Terminology

• EPDM: ethylene propylene diene monomer rubber (ASTM D1418 M class)
• Vulcanization: sulfur crosslinking that turns natural rubber into a thermoset
• Diene (ENB, DCPD, VNB): comonomer, typically 2 to 12 percent, enabling sulfur crosslinking
• Elastomer: polymer with rubber-like elasticity
• Shore A: durometer hardness scale

History and demand

Invention

• 1839: Charles Goodyear redeveloped vulcanization
• 1909: synthetic rubber first made, as demand began to outstrip natural supply

Sourcing

• Natural rubber: about 14.5 million tonnes in 2024, led by Thailand and Indonesia; Asia produced about 90 percent in 2021 (OPIS, other sources)

Demand trend

• Rubber production exceeded 29 million metric tonnes in 2022, over 50 percent natural (about 15.1 million tonnes); synthetic rubber exceeded 15 million tonnes in 2017 to 2019 and was slightly lower in 2020
• Supply concerns include plant disease, climate change, and price volatility

Composition and production

Raw materials

• Natural rubber: cis-1,4-polyisoprene, molecular weight 100,000 to 1,000,000 daltons, up to 5 percent other material by dry mass
• EPDM: ethylene, propylene, and a diene, compounded with fillers such as carbon black and calcium carbonate and plasticizers; functional only when crosslinked

Properties

Physical

• EPDM density: 0.90 to over 2.0 g/cm³ by compound

Mechanical

• EPDM tensile strength: about 17 MPa (about 2,500 psi) at failure
• EPDM elongation: at least 300 percent at fracture
• EPDM hardness: Shore A 30 to 90

Thermal and moisture

• EPDM service temperature: minus 50°C to 150°C (minus 58 to 302°F); glass transition minus 54°C (minus 65°F)

Durability

• EPDM UV and ozone: superior to unsaturated rubbers such as natural rubber, SBR, and neoprene; properly formulated, lasts outdoors for years or decades

Standards

Material specifications

• ASTM D1418: rubber nomenclature (EPDM is M class)
• ASTM D4637: EPDM sheet roofing

Uses in buildings

Building elements

• EPDM Roofing: single-ply roofing membrane
• Sealants and Flashing: gaskets, weatherstripping, and seals

Pros and cons

Pros

• Resists heat, light, and ozone
• Service range minus 50 to 150°C
• Roof membrane does not pollute rainwater runoff

Cons

• Functional only when crosslinked
• Natural rubber supply is concentrated in Asia (about 90 percent)
• Natural rubber is unsaturated and less resistant to ozone and UV than EPDM

Manufacturing and cost

Main manufacturers and suppliers

• Carlisle SynTec
• Elevate
• Versico
• Johns Manville

Trade association: SPRI.

Sources

• Wikipedia: Ethylene propylene diene monomer rubber, https://en.wikipedia.org/wiki/Ethylene_propylene_diene_monomer_rubber
• Wikipedia: Natural rubber, https://en.wikipedia.org/wiki/Natural_rubber
• UpCodes: 2024 IBC Chapter 15 roof assemblies, Chapter 15 Roof Assemblies and Rooftop Structures: Department of Defense Building Code 2024 | UpCodes
• Wikimedia Commons: Natural rubber tree.jpg, photo by DelwarHossain (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Natural_rubber_tree.jpg
• Chemical Market Analytics: natural rubber market insights, https://chemicalmarketanalytics.com/?p=31814