Abhijit Venkatesh and Lilian Forsberg, PhD students (and top athletes!) at the division of Engineering Materials, taking on the cellulose composite challenge.

Costumizing sustainable composities - the cellulose challenge

Finding more sustainable materials is one important goal for researchers at the Division of Engineering Materials. One way is to decrease the use of fossil-based materials in composites and polymers. That is where cellulose fits in, as a renewable and inexpensive material used as the composite matrix.
​Lilian Forsgren and Abhijit Venkatesh, both PhD students in the research group Polymeric materials and composites, are studying how to better use cellulose fibers in composites.
-    We both study cellulose composites but it differs in which part of the cellulose structure we examine. Cellulose can be found abundantly is a very important component of plants and trees, basically providing structural integrity. It has a hierarchical structure where each part has a bit different mechanical property. First, there are thin fibers, so called microfibrils. These microfibrils are in turn made up of even smaller fibers called nanofibrils. It is these cellulose nanofibrils (CNF) that we are interested in. The cellulose nanocrystals (CNC) that Lilian works with is just the crystalline part of CNF and they are obtained by using acids, says Abhijit Venkatesh and continues:
PhD student Abhijit Venkatesh
-    I deal with understanding the processing of cellulose nanofibrils reinforced thermoplastic composites, and how the processing parameters affect the final properties, continues Abhijit Venkatesh. The benefit of using cellulose as reinforcement is that it could help to replace or complement the currently used reinforcements like glass- and carbon fibers. It could also strengthen polymers, which are inherently rather weak, to be used as structural materials.

-    My focus is on cellulose nanocrystals. We are trying to customize cellulose to better fit and work with the polymer matrix, but also to understand the challenging mechanisms of cellulose, regarding thermal degradation, moist adsorption and discoloration, says Lilian Forsgren.

Sustainability is a strong driving force, which go for them both. They give an example of possible new biodegradable product: Consider a milk carton cap made out of plastic. If this plastic were replaced with CNF instead, we could reduce the amount of plastic used to produce the cap. Or even totally degradable if starch or corn could be in the matrix.
PhD student Lilian Forsgren
-    I like to be part of the development towards a more sustainable future, no matter how big impact my project will have, every small contribution will make a difference all together, says Lilian and continues:
-    I did my bachelor at the Industrial Design Engineering programme at Chalmers but found materials to be very interesting and hence did my master in Materials Engineering. I enjoy challenges and are eager to gain more knowledge. I really enjoy working with cellulose since it is a fantastic material and it’s a more sustainable alternative compared to many materials used today.

-    My background differs since I come from Bangalore, India, where I took my Bachelor in the field of Mechanical Engineering. After coming to Sweden 2013, completing my master thesis in Materials Engineering, I found the environment to be calm and productive which pursued me to stay and do my PhD here at Chalmers, says Abhijit. And I like to be part of the move towards a more sustainable society. I think the usage of CNF, which is biodegradable, renewable, abundantly available (in all plant sources) and light weight, in itself is the sustainable perspective. Since the source of cellulose is from Sweden this makes it much more sustainable as Sweden has one of the most sustainable forest industries on the world.

Another interesting fact – they are both top athletes within in their sports. Lilian Forsgren is running in the Swedish national team in Orienteering and  Abhijit Venkatesh play for Swedish National Cricket team. Can the competitive spirit be of help in the daily work as a researcher?
-    Being determent and setting up a personal goal is a similarity, that might be same the mindset as when I compete in my sport. I set up goals and can be very effective, Lilian says.
-    I like to think of research as a team game. I am very good to talking and teambuilding, which is something I learned as a coach in my sport. And to have will power, to have a fixed goal, pushing yourself – that helps, says Abhijit.

They agree upon the “never give up"-thing, especially after many failed experiments, you still need to go on.
-    Well, there is a competitive downside also, says Lilian. When I had a series of bad turnouts on my experiments, I was really frustrated. But since there is no physical competitor in this case, you must let it go and get back on track.

They are both halfway through their research and will present their licentiate thesis in September. What are the results so far?
-    We have been able to graft side chains onto the molecule of cellulose Nano crystals, performing an increased thermal stability and interesting mechanical properties of the composites produced with these grafted Cellulose Nanocrystals adding them into a polymer matrix, says Lilian. This means we have found a possible way to overcome some of the main challenges such as avoiding degradation at low temperatures and increased strength and thermal stability.
-    There are some good results soon to be published, where we managed to make crystal clear, transparent composites that can be used as reinforcement. That is cool, Lilian finishes.

Transparent composite with cellulose nanocrystalsMixed and dried material, flaky shards.

Pictures, to the
left: This is a composite with 10% surface grafted CNC (cellulose nanocrystals) and EAA polymer. As you can see, the composite is transparent (the Chalmers logo is on a printed paper below). 3 out of 4 variants of composites with CNC in the study are transparent. (Photo: Marcus Folino)
Pictures to the right: Mixed and dried composite material. The plastic and cellulose are mixed in aqueous solution, and when air dried these shards of material are formed. Afterwards, they are moulded into composites, as the one in the first picture. (Photo: Marcus Folino)

-    The big challenge is that cellulose likes water and polymers usually don’t. When you put them together they tend to separate and makes the composite more fragile. The main results of my research so far lie in the fact that wet processing techniques is successful in producing excellent composites. It also helps us to achieve high CNF loading contents while not sacrificing mechanical properties. The problem is to upscale the process for industry because it is still too expensive but we will hopefully solve that, says Abhijit.

Learn more about the research: Surface treatment of cellulose nanocrystals (CNC): effects on dispersion rheology.
You can also follow Lilian and Abhijit when they are hosting the Chalmers Production instagram account 28-30 May, reporting from Nordic Polymer Days 2018, Copenhagen.
A closely related research within polymer science is presented May 24th at the docent lecture where Roland Kádár talks about “Polymer Rheology and Processing”.

Quick facts Lilian Forsgren
Living in: Gothenburg
Family: Boyfriend and family with two brothers and two lovely nieces.
Interests: Love running and nature, especially high mountains.
Read more about Lilian Forsgren

Quick facts Ahbijit Venkatesh
Living in: Gothenburg
Family: Parents, two siblings (who are twins – boy and a girl) and my lovely wife.
Interests: Love being out in the nature and coaching cricket.
Read more about Abhijit Venkatesh

Division Engineering Materials

Text and photo: Carina Schultz

The PhD students in front of a machine
Abhijit Ventaesh and Lilian Forsgren in front of the compression moulding machine, in the Materials Processing Lab at Chalmers, where the samples of composites are moulded.

Samples of composites
Samples of moulded cellulose composites.

Published: Mon 21 May 2018. Modified: Wed 30 May 2018