Research on surface weather resistance

How to maintain performance over time?

The design of high-competition athletic track surfaces involves the development of materials that guarantee uniform performance in any use condition and at any point on the surface, and that are able to maintain their performance over time.

MONDO prefabricated track surfaces comprise two different layers of solid rubber that are joined together through a vulcanization process and then are installed according to a strict protocol, which—along with surfaces’ homogeneous thickness, controlled composition and viscoelastic performance consistency— guarantee unequalled  uniform performance. 

MONDO track surface formulations are designed to guarantee the right degree of slip resistance in both dry and wet conditions while maintaining the same elastic performance over a wide temperature range to ensure a consistent elastic response, regardless of the season and climate where they are installed.

However, maintaining performance over time is  one of the most challenging activities in Research and Development. Indeed, there are very few products made of coloured rubber which are permanently exposed to an outdoor environment.

Running tracks are exposed to solar radiation and the ozone, sudden changes in temperature and humidity and rain and undergo periodic cleaning which involves chemical detergents at times.

Since the 1970s, the MONDO laboratories have therefore been looking for new methods that can be used to assess in a relatively short space of time phenomena that normally occur over a period of years with the aim of designing products that increasingly withstand the various climatic conditions which are the main cause of material ageing.

In the early 1990s, MONDO began to use the first formulations created specifically for outside installation.

Since then, several instruments have been introduced to the MONDO laboratories which are useful for measuring and assessing the behaviour of materials: MONDO currently has its own ovens for simulating thermal ageing under various temperature and air change conditions, a climatic test chamber for simulating thermal and humidity cycles, a Xenotest rotating rack and a Q-Sun flat plane test chamber for simulating exposure to solar radiation and rainfall cycles, and an ozonometer for exposing materials to oxidising environments.

Since 2009, additional technical checks have been added to the artificial ageing protocols: as well as changes in mechanical properties which have been measured since the 1990s, by introducing a differential scanning calorimeter to its laboratory in 2009, MONDO has also been able to measure the oxidation times of its tracks which are exposed to heat. 

Since 2016, in collaboration with the Politecnico di Milano and international laboratories, MONDO has conducted research to understand how atmospheric elements affect a track’s aging and performance characteristics over time, which enabled the company to make design enhancements, that can extend a track’s life and performance.

The ageing phenomena of materials subjected to extreme climates have been studied at Q-Lab Arizona in the United States, one of the largest outdoor testing facilities in the world.

MONDO provided some formulation samples specifically designed for ageing phenomena study, which have been subjected to natural outdoor exposure tests for over two years.

The same materials were subjected to external exposure tests and artificial ageing tests at the MONDO laboratory in Gallo d'Alba in Italy, and at the laboratory of the Department of Chemistry, Materials and Chemical Engineering of the Politecnico di Milano.

The collaboration with the Politecnico di Milano has allowed MONDO to conduct the world’s first study on the ageing process of athletic track surfaces, with the aim of identifying an accelerated artificial ageing method able to simulate, in a relatively short time, the effect of natural ageing and the most appropriate methods to test the performance of the tracks after ageing.

At the beginning of 2017, in a move to continue to improve its laboratories, MONDO introduced a latest generation dynamometer in order to apply protocols for checking the mechanical behaviour of the track if subjected to compression and installed a thermogravimetric balance to analyse the thermal decomposition of its surfaces.

To examine the structural modifications that the track surface undergoes, MONDO also uses modern electron microscopy and spectrophotometric analysis techniques on a daily basis.

The first test results, to which were added the results obtained from analyses of samples of tracks previously tested, have allowed MONDO to introduce new, innovative procedures for age testing and materials verification, and to improve track design and quality control procedures.

Furthermore, the new procedures have enabled MONDO to conduct more in-depth analyses and tests of UV filters, antioxidant and anti-ozone components, and types of polymer and mineral fillers, and apply the results to optimize the additives that protect track surfaces from atmospheric agents.

The results of this research are clear: although we cannot stop the ageing of a material that is exposed to the outdoors, this process can be slowed down and the durability of the sports surfaces increased by correctly balancing the polymer system and additives. The first result of these studies is the Olympic track in Tokyo: the changes made to the formulations designed for top-level competition will be applied to the whole range of outdoor installation surfaces.

Thanks to these techniques, further developments are likely which will create increasingly higher performing products and, in particular, develop products designed for specific areas in the world where there is more exposure to UV rays or higher temperature differences.

References

Ageing in athletics tracks: A multi-technique experimental investigation, Polymer Testing, May 2018

Stefano Tagliabue 1, Luca Andena 1,2, *, Andrea Pavan 1, Andrea Marenghi 3, Emanuele Testa 3 and Roberto Frassine 1

1 Politecnico di Milano, Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”,
Piazza L. da Vinci, 32, Milan (Italy)
2 Politecnico di Milano, Engineering, Exercise, Environment, Equipment for Sport (E4Sport) Lab,
Piazza L. da Vinci, 32, Milan (Italy)
3 Mondo S.p.A., Piazzale Edmondo Stroppiana, 1, Alba (Italy)