Abstract: A method is presented for the accurate quantitative determination of amounts of reactive (water and ethanol) and non-reactive N-methyl-2-pyrrolidone (NMP) volatiles in graphite-polyimide prepreg samples. The method is also applicable to other condensation-curing and/or solvent-impregnated prepreg systems, regardless of the type of reinforcement. Prepreg samples are heated in a containment chamber and the volatiles are subsequently flushed from the chamber with dry nitrogen gas. The volatiles are condensed, weighed, and analyzed via gas chromatography to determine the volatile composition. The method offers a means of purging the extremely tightly held, relatively non-volatile NMP solvent from the resin matrix by means of high temperatures applied to the sample chamber. The higher volatility reaction products are also captured by means of the specially designed very low temperature condenser. An internal check (collection efficiency) on the accuracy of the results is included in the test method.

Abstract: A condensing apparatus is provided which can be used in gas chromatography measurements to determine N-methyl-2-pyrrolidone (NMP) content in polyimide prepreg. The condenser comprises a straight vertical section of thin-walled copper tubing followed by an ascending helical coil surrounding the straight section. The condenser is equipped with valves at the inlet and outlet which are capable of withstanding the combination of high and low temperatures as well as being resistant to damage by aggressive solvents. Liquid condensate accumulates at the bottom of the coil, making decanting easy. The condenser apparatus of the present invention yields very high collection efficiencies for volatile mixtures with a very wide range of boiling points. The condenser is very compact and lightweight and does not require any packing insulation to achieve the high collection efficiencies. Maintenance and cleaning are greatly simplified by the absence of packing.