Materials makers are coming up with a variety of ways to make structural composites, from recycled plastic bottles that become weight-bearing elements of heavy load bridges to substituting coconut fibers for traditional ceramic fibers in biocomposite tiles for walls and floors. Now a thermoplastic-mineral composite replicates wood's fibrous structure and is contending with wood, wood plastic composites, plastics, and metal in a range of structural applications.
The material is a fully fiberized, molecularly oriented, lineal composite system from Eovations, which is licensing the technology, said Claude Brown, vice president of technology & innovation for Eovations, in an interview. At present, structural applications include marine uses for docks, pier, seawalls, and pontoons, as well as the cargo decks of vehicles and truck liners. One of the company's primary near-term focuses is the building industry, where it can be used as a Trex replacement for structural framing, as well as for non-structural uses.
Eovations's mineral/thermoplastic composite has a modulus of elasticity between 500,000 psi and 800,000 psi, but a modulus of rupture of zero. It can flex extremely well, but does not have a catastrophic failure mode. (Source: Eovations)
But it's a bit different from other wood and polymer composites like Trex. The company uses a proprietary extrusion/drawing process to combine mineral particles with a thermoplastic matrix. It's a composite because it combines two distinct materials and phases, Brown told us. Half of the composite consists of polymer, mostly polypropylene, and the other 50 percent is a mineral filler. The process first creates a small-scale fiber matrix, and then orients polymer chains within the individual fibers into a composite structure.
Eovations uses several mineral fillers. These are present primarily as a physical nucleation site, not a chemical nucleation site, since their chemistry is less important than the right size and aspect ratio, Brown said. The material also replicates the structure of wood with an internal closed cell structure that reduces the weight of the material without sacrificing its strength. Open spaces are included as capillary-like structures between the strands, so that about 56 percent of the composite's volume is air.
The new composite has a much higher modulus of elasticity at 500,000 psi to 800,000 psi than Trex, for example, which is typically 300,000 psi, and it costs about the same as similar synthetic decking products for construction uses. It does not have a catastrophic failure mode: the modulus of rupture is zero. That means it can be valuable as a hurricane-proof material, said Brown.
"A piece of it 5/16 inches thick can pass all the hurricane standards by itself, not including any other structure. A 55 mph wind leaves only a small impression, about 3/8 inches, but it bounces off of the structure," he told us. The composite's moisture absorption is less than 0.2 percent and densities are between 0.5g/cc and 1.0 g/cc (you can access the technical data sheet here).
The material's wide processing window means that properties of the finished composite, such as density, can be customized. It can be worked like wood with common woodworking tools, including cutting, sawing, machining, and drilling. Conventional fasteners such as nails, screws, and staples can be used, and their acceptance and hold is even better than wood's.
The technology was originally developed at Dow Chemical, but never commercialized, according to Brown. Eovations's parent company, Universal Forest Products, bought the technology from Dow in 2010.
"Which is worse for the environment, manufacturing these composite materials or logging the equivelent amount of wood?"
Logging industry is careful to point out the renewable resource that is lumber, and that they plant a large number of trees every year to replace what was cut. I don't think it's as easy to make that statement with regard to polypropylene.
Dave, the absence of a catastrophic failure mode (the modulus of rupture is zero) typically doesn't mean the material doesn't fail: it means it doesn't fail catastrophically, or, it bends before it breaks as you said. TJ, I agree about your comparison with plastic--anyone planted any plastic trees lately?
Ann, I wasn't talking about plastic trees; I was thinking about the renewable feedstocks we'd discussed several months ago. You mentioned that such feedstocks are no longer food-based such as corn, but still organic based.
Interesting development. Nice to see these sort of efforts moving forward. They may not always be the most cost effective, but it's a step in the right direction. I wonder if this is one of those "we can do it in the lab, so let's see if we can sell it" sort of things or if they actually had a specific market in mind.
Lou, I thought the hurricane-resistance use was one of the most intriguing and unique about this material, aside from the more mundane uses like deck replacement. Chuck, this is not aimed at high load-bearing structural components such as bridge beams: as we state, it's for lighter construction uses such as decks and pontoons.
The original question was worse for the environment - structural members made from wood or the composites described in the article.
The lumber industry sells itself as renewable because the companies plant trees to replace the ones harvested, and the renewal process is pretty straight forward - Cut down a forest, make lumber, plant seedlings in the now-cleared area, come back in 20 years or so and repeat.
IF the composites are made from organic feedstocks, they may be the equal of wood's impact on the environment. If they're made from petrochemicals, one would probably have to say they have a larger impact.
TJ, thanks for the clarification. Determining that would probably take a detailed lifecycle analysis. Although these are now voluntary, and not nearly as common as many of us would like, I hope that someday they'll be required as an item on the data sheet.
@Ann: The fact that something bends before it breaks doesn't mean that it doesn't have a catastrophic failure mode -- it just means that it bends first. If you continue to load it, it will fail catastrophically, sooner or later. (Steel bends before it breaks, too, but you can point to any number of catastrophic failures of steel structures).
And "the modulus of rupture is zero" is just plain wrong. As I said, modulus of rupture is a measure of the load-carrying capacity of a beam. If the load-carrying capacity were zero, it would be useless.
Modulus of rupture just isn't a useful number for something that yields before it breaks, since the equation assumes no yielding.
By experimenting with the photovoltaic reaction in solar cells, researchers at MIT have made a breakthrough in energy efficiency that significantly pushes the boundaries of current commercial cells on the market.
In a world that's going green, industrial operations have a problem: Their processes involve materials that are potentially toxic, flammable, corrosive, or reactive. If improperly managed, this can precipitate dangerous health and environmental consequences.
With LEDs dropping in price virtually every year, automakers have begun employing them, not only on luxury vehicles, but on entry-level models, as well.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 5
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
3 
