Discovery Could Make Recycling Much Easier
From: Robina Suwol
Date: 11 Dec 2003
Remote Name: 188.8.131.52
DISCOVERY COULD MAKE RECYCLING MUCH EASIER FOR SOCIETY
Date: 28 Nov 2003
By Paul Rincon, BBC News Online Science Staff
Scientists have moved a step closer to the large-scale recycling of plastic,
one of the great environmental problems of the 21st Century.
Researchers have worked out a way to mould plastics into shape without
At present, plastics are exposed to high temperatures until they are soft
enough to be pressed into new shapes, something that weakens them.
The US researchers have published their study in the journal Nature.
The new method allows the plastics to be reprocessed without visibly
damaging the molecular chains they consist of.
The team from Massachusetts Institute of Technology (MIT) in Cambridge, US,
mixed powdered polystyrene - a "hard" plastic - with a powdered soft plastic,
such as polybutyl acrylate.
When pressure was applied to these powdered plastics in a mould, the hard
component dissolved into the soft component making it malleable and easy to
The scientists shredded and remoulded these plastics up to 10 times and saw
no change in their properties.
"It is quite similar to the processes we use that are already part of the
plastics manufacturing process," said Dr Anne Mayes of MIT, who led the
The key difference, said Dr Mayes, was the use of hard and soft components
in the plastics.
The plastics were remoulded at room temperature This removes the need to
heat plastics to high temperatures and would reduce the high quantities of
energy used to heat and then cool the moulds at manufacturing plants.
The technique may also require lower amounts of additives, such as
flame-retardants and ultraviolet stabilisers to be applied to
The process could go a long way to making large-scale recycling of plastics
"It would be useful for recycling, provided it really does not [degrade the
plastics]," said Dr Hazel Assender, a materials scientist
at the University of Oxford.
"It also needs to be a viable industrial process."
Dr Assender said there were many other issues impeding large-scale plastics
recycling. For example, plastics need to be sorted so that the same types are
At the moment, there are few alternatives to doing this by hand. Plastic
recycling is currently very costly, making it difficult for
recycling firms to recover the costs.
"Right now we have to learn more about what [this technique] can do and what
it can't do," said co-author Juan Gonzalez-Leon of MIT.
Mr Gonzalez-Leon said the technique could improve controlled drug delivery
systems. This includes devices implanted under the skin to administer
medicines inside a person's body.
These are made by implanting drugs in a polymer matrix and they work by
releasing the drug slowly as the polymer erodes.
But many proteins lose their shape and function when exposed to temperatures
above 37C and might be harmed if the polymer matrix part of the drug delivery
device is heated.
Moulding the devices at room temperature could eliminate this problem.
Last changed: March 14, 2006