Polymers, stronger than steel

Fifty years ago, the University of Groningen launched a separate degree programme in polymer chemistry with its own programme of research. Students signed up in droves. Polymer chemist Albert Pennings left DSM to join the staff, and he brought a very strong fibre with him.

‘It’s amazing what you can discover by stirring in a pot.’ Albert Pennings, Emeritus Professor of Polymer Chemistry, has said in numerous interviews. He was stirring a polyethylene solution when he saw thread-like crystals appear. That was in 1963, and it would be a few more decades before these threads could be used in bulletproof vests and the shorts that protect cyclists when they fall.

Pennings was working at the chemical company DSM in 1963, but his fascination with polymers – long chains of simple repeating units, for example the long chains of ethylene that form polyethylene (PET) – dated from his chemistry studies in Leiden. He was taught by Professor Jan Hermans, who had previously been Professor of Physical Chemistry in Groningen (from 1946 to 1953). When Hermans transferred to the University of Syracuse in New York, he asked Pennings to accompany him as a PhD student.

Rocket industry

‘Those were exciting times, with the development of nylon, for instance. There was a lot going on.’ Pennings conducted research into cellulose, which was used to make viscose, the basic ingredient for yarn and for cellophane. ‘I once visited a factory that made viscose yarn. Half of the windows were broken and it was freezing cold. I asked the director why he didn’t repair the windows. He said they didn’t have the money to do so.’ Viscose eventually lost out to nylon, which was much cheaper to produce.

Pennings started to look at other polymers, and at the end of his PhD had interviews with numerous companies and research institutes. ‘The captains of industry came to the University to talk to graduates. I could have gone to DuPont, done cancer research, joined the rocket industry or worked with membranes: you name it.’ The only thing was that he was not American and was thus not allowed to work in the US after his two-year PhD. So he returned to the Netherlands instead.

‘Back in the Netherlands, I went to Akzo and the Algemene Kunstzijde Unie. But I was married and we had a child by then, and there was no housing available near those companies. So I opted for DSM in Geleen.’ At DSM, he noticed that polyethylene formed threads if you stirred the solution. A manager who was anything but a visionary dampened his enthusiasm, Pennings recounts. ‘“Fibre? If I wanted a fibre, I’d order one”, he yelled at me.’

Patents

Pennings thought that the fibres could be very strong. So he continued his research when, after 11 years at DSM, he was appointed by the University of Groningen in 1971 to support Ger Challa , the founder of the Department of Polymer Chemistry there. ‘The flow-induced crystallization that I had seen was special.’ One of Pennings’s PhD students, Arie Zwijnenburg, teased out strands from a polyethylene solution diluted with paraffin. That produced a thread that was rigid and strong.

Still unenthusiastic about strong threads, DSM nevertheless helped fund Pennings’s research, in exchange for patents. ‘That was customary then,’ Pennings smiles. The strong synthetic fibre by the name of Dyneema only broke through in 1990, in such products as bulletproof vests and recently in the cycling shorts of the Giant Alpecin team. These shorts prevent abrasions to the legs and backside during a fall. The full story was recently published on a special website.

But Pennings’s work didn’t hang on this single thread. He had also set his sights on polymers made from lactic acid. ‘These were suited to medical use. Lactic acid is a substance that the body itself produces. It forms polymers with a helix structure, which have all sorts of fantastic properties.’

Plastic soup

The research and teaching at the Department of Polymer Chemistry in Groningen was very broad. ‘That was how Challa envisaged it, and he was quite right. The combination of the chemistry of polymers, their physical properties and the focus on applications came to define the “Groningen School”. This approach was later adopted by the technical universities. Our people became professors there.’

Pennings is aware of the disadvantages of plastics too. The plastic soup is a problem, but he says, again with a smile, ‘they’re now going to fish it out with a polyethylene line. This floats on water and is very strong!’

Pennings retired in 1997 and now lives in Belgium. ‘I still do a bit every now and then, but very little in Groningen.’ He is looking forward to the symposium to celebrate the department’s 50th anniversary. ‘I’d like to see my former students again.’ There’s still plenty for his successors to do, he says. ‘There are still so many fundamental questions in this field. With all those good people, they should be able to achieve something truly great.’

In 1967, the University of Groningen was the first university in the Netherlands to host a department solely dedicated to polymer science. This will be celebrated on 30 June with a symposium.

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