Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1990-04-05
1991-11-12
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
264 26, 521183, 521184, 521185, 521189, C08V 902, B29C 3500
Patent
active
050648675
ABSTRACT:
Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, prior to the application of the microwave radiation, the body of polyimide precursor is compressed at a pressure that will reduce the bulk volume of the precursor and heated to a temperature below that at which any substantial foaming occurs. to accomplish the foaming, one further embodiment of the invention employs microwave radiation directed upon the top, sides and ends of the body of above-treated polyimide precursor and of the foam structure as it is developing maintaining the developing foam under a substantially vapor-impermeable microwave compatible shroud. The extent to which the microwave radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure.
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Barringer James R.
Broemmelsiek H. Eugene
Gregory Porter W.
Lanier Carroll W.
Lee Raymond
Ethyl Corporation
Foelak Morton
Hammond Richard J.
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