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The Future is Plastic ... Bridges
ches_grin writes "BusinessWeek reports on the latest in bridge-building technology, where new materials and techniques are allowing bridges to be built in places that were previously thought impossible. New plastics are allowing bridges to be lighter and stronger than concrete, and 'using cables and new suspension techniques, these bridges traverse bodies of water that were once too deep, too soft-floored, or too earthquake-prone for conventional methods.' The article also includes a slideshow of some of the most innovative bridges, some still under construction."
Any plastics (I'm assuming these are thermoform) that can't be recycled can be converted into raw energy in Mr. Fusion. It's not like recycling is even all that good, the energy cost is higher than producing new plastic, and the quality of the recycled plastic is not as good.
-mrxak
Onions Will Kill You
Here are some links about dihydrogen monoxide:
Stroller.
As someone who works in this field ("I am a polymer chemist" blah blah blah), you hit it right on the head regarding recyclability.
The main problem regarding the recycling of most plastics is that it's currently a heckuva lot cheaper to make new plastic from raw materials than it is to recycle existing materials. For example, soda bottles consist of several layers, each engineered to be slightly different: One layer prevents oxygen from entering the bottle, one prevents carbon dioxide from leaving the bottle, one layer has an antibacterial component to keep microscopic bugs from feasting on the sugars inside, etc. These layers have to be separated during the recycling process, and added complexity increases the cost.
Most plastic raw materials are byproducts of oil refining, and as the price of oil rises, so does the price of plastics -- we'll probably see more of a push to recycle in a few years.
Even thermoset (or thermoformed) plastics can be recycled to a small extent. While they cannot be repolymerized into new materials, they can be shredded and used in things like new plastic composites, rubbers and asphalts. Not to mention that there's a push in R&D to design new alternatives to thermosets that have comparable strength, but can be chemically degraded and reused.
-- The other Dr. Phil
>A couple months ago, I got into a discussion about the WTC collapse. One thing that was mentioned is that a large part of the collapse was due to the extreme temperatures of burning jet fuel weakening the elastic modulus of the steel-framed structure.
Doesn't sound like a good discussion then. Most of the jet fuel exploded outside the building. A half-hour later, there were people standing in the impact zones. Chief Palmer reached the 78th floor and reported that they could "knock it down with two lines."
The WTC collapses may be a tricky structural subject, but extreme temperatures is probably the biggest, most easily proved flaw in the argument.
FRP - Fiber Reinforced Polymer really means composites. In this case, probably some type of fiberglass or carbon fiber composites. To merely call it plastic is a little misleading, especially since not all polymers used in composites are plastics. Technically, even concrete is a composite, but obviously of a different nature than we're discussing here.
Also, this is only relatively new. This is one of those repeat stories that comes up from time to time when some editor thinks he's stumbled upon something incredible. I think I saw an article about "glass" bridges in Popular Mechanics 7-8 years ago (meaning fiberglass, actually, but that didn't stop the PM artists from drawing pictures of transparent bridges). For several years, a largely composite cable stayed bridge has been in planning stages as a replacement for an old span on Interstate 5 in California.
More currently, I interned with a company that assisted with a fiberglass reinforcement of a small concrete and steel bridge near Mt. Hood in Oregon. The city of Portland and Martin Marietta Materials recently replaced the slippery-when-wet steel deck on the Broadway Bridge in downtown Portland with a composite deck that performs comparably to concrete for traction and longevity, but is light enough not to interfere with raising the drawspan. Two more bridges in Portland are slated for similar modifications.