Microwave Polymerization of Embedding Resins For Biological/Biomedical Elecron Microscopy
- PDF / 1,304,684 Bytes
- 7 Pages / 420.48 x 639 pts Page_size
- 98 Downloads / 148 Views
MICROWAVE POLYMERIZATION OF EMBEDDING RESINS FOR BIOLOGICAL/BIOMEDICAL ELECRON MICROSCOPY B.L. Giammara*, D.J. Birch*, and D.O. Harper** *Graduate Programs and Research, **Department of Chemical Engineering, Univ. of Louisville, Louisville, KY 40292 ABSTRACT The use of microwave energies for polymerization of epoxy and other commercially available resins, used routinely in electron microscopy methodologies, shows promise for diagnostic pathology where rapid methods can be crucial. Many desirable embedment properties, such as specimen infiltration, color, hardness, rough trimming, and ability to stain, are necesssary. The properties necessary for cutting 1 micron semithin sections and 700 Angstrom ultrathin sections (that can withstand pentration by a 100 kV electron beam for image formation) must be maintained. In this study, six epoxy resins and one unsaturated polyester resin were used, the latter in a variety of recipes. Each formulation was subjected to microwave power levels from 400 to 700 W for 1 to 15 minutes. Selected specimen embedments tested well and significantly reduced traditional convection oven polymerization time from two days to a few minutes. INTRODUCTION Microwave energy [1] is readily available in ovens with a "magnetron tube" that converts the 120V/6OHz AC current into electromagnetic waves with a frequency (in the U.S.) of 2450 MHz If these waves travel at near the speed of light (300 Mm/s), then they are about 12 cm long; they have a width of about 0.5 cm. Their penetration depth in materials is around 2 to 4 cm; the shorter the wavelength, the deeper the penetration. These ovens were designed to excite polar molecules with groups such as -OH, -CO-, and -C02; hence, the frequency provided is standardized and may not be varied. Therefore, polymerization reactions involving compounds with similar groups are expected to be influenced by exposure to microwave energy. As the absorption of the energy increases, the temperature of the material increases, and the rate of its reaction increases, thereby shortening the time necessary to achieve a given extent of reaction. Most ovens provide some means of scattering the microwaves, having them bounce off of the oven sides and base, in order to provide uniform temperatures. Some models provide rotating tables to enhance this randomness. A uniform temperature throughout the oven isconsidered essential to obtain consistent quality in polymerizing materials.
Mat. Res. Soc. Symp. Proc. Vol. 189. 01991 Materials Research Society
348
The purpose of this study was to determine what set of components and microwave conditions would yield the best embedding media for use in biological/biomedical electron microscopy. METHODS AND MATERIALS Six different epoxy resins for electron microscopic applications, particularly transmission electron microscopy were used [2]: Araldite 502, Celanese 5048, Epon 812, (TEM), Each of these were mixed Maraglas, Polybed 812, and TAAB 812. nadic methyl anhydride in a dodecenyl succinic anhydride (DDSA), (NMA), and 2,4,6-tris(dime
Data Loading...
