Polymers, Polymers, Everywhere! A Workshop for Pre-High School Teachers and Students Marie Sherman Ursuline Academy, 341 S. Sappington, St. Louis. MO 63122
It is no exaggeration to state that synthetic polymers are found everywhere in our daily lives. In fact, if all synthetic polymers were taken away from us, we would probably be left with only a leather belt and a piece of metal jewelry! In spite of the importance of synthetic polymers, these "giant molecules" have been almost entirely ignored in prehieh variable treatment " school science texts and are eiven " (one page to an entire chapter) in secondary chemistrytexts. Polvmer ex~erimentsare usnallv absent from the secondarv laboratory manuals, and are not even mentioned in pre-high science activitv books. A teaching package on polymer chemistry, sponsored by NSTA (I), gives an excellent introduction t o polymers for secondarv siudents, but the suggc.itcd experi!&ts involve sulwnr, and prowrlurr.; that would be unsuitable fur prchigh students. The polymer reactions described in texts on chemical demonstrations (2) do not seem appropriate for pre-high teachers, because of either the unavailability of chemicals or the dangers inherent in them. This situation led to the development of a hands-on polymer workshop for pre-high school teachers and students that would (1) enable pre-high teachers to cammunicste basic polymer con-
cepts to their students, (2) provide hands-on experience with real polymers, and (3) utilize polymeric materials that are safe and easily available at
low cost. Twenty-five teachers of grades 5-8 were first given the two-hour workshop to become familiar with polymer theory and to ~ r a d i c ethe exoeriments. Thev were then eiven a kit of samples of all wurkshq~materials pldcomplete instrucriuns to take back to their classrooms. This u,orkshov was also given for five groups of junior high students. ~ e i c h e r s and students alike expressed enthusiasm for the materials. Workshop Actlvltles 1. Polymer Awareness. The purpose of this activity was to make the participants "polymer aware". They used a list of some 250 common polymeric products, given in the NSTA publication (I), and circled all the items encountered during the past week. 2. Making a Polymer Model. Each person made an ethylene model (eum droos of two different colors. connected with toothpicks or pipe cleaners) and then hookdd the molecules toeether to form a eiant ~olvethvlenemolecule. (One could aiso use the wooden balls-and sticks from regular molecular model sets, but the author wanted to use mainly materials that would he easily available to pre-high teachers.) The essential terms, "monomer", "polymer", "thermoplastic", and "thermoset polymers", were introduced a t this point. These terms were illustrated on an overhead projector with paper clips representing monomers and paper clip chains representing polymers. The repeating molecular structures of familiar polymers such as polyethylene, polystyrene, and Teflon were also shown on the projector. 3. A Thermoset Polymer-Epoxy Putty.' Using epoxy putty from a hardware store, the participants molded a shape and set i t aside to harden. Manv observed that the polimer mixture became warm as i t hakdened, and this was 868
Journal of Chemical Education
discussed in the framework of chemical bonds being formed and energy being released. The term "cross-linking" was used here, with overhead projections to illustrate. Giant plastic paper clip chains held by several participants were "cross-linked" with other clips, to demonstrate the threedimensional nature of cross-linking. 4. A Thermoplastic Polymer-Friendly P l a ~ t i c .This ~ easy-to-work modeling material (actual composition is proprietary information) proved to be invaluahle in the workshop (3).I t comes in ivory granules and is widely sold in art supply stores. When placed in hot water (90-100 O C ) , i t quickly softens and can be molded and manipulated for about 5 min before starting to harden. As with all thermoplastics, it can he reheated and remolded any number of times. The relation of heat and the type of molecular bonds make a nice contrast with the observed properties of the epoxy putty, which cannot he remolded. ~ r i e n d l yPlastic is now available in colors and metallic sheens, which makes it even more attractive to both children and adults. 5. Make Your Own Slimy Stuff-"Super Gloop". This interesting material, a gel of poly(viny1 alcohol) cross-linked with borax (sodium borate), was made according to the directions given in two recent articles in this Journal (4, 5). The elastic, bouncy, semi-solid, slow-flowing properties of this gel fascinate everyone. The participants used food coloring to color their "Super Gloop", and took it home in plastic hags. Suggestions were given for further home or school experiments using the gel. When the workshop was given for children, an informational card was sent home, explaining that although the material was nontoxic, it should not he given to children under five years of age or to pets, nor should it he misused in other ways. 6. A Polymer That Loves Water-Super S l ~ r p e rOne.~ half teaspoon of this superabsorbent powder (synthetic sodium polyacrylate) will almost instantaneously gel 100 mL of water in a plastic cup. The workshoppers took note of the strange properties of the "gelled" water, and carried i t home in plastic hags for further experiments. Practical uses (such as in disposable diapers) for this type of polymer were developed in the discussion. 7. G r o - A - S a ~ r u sThese .~ interesting polymeric creatures will absorb 25-30 times their own volume of water, without losing their proportions or becoming mushy. Although their exact composition is proprietary information, it is probable that they are a mixture of synthetic superabsorbent and an elastomer polymer (6). These "critters" can be used in the classroom as if they were living animals, and growth charts can be tabulated and graphed. They will also shrink back to their original size and mass when taken out of the water. Apparently they can grow and shrink many times without 1 Epoxy Putty. TruBond brand, was purchased from a True Value hardware store. Informationmay be obtained by writing The Friendly Plastic tompany Ltd., 6565 Gunpark Drive, Suite 150, Boulder, CO 80301. Information may be obtained by writing Blake Kuster. Grain Processing Gorp.. 1600 Oregon St., Muscatine, IA 52761. Gro-A-Saurus may be obtained from Stravina, Inc.. 19850 Nordhoff Place, Chatsworth,CA 91311
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deteriorating. Othervariables sucirasheight and density can also be measured as the animals grow and shrink. More sophisticated students can calculate the amount of water absorbed per gram of polymer and even make slices of the material for microsco~icexamination. 8. Workshop wrap-up. Suggestions for experimenb with other easily available polymers were given: (1) Tyveks polyithylene nonwoven fabric-test
properties such as strength and moisture permeability (7). (2) Films of dried Elmer's Glue-All6-observe its properties as it dries; test solubility and strength. (3) Household wrap-test tensile strength and moisture permeability. (4)Water-solubleplastic hags7used by hospitals for sailed linen* test solubility at various temperatures;test tensile strength. ( 5 ) Heat-shrinkplastic tubing from Radio Shack-temperature required and amount of shrinkage. Tyvek is a registered trademark of the Du Pont Company. Elmer's Glue-Ail is a registered trademark of the Du Pont Comoa-
(6) Disposable diapers-typw of polymers and special properties of each (8). (7) ~iodegiadahilityof different polymers-bury samples in soil; expose to weather; dig up and examine at intervals.
Participants brainstormed ideas for practical classroom andlor science fair projects, based on the above suggestions. This workshop on polymers has a t least two tangible benefits for pre-high school teacher$: (1) They can relate chemistry to innumerable items that are used
by the studentsdaily; this emphasizes the impadof science and technology on our lives. (2) Many stimulating "How?" and "Why?" and "What if?" questions naturally occur to both students and teachers while working with these materials. Such open-ended questions can lead to productive and satisfying classroom adventures in chemistry. The author will be happy to correspond with secondary or pre-high teachers who wish to offer similar polymer workshops in their local areas.9
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Water-soluble bags (polyvinyl chloride film) are distributed by Medline Industries, #1 Mediine Place, Mundelein, IL 60060. The Polymer Education Newsletter may be obtained free by writing Jane C. Vogl, Div. of Polymer Chemistry, Polytechnic Institute of New York, 333 Jay Street, Brooklyn. NY 11201. For a complete copy of workshop directions, lists of materials. and instructions for poly(viny1 alcohol) and borax solutions, please send 52.00,to cover copying costs and postage, to the author.
1. Bioam, W.: Groves, P.; Halsted. D.: White, M. Polymer Chemistry: National Seienee Teachers Association: Washingtan, DC, 1985. 2. Shakhashiri, R.2. Chamicol Damonairolions: Univ of Wiomnsin: Madimn, WI, 1983: "..,I
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3. Bell,W. L. J. Chrm. Educ. 198%62,240. 4. Casarsa, E. 2.; Sacquis, A. M.: Van Dyke, C. H.J. Chem. Edue. 1986,63,57 6. Sarquis, A. M. J . Chem. Edvc. 1986.63.60,
Volume 64
Number 10
October 1987
889
