Innovating with elastomers

Materials World magazine
,
1 Sep 2014

Car tyres that can change properties depending on conditions and elastics that contract with electric current are just two of the exciting possibilities for the future of elastomers. James Perkins reports from the KTN Innovation with Elastomers event.

Filling in the blanks
Fillers such as carbon black have been added to elastomers for more than 100 years to improve the qualities of the materials, but scientists are still working out how they do this.

Researchers at Queen Mary University of London (QMUL), led by Professor James Busfield, Head of the Soft Matter Research Group, are among many across the globe working to solve this conundrum. An array of microscopy and modelling techniques are being applied, including focused ion beam SEM and 3D TEM, but there is still no clear answer. Busfield believes multi-scaled computer models are the way forward. The models have so far been inaccurate, ‘though I can imagine that will change in my working career’.

Areas being studied include chain breakage at the interface between the rubber and the fillers, slipping of molecules, rupture of clusters of fillers, chain disentanglements and changes in electrical resistivity in carbon black under strain. Tyre manufacturers are pouring funds into various projects to solve this puzzle, with the winner set to capitalise handsomely on the answer.

3D printing with rubber
Research Fellow at Loughborough University, Dr Jane Clarke is part of a team that has tested methods for 3D printing with elastomers. Inkjet printing has been successful with latex and this is where the team focused its research. Five types of latex were tested for inkjet printing suitability – carboxylated butadiene-acrylonitrile (XNBR), carboxylated styrenebutadiene (XSBR), chlorobutadiene (ClBR), natural rubber (NR) and prevulcanised natural rubber.

As part of the experiment, the team printed a 2cm x 2cm square of latex comprised of 10 layers onto a silicon-coated paper, for a thickness of about 18μm. Materials were judged on three criteria – particle size, viscosity and surface tension. Of the materials tested, XSBR was the most suitable, even though its surface tension was above the preferred range.

Dielectric elastomers
The potential of the dielectric elastomer will soon be unlocked, and when it is, it will be a watershed moment for the material, says Busfield. The devices are made of an insulating elastomer film sandwiched between two compliant electrodes, forming a deformable capacitor.

There are about six devices with commercial potential under investigation at QMUL, though Busfield can only discuss two of them – a biomimetic lens and a braille reader. The lens has potential to aid in the miniaturisation of smartphones.

Busfield says, ‘Your phone works out the ideal focal length by moving the lens backward and forward, but we are looking at having the lens at a fixed point in the camera and changing its curvature.’ The dielectric elastomers have the same sort of stiffness, strength and stretchability as human muscle, leading to potential application in exoskeletons that could support a disabled person, or increase the capabilities of a soldier, firefighter or police officer.  

£4bln Annual turnover of the UK rubber industry, 49% of which comes from tyre sales

576 Enterprises in the UK rubber industry in 2012