What is EPDM Rubber？
Definition and Composition
EPDM rubber, or Ethylene Propylene Diene Monomer rubber, is a synthetic rubber composed of ethylene, propylene, and a diene monomer. It is a terpolymer with a saturated hydrocarbon backbone and unsaturated side chains. The diene monomers commonly used in EPDM production include ethylidene norbornene (ENB), dicyclopentadiene (DCPD), and vinyl norbornene (VNB). EPDM is derived from polyethylene, with 45–85 wt% of propylene copolymerized to reduce crystallinity. The molecular structure of EPDM, with its saturated backbone and flexible side chains, imparts excellent properties such as high thermal stability, ozone resistance, weather resistance, and low-temperature flexibility.
Properties of EPDM Rubber
- Excellent heat resistance (can withstand 150°C continuously and 200°C intermittently)
- Superior ozone, weathering, and chemical resistance
- Good electrical insulating properties (suitable for 45-65 kV applications)
- Flexibility at low temperatures
- High molecular weight and long-chain branching for good processability
The properties can be tailored by varying the ethylene/propylene ratio, diene type/content, molecular weight, and degree of long-chain branching during polymerization.
How is EPDM Rubber Made?
The production of EPDM (Ethylene-Propylene-Diene Monomer) rubber involves several key steps:
- Raw Material Preparation: The primary raw materials include ethylene, propylene, and a non-conjugated diene monomer (typically dicyclopentadiene or ethylidene norbornene). These monomers are carefully weighed and mixed according to the desired formulation.
- Polymerization: The monomer mixture is fed into a polymerization reactor, where it undergoes copolymerization under controlled temperature and pressure conditions, typically using a Ziegler-Natta or metallocene catalyst system. The resulting polymer is a terpolymer with a saturated hydrocarbon backbone and unsaturated side chains.
- Compounding: The EPDM polymer is then compounded with various additives, such as reinforcing fillers (carbon black, silica), processing aids, antioxidants, and curing agents (peroxides or sulfur-based systems). The compounding process is carried out in internal mixers or two-roll mills to ensure homogeneous dispersion of the additives.
- Vulcanization: The compounded EPDM compound is then vulcanized (cured) to create a three-dimensional crosslinked network. This can be achieved through various curing systems, such as peroxide curing or sulfur curing, depending on the desired properties and application. The vulcanization process is typically carried out in a mold or continuous vulcanization line at elevated temperatures.
- Finishing and Packaging: After vulcanization, the EPDM rubber is cooled, stripped from the mold or extruded into the desired shape (e.g., sheets, strips, or profiles). The finished EPDM rubber products are then inspected, packaged, and prepared for shipment or further processing.
Throughout the production process, strict quality control measures are implemented to ensure consistent product quality and performance. The specific formulations, processing conditions, and curing systems can be tailored to achieve desired properties, such as heat resistance, weather resistance, chemical resistance, and mechanical strength, for various applications in the automotive, construction, and industrial sectors.
Applications of EPDM Rubber
EPDM rubber is widely used in various applications due to its exceptional properties, including:
- Automotive Industry: It is extensively employed in automotive exterior sealing systems, such as weather strips around doors, trunks, and hoods. Its exceptional air and ozone resistance, combined with compounding adaptability, results in high-performing profiles at a low cost, sealing off water, dirt, and noise for the vehicle’s lifetime.
- Building and Construction: EPDM rubber is utilized in waterproofing membranes for roofing systems, thanks to its outstanding weathering resistance, flexibility, and durability. It is also used in sealing and insulation applications in the construction industry.
- Wire and Cable Insulation: The excellent electrical insulation properties, heat resistance, and chemical resistance of EPDM rubber make it suitable for insulating wires and cables in various industries, including automotive, construction, and electrical.
- Hoses and Tubing: EPDM rubber’s resistance to heat, ozone, and chemicals makes it an ideal material for manufacturing hoses and tubing used in automotive, industrial, and chemical applications.
- Gaskets and Seals: The versatility of EPDM rubber allows it to be molded into various shapes and sizes, making it suitable for gaskets and seals in various industries, such as automotive, aerospace, and chemical processing.
- Rubber Goods: EPDM rubber is used in the production of various rubber goods, including belts, hoses, gaskets, and seals, due to its excellent resistance to aging, ozone, and chemicals.
EPDM rubber’s unique properties, including excellent weathering resistance, heat resistance, and chemical resistance, make it a versatile material suitable for a wide range of applications across various industries.
Application Case
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| EPDM Rubber Automotive Seals | Exceptional air and ozone resistance, compounding adaptability for high-performing and cost-effective sealing profiles that seal off water, dirt, and noise for the vehicle’s lifetime. | Automotive exterior sealing systems, such as weather strips around doors, trunks, and hoods. |
| EPDM Rubber Roofing Membranes | Outstanding weathering resistance, flexibility, and durability, providing long-lasting waterproofing solutions for roofing systems. | Building and construction industry for waterproofing and sealing applications. |
| EPDM Rubber Wire and Cable Insulation | Excellent electrical insulation properties, heat resistance, and chemical resistance, ensuring reliable and durable insulation for wires and cables. | Automotive, construction, and electrical industries for insulating wires and cables. |
| EPDM Rubber Hoses and Tubing | Resistance to heat, ozone, and chemicals, enabling the manufacture of durable and reliable hoses and tubing for various applications. | Automotive, industrial, and chemical applications requiring hoses and tubing with exceptional resistance properties. |
| EPDM Rubber Gaskets and Seals | Excellent compression set resistance, flexibility, and chemical resistance, providing long-lasting and reliable sealing solutions in various environments. | Industrial machinery, appliances, and equipment requiring gaskets and seals with superior sealing performance. |
Latest Technical Innovations
Improved Crosslinking and Vulcanization
Recent advancements in EPDM rubber focus on enhancing crosslinking and vulcanization processes for better mechanical properties and durability. The use of polyfunctional monomers (PFMs) like ethylene glycol dimethacrylate (EGDMA) and trimethylolpropane triacrylate (TMPTA) as co-agents in radiation crosslinking has shown remarkable improvements in gel content, crosslinking density, and mechanical properties. For instance, adding 5 phr of TMPTA to EPDM resulted in an 188% increase in tensile strength compared to neat EPDM at 50 kGy irradiation dose.
Compatibilization with Other Rubbers
Blending EPDM with other rubbers like silicone rubber (MVQ) can enhance specific properties while mitigating drawbacks. Reactive compatibilization methods using maleic anhydride-grafted EPDM and gamma-aminopropyltriethoxysilane have shown promising results in improving the strength and compatibility of EPDM/silicone rubber blends.
Incorporation of Functional Additives
Incorporating functional additives like compounds containing carboxyl groups and unsaturated carbon chain structures can significantly improve the bonding strength and mechanical properties of EPDM materials. These additives enable EPDM to be processed through conventional vulcanization processes while enhancing overall rubber properties.
Technical challenges
| Improving Crosslinking and Vulcanization of EPDM Rubber | Enhancing the crosslinking and vulcanization processes of EPDM rubber through the use of polyfunctional monomers (PFMs) like ethylene glycol dimethacrylate (EGDMA) and trimethylolpropane triacrylate (TMPTA) as co-agents in radiation crosslinking, leading to improved gel content, crosslinking density, and mechanical properties. |
| Compatibilization of EPDM with Other Rubbers | Developing reactive compatibilization methods, such as using maleic anhydride-grafted EPDM and gamma-aminopropyltriethoxysilane, to improve the strength and compatibility of EPDM blends with other rubbers like silicone rubber (MVQ). |
| Incorporation of Functional Additives in EPDM | Incorporating functional additives containing carboxyl groups and unsaturated carbon chain structures into EPDM to significantly improve the bonding strength and mechanical properties of the EPDM material. |
| Improving Fluidity and Vulcanization of EPDM | Using liquid polybutadiene or liquid butadiene-styrene oligomers as the third monomer in EPDM to enhance the fluidity in the early stage of vulcanization while ensuring the performance of the vulcanized rubber, making it suitable for continuous vulcanization processing. |
| Enhancing Tear Resistance of EPDM | Developing tear-resistant EPDM rubber materials by incorporating composite fiber-based capsule materials, which can form a compact cross-linked network structure within the rubber matrix, effectively improving the crosslinking degree and mechanical properties, particularly tear resistance. |
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