What is EPDM Rubber?
First things first—what’s EPDM? EPDM stands for Ethylene Propylene Diene Monomer. It’s a type of synthetic rubber that’s super flexible and durable. It’s great for outdoor applications because it can handle extreme temperatures and resist UV rays, ozone, and chemicals.The injection molding process is a highly efficient way to shape EPDM rubber into the desired form.
This comprehensive table provides a detailed overview of EPDM rubber’s characteristics, including density, hardness, tensile strength, and more, alongside key injection molding parameters such as temperature, pressure, and cycle times.
| Property | Description |
|---|---|
| Density | 0.86 – 1.00 g/cm³ |
| Hardness | 50 – 80 Shore A |
| Tensile Strength | 8 – 20 MPa |
| Elongation at Break | 200 – 600% |
| Compression Set | ≤ 25% (at 70°C for 22 hours) |
| Tear Strength | 20 – 50 kN/m |
| Temperature Range | -50°C to +150°C (-58°F to +302°F) |
| Tensile Modulus | 1 – 5 MPa (low strain) / 2 – 10 MPa (high strain) |
| Flexural Modulus | 2 – 8 MPa |
| Temperature | 160°C – 180°C (320°F – 356°F) |
| Injection Pressure | 700 – 1,500 bar (10,000 – 21,750 psi) |
| Mold Temperature | 40°C – 80°C (104°F – 176°F) |
| Cycle Time | 30 – 90 seconds |
| Vulcanization Time | 5 – 20 minutes |
The Basics of Injection Molding
Before we dive into the specifics of EPDM, let’s quickly review what injection molding is. It’s a manufacturing process where melted material is injected into a mold to create parts. This process is efficient, precise, and great for high-volume production. You basically heat up your material until it’s liquid, inject it into a mold, let it cool, and then—voilà!—you’ve got your part.
Why EPDM for Injection Molding?
EPDM is an excellent choice for injection molding because it’s:
- It remains flexible at both high and low temperatures.
- It resists aging and weathering.
- It holds up well against ozone and UV rays.
- While not the cheapest material, it offers a good balance of cost and performance.
EPDM Rubber Injection Molding Process
Injection molding is a process where material is heated until it becomes molten and then injected into a mold to create a part. For EPDM rubber, this involves a few extra steps to ensure the final product is of high quality. Here’s a step-by-step breakdown:
Step 1: Preparing the Raw Materials
The EPDM rubber injection molding process starts with the careful selection and preparation of raw materials. The primary raw materials for EPDM rubber are ethylene, propylene, and a diene monomer. These materials are mixed in precise proportions to create the desired polymer blend.
Once mixed, the blend is fed into a reactor where it undergoes a polymerization reaction under high pressure and temperature conditions. This reaction transforms the mixture into a molten EPDM rubber that’s ready for the next step.
Step 2: Compounding the EPDM Rubber
Once the polymerization reaction is complete, the resulting EPDM rubber is in a molten state. It’s then cooled down and solidified into a form that’s easy to handle and process. This solidified rubber usually comes in the form of pellets or sheets.
Next, the EPDM rubber undergoes a compounding process, where various additives are mixed in to improve its properties. These additives can include fillers like carbon black or silica, which enhance the rubber’s strength and durability. Plasticizers and processing aids may also be added to improve flexibility and workability.
Step 3: Setting Up the Injection Molding Machine
With the compounded EPDM rubber ready, it’s time to set up the injection molding machine. This involves selecting the appropriate mold, which is a metal frame that contains the desired shape and size of the final product. The mold is heated to the optimal temperature, typically between 50°C and 100°C, depending on the specific EPDM rubber formulation.
The injection molding machine is also adjusted to the correct settings, including nozzle temperature, injection speed, and mold clamping pressure. These settings vary depending on the type of EPDM rubber being used and the desired outcome.
Step 4: Injection Molding the EPDM Rubber
Now, the actual injection molding process begins. The compounded EPDM rubber is fed into the injection molding machine, which melts it down to a viscous liquid. This liquid rubber is then forced into the mold under high pressure, filling every corner and detail of the mold cavity.
The mold is then allowed to cool, allowing the EPDM rubber to solidify and take on the shape of the mold. Once the rubber is fully cured, the mold is opened, and the finished product is ejected.
Step 5: Post-Processing and Quality Control
After the EPDM rubber is molded, it may undergo some post-processing steps, such as trimming excess material or applying a finish. Then, it’s inspected for quality to ensure it meets the required standards. This includes checking for defects, measuring dimensions, and testing the rubber’s properties.
Common Applications of EPDM Rubber Parts
Here are some of the most common uses for EPDM rubber parts:
- Automotive seals and gaskets
- Automotive hoses
- Roofing membranes
- Expansion joints
- Window and door seals
- Vibration isolators
- Industrial gaskets and O-rings
- Industrial pipes and tubing
- Appliance seals
- Sporting goods components
- Irrigation system hoses
- Protective covers for agricultural machinery
- Boat seals
- Dock and boat fenders
- Electrical cable insulation
- Connector seals
- Medical device seals
Advantages and Disadvantages of EPDM Injection Molding
These factors can help in deciding if EPDM is the right material for your specific injection molding needs.
Advantages
- Durable and weather-resistant
- Flexible across a wide temperature range
- Good chemical resistance
- Cost-effective for high-volume production
- Maintains shape after compression
- Low water absorption
Disadvantages
- Not suitable for petroleum products
- Limited high-temperature use
- Lower mechanical strength compared to some rubbers
- Requires precise processing
- Needs vulcanization
- Not ideal for certain chemicals
What is the Difference Between EPDM and Rubber?
EPDM is a synthetic rubber known for its resistance to weather, UV rays, and heat, staying flexible in various temperatures. “Rubber” is a broader term that includes various types, such as natural rubber and synthetic rubbers like SBR and NBR, each with different properties and uses.
Choose BOYI for Expert Custom Rubber and Plastic Parts
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FAQ
EPDM should be stored in a cool, dry place, away from direct sunlight and moisture to prevent degradation.
Lead time varies depending on complexity and quantity, but it typically ranges from a few weeks to a couple of months, including mold preparation and testing.
EPDM is generally not recyclable through standard recycling processes, but some specialized methods may be available for recycling or reusing EPDM material.
Injection molding involves injecting molten rubber into a mold under pressure, while compression molding involves pressing rubber between two heated molds. Injection molding usually offers higher precision and faster production rates.
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
