What is microfibrillated cellulose?
The cellulose polymer is a naturally occurring linear polymer made of repeating units of glucose. Single polymers are stacked together forming fibrils, and these fibrils stack together again to form the cellulose fiber structure that is present in nature. This makes for a very interesting supramolecular structure that consists of both crystalline and amorphous regions.
Microfibrillated cellulose (MFC) is obtained through a fibrillation process of cellulose fibers. Using mechanical shearing, the cellulose fibers are separated into a three dimensional network of microfibrils with a large surface area. The obtained fibrils are much smaller in diameter compared to the original fibers, and can form a network or a web-like structure as seen in the image below.
Scanning Electrone Microscope image of WEIDMANN microfibrillated cellulose WMFC Q_standard.
Image courtesy of WEIDMANN Fiber Technology.
How is this material different from cellulose itself?
Exilva, one of leading blogs on nanocellulose, nicely explains what the difference is.
- As mentioned earlier, MFC is obtained by fibrillating cellulose fibers longitudinally, and thus obtaining a three dimensional network of cellulose microfibrils, which has a much higher surface area than regular cellulose fibers or powdered cellulose. This leads to some very interesting properties like very high water holding capacity and ability to form strong gels at low concentrations due to a larger number of hydroxyl groups, which comes in handy in applications such as controlling drying time of coatings and concrete, stabilizing water based formulations or keeping a surface longer wetted.
- Microfibrils in MFC have diameters in nanometers and lengths in micrometers, which makes them long and thin. This high aspect ratio makes the material high strength as useful in applications such as reinforcements for composites, films and barriers.
- Even though microfibrillated cellulose is not soluble in water, it can exhibit some properties as water soluble cellulose derivatives. At the same time, it has some advantages over those derivatives such as being stable over the whole pH range, at high salt concentrations and at high temperatures.
Why microfibrillated cellulose is of interest right now:
Microfibrillated cellulose has been present in the academic sector since the 1980’s, but the interest for this material has been growing significantly in the industry sector recently, as it is becoming commercially available.
Based on Packaging Digest, this is definitely one of top five “exciting, emerging sustainable packaging materials to watch for”.
The first benefit of using this material is that it can strengthen and lighten fiber materials sustainably, obtaining products with reduced material use but with the same performance. For example, using just 1% of MFC can result in a 15% to 20% product performance improvement. The MFC fibers can give a material that is stronger and stiffer than glass or carbon fiber and more lightweight at the same time.
Secondly, the material provides excellent oxygen and moister barriers. MFC can be used in the form of film, nanocomposites and paper coatings. For example, oxygen transmission rates (OTR) of 4 -10 mL/m2day and a water vapor transfer rate (WTR) as low as 0.4 g/m2day for MFC films have been reported.
Finally, the material can be extracted from plant waste thus providing a good competitive price point. In addition to that, its mode of production has completely changed, as many forms of optimization have been developed in the last few years. New sources, new mechanical processes, and new pre- and post-treatments are currently under development to enable the use of MFC materials on an industrial scale. As an example of MFC producers already in the market is WEIDMANN Fiber Technology. They not only produce MFC for novel and engineered applications, but also offer know-how related to MFC properties and uses.
Featured image shows WEIDMANN microfibrillated cellulose WMFC Q_advanced. Courtesy of WEIDMANN Fiber Technology.
