Abstract:The thermal insulation properties of thermoplastic polyurethane elastomer nanocomposites were characterized at different heat fluxes. Thermoplastic polyurethane elastomer was modified with different loadings of montmorillonite nanoclays and carbon nanofibers (CNFs) via twin screw extrusion processing. The addition of nanoparticle into thermoplastic polyurethane elastomer resulted in the formation of a char layer and modified the thermal insulative properties of the material. It was found that thermoplastic pol… Show more
“…An overall homogeneous dispersion of nanoclay platelets in exfoliated state was achieved, which confirms results obtained previously on MMT nanocomposites compounded using the same approaches. 13,40,41 In all TEM observations, the nanoclay platelets were primarily oriented along the fiber axis. Figure 1.Transmission electron micrographs of electrospun PA6 fibers containing nanoclay platelets in progressive magnification with scale bars of 200 nm (a), 100 nm (b), and 50 nm (c).…”
Flame retardant polyamide 6 (nylon 6) nanocomposite nanofibers containing montmorillonite clay (MMT) platelets and intumescent non-halogenated flame retardant (FR) additives were processed by electrospinning. Different methods of mixing nano fillers before electrospinning were explored and compared. It was found that high loadings of nanoclay particles affected the electrospinnability of the nanocomposite material. Good dispersion and exfoliation of nanoclay platelets within individual nanofibers was verified by transmission electron microscopy. The degradation temperature of nanocomposite samples was lower than pristine nylon 6 samples. However the degradation of all nanocomposite formulations was overall slower. Moreover, the difference in residual char weight after decomposition was significant. Microscale combustion calorimeter results show that FR particles played a major role in reducing flammability of the material in both solution- and melt-compounded samples, while MMT nanoclay was effective in improving char residue and in reducing flammability in high-shear melt premixed samples.
“…An overall homogeneous dispersion of nanoclay platelets in exfoliated state was achieved, which confirms results obtained previously on MMT nanocomposites compounded using the same approaches. 13,40,41 In all TEM observations, the nanoclay platelets were primarily oriented along the fiber axis. Figure 1.Transmission electron micrographs of electrospun PA6 fibers containing nanoclay platelets in progressive magnification with scale bars of 200 nm (a), 100 nm (b), and 50 nm (c).…”
Flame retardant polyamide 6 (nylon 6) nanocomposite nanofibers containing montmorillonite clay (MMT) platelets and intumescent non-halogenated flame retardant (FR) additives were processed by electrospinning. Different methods of mixing nano fillers before electrospinning were explored and compared. It was found that high loadings of nanoclay particles affected the electrospinnability of the nanocomposite material. Good dispersion and exfoliation of nanoclay platelets within individual nanofibers was verified by transmission electron microscopy. The degradation temperature of nanocomposite samples was lower than pristine nylon 6 samples. However the degradation of all nanocomposite formulations was overall slower. Moreover, the difference in residual char weight after decomposition was significant. Microscale combustion calorimeter results show that FR particles played a major role in reducing flammability of the material in both solution- and melt-compounded samples, while MMT nanoclay was effective in improving char residue and in reducing flammability in high-shear melt premixed samples.
“…So as to advance SRM internal insulation, Koo and colleagues created ablatives using two thermoplastic polyurethane elastomers (TPU)) (Dow Chemical Pellethane ® 2102‐90A and Bayer Material Science Desmopan ® DP 6065A) as the base polymer and incorporated them with different amounts of nanomaterials using twin‐screw extrusion . The nanomaterials used were Southern Clay Products Cloisite ® 30B montmorillonite (MMT) clays, Applied Sciences Pyrograf® PR‐19‐XT‐LHT carbon nanofibers (CNFs), Hybrid Plastics SO‐1458 Polyhedral Oligomeric Silsesquioxanes (POSS®), and Arkema Graphistrength® C100 multi‐walled carbon nanotubes (MWCNTs) .…”
Section: Introductionmentioning
confidence: 99%
“…The effects of weight loadings of layered clay, CNF, and MWCNT on the thermal and flammability performance of this novel class of materials have been explored using a variety of test protocols and methods, such as thermogravimetric analysis, radiant panel experimental apparatus, UL 94, and cone calorimeter. Selective TPUs were then tested using a scaled SRM, an oxyacetylene torch, and scaled hybrid rocket motors with the intent to develop them for SRM insulation applications . Two commercial TPUs were melt‐blended with various loadings of these nanofillers, using twin‐screw extrusion.…”
“…A standard flammability test performed on polymers is the UL 94 test [29]. Of the three types of UL 94 test setups: surface burn, vertical burn, and horizontal burn tests; the vertical burn test was run on the Desmopan ® nanocomposite formulations.…”
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TITLE AND SUBTITLEExperimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket
PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBERThe University of Texas at Austin, Dept. of Mechanical Engineering, 1 University Station, C2200, Austin, TX 78712-0292
SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Dr. Charles Y-C Lee AFOSR AFOSR/NL 875 N. Randolph St., Ste. 325
SPONSOR/MONITOR'S REPORTArlington, VA 22203
NUMBER(S)
DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Research objective is to develop a modeling framework for simulating the insulative behavior of thermoplastic polyurethane elastomer nanocomposites (TPUNs) for solid rocket motors (SRMs). This research combines numerical modeling and experimental characterization of TPUNs for SRM insulation. Two families of TPUNs based on nanoclay, carbon nanofiber (CNF), and multiwall carbon nanotubes (MWNT) were developed. TGA experiments were conducted on Kevlar-EPDM, TPU, TPUN-clay, TPUN-CNF, and TPUN-MWNT in both air and nitrogen at low heating rates. Kinetics was calculated using isoconversion technique. High heating rate TGA was conducted on selective TPUNs. Flammability tests indicated TPUN-clay has the toughest char, followed by TPUN-MWNT, then TPUN-CNF. We connected the population balance framework to atomistic calculations to determine what aspects of the atomistic simulations would likely affect the meso-scale evolution. We focused on understanding the role that the scission kernel has on the overall degradation process and also on the role of the stoichiometry parameter has on the overall degradation kinetics. We began using the atomistic simulation code RXN MD to compute scission kinetics parameters. We recognized that the critical issue in characterizing a particular materials ablation rate could be captured by investigating the steady state ablation proc...
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