Nanofibres the answer to biodegradable ultra-absorbent materials
Ultra-absorbent materials which are also biodegradable could be a commercial reality in the near future, thanks to new research into nanofibres.
Superabsorbent polymers (SAPs) are the material behind the ability of disposable diapers, sanitary napkins, and other products to soak up copious amounts of liquid. SAPs can absorb many times their own weight in liquid. For example, the average diaper is able to absorb 30 times its own weight in fluids.
However, SAPs are not biodegradable. Under ideal conditions, diapers may take as long as 500 years to degrade. SAPs have also been linked to health problems such as Toxic Shock Syndrome, a finding that led to a ban on using them in tampons.
The team, from the Indian Institute of Technology (IIT) Hyderabad, say that the new material, which is made of electrospun cellulose acetate nanofibres, has the edge over SAPs: they are safer biologically, and also biodegrade quickly.
These properties mean that these nanofibres are a good potential replacement for SAPs in female hygiene products.
"Prolonged use of commercially available products could lead to toxic shock syndrome and other conditions, so it’s vital to develop a safe alternative to SAPs,” explained Dr Chandra Shekhar Sharma, from the IIT's Department of Chemical Engineering.
"We propose to eliminate the use of harmful, non-biodegradable superabsorbent polymers from commercially available sanitary napkins without compromising the performance, and even enhancing absorbency and comfort."
The nanofibers are long and very thin fibers made using a technique called elecrospinning – spinning using electricity. They are more absorbent than existing materials thanks to their large surface area compared to their volume. In tests against SAP-laden commercially available sanitary napkins, the researchers found them to be even more absorbent.
The material used in commercially available sanitary napkins is made up of flat, ribbon-like fibres that are about 30 micrometers thick. The nanofibres, on the other hand, are about 150 nanometers thick – about 200 times thinner. This contributes to the porosity of the nanofibre material, thus improving absorbency as well as comfort.
The researchers also tested two alternative versions of the nanofibre material with SAPs added and found the blends were not as absorbent as the nanofibres alone.