MIL-HDBK-17-1F Volume 1,Chapter 4 Matrix Characterization weight distribution and chain structure. Principle Polymer is coated onto silica particles packed in thermostated column and separated according using solvent gradient elution.Polymer solubility decreases with increasing MW. Dynamic melt rheological method involving measurement of spectrum of diffusional relaxation times for polymer during oscillatory deformation. Extraction,filtration,and centrifugation are employed to isolate soluble polymer from gel.MW of soluble polymer is determined separately. Molar volume of crosslinked polymer immersed in swelling liquid and density of the swollen polymer are determined.Theory of partial molar free energy of mixing is ap- plied. Principle Same as above but also involves measurement of the low-frequency line broadening of the central Rayleigh line of the scattered light.The structure of polymers in both dilute and concentrated solutions can be analyzed. Separates polymers according to their size and shape in solution.An elution tech- nique,like chromatography,except that a field/gradient(thermal,gravitational,flow, electrical,etc.)is applied perpendicular to the axis of solution flow through a capillary or ribbon-shaped channel and a single phase is employed. Liquid chromatography technique based upon equilibrium distribution of polymer molecules between a non-aqueous binary solvent mobile phase and a nonpolar sta- tionary(packing)phase. Liquid chromatography technique involving the use of a mobile phase under super- critical conditions (100 bars,250C). Measurement of amplitude of neutron scattering momentum vector for polymer in di- lute solution or blend with another polymer.Scattering angle and polymer concentra- tion are varied.Deuterated solvents are used.Dilute solid solutions and polymer blends have been studied. 4-11
MIL-HDBK-17-1F Volume 1, Chapter 4 Matrix Characterization 4-11 weight distribution and chain structure. Principle Polymer is coated onto silica particles packed in thermostated column and separated according using solvent gradient elution. Polymer solubility decreases with increasing MW. Dynamic melt rheological method involving measurement of spectrum of diffusional relaxation times for polymer during oscillatory deformation. Extraction, filtration, and centrifugation are employed to isolate soluble polymer from gel. MW of soluble polymer is determined separately. Molar volume of crosslinked polymer immersed in swelling liquid and density of the swollen polymer are determined. Theory of partial molar free energy of mixing is applied. Principle Same as above but also involves measurement of the low-frequency line broadening of the central Rayleigh line of the scattered light. The structure of polymers in both dilute and concentrated solutions can be analyzed. Separates polymers according to their size and shape in solution. An elution technique, like chromatography, except that a field/gradient (thermal, gravitational, flow, electrical, etc.) is applied perpendicular to the axis of solution flow through a capillary or ribbon-shaped channel and a single phase is employed. Liquid chromatography technique based upon equilibrium distribution of polymer molecules between a non-aqueous binary solvent mobile phase and a nonpolar stationary (packing) phase. Liquid chromatography technique involving the use of a mobile phase under supercritical conditions (100 bars, 250°C). Measurement of amplitude of neutron scattering momentum vector for polymer in dilute solution or blend with another polymer. Scattering angle and polymer concentration are varied. Deuterated solvents are used. Dilute solid solutions and polymer blends have been studied
MIL-HDBK-17-1F Volume 1,Chapter 4 Matrix Characterization What requirements does the characterization technique impose upon the sample? Is it necessary to isolate the polymer or prepolymer from other sample components? It should be recognized that the properties of polymer compounds and prepolymer formulations are often quite different from those of the pure polymers and polymer precursors.Polymer properties are greatly influenced by the presence of other components,e.g.,fillers,additives,processing aids,dyes,re- sidual catalysts,impurities,solvents and other polymers,low MW oligomers and monomers. One must decide whether the specimen needs to be modified or specially treated for a particular analysis.Chemical structure,thermal transition behavior and solubility determine what can be done with a specimen.Operations,such as heating or extraction,may alter morphology or change the chemical composition of a specimen and thereby affect its properties and compromise the validity of certain tests. Many characterization techniques require polymer specimens to be modified or have a particular shape or form.If a specimen does not conform precisely to test criteria,the test may be invalid.On the other hand,in order to apply certain techniques(e.g.,light scattering and membrane osmometry for MW analy- sis),it is essential that the polymer be totally isolated from nonpolymeric components. Knowledge of the type of polymer or prepolymer is important in developing characterization proce- dures.If the material is unidentified,a simple series of tests (Level I in Figure 4.4.6(a))may be applied. first to answer the question of whether the sample actually contains polymer,and then to determine its characteristics and identify the polymer or prepolymer. Specimen modification for Level I merely involves breaking or cutting a small section from the sample and,if possible,further reducing the specimen size by grinding.To facilitate thermal and spectroscopic analysis and solubility testing,the specimen should have a large surface area.Liquid and heterogeneous specimens should be thoroughly mixed before removing an aliquot for analysis.Each test can be run us- ing as little as 10 mg sample. Structural and compositional information obtained by the tests in Level I is used to help develop more sophisticated specimen preparation schemes and support the application of more detailed or specialized characterization techniques.The major concern of Level ll is representative sampling and insuring that specimen modification procedures(cutting,grinding,molding,etc.)do not compromise polymer character- istics to be evaluated.Level ll also addresses the"quantitative"aspects of sample composition(percent polymer,additives,volatiles,and inorganic and other organic residues)and,if necessary,deals with the identification of nonpolymeric components. A general scheme for polymer analysis is illustrated in Figure 4.4.6(b).The polymer sample should be uniform and have a large surface area.Once volatile components are removed,the polymer can be di- rectly analyzed,or a variety of techniques(e.g.,extraction,precipitation,filtration,liquid chromatography) may be applied to isolate the polymer.If required,special procedures are applied to prepare the polymer sample for chemical characterization-molecular weight,molecular weight distribution,and chain struc- ture evaluation,and bulk characterization (Level lll in Figure 4.4.6(a)). Whenever possible,complementary techniques should be used for the chemical quality assurance of resin materials.Techniques,such as HPLC and IR spectroscopy,are fundamentally different from one another and provide direct,but different,information about a resin's composition.If appropriate test methods are applied,HPLC and IR spectroscopy are usually powerful enough to detect differences or changes in the chemical compositions of resins.DTA and DSC complement HPLC and IR spectroscopy by providing information relating to the handleability (i.e.,the T.and extent of reaction of the resin)and the processability of the prepreg.TGA and GC head-space analysis techniques for volatile components are secondary,but important,techniques.Special techniques for analyzing specific components or elements should be used if knowledge of the concentrations of the components is critical for processing the resin or if their presence could adversely effect the performance and durability of the cured composite.The in- formation provided by mechanical,rheological,and dielectric analysis techniques is related to the chemi- cal composition of the prepreg resin and thereby complements the more direct chemical techniques. 4-12
MIL-HDBK-17-1F Volume 1, Chapter 4 Matrix Characterization 4-12 What requirements does the characterization technique impose upon the sample? Is it necessary to isolate the polymer or prepolymer from other sample components? It should be recognized that the properties of polymer compounds and prepolymer formulations are often quite different from those of the pure polymers and polymer precursors. Polymer properties are greatly influenced by the presence of other components, e.g., fillers, additives, processing aids, dyes, residual catalysts, impurities, solvents and other polymers, low MW oligomers and monomers. One must decide whether the specimen needs to be modified or specially treated for a particular analysis. Chemical structure, thermal transition behavior and solubility determine what can be done with a specimen. Operations, such as heating or extraction, may alter morphology or change the chemical composition of a specimen and thereby affect its properties and compromise the validity of certain tests. Many characterization techniques require polymer specimens to be modified or have a particular shape or form. If a specimen does not conform precisely to test criteria, the test may be invalid. On the other hand, in order to apply certain techniques (e.g., light scattering and membrane osmometry for MW analysis), it is essential that the polymer be totally isolated from nonpolymeric components. Knowledge of the type of polymer or prepolymer is important in developing characterization procedures. If the material is unidentified, a simple series of tests (Level I in Figure 4.4.6(a)) may be applied, first to answer the question of whether the sample actually contains polymer, and then to determine its characteristics and identify the polymer or prepolymer. Specimen modification for Level I merely involves breaking or cutting a small section from the sample and, if possible, further reducing the specimen size by grinding. To facilitate thermal and spectroscopic analysis and solubility testing, the specimen should have a large surface area. Liquid and heterogeneous specimens should be thoroughly mixed before removing an aliquot for analysis. Each test can be run using as little as 10 mg sample. Structural and compositional information obtained by the tests in Level I is used to help develop more sophisticated specimen preparation schemes and support the application of more detailed or specialized characterization techniques. The major concern of Level II is representative sampling and insuring that specimen modification procedures (cutting, grinding, molding, etc.) do not compromise polymer characteristics to be evaluated. Level II also addresses the "quantitative" aspects of sample composition (percent polymer, additives, volatiles, and inorganic and other organic residues) and, if necessary, deals with the identification of nonpolymeric components. A general scheme for polymer analysis is illustrated in Figure 4.4.6(b). The polymer sample should be uniform and have a large surface area. Once volatile components are removed, the polymer can be directly analyzed, or a variety of techniques (e.g., extraction, precipitation, filtration, liquid chromatography) may be applied to isolate the polymer. If required, special procedures are applied to prepare the polymer sample for chemical characterization - molecular weight, molecular weight distribution, and chain structure evaluation, and bulk characterization (Level III in Figure 4.4.6(a)). Whenever possible, complementary techniques should be used for the chemical quality assurance of resin materials. Techniques, such as HPLC and IR spectroscopy, are fundamentally different from one another and provide direct, but different, information about a resin's composition. If appropriate test methods are applied, HPLC and IR spectroscopy are usually powerful enough to detect differences or changes in the chemical compositions of resins. DTA and DSC complement HPLC and IR spectroscopy by providing information relating to the handleability (i.e., the Tg and extent of reaction of the resin)and the processability of the prepreg. TGA and GC head-space analysis techniques for volatile components are secondary, but important, techniques. Special techniques for analyzing specific components or elements should be used if knowledge of the concentrations of the components is critical for processing the resin or if their presence could adversely effect the performance and durability of the cured composite. The information provided by mechanical, rheological, and dielectric analysis techniques is related to the chemical composition of the prepreg resin and thereby complements the more direct chemical techniques