Research Initiative: Rayon and Polypropylene

Delia Tacheny
INT 323 - Textiles, Materials, and Sourcing

Last week, we covered a lot of topics in our book, so this week we took a break from the textbook to focus on some other things. That being, said, this week's blog is focused primarily on our research initiative assignment of the week.

Research Initiative: Rayon and Polypropylene

We were asked to select two links to watch, learn from, and discuss in our blogs. The two links I selected were videos: one on the production of Rayon, and the other on Polypropylene. 

RAYON:

The video on Rayon was intriguing because it was actually just an experiment, not mass production. Watching the experiment being conducted however gave me better insight into the chemical process behind the production of Rayon. Rayon is also known as artificial silk, but interestingly enough, the natural material used in Rayon is cotton. In the experiment, the primary chemical substance he used was a basic copper carbonate, made from copper sulfate and baking soda combined. He poured 4 grams of the aquamarine carbonate into a beaker, and then he added about 40 mL of a 25% concentrate Ammonia solution; the formed solution is bright blue. The copper carbonate doesn't react entirely with the Ammonia, so a little bit of residue remains on the bottom; so, to ensure the experiment works, he pours the liquid into a clean beaker. The compound has unique properties, one of which is dissolving cotton wool. The highly soluble cotton forms a "viscose" which is the raw material in the production of Rayon; the viscose is noticeably thicker. To form the actual artificial silk, he fills a syringe with the solution and injects a stream of the viscose into a sulfuric acid solution. Once in contact, the cellulose from the viscose begins to polymerize, while the compound of the copper dissolves, leaving thin blue fibers of Rayon. Eventually the copper salts are completely washed from the fibers, and they become colorless. Next, he dips the fibers in bleach and is then able to feel them. His production of fibers were soft and easily torn; he says this is due to him using too thick of a needle -- thinner fibers will be more durable. Overall, the video was a great way to learn more about Rayon. 

I did some separate research to compare the experiment to mass manufacturing of Rayon, and I believe the experiment represents the process well. In Rayon manufacturing, sheets of cellulose (from wood pulp or cotton linters) are steeped in sodium hydroxide, producing sheets of alkali cellulose. The sheets are then dried, shredded, and aged in metal containers for a few days, with the temperature and humidity being carefully controlled. These crumbs are then churned with liquid carbon disulfide, which turns the mixture into sodium cellulose xanthate -- orange-colored crumbs. This is than bathed in a caustic soda, creating a viscose solution. At this point, any dyes are then added, and the solution is filtered and once again stored for up to 5 days. Following this period, the liquid is forced through a spinneret into an acid bath, which solidifies the filaments. For staple fibers, they use a larger spinneret with larger holes, and for filament fibers, a spinneret with smaller holes is used. After the fibers are produced, they will go through whatever spinning process necessary to make a yarn. 

POLYPROPYLENE:

The Polypropylene Video was highly technical and focused heavily on the chemical side of Polypropylene. There are three chemical structures of Polypropylene: 1) Isotactic, 2) Syndiotactic, 3) Atactic. Isotactic is the structure used for fibers and plastics as the stereoregularity of the polymer chains gives closer packing, and the high crystallinity gives it good strength, making it suitable for fibers. The other two structures have very low crystallinity. When using a catalyst, the polymerization process has three phases -- solution phase, mass phase, and gas phase. The overall process is somewhat complex, but the images below illustrate it fairly clearly. There are actually two processes: the suspension process and gas phase. Some properties of Polypropylene are that its density is 0.9 gm/cc; its moisture regain is between 0.01 and 0.1 percent; its melting temperature is between 160-170 degrees Celsius; and it is resistant to most acids, Alkalies, bacteria, and mildew. Polypropylene has many applications. 

Sources:

YouTube. (2014). Making Rayon Fiber - Artificial silk, chemical experiment! YouTube. Retrieved October 1, 2023, from https://www.youtube.com/watch?v=f_AvqnMTJjg.

Rayon. How Products Are Made. (n.d.). http://www.madehow.com/Volume-1/Rayon.html

YouTube. (2016). Polypropylene. YouTube. Retrieved October 1, 2023, from https://www.youtube.com/watch?v=GU0O4htqVzI.