Tag Archives: plastic

Plastic, Heal Thyself!

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Blood is a remarkable substance: it transports vital oxygen to nourish our cells, it carries signalling chemicals that control our actions, it delivers armies of substances, at a moment’s notice, to ward against bodily infection and injury. Now, imagine a similar, bio-mimetic process in plastic, which remarkably allows a plastic material to heal itself.

From New Scientist:

If you prick it, does it not bleed? Puncture this plastic and it will heal itself with oozing fluids, in a process that mimics the way blot clots form to repair wounds. The plastic could one day be used to automatically patch holes in distant spacecraft or repair fighter jets on the fly.

So far, efforts to develop materials that fix themselves the way biological tissue mends itself have been limited. Scott White at the University of Illinois at Urbana-Champaign and his colleagues developed one of the first versions in 2001, but that material could only heal microscopic cracks.

Now his team have created a plastic lined with a type of artificial vascular system that can heal damage large enough to be visible to the naked eye.

The key is a pair of liquids that react when they are mixed. One fluid contains long, thin molecules and the other contains three-sided molecules. When the fluids mix, the molecules join together to create a scaffold, similar to the way blood platelets and fibrin proteins join to form a clot.

After a few minutes of contact, the liquids turn into a thick gel that fills the damaged area. Over a few hours, other ingredients within the fluids cause the gel to harden.

Strength from weakness

To test the concept, the team ran separate channels of each liquid through a plastic square and punctured it, creating a 4-millimetre hole with 35 millimetres of surrounding cracks. This also tore open the fluid channels.

Pumps on the edge of the plastic square squirted the fluids into the channels, where they oozed out and mixed, filling the hole and the radiating cracks within 20 minutes. The material hardened in about 3 hours, and the resulting patch was around 60 per cent as strong as the original plastic.

Holes larger than 8 millimetres proved more difficult to fill, as gravity caused the gel to sag before it could harden. The team thinks using foams in place of fluids would fill larger gaps, but they haven’t tested that idea yet.

Eventually, White and his team envision plastics with multiple criss-crossing channels, to ensure that the fluids always overlap with a damaged area. Embedding this synthetic vascular network would weaken the original material, but not by much, they say.

“You pay the price for being able to repair this damage, but it is certainly one that nature has figured out how to tolerate,” says team member Jeff Moore, also at the University of Illinois. “If you just look to things like bone or trees, they are all vascularised.”

Read the entire article here.

Image: Self-healing materials fix large-scale damage. Courtesy of University of Illinois at Urbana-Champaign.

The Plastic Bag Wars

[div class=attrib]From Rolling Stone:[end-div]

American shoppers use an estimated 102 billion plastic shopping bags each year — more than 500 per consumer. Named by Guinness World Records as “the most ubiquitous consumer item in the world,” the ultrathin bags have become a leading source of pollution worldwide. They litter the world’s beaches, clog city sewers, contribute to floods in developing countries and fuel a massive flow of plastic waste that is killing wildlife from sea turtles to camels. “The plastic bag has come to represent the collective sins of the age of plastic,” says Susan Freinkel, author of Plastic: A Toxic Love Story.

Many countries have instituted tough new rules to curb the use of plastic bags. Some, like China, have issued outright bans. Others, including many European nations, have imposed stiff fees to pay for the mess created by all the plastic trash. “There is simply zero justification for manufacturing them anymore, anywhere,” the United Nations Environment Programme recently declared. But in the United States, the plastics industry has launched a concerted campaign to derail and defeat anti-bag measures nationwide. The effort includes well-placed political donations, intensive lobbying at both the state and national levels, and a pervasive PR campaign designed to shift the focus away from plastic bags to the supposed threat of canvas and paper bags — including misleading claims that reusable bags “could” contain bacteria and unsafe levels of lead.

“It’s just like Big Tobacco,” says Amy Westervelt, founding editor of Plastic Free Times, a website sponsored by the nonprofit Plastic Pollution Coalition. “They’re using the same underhanded tactics — and even using the same lobbying firm that Philip Morris started and bankrolled in the Nineties. Their sole aim is to maintain the status quo and protect their profits. They will stop at nothing to suppress or discredit science that clearly links chemicals in plastic to negative impacts on human, animal and environmental health.”

Made from high-density polyethylene — a byproduct of oil and natural gas — the single-use shopping bag was invented by a Swedish company in the mid-Sixties and brought to the U.S. by ExxonMobil. Introduced to grocery-store checkout lines in 1976, the “T-shirt bag,” as it is known in the industry, can now be found literally every where on the planet, from the bottom of the ocean to the peaks of Mount Everest. The bags are durable, waterproof, cheaper to produce than paper bags and able to carry 1,000 times their own weight. They are also a nightmare to recycle: The flimsy bags, many thinner than a strand of human hair, gum up the sorting equipment used by most recycling facilities. “Plastic bags and other thin-film plastic is the number-one enemy of the equipment we use,” says Jeff Murray, vice president of Far West Fibers, the largest recycler in Oregon. “More than 300,000 plastic bags are removed from our machines every day — and since most of the removal has to be done by hand, that means more than 25 percent of our labor costs involves plastic-bag removal.”

[div class=attrib]More from theSource here.[end-div]