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The chemical technology required to produce common products can serve as the basis for fascinating student research projects. We found this to be the case for the creation of rayon from cellulose. The cuprammonium rayon process provided challenges and surprises in a teacher-student joint investigation. The literature describes several different methods; we decided to find the "best" method for use in the high school laboratory. Our school offers the opportunity for independent study to any interested student and it is up to the student and teacher to set goals for the year of study. Credit is assigned on the basis of the number of meetings per week. The student (LJP) enrolled in an independent study course and we met twice a week for a semester to do experimental work. The project continued into a second semester for extensions to the rayon process and preparation of a science fair presentation. The choice of in-depth study of a particular chemical process rather than enrollment in a traditional second-year course required a one year commitment by both student and teacher, but it proved valuable to both of us.
The Rayon Process
Dissolving cellulose and then regenerating it in acid (or sometimes base) makes rayon. The procedure for making rayon involves aqueous ammonia or sodium hydroxide, which is reacted with aqueous copper(II) sulfate solution to precipitate copper(II) hydroxide. The solid is dissolved with concentrated aqueous ammonia to form Schweitzer's reagent for the digestion of cellulose. Rayon is formed when cellulose is regenerated in an acid medium. Our initial laboratory time was spent trying the procedures in the literature, as there were several choices. It was puzzling as well as frustrating when dozens of unsuccessful trials were performed. Finally a successful method was identified. Then we concentrated on improving the formation of rayon fibers and later experimented with making rayon disks. We received advice about commercially prepared cuprammonium rayon through email correspondence with Courtaulds in the United Kingdom, the Kidney Center at Washington University in St. Louis, and Terumo Medical Corporation in New Jersey.
Several Variations Were Identified
In a literature search of the cuprammonium rayon process we found that several variations in starting materials are...