Eco-friendly paper straws that do not become soggy but remain completely biodegradable have been developed by a team at the Korea Research Institute of Chemical Technology.
The researchers said their straws are easy to mass-produce and could quickly replace current products in response to new regulations designed to limit single-use plastics.
Many of the paper straws that are currently available to buy are typically coated in polyethylene (PE) or acrylic resin – the same material used for making plastic bags and adhesives. This is because straws made of paper alone become soggy when they come in contact with liquids, thus losing their core functionality.
Previous studies have reported that polyethylene coating on discarded paper cups can disintegrate into small particles without being fully decomposed and thus become microplastics in the environment.
To develop the new straws, the researchers synthesised a common biodegradable plastic – polybutylene succinate (PBS) – by adding a small amount of cellulose nanocrystals to create a coating material.
The added cellulose nanocrystals are the same material as the main component of paper which allows the biodegradable plastic to firmly attach to the paper surface during the coating process.
Conventional paper straws typically bubble extensively when left in carbonated beverages because the uncoated part easily combines with water, whereas the coated plastic part repels water, causing the drink to contact the uneven surface of the paper straws.
The new straws do not become soggy easily or create as many bubbles because the coating material uniformly covers its surface. The coating material is made of paper and biodegradable plastic and therefore will decompose and degrade completely.
The research team found that these eco-friendly paper straws maintain their physical integrity in hot drinks as well as cold and could be used to stir various beverages such as water, tea, carbonated drinks, milk and other drinks containing lipids.
Conventional paper straws were shown to bend significantly when a weight of approximately 25g was suspended after the straw was dipped in cold water at 5°C for one minute.
In contrast, the new paper straw did not bend as much even when the weight was more than 50g under the same conditions.
The team further demonstrated that their straw decomposes well, even in ocean and soil conditions. In general, paper or plastic decomposes much more slowly in the ocean than in soil because of its low temperature and high salinity, which impede the growth of microbes.
The researchers performed a decomposition test in a marine environment by immersing the straw samples at a depth of 1.5–2m on the coast near Pohang, South Korea.
Regular plastic straws and corn plastic straws did not decompose after 120 days. Conventional paper straws preserved their shape and lost only 5 per cent of their total weight. In contrast, the straws developed by the research team lost more than 50 per cent of their weight after 60 days and decomposed completely after 120 days.
“This technology is but a small step toward the direction we need to take in this era of plastic,” said head researcher, Dr Oh Dongyeop.
“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 convenient disposable plastic products to various eco-friendly products, our future environment will be much safer than what we now worry about”.
Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.