H.L. Anderson, F. R. ones' and R. H. Wood Universily of Delaware Newark
A Simple Method of Coating with Polyethylene
In many chemical investigations one would like to use metal components such as reaction vessels, etc., with the stipulation that the object remain inert to the reaction being investigated. For this purpose a thin film of polyethylene can be applied to the metal surface, rendering it inert to many reagents. I n our laboratory we have been concerned mostly with coating the aluminum vessels of a twin calorimeter. However, we have also successfully coated copper and stainless steel. The object is coated by placing it in an oven at 160180" C for approximately 15 min, then removing it from the oven and applying a l-mil film of polyethylene as quickly as possible. The object is then returned to the oven for another 15-min heat treatment. This 1 Present address E. I. duPont deNemoum and Co., Martinsville, Virginia.
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Journal of Chemical Educofion
procedure is repeated for as many coats as necessary. We usually apply about ten coats of polyethylene, resulting in a 10-mil coating, free of pin holes. The critical stage in the procedure is the manner in which the polyethylene is sprayed on. For a smooth coat that will not peel away from the object, it is imperative that thin coats be applied. We have found that the best technique for applying the polyethylene is to spray M-620 polyethylene powder2 with an apparatus similar to the common laboratory wash bottle, except that the air inlet goes to the bottom and the exit t o the top of the bottle. Air is forced through the bottle a t a rate which will not blow the polyethylene out unless the bottle is gently tapped. The resulting spray should have a low powder-to-air ratio. With our apparatus ahout 5-10 passes were required for each l-mil coat. %
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