In the heart of the University of Twente, a remarkable woman is dedicated to unravelling the intricate complexities of a material that has shaped our world for centuries: rubber. Professor Dr Anke Blume, the Chair of Elastomer Technology and Engineering, has spent her career exploring the fascinating properties and potential of this versatile substance.
From her early days at the German Rubber Institute (DIK), her experience working for nearly 25 years at Degussa / Evonik Industries to her current role at the University of Twente, Anke has been captivated by rubber’s unique characteristics and the endless possibilities it offers. Her passion for the field is evident in her enthusiasm for sharing her knowledge and inspiring the next generation of rubber scientists.
Anke (right: honored with the ACS Rubber Division's Melvin Mooney Distinguished Technology Award, being the first female to receive this award)
In this interview, we delve into Professor Blume’s journey, her groundbreaking research, and her vision for the future of elastomer technology. As we explore the challenges and opportunities facing the industry, we gain a deeper appreciation for the vital role rubber plays in our modern world.
"We are surrounded by rubber products but typically we are not aware of them. When we slip into our shoes, we are walking comfortably thanks to rubber soles. When we are closing our window it is tightly sealed thanks to a rubber seal. When we drive inside a car, we drive safely and with high comfort thanks to tyres made out of rubber and thanks to rubber-based motor mounts which eliminate the vibration of the engine. When a baby is crying we can calm him / her down thanks to a rubber-based pacifier. These are only a few examples of daily-life rubber products which we highly benefit from."
"Following the current trend of sustainability, also the rubber industry is heading for fully sustainable products. In the case of rubber, this is quite challenging: producing a rubber product can be compared to producing a cake: many different ingredients are required, and they need to be mixed and heated up in the end to get the final product. To reach the goal of a fully sustainable rubber product, all these ingredients need to be sustainable. Quite a challenge!"
The elastic response
"The 'heart' of a rubber compound is the elastomer which gives the elastic response. This is a unique property. Imagine how much less fun we would have without playing with elastic rubber balls! Besides the fun part, this elastic property brings the comfort of walking with elastic shoe soles and driving on elastic tyres. Additionally, rubber can be used also as a damper. In Japan, whole skyscrapers are built on rubber dampers which protect the buildings from any damage during an earthquake. What a fantastic material!"
Latex from the rubber tree
"Such an elastomer can be produced from the latex from the rubber tree. This is the milky substance which gets out of the tyre when you cut the bark. It is also known for dandelion, the little yellow flowers on our meadows. This elastomer is built out of very long polymer chains. Assume a plate with spaghetti! These individual polymer chains, the individual “spaghetti”, need to be reinforced by fillers but also by connecting the chains. In this way, a strong 3D network can be formed on a molecular level. This network delivers the strength to withstand high elongations, to be deformed under external stress and to get back to the original shape when the external stress is gone. This happens e.g. when a ball is bounced: When it touches the ground, the lower side is deformed, it jumps back and gets reformed. Isn’t this also a bit of magic?"
3D network
"To make sure that this magic works also for tyres and other rubber products, the 3D network has to be well-formed. To do so, Charles Goodyear already discovered in 1839 that sulfur forms bridges between these polymer chains. Later it was found that the process can be accelerated by activators like Zinc oxide and stearic acid and accelerators like Diphenyl guanidine (DPG) and N-cyclohexyl-2-benzothiazole sulfenamide (CBS). This means when a rubber compound is produced, like a cake, all these ingredients need to be mixed and then heated up to form the required 3D network. When all ingredients are chosen in the right way, including additional reinforcing fillers, processing aids and antioxidants, the properties of the final rubber product can be tailor-made. It is quite obvious that the rubber part of the pacifier has very different requirements than a tyre tread compound. This is the challenge for each product, to create it in such a way that the individual demands are fulfilled."
Sustainable ingredients
"This challenge becomes now even bigger when another demand is added: Use only sustainable ingredients! Many investigations are ongoing. The most difficult part is the replacement of the whole package which is required to establish the above-described 3D network."
"Here another aspect needs to be considered: one of the biggest rubber products is tyres. The tyre tread is abraded during the lifetime of the tyre, contributing in this way to microplastic pollution (which contributes nearly 30 per cent to the overall microplastic pollution). Such an abraded tyre contains the activator Zinc oxide which can be washed out from the abraded tyre wear particle (TWP) by water (rain, groundwater, water from rivers or seas). Zinc oxide is toxic to all aquatic organisms. Additionally, the accelerator DPG is used for the formation of the 3D network. Its reaction product aniline is also toxic. For this reason, there is a high need to replace both substances but up to now, no replacement was found."
"Just recently, we found that the formation of the 3D network in modern tyre treads follows a completely different mechanism than assumed for more than 100 years. The elastomer was changed to a synthetic one, having a different structure. The established production way by adding the whole package of ingredients to build the required 3D network worked very well also for this elastomer, therefore, it was assumed that the mechanism to form this 3D network was the same. We discovered now that it is a completely different one! What is the great news here: this new mechanism does not need the use of Zinc oxide and DPG! The 3D network is formed in a very sufficient way even in the absence of both substances. The resulting tyre tread compound showed the required performance! This was a great surprise. We repeated the experiments several times and carried out many fundamental studies to understand the reason for this. Now we have reached the point where we can say that we have successfully deciphered this new mechanism."
New TYRE tread compounds do not need any longer Zinc oxide and DPG
"This finding will enable all tyre producers to produce tyre tread compounds without these two critical substances. This means that also the production costs are lower which is always another big issue for all producers. It cannot (up to now) be avoided that tyres get abraded but in this way, the TWP will not release any longer toxic Zinc oxide or aniline. This is a very big step forward to reaching the goal of developing fully sustainable tyres. We will continue our research, heading for the goal of developing 100% sustainable fully functional rubber products. There is much more to do, we are ready for this challenge. What we learned from this latest discovery: never take something for granted when a tiny detail has changed in the system."
The fascination of rubber is waiting
When a young researcher likes challenges, wants to contribute to a greener environment by reducing microplastic pollution and faces the challenge of introducing bio-based as well as recycled materials into new rubber compounds, (s)he should join our team.