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This study investigates the moisture absorption characteristics of the ULTEM® 9085 filament and how the uptake concentration affects the quality of material extrusion manufactured 3-D parts. The filament was exposed to humidity conditions to achieve various moisture concentrations (0, 0.05, 0.1, 0.16, 0.4 and 0.8 wt.%) and corresponding printed parts were evaluated for mechanical performance using tensile test dogbones. The rate of transport was modeled by Fickian diffusion and diffusion coefficients were obtained for various exposure conditions. Moduli, strain to failure and ultimate strength were evaluated in the XY (flat horizontal) and ZX(vertical) direction relative to the build plate orientation. Image analyses of cross-sections as well as their corresponding fracture surfaces were evaluated for consolidation, porosity distribution and failure behavior. Mechanical test data showed a significant decrease in tensile strength (>60%) and failure strain (>50%) over the range of filament moisture levels investigated. A decrease in failure strain of 41% was observed with moisture levels as low as 0.16%. This degradation was especially sensitive in parts printed in the vertical direction, which resulted in an ultimate failure strain of only 1%. The changes in mechanical performance are believed to be due to a combination of entrapped volatiles resulting in increased porosity at higher moisture levels as well as moisture induced pseudo-crosslinking at lower concentrations. Optical micrographs showed that specimens with 0.16% moisture or greater were filled with observable porosity and increased surface roughness. The rheological behavior of extruded material indicated plasticization as evidenced by melt flow index measurements and changes in the flow characteristics of moisture-exposed extrudate. DMA data show a distinct decrease in Tg with increased moisture content, which is consistent with plasticization. The absorption characteristics at room temperature lab conditions indicate that the material will reach an unacceptable level within one hour of room-temperature exposure. This investigation emphasized the need for awareness of the moisture sensitivities of ULTEM® 9085 when manufacturing high-quality material extrusion processed structures.

Low reflective coatings or surfaces have wide applications in the fields of aerospace, energy, military, defense, and daily life. Optical baffles and sensors are important components of space-borne instruments, which require low-reflectivity surfaces to minimize stray and reflected light for improving their image resolution to facilitate the direct exoplanet detection and characterization, as well as the sensitivity for missile defense and satellite-based surveillance systems. The excellent mechanical, thermal, optical, and electrical properties of carbon nanotubes (CNTs) make them as ideal coating materials for obtaining low reflectivity surfaces for various applications. In this presentation, Faraday Technology Inc. demonstrated the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition. The low-reflectivity CNT coatings have been successfully deposited on a variety of geometries: flat coupons, curved surfaces, sharp edges, and internal and external surface of square tubes using the FARADAYIC® EPD process with different anode-cathode configurations (Figure 1 A). The CNT coatings show the total hemispherical reflection of 0.4% ~ 0.8% across visible to near infrared (NIR) wavebands (Figure 1 B). The CNT coatings withstood simulated launch conditions vibration tests, and no weight loss and optical degradation were observed. The atomic erosion resistance of the CNT coatings was evaluated in a simulated low earth orbit (LEO) environment. The CNT coatings showed enhanced resilience to LEO O-atom erosion when compared to Kapton and HOPG. The UV radiation effects on the coatings are under investigation. The developed economic and scalable technology for producing CNT black coatings on desired substrates can not only be used for minimizing stray and reflected light for space-borne instruments, but also be beneficial for optoelectronic fields for minimizing unwanted surface reflections for solar thermal power generation and storage, solar-driven steam generation for sanitization and water purification, and so on. Figure 1

Unshielded carbon nanotube (CNT) yarns were exposed in Low Earth Orbit (LEO) for 2.14 years on the exterior of the International Space Station (ISS) as part of a Materials International Space Station Experiment (MISSE-8), Payload and Optical Reflector Materials Experiment III. This work is the first to expose any commercial, continuous CNT material in a high-fluence atomic oxygen (AO) natural space environment with sample recovery. Although some chemical changes and surface roughening were observed in both the ram- and wake-exposed samples, none of the CNT yarn samples were catastrophically damaged. Yarn erosion was greater in the ram direction. Scanning electron microscopy (SEM) images showed a porous morphology that was mostly confined to the outer 1% of the yarn. This was consistent with the high degree of disorder observed in the Raman spectra. SEM micrographs also revealed that under the outer amorphous layer of oxidized carbon were pristine carbon nanotubes that were not attacked by the AO. The mechanical (tensile) data showed fairly good strength retention of the yarns exposed in the wake direction, while ram exposure resulted in a 25% strength decrease. Electrical resistivity measurements revealed that both the wake and ram samples were slightly more resistive than the control samples.

Space observatory missions requires the development of low-reflectivity surfaces for space-borne instruments, such as seeker telescopes, optical sensors, etc., to minimize stray and reflected light across the visible and infrared wavebands for facilitating the direct exoplanet detection and characterization. For example, in order to improve the sensitivity of missile-defense sensors and seekers, baffles are used within optical telescopes to reduce stray light. Some materials (e.g., aluminum, beryllium, etc.) are too reflective to use as absorptive baffles without surface processing, although they have lightweight and good thermo-structural properties, and survive harsh environments. Black surface coating treatments have been demonstrated as effective approaches to obtain low reflective surfaces. The surface features and intrinsic properties of the coating materials play an important role for scattering, absorbing, or trapping light. The excellent optical absorption performance and light weight of carbon nanotubes (CNTs) make them as ideal coating materials for obtaining low reflectivity surfaces. In this presentation, we will discuss the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition technology. The low-reflectivity CNT coatings have been successfully deposited on various surfaces, including flat, bent, and sharp substrates. The CNT coatings show the reflectance of 0.4% ~ 0.8% across visible to near infrared (NIR) wavebands. Within this context, Faraday Technology Inc. demonstrated the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition. As shown in Figure 1, the uniform CNT coatings are formed on an aluminum (Figure 1, Inset (Right)), and the diffuse reflectance of the CNT coatings is ~ 0.5% over the visible range. We also demonstrated the potential to apply CNT coating on the internal diameter of cylinders at room temperature (Figure 1, Inset (Lef)t). Faraday are currently working on developing CNT coatings on the surface of absorptive baffle materials, such as beryllium and aluminum. The developed economic and scalable technology for producing CNT black coatings on desired substrates can not only be used for minimizing stray and reflected light for space-borne instruments, but also offer potential applications in other optical related devices which request low reflective surfaces, such as solar cells. Acknowledgements: The financial support of NASA SBIR/STTR program through contracts No. 80NNSC18P2062 & 80NSSC19C0177 is acknowledged. Figure 1

Nanocomposites of polyaniline nanofibers and polyimide were fabricated and studied using small angle neutron scattering (SANS). The immiscible nature of the conformationally dissimilar polyaniline nanofiber and polyimide host is established by a series of experiments involving neutron scattering. Based on these techniques, we conclude that the crystal structure of the polyimides is not disrupted, and that there is no mixing between the two components on a molecular level. The morphology of the conducting salt component was analyzed by SANS data and was treated by two common models: Debye–Bueche ( D –B) and inverse power law (IPL). Due to deviations in the linear curve fitting over a large scattering range, neither the D-B nor the IPL model could be used to characterize the size and shape of all PANI-0.5-CSA (polyaniline camphor sulfonic acid doped polymer)/polyimide blend systems. At 1 and 2% concentration, the D–B model suggested salt domains between 20 and 70 A with fractal geometries implied by the IPL model. As salt concentrations increased to 5%, the structures were observed to change, but there is no simple structural model that provides a suitable basis for comparison.

Carbon nanotube ink chemistry and the proper formulation are crucial for direct-write printing of nanotubes. Moreover, the correct surface chemistry of the self-assembled monolayers that assist the direct deposition of carbon nanotubes onto the substrate is equally important to preserve orientation of the printed carbon nanotubes. We report that the successful formulation of two single walled carbon nanotube (SWNT) inks yields a consistent, homogenous printing pattern possessing the requisite viscosities needed for flow through the microcapillary nozzles of the inkjet printer with fairly modest drying times. The addition of an aqueous sodium silicate allows for a reliable method for forming a uniform carbon nanotube network deposited directly onto unfunctionalized surfaces such as glass or quartz via inkjet deposition. Furthermore, this sodium silicate ingredient helps preserve applied orientation to the printed SWNT solution. Sheet resistivity of this carbon nanotube ink formula printed on quartz decreases as a function of passes and is independent of the substrate. SWNTs were successfully patterned on Au. This amine-based surface chemistry dramatically helps improve the isolation stabilization of the printed SWNTs as seen in the atomic force microscopy (AFM) image. Lastly, using our optimized SWNT ink formula and waveform parameters in the Fuji materials printer, we are able to directly write/print SWNTs into 2D patterns. Dried ink pattern expose and help orient roped carbon nanotubes that are suspended in ordered arrays across the cracks.

Enhancing epoxy adhesives using nanoscale fillers requires understanding processing-structure–property relationships as a function of nanoscale filler loading. In particular, the effects of adding nanoscale reinforcement to filled epoxies, such as those qualified for space applications, have yet to be characterized. In this effort, the addition of single-walled carbon nanotubes (SWNTs) to Hysol 9309.2 epoxy was investigated using a multi-scale mechanical characterization approach. Effects of SWNTs on the kinetics of epoxy curing were characterized and modeled using macromechanical dynamic mechanical analysis (DMA). Adhesion between SWNTs and microfiber reinforcement was identified with scanning electron microscope (SEM), and effects of SWNTs on mechanical properties of the filled epoxy were quantified using micromechanical tensile testing. Effects of SWNT reinforcement on mechanical behavior of the epoxy matrix were also characterized using nanomechanical characterization. This multi-scale mechanical characterization enabled the effects of SWNTs to be isolated from the epoxy and filler phases inherent in the adhesive.

Various diameters of polyaniline (PANI) nanofibers were easily made by varying the sweep rate in the electrochemical polymerization of the aniline monomer. At a sweep rate of 5 mV/s, the PANI nanofibers have an average diameter of 450 nm with a median of 440 nm. The fibers are short, on the order of a few microns in length, and exhibit a branched geometry. Increasing the sweep rate to 50 mV/s produced longer nanofibers with a smaller average diameter of 200 nm. Nanofibers synthesized at 100 mV/s were noted to be smaller with an average and median diameter of 100 nm. These results illustrate the ease in which the morphology of nanostructured PANI can be altered and indicate that the method has the potential to create multi-diameter fibers or mixed-morphology materials.

Small-angle neutron scattering (SANS), nuclear magnetic resonance (NMR), wide-angle and small-angle X-ray scattering (WAXS and SAXS) measurements were carried out to investigate the three morphological forms of polyaniline emeraldine base (PANI-EB): unstructured, microtubes, and nanofibers. Although the chemical backbone between these two materials is quite similar, their solid structures are quite different, showing differences in the molecular conformation and supramolecular packing. Detailed solid-state 13C and 15N NMR characterization of PANI nanofibers (compared to the unstructured, granular form) revealed a slight variation in the structural features of the polymer that led to some differences in the chemical environments of the respective nuclei. The presence of two extra-sharp peaks at 96.5 and 179.8 ppm is a distinct feature found exclusively in the nanofiber spectra. Moreover, the crosspolarization (CP) dynamics study disclosed the presence of a complete set of sharp NMR peaks that are responsible for the presence of a more ordered morphology in the nanofiber. Small-angle neutron scattering indicated very sharp interfaces in the PANI fibers, which are well organized and have extremely sharp domains within the length scales probed (not, vert, similar10–1 nm). Overall, the X-ray scattering and spectroscopy data suggest that the nanofiber form is structurally different from the unstructured, PANI-EB powder. These differences are manifested, in part, by the additional chemistry occurring during the synthesis of the nanofibers.

We report the progress of alignment and organization of single-walled carbon nanotubes (SWNTs). Using single strands of DNA, as-received bundled SWNTs are effectively dispersed in a water-based medium under light. This high level of dispersity was evident from the resulting stable, homogeneous solutions provided by the helical wrapping of the DNA to the SWNT. We have also demonstrated that these DNA-coated carbon nanotubes can be orientated with non-contact methods. Specifically, we utilize a modified inkjet printer as a tool for direct printing and alignment of DNA-wrapped carbon nanotubes on a treated mica substrate. In addition, we see evidence of orientation due to centrifugal forces in the radial direction of the spin coater. These layers of oriented tubes are characterized by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). The inkjet fabrication process is a promising method for increasing the directional strength of high strength, carbon nanotube materials.

In this work, polyaniline/poly(sulfonated styrene) (PANI–PSS) nanofiber composites were prepared by an interfacial method. The in situ polymerization technique of these PANI nanofibers in the presence of sulfonated polystyrene allowed for the growth of PANI 2-D nanostructures embedded in the polymerized sulfonated host. This facile approach enables a self-assembly of these nanofibers into a workable, robust, conductive composite which can be processed and cast from water. A low accelerating voltage scanning electron microscopy (SEM) was used to image these twisted fibers within the bulk of the cast film. In addition, the SEM confirmed the self-assembly of these 40–50 nm fibers within the host PSS to yield an electrically conducting composite film.

Self-assembled polyaniline micro/nanotubes were synthesized by a template-free method. Changing the molar doping level ratio [Aniline]:[dopant] from 0.25 to 2 increased the polyaniline tube (PAT) diameter by three orders of magnitude. Bulk conductivity of the tubes was demonstrated for both micro- and nanotubes and varied from 0.01 to 1.2 S/cm. When microtubes were solution-blended with polyurethane, a highly dispersed fractal network of tubes was observed, and the resulting blend conductivity was 1×10−5 S/cm and 1×10−3 S/cm for 0.5% (wt/wt) and 2% (wt/wt) PANI microtube loadings, respectively. These values were sufficient for the minimal value needed (1×10−6 S/cm) for charge mitigation. The promising results of this program lend themselves to developing an all-polymer microtube-conducting composite that has sufficient conductivity and transparency to mitigate electrical charge in lightweight space structures.

Blends of polyaniline protonated with functionalized sulfonic acids dopant and various block copolymers of poly (1,4-butylene terephthalate)-co-polytetramethylene oxide having variable proportion of hard to soft segment can be cast as freestanding films from hexafluoro-2-propanol solution. The electrical conductivity of these blends showed percolation threshold values below 1%, a behavior which is indicative of a fibrillar network phase-separated morphology. A significant effect of the counter-ion of the functionalized acid dopant was noted. Polyaniline doped with camphor sulfonic acid or with methane sulfonic acid produced higher conductivity values than polyaniline doped with dodecylbenzene sulfonic acid. The hard segment in the insulating copolymer was found to suppress the electrical conductivity of the resulting compositions. The phase-separated morphology in these blends was confirmed from the observed approximate linear relation of the specific volume on the composition of the blend.

Electrically conducting networks based on polyaniline−camphorsulfonic acid (PANI-HCSA), blended with crystalline and amorphous polyamides (nylon 6 and Selar), and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS), blended with poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA), were prepared from solution. These blends exhibited a conductivity that rises smoothly and rapidly from the insulating state with increasing conducting polymer content. When the conducting polymer salts are blended with insulating crystalline hosts, they show a more rapid increase in conductivity relative to blends prepared using amorphous hosts. This faster rise in electrical conduction stems from the presence of more developed conductive pathways in the crystalline host blends due primarily to the crystallization driven exclusion of the conducting polymer into the interspherultic region as seen by transmission electron microscopy (TEM). In the PANI-HCSA/nylon 6 blends conductivities of 1 S/cm are found at ...

The properties of blends, cast from hexafluoro-2-propanol, of nylon 6 and of nylon 12 with polyaniline doped with various functionalized organic acids were investigated using differential scanning calorimetry and microscopy. The glass transition temperature of the as-cast and dried blends of polyaniline with either nylon displayed a composition-independent relationship indicative of a phase-separated morphology irrespective of the functionalization of the sulfonic acid dopant. Although electron microscopy data also showed phase-separated morphologies, the PANI domain size within the nylon matrix was found to be dependent upon the functionalized acid dopant. A decrease in the melting transition temperatures of nylon 6 and associated enthalpies with blend composition is attributed to the effects of dissociation and degradation processes occurring during thermal analysis. We suggest that the effusion of the resulting thermally induced species from within the polyamide domain disrupts the crystalline structur...

Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) techniques were used to characterize the PANI-0.5-HCSA morphology in nylon blends. SAXS shows that the polyaniline (PANI) salt resides mainly in the inter-spherulitic region of the nylon host. The morphology of the conducting salt component was analyzed by SANS data and was treated by two standard models: Debye—Bueche (D—B) and inverse power law (IPL). Due to deviations in the linear curve fitting over a large scattering range, neither the D—B nor the IPL model could be used to characterize the size and shape of all PANI-0.5-HCSA/nylon blend systems. At 3 vol.% PANI loading concentrations, the D—B model suggested salt domains with characteristic lengths of 22 nm for the nylon 12 blend. This differs in the blend reported with nylon 6 where the IPL model indicated a fractal geometry. As salt concentrations are increased in both nylons, the structures are observed to change, but there is no simple structural model that provides a suitable basis for comparison.

The structure of blends of Nylon 6 with deuterated polyaniline emeraldine base (D-PANI-EB) and fully doped D-PANI salts (D-PANI-ES) formed from camphorsulfonic acid (CSA), methanesulfonic acid (MSA), or dodecyl benzenesulfonic acid (DBSA) were investigated by small-angle neutron (SANS) and X-ray scattering. The blends were formed from hexafluoro-2-propanol solutions and had volume fractions of 0.038, 0.20, and 0.40 for D-PANI/CSA, 0.20 and 0.40 for D-PANI/MSA, 0.24 and 0.44 for D-PANI/DBSA, and 0.07, 0.14, and 0.31 for D-PANI-EB. The SANS results are compared with a number of standard models for two-phase systems. No evidence was found for significant molecular mixing. In some cases the inverse power law model is in reasonable agreement with observations, and in the case of the lowest concentration of D-PANI/CSA there is an indication of mass fractal structure. This was not found at the higher concentrations. The results establish that the blends with the smaller more polar dopants CSA and MSA behave similarly and are unlike either the D-PANI/DBSA blends or those with D-PANI-EB. There is evidence that the simple picture of two pure phases is inadequate for these materials. With the exception of the D-PANI/DBSA blend which has a relatively low scattering contrast, the results indicate that the lower limit of volume fraction for application of SANS is a few percent D-PANI-ES in Nylon 6. X-ray scattering was used to demonstrate the presence of Nylon 6 lamellae and residual peaks attributable to the pure components.

Using an interfacial polymerization technique, polyaniline (PANI) nanofibers are grown on Au electrodes which were pre-treated with a self-assembled monolayer (SAM) of 4-aminothiophenol (ATP). The ATP monolayer facilitates the growth of PANI nanofibers onto the Au surface to yield a durable polymer/metal interface. This nanostructuring procedure is a feasible approach to anchoring PANI nanofibers to Au and allows for better control over conventional processing of polymer-based nanofibers.

Arrays of conducting polymer composite vapor detectors have been evaluated for performance in the presence of the nerve agent simulants dimethylmethylphosphonate (DMMP) and diisopropylmethylphosponate (DIMP). Limits of detection for DMMP on unoptimized carbon black-organic polymer composite vapor detectors in laboratory air were estimated to be 0.047-0.24 mg m-3. These values are lower than the EC50 value for the nerve agents sarin (methylphosphonofluoridic acid, (1-methylethyl) ester) and soman, which have been established as equals 0.8 mg m-3. Arrays of these vapor detectors were easily able to resolve signatures due to exposures to DMMP from those due to DIMP or due to a variety of other test analytes in a laboratory air background. In addition, DMMP at 27 mg m-3 could be detected and differentiated from the signatures of the other test analytes in the presence of backgrounds of potential interferents in the background ambient, including water, methanol, benzene, toluene, diesel fuel, lighter fluid, vinegar and tetrahydrofuran, even when these interferents were present in much higher concentrations than that of the DMMP or DIMP being detected.

Polyanilines are of particular current interest primarily due to their relative ease of synthesis, low cost and stable conductivity in air. The insulating, polyaniline emeraldine base (PANI-EB) form becomes electrically conducting by preferential protonation or doping the imine nitrogen sites to yield an electrically conducting polyaniline emeraldine salt (PANI-ES). In this paper, wide and small angle X-ray scattering techniques (i.e., WAXS and SAXS) and light microscopy are used to characterize the influence of the dopant`s structure on the morphology of both polyaniline salt and blend. In an attempt to modify the morphology of the PANI-ES, the authors have evaluated a number of doping acids (i.e., methane sulfonic acid (HMSA), butane sulfonic acid (HBSA), dodecyl benzene sulfonic acid (HDBSA) and camphor sulfonic acid (HCSA)) that vary in size and polarity to better understanding the role of the acid in PANI-ES`s morphology and the resulting electrical conductivity. The other goal was to investigate the effect of the counter-anion structure on the nature of the phase separated PANI-ES network. The shape of the PANI-ES network in the host polycaprolactam has important implications on the nature of conduction behavior and the final electrical conductivity of the blend.

We demonstrate the controlled desorption of adventitious dopants on networks of single-walled carbon nanotubes (SWNTs) with 100 keV proton irradiation. Networks of sorted metallic, semiconducting SWNTs, and unsorted SWNTs were investigated. The removal of dopants was indicated by an increase in sheet resistances along with an increase in the absorption of the low energy absorption band of semiconducting SWNTs. Semiconducting and unsorted SWNT networks exhibited the largest change in their sheet resistance, which indicates the conductivity of unsorted SWNT networks is dominated by the tube-tube junctions of semiconducting SWNTs.