Artificial representation of a space elevator. Source: NASA

Plastic: inspiration for space research scientists

Space with its endless expanses is an inspiration not just for the creators of science fiction literature, Hollywood films or TV series. Space is a challenge to the scientific community too – and one that can only be tackled with the help of different materials. Plastic is one of them ...

Materials for space stations or satellites are put into orbit by rockets at present. “But this is not just expensive; it consumes valuable raw materials too”, says Professor Dr Klaus D. Jandt from Friedrich Schiller University in Jena. “Because rockets can only be used for transport purposes once. This explains why an intensive search is currently being made for alternative ways to put things into orbit”, says the Material Science Professor.

Jandt and his colleagues have high hopes for the concept of a space lift, in which a “cabin” travels from the surface of the earth to a geostationary space station and releases satellites directly there.

The material scientists from Jena have now succeeded in making major progress in development of the basis for this: as the physicist Matthias Arras, Professor Jandt and their colleagues from Jena University report in the current issue of the well-known American journal “Carbon”, they have developed a new polymer-ceramic composite that has the potential to be used later on in a space lift.

Carbon nanotubes (CNT) are the basis for the innovative new material. “These cigar-shaped tubes made of pure carbon have up to 30 times higher tensile strength than steel and are substantially lighter as well”, explains Jandt. He explains that this makes them a particularly attractive proposition for use as a “lift cable” into orbit, which would need not only to have extremely high tensile strength but also be very light. “Such a cable could not be made from any other material that has been known up to now”, says Jandt.

However, the CNTs can only realise their full potential when they are all aligned in the same direction, “somewhat like cigars in a box”, says Professor Jandt and continues: “Aligning the CNTs, which have a diameter of only a few billionths of a metre, is still causing problems.”

And this is exactly where the research scientists from Jena have now achieved a breakthrough. They first of all incorporated the CNTs in a polymer melt, which was then stretched (pulled) extensively. “Stretching the plastic melt creates a highly aligned polymer substrate”, explains Matthias Arras, a doctoral student in Professor Jandt’s team. This means that the polymer substrate already has very high tensile strength in itself. When the polymer melt solidifies, some of the polymer takes on an amorphous form and interface crystallisation occurs. During the stretching process, crystals grow on the carbon nanotubes in an orderly pattern and bond with them. “In the course of the stretching process, the polymer chains of the amorphous part of the polymer lock with the crystals on the carbon nanotubes and as a result pull all of them in the same direction”, explains Arras. “The result is extremely high alignment of the nanotubes, something that has not be observed in polymers in this form up to now.”

Arras MML et al. Alignment of multi-wall carbon nanotubes by disentanglement in ultra-thin melt-drawn polymer films. Carbon (2013),