TAGS: Sustainability / Natural Coatings Smart Coatings
Researchers from Aalto University develop a way to turn a waste material from wood into a bio-based transparent film that can be used for anti-fogging or anti-reflective coatings on glasses or vehicle windows. In addition to offering an alternative to the toxic synthetic materials currently used, this approach transforms a waste product into a valuable carbon sink.
Esterification of Acetylated Lignin
Lignin is an abundant waste product in paper and pulp production that is very difficult to process, so it’s usually burned to produce heat.
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Optical coatings need to be transparent, but so far, even rather thin lignin particle films have been visible. We knew that small particles appear less turbid, so I wanted to see if I could make invisible particle films by pushing the particle size to a minimum,” said Alexander Henn, doctoral researcher and the study’s lead author.
The team used acetylated lignin and developed an improved way to esterify it in a reaction that takes just a few minutes and happens at the relatively low temperature of 60 degrees Celsius.
In addition to anti-fogging and anti-reflective coatings, the new approach can also make colored films from lignin nanoparticles. By controlling the thickness of the coating and using multi-layer films, the team created materials with different structural colors.
Photonic Properties
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Sahar Babaeipour’s efforts were key to controlling the particles’ photonic properties,” continued Henn, adding that researchers Paula Nousiainen and Kristoffer Meinander brought expertise in lignin chemistry and photonic phenomena, respectively, helping the team make sense of their results and use them effectively.
According to the team’s feasibility study, the ease of the reaction and its high yield mean that it could profitably be scaled up to industrial levels.
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Lignin-based products could be commercially valuable and simultaneously act as carbon sinks, helping relieve the current fossil fuel-dependence and reduce carbon dioxide emissions,” said Professor Monika Österberg. “
High value-added applications like this are important to drive lignin valorization and move us away from using lignin only as a fuel.”
Source: Aalto University