Encapsulation Research

The Institute's expertise in microencapsulation technology has led to advances in a number of consumer products including detergents, bleaches, cosmetics, floor polishes, carpet cleaners, deodorants, toothpastes, paints, and photographic film. Microcapsules have also been developed for the agricultural industry to provide sustained-release insecticides and herbicides.

For almost five decades, SwRI has been a leader in microencapsulation research, development, and prototype production. This year, the Institute conducted approximately 50 projects in the areas of pharmaceutics, medicine, agriculture, nutrition, food, environmental protection, product safety, adhesives, and polymers. The Institute uses physical and chemical techniques to manufacture a variety of water soluble and insoluble capsule shell materials that offer specialized release characteristics.

In a project for the Naval Air Warfare Center (NAWC), Institute engineers prepared sustained-release microcapsules containing a low-chromate corrosion inhibitor that will be used in the development of primer coatings for naval aircraft. SwRI researchers designed three microcapsule formulations that deliver the corrosion inhibitor to a crack site at three diffusion rates. Fatigue and stress-induced crack tests are in progress at NAWC to evaluate the effectiveness of the new coatings.

In another project for NAWC, the Institute developed a one-part epoxy adhesive for use in aircraft repair. Encapsulated curatives keep the adhesive stable at ambient conditions. With a commercial partner, SwRI has filed a joint patent for the encapsulation process, which isolates the curative from the epoxy resin until heat is applied. Paste and film forms of the adhesive have been delivered to NAWC for testing.

Institute researchers have identified and tested several hydrogel polymers to encapsulate pancreatic islet cells for possible use in the treatment of Diabetes mellitus (Type I). Results of in vitro tests showed high biomembrane diffusion rates for nutrients essential to islet cell viability as well as insignificant permeation of larger molecules, such as immunorejection-causing antibodies. SwRI is working with researchers at the Pittsburgh Transplantation Institute to harvest pancreatic islets and conduct preclinical biocompatibility studies. In vivo studies using microbeads prepared from an alginate-based biopolymer have shown excellent biocompatibility in rats.

Through internally funded research, SwRI scientists demonstrated that uniform microcapsules can be formed at high production rates when an externally induced vibrational frequency is applied to a stationary nozzle device. Other microencapsulation processes result in considerable size variation and thus fewer useable microcapsules. Production rates can be up to 10 times higher on a per nozzle basis when vibration is used.

Beta carotene is added to foods such as cereal to provide a source of vitamin A. Microencapsulation is used to protect the beta carotene against oxidation, to prevent reaction with other additives, and to provide color masking. Each capsule measures only 500 microns in diameter, comparable to the size of a grain of table salt.

In continuation of a project for the Electric Power Research Institute (EPRI), the Institute is supplying controlled release fumigant ampules to combat the persistent problem of fungi damage in wooden utility poles. The multiyear study will examine how effectively the ampules control fungal infestation over extended periods of time at utilities throughout the United States. The study is being conducted by Oregon State University, and EPA registration of the fumigant ampule has been completed.

SwRI recently acquired a pilot-scale microcapsule drying unit that will be dedicated to the encapsulation of flavors, fragrances, and other food ingredients. The spray dryer produces test batches at a rate of more than 20 pounds of microcapsules per hour, depending on the materials used.

1996 Annual Report SwRI Home