Polyester Embedding 85 



Dioxane in Double Embedding 



1 . Fix, decalcify if necessary, and wash. 



2. Dioxane: 2 hours. 



3. Dioxane-nitrocelhilose: 3 days. 



dioxane 70.0 ml. 



2% nitrocellulose 30.0 ml. 



4. Dioxane: 2 hours. 



5. Dioxane-paraffin (50:50): 2 hours. 



6. Paraffin, 3 changes: 20 minutes, 30 minutes, 1 hour. 



7. Embed, and section immediately. 



At UCLA, this method \vas used successfully on hard fish with scales 

 intact. (Also see Brown, 19-48) 



Polyester Embedding 



Polyester resins are plastics (polymers) formed by the esterification 

 reaction (forming a compound from an alcohol and an acid by removal 

 of water) between polyhydric alcohols and polybasic acids. These 

 resins exhibit a wide range of properties and are utilized in a diversity 

 of commercial and scientific endeavors. The alcohols most commonly 

 used are ethylene, propylene, 1,3 and 2,3 butylene and dipropylenc 

 glycols. Unsaturated dibasic acids may be maleic anhydride or fumaric 

 acid. Saturated dibasic acids may be phthalic, adipic and azelaic acid, 

 and chlorinated acids or anhydrides. 



A polyester as used here is an luisaturated polyester base resin dis- 

 solved in a polymerizable monomer, is suitably diluted with the mono- 

 mer and supplied as a viscous fluid. The monomer (smallest unit enter- 

 ing into the formation of high molecular weight polymers) can be 

 styrene, vinyl toluene, diallyl phthalate, methyl methacrylate, triallyl 

 cyanurate or several other vinyl monomers. 



To promote polymerization at the time of use a catalyst must be 

 added to modify the velocity of the reaction without becoming a part of 

 the product. The curing, as this is called, is sometimes accomplished 

 with elevated temperature and sometimes by the use of an "accelerator" 

 or "promoter" in addition to the catalyst. The speed of cure depends 

 on the amount of catalyst and ac c elerator used and \aries with different 

 resins. 



