Microfibrillated cellulose (MFC) is a natural and sustainable material derived from cellulose. As for any process, it is important to have good control of the raw material when producing MFC. For cellulose, the picture is slightly more complicated since there are many cellulose sources that can be used as raw material, and each of them will lead to different MFC qualities. In this blog post I will introduce you to different raw materials, how the processing of the different raw materials can affect the MFC quality and how to deal with the natural variations in the raw material.
Various cellulosic sources for Mfc production
MFC in general can be produced from numerous cellulosic raw materials. Some examples are wood sources such as spruce, pine, bamboo and eucalyptus, or vegetable and plant sources such as citrus fruit, sugar beet, flax and hemp. The cellulose fibers in these sources are different with regards to for example fiber length, degree of polymerization (chain length of the cellulose polymers), crystallinity and parenchymal cells. This will be reflected in the quality of the resulting MFC. You can read more on these topics in articles from Zimmermann and co-workers and Alia and co-workers.
Source and process
Both the source of the raw material and the process it undergoes influences the MFC quality. For example, extraction and purification steps may change the raw material. Firstly, the amount of lignin, hemicellulose and other components in the raw material will vary accordingly and might change the surface properties or morphology of the fibrils/fibers.
Secondly, different processing and purification methods of the cellulose pulp might lead to different amounts and types of functional groups on the surface of the microfibrils. This again could affect the stability of the MFC at high temperatures or in alkaline or acidic environments.
The purity of the cellulose pulp will, of course, also be reflected in the MFC material: Highly purified cellulose pulp result in a more consistent MFC quality while MFC material made from highly purified cellulose is white and odorless.
How to deal with variations in the raw material?
Dealing with products derived from nature, one is used to have variations in quality. This is due to the variations in the feedstock, be it hardwood sources, softwood sources, vegetable sources or plants. To counteract these natural variations the MFC producer must have good methods for analyzing the raw materials, a set and stable production process and good quality control so that the variations in the resulting MFC can be minimized. Solid producers of cellulose are often experienced in characterizing their sources and minimizing the variations in the end products.