MIL-HDBK-17-1F Volume 1,Chapter 5 Prepreg Materials Characterization an aliquot(e.g.,10 mL)of the filtered solution is transferred to a pre-weighed aluminum pan(weight WA)which is then placed into a fume hood to evaporate the solvent.A stream of filtered air or nitro- gen can be directed over the surface of the pan to accelerate evaporation.After 9 mL or more of the solvent is removed leaving an oily residue of resin,the pan can be placed in a vacuum oven and heated at about 50C for several hours to remove residual solvent.After cooling to room tempera- ture,the pan is reweighed(WA)and the resin content is calculated- 5 wt-%soluble resin =100%x(WA-WA)x- 5.5.1(e) Wo Differences in the weight-percent resin determined using Equations 5.6.1(b)and 5.6.1(e)may be at- tributed to the presence of volatiles and insoluble(nonfibrous)components in the prepreg. 17.Insoluble content.The amount of insoluble components may be determined by the following proce- dure.An aliquot of the solution from step 12 can be centrifuged to precipitate the insoluble compo- nents.The precipitate is washed at least three times with the solvent,dried,and weighed. 5.5.2 Procedure for HPLC/HPSEC analysis of glass,aramid,and graphite fiber prepregs Mix resin solution(prepared in Section 5.5.1,step 12)on a vortex mixer and immediately filter about 4 mL of the resin sample solution through a 0.2 um Teflon TM membrane filter into a dry,clean glass vial. Immediately cap the vial to prevent contamination and solvent loss.The sample is now ready for HPLC analysis. If the HPLC analysis is not run immediately,the sample solution should be kept in a cool,dark loca- tion.If care is taken during storage,the THF solution will remain stable and may be analyzed weeks after its preparation with no apparent effect on the HPLC analysis. 5.5.2.1 Reverse phase HPLC analysis The epoxy resin prepreg analysis can be run using any of a number of commercially available HPLC instruments.An integrator/recorder or state-of-the-art HPLC data analysis system is recommended for data acquisition,plotting,and reporting.HPLC operating conditions were selected for simplicity and com- patibility with most commercial HPLC equipment. HPLC System:Waters Associates model-244 instrument with M6000A solvent delivery systems, M720 system controller,710B WISP auto-injection system,M440 UV detector,and M730 data module. Similar systems available from other manufacturers may also be used. Solvents:Acetonitrile(distilled-in-glass)and reagent grade water prepared from distilled water using a Millipore Milli-Q2(Millipore Corp.,Bedford,MA)or equivalent water purification system.Purging the sol- vents with helium is recommended. Column:Waters Associates uBondapak C18.(Similar columns available from other manufacturers may also be used). Injection Volume:10 mL Flow Rate:2.0 mL/min 5-6MIL-HDBK-17-1F Volume 1, Chapter 5 Prepreg Materials Characterization 5-6 an aliquot (e.g., 10 mL) of the filtered solution is transferred to a pre-weighed aluminum pan (weight WA) which is then placed into a fume hood to evaporate the solvent. A stream of filtered air or nitro￾gen can be directed over the surface of the pan to accelerate evaporation. After 9 mL or more of the solvent is removed leaving an oily residue of resin, the pan can be placed in a vacuum oven and heated at about 50°C for several hours to remove residual solvent. After cooling to room tempera￾ture, the pan is reweighed ( A W’ ) and the resin content is calculated - wt- % soluble resin = 100% x(W -W ) x 5 W A ’ A o 5.5.1(e) Differences in the weight-percent resin determined using Equations 5.6.1(b) and 5.6.1(e) may be at￾tributed to the presence of volatiles and insoluble (nonfibrous) components in the prepreg. 17. Insoluble content. The amount of insoluble components may be determined by the following proce￾dure. An aliquot of the solution from step 12 can be centrifuged to precipitate the insoluble compo￾nents. The precipitate is washed at least three times with the solvent, dried, and weighed. 5.5.2 Procedure for HPLC/HPSEC analysis of glass, aramid, and graphite fiber prepregs Mix resin solution (prepared in Section 5.5.1, step 12) on a vortex mixer and immediately filter about 4 mL of the resin sample solution through a 0.2 µm Teflon™ membrane filter into a dry, clean glass vial. Immediately cap the vial to prevent contamination and solvent loss. The sample is now ready for HPLC analysis. If the HPLC analysis is not run immediately, the sample solution should be kept in a cool, dark loca￾tion. If care is taken during storage, the THF solution will remain stable and may be analyzed weeks after its preparation with no apparent effect on the HPLC analysis. 5.5.2.1 Reverse phase HPLC analysis The epoxy resin prepreg analysis can be run using any of a number of commercially available HPLC instruments. An integrator/recorder or state-of-the-art HPLC data analysis system is recommended for data acquisition, plotting, and reporting. HPLC operating conditions were selected for simplicity and com￾patibility with most commercial HPLC equipment. HPLC System: Waters Associates model-244 instrument with M6000A solvent delivery systems, M720 system controller, 710B WISP auto-injection system, M440 UV detector, and M730 data module. Similar systems available from other manufacturers may also be used. Solvents: Acetonitrile (distilled-in-glass) and reagent grade water prepared from distilled water using a Millipore Milli-Q2 (Millipore Corp., Bedford, MA) or equivalent water purification system. Purging the sol￾vents with helium is recommended. Column: Waters Associates µBondapak C18. (Similar columns available from other manufacturers may also be used). Injection Volume: 10 mL Flow Rate: 2.0 mL/min