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Dispersion of Microfibrillated Cellulose – a critical success factor

Posted by Marianne Rosenberg Read 12. April 2016

dispersion of microfibrillated celluloseMicrofibrillated cellulose (MFC) is a sustainable and environmentally friendly additive. It can improve, for instance, cosmetic, paint or agricultural formulations, and it can potentially replace several other additives. But how can you make sure that you are getting the most out of the MFC when you are using it in your products? One of the most essential things to remember is that good dispersion is very important and that the MFC should be properly incorporated into your formulations. In this article I will give you some guidance on to how to get this right from the beginning.

Why is it important to disperse MFC correctly?

MFC consists of an entangled and flexible three dimensional network of long and thin cellulose microfibrils. These cellulose microfibrils have a high affinity for water and also for each other. It has a high surface area and a high water holding capacity, meaning that strong gels are formed even at low concentrations in water. When diluted in water or incorporated into a formulation, the strong network has to be disrupted so that the microfibrils can interact with the new surrounding medium and form a new network structure When you achieve this fine homogenous dispersion of the cellulose microfibrils throughout your formulation, you obtain the strong network structure that gives you all the interesting properties MFC has to offer.

how to best incorporate MFC?

There are several ways of achieving a good dispersion depending on the type of formulation and the equipment that you have available.

Some of the most important things to consider:

  • When adding MFC into a formulation, it can be a good idea to:
    • Add it to the most polar phase of your formulation, preferably in the water phase
    • Add it early in the formulation process, for example in the grind phase with pigments and fillers
    • Ensure that the whole dispersion volume is homogenously mixed and that you have an efficient transfer of the energy from the stirrer to the full volume of the dispersion
  • It is a robust material and can be added in a homogenizing or milling step. If you have a process step that could help the dispersion, it is wise to add it before, or in, these steps.
  • In an emulsion, the MFC should be added to the water phase before mixing with the oil phase
  • If you are diluting to a very low concentration, in a low viscosity medium, you might need high shear equipment. It might also be a good idea to make a more concentrated dispersion and dilute afterwards
  • The higher the dry content of the MFC, the more energy and high shear will be required in order to disperse it properly. 

What type of equipment can you use?

When dispersing MFC, it is preferable to use high shear equipment. Lower shear equipment can also be used, but it takes longer to achieve sufficient dispersion (dispersion is a function of both time and shear force).

Below is a list of examples of equipment and dispersing times based upon our experiences.

Equipment

Stirring speed (RPM)

Time (min)

Ultra turrax

10 000

4

Dispermat dissolver

2000

10

Propeller mixer

2000

15

IKA-stirrer (3 blade mixer)

750

20

 

 

 

 

 

How to evaluate the quality of the dispersion?

When you are evaluating the incorporation into your formulation, you should look for a homogenous dispersion that does not contain any lumps or visible aggregates. The MFC gives a very smooth and cream-like dispersion. When dispersed correctly, you should not see any lumps. Immediate sedimentation or phase separation might also indicate insufficient dispersion.

A general advice when you do not obtain the expected effect in your formulations, is to examine the dispersion method and order of which the ingredients are added. If you suspect there is a problem with the dispersion, it might be a good idea to test different dispersion times and methods and see if this makes a difference.

The take-home message is that when using MFC in your formulations, it is very important to notice that good dispersion is a critical factor for success.

 > Read also: What is MicroFibrillated Cellulose (MFC)?

 

Download our FREE eBook  Microfibrillated Cellulose at a glance

 

Topics: MFC


Marianne Rosenberg Read's photo

By: Marianne Rosenberg Read

Marianne Rosenberg Read is a research scientist working with microfibrillated cellulose. Through her six years of working with MFC she has gained experience in characterizing microfibrillated cellulose as well as working with process, production and development of new applications for microfibrillated cellulose. Marianne has a PhD in metal organic chemistry and catalysis.

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