General Questions
What is microfibrillated cellulose (MFC)?
Microfibrillated cellulose (MFC) is a small building block of wood. The microfibrills form bundles that make up the cellulose fibers. During the production we carefully separate the microfibrills with a mechanical process to achieve a fine network.
From a chemical point of view, MFC is a polymer consisting of cellobiose monomers that are put together by β-1,4-glycosidic bonded glucose molecules (saccharide).
What is the difference between bacterial cellulose, CNC and MFC?
As the name already states, bacterial cellulose is produced by certain bacteria (i.e Acetobacter xylinum). The bacteria produce a fine, highly pure network of cellulose fibrils with high crystallinity that is almost impossible to reproduce industrially.
Cellulose nanocrystals (CNC) are produced by hydrolysis of the amorphous region of the fibrils. Crystalline nanoparticles with needle/whisker like shapes are formed that can self-assemble and have birefringence.
Microfibrillated cellulose are long, thin fibrils that consist of amorphous and crystalline regions and form a network. They are produced by mechanical treatment with or without enzymatic or chemical pretreatment.
What is the difference between MFC, CMF, CNF, nanocellulose and other synonyms?
Since the terms for nano- and microscaled cellulosic particles are not yet defined, the same material can have different names.
Often microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), cellulose microfibrils (CMF), cellulose nanofibrils and nanocellulose refer to the same material.
The confusion with nano- and microfibrillated cellulose comes from the dimension of the fibril. On the one hand the diameter of the fibrils is only several nanometers thick, on the other hand, the length is in the micrometer range. Therefore, depending on which dimension the focus is on, the product is named differently.
The term nanocellulose should never be used to describe a material because it is often used as an umbrella term and also includes nanocrystalline and bacterial cellulose.
We will always refer to our products as MFC.
Is MFC dangerous for the health?
According to European directives on classification of hazardous substances and preparations, MFC requires no statutory label.
How can I decide which products fit my needs best?
The best way is to ask us. With our experience we can advise you on what product fits your requirements and offer support during the entire development phase.
Technical Questions
What is the composition of MFC?
Standard microfibrillated cellulose produced by the Weidmann process has no additional chemicals. The process is purely mechanical and the product will only consist of pulp and water.
What functional groups are present on the surface of the microfibrils?
Our products have mainly hydroxyl groups present on the surface that can be used for modifications. Carboxyl groups can also be found because the pulp never consists of 100 % pure cellulose.
Is it possible to modify the MFC?
Yes, due to available hydroxyl and carboxyl groups present on the surface of the fibrils, MFC can be modified with a lot of different approaches (i.e. silanization and/or silylation, esterification, carboxymethylation).
Can I further concentrate the water dispersed products in my lab, and if so, how?
Centrifugation is the best way to concentrate the products. We typically centrifuge five (5) minutes at 12745 g. Vacuum filtration using filters with tight pore size can also be used, however this method is very time consuming as the filter paper clogs quickly and drains slowly. When filtering, ensure that the filtrate is entirely clear. A cloudy filtrate indicates product loss through the filter.
What are solvents for MFC?
Solvents for MFC can be divided into two categories: non-derivatizing and derivatizing solvents.
Non-derivatizing solvents dissolve the cellulose by intermolecular forces only. In aqueous media inorganic complexes (e.g. Cuam, Cuen), bases (e.g. 10% NaOH), mineral acids and melts of inorganic salt hydrates can be used.
To dissolve cellulose in non-aqueous media, the following mixtures are recommended: organic liquid/inorganic salt (e.g. N,N Dimethyllacetamide/LiCl), organic liquid/amine/SO2 (e.g. Dimethylsulfoxide/Triethylamine/SO2) and ammonia/ammonium salt (e.g. NH, NH4SCN).
For derivatizing solvents dissolution occurs in combination with formation of “unstable” ether, ester, or acetal derivatives that can be reversed by changing pH or solvent.
Examples for common solvents that dissolve cellulose are DMS, DMSO, THF. Furthermore, trifluoroacetic acid, formic acid and N,N Dimethylformamide/N2O4 are recommended.
Source: Heinze, T.; Koschella, A. – Solvents applied in the field of cellulose chemistry – A mini review
Are unique sample preparation techniques for SEM (Scanning Electron Microscopy) imaging required when using the products?
In order to increase the electron density of microfibrillated cellulose particles so that they are visible under SEM, gold or platinum sputtering is needed.
We use the following procedure: A piece of conductive glass is applied to an aluminum stage using 5 mm carbon tape. One droplet of diluted sample (<<0.5 wt.%) is dropped on the glass and the stage is put in a fume hood overnight to dry or in a vacuum oven operating at low temperature for a few hours.
Alternatively, the drying of the sample can be done with liquid nitrogen and subsequent vacuum drying or with supercritical CO2 drying. The dried sample is coated with 60 seconds gold/platinum sputtering with a thickness in the order of 1-2 nm.
Handling Questions
What kind of storage is best for the products?
Store the products in a cool, dry place and ideally use the whole container at once.
Can I freeze the water dispersed products to increase shelf-life?
No, the forming of ice crystals during freezing will push the fibrils together and therefore agglomerate them.