Microfibrillated cellulose (MFC) has been present in the academic sector since the 1980’s, but it is completely newborn in a commercial sense as it is now becoming commercially available. In this blog post I will try to give you a brief overview of why MFC is different from the other commercially available cellulose products.
What is cellulose?
Cellulose was discovered in 1838 by a French scientist called Anselme Payen. He started looking more closely into plant and plant matter. He managed to isolate the cellulose from the plant matter, thus finding the key to its chemical formula.
The cellulose polymer is a linear polymer that consists of D-glucose units linked together. In nature, however, the cellulose polymers are not present as single polymers but are rather arranged in quite an interesting supramolecular structure. Simply explained, the cellulose polymers are stacked together forming fibrils, and these fibrils again form the cellulose fiber structure that is present in nature.
The cellulose fiber structure consists of both crystalline and amorphous regions. This cellulose fiber structure is the basis of a variety of different cellulose products and qualities that has been developed throughout the years.
The table below, show some of the most common commercially available cellulose products compared to MFC. You may recognize some of these cellulose products.
- Milled and fractionated cellulose fibers
- Acid hydrolysis of cellulose fibers
- High crystallinity, low aspect ratio
- Chemically modified cellulose
- Soluble polymers
Microfibrillated cellulose (MFC)
- Fibrillation of cellulose fibres longitudinally
- High aspect ratio
- 3D network of microfibrils
How does microfibrillated cellulose differ from other cellulose qualities?
I will give you three main reasons why I believe MFC is a completely new and different cellulose product:
- Much higher surface area than other cellulose products
MFC is made by fibrillating cellulose fibers longitudinally, giving an advanced three dimensional network of cellulose microfibrils. As you can imagine, this network of microfibrils have a much higher surface area than regular cellulose fibers or powdered cellulose.
This increased surface area leads to new and interesting properties. For example, in the MFC there are now a lot more available hydroxyl (OH) groups which leads to very high water holding capacity and ability to form strong gels at low concentrations. The latter meaning that the material provides high viscosity and improved stability in formulations even when added in low amounts.
The high water holding capacity can be useful for example in controlling drying time of coatings and concrete, stabilizing water based formulations or keeping a surface longer wetted.
If you want to learn more about the high water holding capacity of MFC, read our blog post, Water Holding Capacity – How Microfibrillated Cellulose does it.
- Much higher aspect ratio than other cellulose products
The three dimensional network in MFC consists of cellulose microfibrils that have diameters in the nanometer range and lengths in the micrometer range. In other words, the microfibrils are very long and thin. Therefore they have very high aspect ratio compared to other cellulose products, like for example, microcrystalline cellulose (MCC), which consists of highly crystalline particles with a low aspect ratio. The high aspect ratio of MFC gives the material high strength and potential for reinforcement of composites, films and barriers.
- Non-soluble, but still inhabits many of the same properties as water soluble cellulose derivatives
Even though MFC consists of a three dimensional network of insoluble microfibrils, its properties can often be compared with those of soluble high molecular weight polymers. For example, it can increase viscosity very effectively and shows an extreme shear thinning effect often seen with high molecular weight polymers.
Examples of cellulose based high molecular weight polymers are cellulose derivatives, such as cellulose ethers (derived from the cellulose fibers by chemical modification). Often, these cellulose derivatives also give a high viscosity and a shear thinning effect, but they can be vulnerable to pH differences, high salt content and high temperatures.
This is an area where the MFC material show very different characteristics to the cellulose derivatives. Due to the non-soluble nature, the material it is very stable over the whole pH range, at high salt concentrations and at high temperatures.
Matches the competition
In conclusion, MFC is a new and special cellulosic material because it represents a hybrid between the insoluble cellulose fibers and the soluble cellulose derivatives, and thereby you can obtain the positive effects of both type of products in one material.
In addition, it also gives new properties like the very high aspect ratio giving potential in reinforcement of materials.
To my mind, MFC is the first cellulose product that can compete head to head, and even outperform, the advanced synthetically derived polymers. This is due to the combination of its ability to hold water, the special rheological properties (extreme shear thinning and high viscosity at rest giving increased stability) and the robustness of the material.