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Cellulose Nanocrystals

The UMaine Process Development Center is now supplying cellulose nano-crystals (CNC) to academic, public and private research groups interested in evaluating this material. This material is manufactured at the US Forest Service’s Cellulose Nano-Materials Pilot Plant at the Forest Products Laboratory (FPL), located in Madison, Wisconsin.   We offer these materials in support of FPL’s objectives of promoting research on the properties of renewable nano-materials and advancing possible commercial applications.

Cellulose nano-crystals are rod-like particles with dimensions of approximately 5 nm in diameter and 150-200 nm long when using wood pulp as the raw material. Larger crystals can be produced using cotton (10 nm by 500 nm) or algae (20 nm by 1000nm).  All of the materials produced at The Forest Products Laboratory material is made from wood pulp.

CNC Production

Cellulose nano-crystals are produced using 64% sulfuric acid to hydrolyze the amorphous regions of the cellulose polymer, leaving the acid resistant crystals as a product. The other main by-product is glucose. The crystals are purified by diluting and neutralizing the acid and then separating the soluble components from the insoluble CNC. This can be accomplished by dilution and settling, filtration on a vacuum filter, or filtration in a membrane unit. FPL uses two stages of dilution and settling to remove about 90% of the salt and sugar. Once the ionic strength is low enough, the sulfonic acid groups on the CNCs provide a stable suspension and the membrane filtration system can be used with continuous dilution and filtration to remove the remaining salt. Batch size is about 20 kg (dry weight) and requires about a week total process time. Batches can be staggered allowing up to three batches to be produced every two weeks.

The final stage is to remove water using the membrane filtration system. This is capable of dewatering to a 5%-11.5% aqueous slurry that is viscous and quite stable for extended storage. There is sufficiently low water content and high enough ionic strength from the sulfuric acid groups on the CNC to limit bacterial or fungal growth in the suspension. We store the suspension in a cold room – do not allow the suspension to freeze. Freezing will cause ice crystals to form in the suspension which seem to exclude the CNC, causing them to form aggregates that cannot be easily separated after thawing.  For applications that require a dry powder material, the FPL freeze dries the CNC and produces a dry powder.

Precautions when Handling.  Be careful when handling CNC as it can get dispersed in air fairly easily. We recommend using a good cartridge type respirator.

Sample Requests

To order samples, please fill in the Nanocellulose Request Form and e-mail it to us at umaine.pdc@maine.edu or  fax it to us at 207-581-4174. Please note that in addition to the cost of the sample, there are shipping and handling charges.  If you have any technical questions you can contact Michael Bilodeau, Director of the PDC (207-581-2387) or Pros Bennett, Managing Director of the PDC (207-949-4176).