General Questions
What is MFC?
Microfibrillated cellulose (MFC) is a small building block of wood. The microfibrills form bundles that make up the cellulose fibers. In our production process we carefully separate the microfibrills with a mechanical process in order 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).
For more information have a look at our Blog.
What is the difference between bacterial cellulose, CNC and MFC?
As the name already says, 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 nearly impossible to reproduce industrially.
Cellulose nanocrystals (CNC) are produced by hydrolysis of the amorphous region of the fibrils. Thus, crystalline nanoparticles with needle/whisker like shapes are obtained 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. So depending on which dimension the focus lays 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 includes nanocrystalline and bacterial cellulose as well.
We’ll always refer to our products as MFC.
Is MFC dangerous for the health?
No, according to European directives on classification of hazardous substances and preparations, MFC requires no statutory label.
Is there an ISO/DIN standard for MFC?
Not yet, but they are working on it.
What is the difference between the products?
The products can be distinguished by raw material (i.e. pulp source, bleached, unbleached), surface area, aspect ratio and surface charge. Depending on the combination of these parameters different secondary qualities like viscosity will be influenced.
How can I decide which products fit my needs best?
The easiest way is to ask us. With our experience we can advise you on what product might fit your requirements best and offer support during the entire development phase. Application specific MFC can be developed by choosing the right plant source, pulping technology, defibrillation technology as well as degree of fibrillation.
How do I request a product sample?
To request a product sample, please fill out the following form: Product Samples
What is the Weidmann production capacity?
The installed capacity is around 500 tons (dry-based) of MFC, depending on the product blend produced. For large MFC demands, the pre-processing is done at Weidmann and the following-steps are done locally.
Why does Weidmann deliver MFC only as a slurry or paste and not dry?
To maintain the special properties of microfibrillated cellulose it is important that the network structure is not destroyed. By reducing the water content in the product the microfibrils come into closer contact with each other and form hydrogen bonds. At a certain solids content the bonds between the fibrils get too strong such that they cannot be separated anymore and form agglomerates. The higher the surface area, the lower is the solids content where agglomeration occurs. Thus, depending on the properties of a product, we can offer maximum solids content from 15 – 30 wt%.
What are the CAS number and INCI term?
CAS: 65996-61-4
INCI: “Cellulose Pulp”
What is the customs tariff number?
For our standard grades the customs tariff number is 4703.2100
Technical Questions
What MFC properties can be generated through the Weidmann production process?
With the Weidmann production process surface area, aspect ratio and surface charge can be tailored specific to the application. Therefore, viscosity, transparency and water retention can be influenced.
What is the composition of MFC?
Standard microfibrillated cellulose produced by the Weidmann process has no additional chemicals inside. The process is purely mechanical and the product will only consist of pulp and water.
What is the influence of water quality on MFC?
Water quality can have an influence on the MFC suspension because the presence/absence of different ions can change the surface charge and thus influence i.e. viscosity. Especially for modifications, only deionized or distilled water should be used.
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. Furthermore, carboxyl groups can be found, because the pulp never consists out 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).
Why do the water dispersed products look like a gel/yoghurt/paste?
Our microfibrillated cellulose forms through hydrogen bonding a network with a high water retention and therefore builds a gel. By increasing the solids content, the product will become a paste.
Can I further concentrate the water dispersed products in my lab, and how?
Centrifugation is the best way to concentrate the products. We typically centrifuge 5 minutes at 12745 g. Vacuum filtration using filters with tight pore size can also be used but 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.
Can I dry and redisperse the water dispersed products?
No, if you want to achieve the same properties as the original product. Drying the water dispersed products will lead to agglomeration of the fibrils through hydrogen bonding.
There are possibilities with chemical modifications, please contact us for further technical discussions.
What is the maximum solids content I can get without loosing quality?
The maximum solids content depends on the quality of the MFC. For lower surface areas solids contents up to 30 wt% can be achieved. Products with higher surface areas can only be concentrated up to 10 wt% due to their huge water retention.
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 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 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?
Water dispersed products should be stored under refrigeration (but do not freeze them!), preferably between 2-10 °C, in a sealed bucket. Powder products should be stored in a dry place away from ignition sources.
What is the layer of water on top of the water dispersed products good for?
Microfibrillated cellulose material depending on its degree of fibrillation will displace water over time. Thus, it is recommended that water dispersed materials are stirred thoroughly before use.
How do I dilute/disperse the product?
The best way to disperse the product on lab-scale is to add water step by step while stirring. For dilution below 5 wt% a high shear device such as an Ultraturrax is needed to activate the suspension.
How do I add MFC to my product?
It is really important that there are high enough shear forces when MFC is added to the product. Otherwise the MFC is not evenly dispersed/distributed and the desired effects will not occur.
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.
If you have any additional questions regarding microfibrillated cellulose in general or our products, please contact us.
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