MFC Application Engineer
As already mentioned in other blog posts, microfibrillated cellulose can be used in a wide variety of applications. Often, MFC has the function of an additive which is used before or during the production process. To retrieve the maximum potential of MFC it is important to disperse and dilute it the right way. Otherwise, the microfibrils will agglomerate and may not bring any positive effects.
It has to be mentioned that our MFC is not available in a dry state but delivered as a suspension. The problem with drying is that the cohesive forces between the microfibrils increase. Thus, the fine fibril network is clumped together and can not be fully redispersed in water anymore.
As a tip, freezing the suspension is not a good idea either! The formation of ice crystals has a similar effect than drying and pushes the carefully separated fibrils close enough together to establish hydrogen bonds.
Depending on the initial solids content of MFC in the product, two different dispersion procedures can be defined.
For initial solid contents bigger than 5 wt% a mixing or kneading device is recommended to obtain a homogeneous suspension with the desired concentration. A good example for such a device is a Kenwood kitchen mixer. If you ask yourself now, why we do not just use a typical laboratory high shear mixer, it has to be noted that a suspension with 10 wt% MFC is not a liquid anymore but resembles the consistency of playdough for kids (and adults 😀 ).
Below 5 wt% solids content the kneading device cannot induce high enough shear forces into the material anymore to further disperse the fibrils. This is when high-shear mixing, for example with a blender or rotor-stator mixer, comes into play. At such low concentrations the high shear is needed to activate the suspension.
For a more detailed description of the procedure, please contact us for our Dispersion and Dilution guide.
I haven’t mentioned dispersion of MFC in polymer matrices on purpose because this would blow up the length of this blog and is an exciting topic in and of itself where a lot of research has been done and is focusing at the moment.