The goal of our Know Your Fibers series is to provide info about different types of fibers for our readers. In this post, we’ll take a look at how cotton compares to viscose rayon.
While cotton and rayon fibers are both made from the same polymer (cellulose), cotton’s cellulose is grown in five to six months by plants. Rayon’s cellulose is produced from trees, which require a much longer time (years) to grow before they are big enough for harvesting. The trees are chemically processed to remove everything (bark, lignin, etc.) but the cellulose, and then the remaining cellulose is regenerated into man-made fibers. Since the molecules in cotton consist of longer cellulose chains than those in rayon cellulose, the longer cotton molecules are also packed more in-line (crystalline areas) with each other than rayon’s more random (amorphous areas) molecules. Both of these molecular qualities combine to make cotton fiber much stronger than rayon fiber.
Unique Properties of Cotton
The same two molecular properties also lead to the amazing fact that cotton fibers increase in strength when wet, whereas viscose rayon fibers lose strength when wet. Improved wet strength is important for dry wipes that are used to absorb spills, and also for added strength in pre-moistened wet wipes. Higher wet strength is also an asset for medical products that are used to clean, protect, absorb bodily fluids, and even to support organs during surgery.
Regenerated Fibers Are Not Natural
Cotton fibers come from plants and there are many varieties of seeds used to grow it. The type of cotton seed used is primarily determined by the conditions in the area where it is planted (wet, dry, short or long growing season, etc.). Viscose rayon can be produced from any number of trees, grasses or even cotton, as they all get their strength from cellulose. Some rayon fibers are produced using bamboo (which is a grass) as the cellulose donor. Recently some false claims were made labeling rayon fiber made from regenerated bamboo plants—consumers were led to believe that these are natural fibers that come directly from bamboo—but “regenerated” is a key word here. Though produced from bamboo, this regenerated viscose rayon fiber is not natural. This caused the Federal Trade Commission (FTC) to take action to have the product manufacturers remove this labeling.
Locally Grown & Processed
Cotton is also grown right here in the USA across the southern tier states, from Virginia all the way to California. There are no (zero!) producers of viscose rayon in North America. For every pound of fiber harvested, there are roughly 1.6 pounds of other useful products being created, such as cottonseed oil, cattle feed, and mulch. In fact, over the last 20 years modern cotton farming techniques have reduced the energy used by 66%. In addition, over those two decades water usage has been reduced by 49%, carbon dioxide emissions has been lowered by 33%, and soil loss has decreased by 34%. All of this has occurred while new seed varieties have reduced the amount of pesticides used by 23%. With cotton farming techniques, less will always mean more, especially when it comes to sustainability.
Purified Cotton vs. Viscose Rayon Production Steps
Let's look at the steps involved in producing purified cotton and viscose rayon. Viscose rayon can be made using any raw scour of cellulose, but since the vast majority produced commercially uses trees, we will take look at that step in production. As you can see by the diagram below, the process is far more simple for producing purified cotton fibers.
Knowing your fibers means understanding everything about them, from how they are farmed to their distinct properties in a variety of situations. While we certainly have our opinion on the winner in Cotton vs. Viscose Rayon, we’ll leave it up to you to decide who takes home the crown.
Editor's Note: This article was first published in December 2013 and has been updated for accuracy and comprehensiveness.