:Mechanical encapsulation: This is the most cost-effective method, where rubber is formed over most of the metal to encapsulate it and join the two together. The bond is very strong and the only way to break it is to cut the rubber.Chemical bonding: Applying a heat-activated adhesive to the metal, placing it into a mold with rubber, and allowing a chemical reaction to take place, which bonds the two substrates together.

    Glue: The simplest method involves applying a very strong glue to both the rubber and metal pieces and sticking them together. This method is tried and true, but the bond strength may not be as strong as with the other methods.

  • Q6: Can EPDM be Heat Welded?
    No, EPDM rubber cannot be heat welded. It will either not change or start to burn when exposed to heat.
About Sungplastic

About Sungplastic

Sungplastic is a plastic product manufacturer with rich experience in injection molding. According to the different product development requirements, we flexibly adjust the manufacturing process to achieve high quality, high efficiency and more economical.

We offer a variety of manufacturing services: Rapid Prototyping, Tool Making, Injection Molding, Product Design and Development, CNC Machining and Metal Stamping. You can choose from a variety of plastics, silicone rubber, or metal for your product. Regardless of mass production or small batch customization, Sungplastic has always been committed to providing assured, efficient and more economical one-stop processing services for your projects.

Contact us for a free quote and project review.

Get a free quote and design analysis today.

We’ll reply you within 6 working hours.
We respect your privacy.

+86 139 2927 4777 (WhatsApp, Wechat)