Spotlight on PhD: Janaina Gianfelice de Castro

8 December 2014

On 11 December, Janaina Gianfelice de Castro (1982) will be awarded her doctorate at the University of Amsterdam (UvA). During her research at the Institute of Physics (IoP), she explored the breakage behaviour of rubber and made discoveries that could save time in rubber production.

What did you discover?

‘In my research, I was looking for a way for accurately determining the point at which the synthetic rubber polymer NBR breaks. NBR stands for nitrile butadiene rubber and is used in ball bearings, among other applications. Silicon dioxide nanoparticles are added for extra strength. The strength of different types of rubber varies, however, as different concentrations as well as different types of silicon are used depending on the rubber. I have discovered that you can use the Griffith theory to calculate the point at which each type of NBR will break when stretched.’

How is this useful?

‘Breakage can occur in ball bearings, causing them to leak. Rubber producers therefore spend a lot of time measuring the strength of their rubber. Knowing the point approximately at which the rubber will break when stretched speeds up this testing process since you know in which range to start your tests, therefore saving time and money.’

How did you start your research?

‘I decided to see if I could describe the breakage behaviour of rubber using the Griffith theory, which required my adapting the theory somewhat. It turned out that I could. It is extraordinary that the modified Griffith theory applied to rubber, since this theory mostly works for linear processes. Rubber does not stretch linearly but abruptly. It would probably be something of an exaggeration to say I can use this to predict the force that will cause rubber to break. There are a number of factors that determine the strength of rubber. But it is true that I have taken the first, difficult step towards making such predictions. More work is needed to investigate the other factors involved.’

Did you always want to become a scientist?

‘No. In fact, I initially had no interest in research at all. I was working as a trainee at Swedish ball bearing manufacturer SKF when I was asked to do this doctoral research. The strong link between this research and the industry appealed to me right away. But I am glad it's behind me now. I do not consider myself a real scientist. I actually have too little patience for it and I do not like having to think about my research at home in the evenings. Next week I start work as a senior representative in the commercial marketing department of SABIC, a plastics manufacturer. It will be an opportunity for me to engage another of my passions, namely communication. I can't wait to start.’


Text: Carin Röst

Janaina Gianfelice de Castro-Institute of Physics

Published by  Faculty of Science