McDonald's: Ex-employee on why straws are made 'larger'
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The scourge of soggy paper straws may soon be no more, as researchers from South Korea have developed economical, easy-to-produce and 100 percent biodegradable alternatives that keep their shape when in use. In an effort to keep them from becoming sodden, conventional paper straws and cups are coated with either polyethylene or acrylic resin, the same materials used to make plastic bags and adhesives. The problem with this approach is that it is rarely fully successful — and it results in products that are difficult to recycle and, when they use polyethylene, are feared to release microplastics into the environment when they break down. In contrast, other alternatives like polylactic acid (aka “corn plastic”) straws and rice straws have their own drawbacks, with the former being resistant to decomposition while the latter are expensive due to how complex they are to mass produce.
The new and fully biodegradable straws were developed by a team of researchers led by Dr Oh Dongyeop of the Korea Research Institute of Chemical Technology.
Dr Dongyeop said: “This technology is but a small step toward the direction we need to take in this era of plastic.
“Turning a plastic straw we often use into a paper straw will not immediately impact our environment, but the difference will be profound over time.
“If we gradually change from using conventional disposable plastic products to various eco-friendly products, our future environment will be much safer than what we now worry about.”
The problem with most paper straws is that their plastic coatings — intended to keep them from getting soggy — fail to attach strongly enough to the surface of the straw itself.
Because of this, the straws become coated with plastic in a non-uniform manner, leaving some parts uncoated.
These uncoated allow the paper to take up water, rendering the straw soggy and allowing it to collapse unhelpfully in on itself.
At the same time, the exposed sections of paper also facilitate the more extensive formation of bubbles when the straws are left in carbonated beverages — another problem.
In their study, Dr Dongyeop and colleagues synthesised a well-known biodegradable plastic — polybutylene succinate — to coat the paper straws.
However, they added to this plastic a small quantity of cellulose nanocrystals, tiny fragments of the same material that makes up the main component of the paper.
These nanocrystals, the researchers explained, allows the polybutylene succinate to firmly attach to the paper straw during the coating process and provide uniform coverage as a result.
In turn, this means that straws do not cause bubble formation in carbonated drinks and do not become soggy easily — neither in hot nor cold drinks, or even when used to stir a variety of different liquids.
In tests, regular paper straws previously dipped in cold water at 41F (5C) for one minute bent severely when a weight of 0.8oz (25g) was suspended from one end.
In contrast, the new straw design did not bend as nearly as much under the same conditions, even when the weight applied to the end was doubled.
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The new straw designs are also easy to mass produce and are fully biodegradable — even in the ocean, where both paper and plastic decompose more slowly as a result of the low temperature and high salinity, which impede the growth of microbes.
To demonstrate this, the team left various straws, including their new design, immersed at a depth of around six feet off of the coast of Pohang, South Korea.
Regular plastic and corn plastic straws were found to not have decomposed at all after 120 days, while conventional paper straws preserved their shape and lost only 5 percent of their total weight.
In contrast, the researchers’ new straws were found to have lost more than half of their weight after 60 days in the ocean — and had completely decomposed after 120 days.
The full findings of the study were published in the journal Advanced Science.
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