What are the problems faced by the military by degradable plastics? They must function in very broad temperature and environmental ranges such as -40 to +120°F - desert, tropic, arctic and temperate zones. This poses serious problems in determining degradation rates. For example, water soluble items would be out of the question in a desert and parts of the arctic on any meaningful timetable. There is a limitation in effectiveness of some systems with pigmentation and coatings. Olive drab or other dark colors would screen out desired ultraviolet energy. There are to date limitations on the plastic materials suitable for degradation. The very high temperature, high strength composites now being used would not be suitable. Therefore military engineering uses are limited. There would be storage problems. Items would have to be protected from ultraviolet source and moisture. To date almost all materials technology is concerned with proprietary materials involving licensing and royalties. In conclusion degradable plastics are still undergoing development. Although the techniques are generally understood, there are few off-the-shelf resin compounds or products. To date the range of known plastics suitable for controlled degradation is quite limited. Because of the very limited materials involved, the biodegradable approach is restricted. The selection of soluble material is also limited to a rather few materials. These items would be dependent on both environment. rainfall and temperature, as well as part thickness. There would also be dimensional stability problems because of their sensitivity to high relative humidity Photodegradable materials present the best candidates for all environments. These materials have the following advantages and disadvantages: The ability to initiate degradation via artificial ultraviolet sources The ability to continually degrade without continuing ultraviolet exposure Disadvantages The rate of degradation is sensitive to pigmentation, coatings, ultraviolet intensity, formulation, and part thickness. The future outlook for degradable systems is very promising, especially in the commercial packaging industry. Although these formulations are proprietary, licenses are being signed and commercial supplies should be available at attractive prices soon. In addition, much effort is being conducted to broaden the range of photodegradable materials. It is expected that the thermoplastic polyesters, polyamides, and polyurethanes will be next. In the miliary, engineering development personnel are becoming increasingly conscious of ecology and I am sure more and more consideration will be given to degradable plastics for discardable items. Thank you. REFERENCES 1. Potts, James E., Robert A. Clendinning and Watson B. Ackart (Union Carbide Corp.) "An Investigation of Biodegradability of Packaging Plastics" Environmental Protection Agency Report - R2-72-046. August 1972, contract No. CPE-70-124. 2. Rodriquez, F. (Cornell University) "Prospects for biodegradable plastics" in MODERN PLASTICS, September 1971. 3. Worne, Howard, E. (Enzymes Inc.) "Biodegradability of synthetic organic polymers" in PROCEEDINGS: PLASTICS AND ECOLOGY - INFLUENCE ON POLLUTION, FLAMMABILITY AND SAFETY. Sponsored by SPE, Palisades Section, October 27-28, 1970. 4. Union Carbide Corporation "New Polycaprolactone Thermoplastic Polymers PCL-300 and PCL-700" undated. 5. Davidson, Robert Land Marshall Sittig (Editors) "Water-Soluble Resins", Reinhold Book Corp., New York, Second Edition, 1968. 6. Rossman, James M. (Hercules Inc.) "Now: A plastic to eat 7. Hercules Inc. or simply dissolve in water" in PACKAGING "Chemical and Physical Properties - Klucel - Hydroxypropyl Cellulose", 1971. 8. Union Carbide Corp. 9. Staff "Polyox Water Soluble Resins", F42506, June 1969. "Technology concentrates degradable polybutadiene". in C&EN, November 29, 1971. 10. DeBell and Richardson 11. Staff Letters dtd 28 Nov 1972, Subject: UV Degradation Catalysts. S/Roy A. White to "New additives make sunshine work” in SPE JOURNAL, April 1971, Vol. 27. |