Thermoplastic Polyolefin
Summary
Thermoplastic polyolefin (TPO) is a blend of a thermoplastic such as polypropylene, an elastomer such as ethylene propylene rubber, and usually a mineral filler. Outdoor use, especially roofing, depends on its resistance to solar UV degradation, so filler and rubber content matter.
Terminology
- TPO: thermoplastic olefin / polyolefin
- EPR: ethylene propylene rubber
- Elastomer phase: EPR, EPDM, ethylene-octene, ethylbenzene, or SEBS
- TPR: thermoplastic rubber; results when rubber exceeds about 40 percent and phase inversion occurs
- Filler: talc, fiberglass, carbon fiber, wollastonite, or metal oxy sulfate
History and demand
Sourcing
- Named producers of the polyolefin elastomers used in TPO include LyondellBasell, Dow, ExxonMobil, and Mitsui Chemicals (market research)
Composition and production
Raw materials
- Thermoplastics: polypropylene, polyethylene, block copolymer polypropylene
- Elastomers: EPR, EPDM, ethylene-octene, ethylbenzene, SEBS, made with metallocene catalysts that stay embedded in the polymer
- Fillers: talc, fiberglass, carbon fiber, wollastonite, metal oxy sulfate
Manufacturing process
- Processed at 210 to 270°C (410 to 520°F) by injection molding, profile extrusion, and thermoforming
- Cannot be blown or made into films thinner than about 1/4 mil (about 6 micrometers)
Properties
Physical
- Density: about 0.92 to 1.1 g/cm³ (about 57 to 69 lb/ft³)
Mechanical
- Flexural modulus: raised by fillers with higher surface area per weight
- Flexibility: rubber above about 40 percent can invert phases into a non-rigid TPR
Durability
- UV: does not degrade under solar UV radiation, unlike nylons
Standards
Material specifications
- ASTM D6878: TPO sheet roofing
Uses in buildings
Building elements
- TPO Roofing: single-ply roofing membrane
Pros and cons
Pros
- Does not degrade under solar UV
- Density near 1 g/cm³
- Adjustable stiffness through filler and rubber content
Cons
- Metallocene catalysts stay in the polymer
- Films thinner than about 1/4 mil cannot be made
Manufacturing and cost
Main manufacturers and suppliers
Trade association: SPRI.
Sources
- Wikipedia: Thermoplastic olefin, https://en.wikipedia.org/wiki/Thermoplastic_olefin
- UpCodes: 2024 IBC Chapter 15 roof assemblies, Chapter 15 Roof Assemblies and Rooftop Structures: Department of Defense Building Code 2024 | UpCodes
- Wikimedia Commons: 2011-05-13-hackathon-by-RalfR-084.jpg, photo by Ralf Roletschek (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:2011-05-13-hackathon-by-RalfR-084.jpg
- MarketResearch.com: thermoplastic polyolefin elastomer (TPO) global market, https://www.marketresearch.com/Prof-Research-v4036/Thermoplastic-Polyolefin-Elastomer-TPO-Global-42073249