Onset Decomposition Temperature Research Articles

Interfacial crystallization of low‐crystallinity elastomer incorporated by multi‐walled carbon nanotubes: Mechanical reinforcement, structural evolution and enhanced thermal stability

ABSTRACTIn this paper, we report interfacial crystallization in olefin block copolymer (OBC) with low crystallinity incorporated by multi‐walled carbon nanotubes (MWCNTs). A hybrid shish‐kebab (HSK) superstructure in nanocomposites is observed that MWCNTs act as central shish and OBC crystals grow perpendicular to the nanotubes axis. The mechanical properties of nanocomposites are significantly improved with incorporation of MWCNTs. The most ideal reinforcing and toughening effect is both observed in nanocomposites with MWCNTs content of 1 wt % that can increase tensile strength by 122% as well as elongation at break by 36%. Efficient load transfer are confirmed with in‐situ Raman spectra that G’ band of MWCNTs in OBC matrix exhibit a downshifting trend and symmetric broadening of line shape which reveals additional macroscale strain from axial extension of MWCNTs in nanocomposites, thus suggesting a certain load is carried by HSK superstructure. The structural evolution of OBC and nanocomposites are investigated by in‐situ wide‐angle X‐Ray Diffraction (WAXD). The Herman's orientation factor of nanocomposites with 2 wt % MWCNTs incorporation is lower than that of neat matrix at mall and intermediate strains, indicating a heterogeneous stress distribution and low compliance of HSK superstructure, which is consistent with in‐situ Raman results. Moreover, the nanocomposites presents significantly enhanced thermal stability. The onset decomposition temperature of nanocomposites with 3 wt % MWCNTs can be 60.2°C higher than that of neat OBC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42368.

Graphite-like carbon nitride and functionalized layered double hydroxide filled polypropylene-grafted maleic anhydride nanocomposites: Comparison in flame retardancy, and thermal, mechanical and UV-shielding properties

Graphite-like carbon nitride (g-C3N4) and borate modified layered double hydroxides (LDH-B) were successfully fabricated by thermal pyrolysis and modified aqueous miscible organic solvent treatment methods, respectively. Then these nano-additives were introduced to prepare polypropylene-grafted maleic anhydride (PP-g-MA)/g-C3N4 and PP-g-MA/LDH-B nanocomposites using a modified solvent mixing strategy. Several important parameters of the nanocomposites including thermal, mechanical and UV-blocking properties were investigated. Results indicated that pure g-C3N4 exhibited 347.6 and 427.2 °C increase in onset decomposition temperature under air and nitrogen conditions, respectively, compared with LDH-B. In case of PP-g-MA nanocomposites, both T-10 and T-50 (the temperature at 10% and 50% weight loss, respectively) were improved by 14.6 and 27.7 °C, respectively, by the addition of g-C3N4 while those only increased by 2.3 and 17.8 °C upon introducing LDH-B. Furthermore, PP-g-MA/g-C3N4 system showed a remarkable increment (9.8 °C) in crystallization temperature while an increase of 4.2 °C for PP-g-MA/LDH-B nanocomposite. Introducing g-C3N4 and LDH-B into PP-g-MA led to a reduction of 28% and 19% in pHRR, respectively. It was noted that the incorporation of g-C3N4 caused significant improvement in storage modulus from 2445.0 MPa for neat PP-g-MA to 2783.5 MPa for PP-g-MA/g-C3N4 while that of PP-g-MA/LDH-B was dramatically decreased by 27.3%. Optical results indicated that PP-g-MA/g-C3N4 was rendered fascinating UV adsorption ability relative to PP-g-MA/LDH-B. It is expected that the novel two-dimensional nanomaterial could bring new creativity into polymer composites.

Thermal analysis for study of the gamma radiation effects in poly(vinylidene fluoride)

Abstract Poly(vinylidene fluoride) (PVDF) has attracted interest in the technology and industrial sectors, due to its mechanical and electrical properties, its resistance to weathering and its thermostability. It is well known that polymer properties change after irradiation. Thermal degradation studies after irradiation of the polymers play an important role in establishing the threshold temperature for breakdown and information about the molecular and crystalline structure. A systematic study of the effects of gamma irradiation on PVDF using DSC, TG, DTA, FTIR and XRD techniques has been conducted. The samples were irradiated with a Co-60 source at constant dose rate (12.0 kGy/h), with doses ranging from 100 kGy to 3000 kGy. The DSC data reveals a decrease in the melting temperature and melting latent heat for increasing doses. There is a remarkable decrease in the melting latent heat ranging from 46 J/kg (pristine sample) to 26 J/kg (3000 kGy). The data analysis suggests that the decrease observed in the onset decomposition temperature is due to the radio-induction of C=C bonds in the crosslinking process and that the increase of the residual amount is due to the radio-induction of C=O bonds, via chain scission.

Organosilicon-Based Electrolytes with Superior Thermal and Electrochemical Stability to Enable High Energy Lithium Ion Batteries

Organosilicon (OS) electrolytes have been developed as a viable alternative to conventional carbonate electrolytes for lithium ion batteries.1,2 A recent trend in the Li-ion industry toward adoption of new materials, including electrolytes, is driven by the desire to deploy larger capacity batteries under broader operating conditions. In addition, the development of new advanced Li-ion chemistries to meet these requirements often require electrolytes with enhanced thermal and electrochemical stability that provide performance across a wide temperature range. This novel organosilicon chemistry involves the merging of a silane with a lithium coordinating functionality, such as polyethylene oxide units. This combination results in solvents comprised of low molecular-weight molecules and having unique properties including high thermal stability, high flash point, low vapor pressure and relatively low viscosities. There is a very broad set of applications for organosilanes and thus many possibilities to finely tune the properties that need to be enhanced in a molecule. Our 1st generation OS compounds, including 1NM3, are characterized by a Si-O bond, which is responsible for the excellent thermal stability of silicone polymers and enabled the production of OS electrolytes with high thermal stability. Encouraged by the successful results for “Gen-1” compounds, Silatronix performed mechanistic studies that identified “Gen-2” structural variants that provide even greater stability under more aggressive conditions. “Gen-2” OS solvents have thermal, chemical, and electrochemical properties that surpass those of the original compounds by introducing a less polar (i.e., more stable) Si-C bond, which is less susceptible to attack by fluorinated species, (e.g., HF and PF5). Silatronix has recently developed and synthesized an entirely new class of OS molecules to provide new (patent pending) “Gen-3” solvents whose thermal, chemical, and electrochemical properties greatly surpass those of the earlier suite of OS compounds. The leading candidate from the “Gen-3” OS structural family is OS3 which showcases greatly enhanced stability and performance attributes when compared to the stable “Gen-2” molecules. Specific examples of performance improvement include higher conductivity and lower viscosity while concomitantly providing superior thermal stability with LiPF6 and enhanced voltage stability at both the cathodic and anodic extremes when compared to both carbonate and previous generation OS solvents. These advanced generation OS solvents represent a new opportunity to dramatically improve high temperature cycling stability, high voltage stability, and safety. For example, the onset temperature for decomposition of “Gen-2” molecules with LiPF6 is increased by at least 50°C compared to “Gen-1”, with significantly lower reaction rates. In contrast, OS3 does not show any significant decomposition with LiPF6 up to 175°C (see Figure 1). In this work, we focus on demonstrating the superior stability and performance attributes of the “Gen-3” molecule OS3. For this we have evaluated the physical properties (e.g., conductivity, viscosity, flash point), thermal and electrochemical stability, and performance in coin cells across a wide temperature range (-30°C to 70°C) with a variety of electrode materials. *RJH and RW have a financial interest in the outcome of this work. Figure 1

Structure‐property relationship of substituted pyrrolidine functionalized CNT epoxy nanocomposite

ABSTRACTCarbon nanotubes (CNTs) based polymer nanocomposites hold the promise of delivering exceptional mechanical properties and multifunctional characteristics. However, the realization of exceptional properties of CNT based nanocomposites is dependent on CNT dispersion and CNT‐matrix adhesion. To this end, we modified MWCNTs by Prato reaction to yield aromatic (phenyl and 2‐hydroxy‐4‐methoxyphenyl) substituted pyrrolidine functionalized CNTs (fCNT1 and fCNT2) and aliphatic (2‐ethylbutyl and n‐octyl) substituted pyrrolidine functionalized CNTs (fCNT3 and fCNT4). The functionalization of CNTs was established by Thermogravimetric analysis (TGA), Raman Spectroscopy, and XPS techniques. Optical micrographs of fCNT epoxy mixture showed smaller aggregates compared to pristine CNT epoxy mixture. A comparison of the tensile results and onset decomposition temperature of fCNT/epoxy nanocomposite showed that aliphatic substituted pyrrolidine fCNT epoxy nanocomposites have higher onset decomposition temperature and higher tensile toughness than aromatic substituted pyrrolidine fCNT epoxy nanocomposites, which is consistent with the dispersion results of fCNTs in the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42284.

Investigation of not fully stable fluids by the method of controlled pulse heating. 2. Short-term thermal stability of polymethyl metacrylate

The short-time thermal stability of glassy PMMA (polymethyl metacrylate) under conditions of high-power local heating has been studied experimentally. For this purpose, a peculiar procedure in the framework of the method of controlled pulse heating of implantable probe has been developed. The procedure is based on combining the thermal shock and monitoring heating functions with characteristic pulse lengths of the order of 1μs and 1ms, respectively. The value of the characteristic probe temperature T*pk was determined, a reproduction of which in a series of measurements under identical parameters of heating function resulted in irreversible changes in the thermal resistance of a polymeric sample. The depth of penetration into the region of thermal instability of polymer (T*pk−Td), where Td is the onset temperature of thermal decomposition in quasi-static process, attains a few hundreds of degrees.

New HAN-based mixtures for reaction control system and low toxic spacecraft propulsion subsystem: Thermal decomposition and possible thruster applications

HAN-based liquid monopropellant has been studied for its possible substitution of hydrazine toxic component. The onset temperature of decomposition was provided by DTA-TG thermal analysis. Moreover, the effect of 5M HNO3 and 5M NH2OH addition on catalytic decomposition was also examined. The major products measured by mass spectrometer were N2, NO, N2O, NO2, H2O and NH3. Otherwise, the burning rates of HAN-based monopropellants were measured from the strand burner videos taken by high speed camera. The effect of methanol addition; as fuel; on the burning rates was demonstrated. On the other hand, HAN-based liquid monopropellant was tested and decomposed in 20N thruster and different catalysts were compared. Honeycomb catalysts were tested instead Shell 405 catalysts, the obtained data demonstrate the improvement of burning reactions and pressure slopes after HAN-based decomposition.

Novel ternary poly(vinyl pyrrolidone)/poly(amide-imide)/ZnO nanocomposite: Synthesis, characterization, thermal and optical performance

Abstract The present work describes the synthesis and properties of polymer composites based on poly(vinyl pyrrolidone) (PVP) as polymer shell and poly(amide-imide)(PAI)/ZnO nanocomposite (ZNC) as efficient filler. At first, the alanine amino acid containing dicarboxylic acid was grafted on the surface of ZnO NPs. Then, modified ZnO (12 wt%) was incorporated into the PAI matrix under ultrasonic irradiations. The obtained hybrid ZNC showed high thermal stability and the size of the NPs in the TEM image of ZNC was about 31 nm. Secondly, PVP NCs with different ZNC loadings such as 2, 4 and 6 wt% were prepared via ultrasonication. Transmission electron microscopy (TEM) observations showed that the ZnO NPs were uniformly and highly dispersed in the PVP matrix. The UV–vis results exposed that the high UV-shielding efficiency of the obtained composites. Thermal analysis represented that the onset decomposition temperatures of the obtained PVPNCs had remarkable increasing in compared to the neat PVP due to the presence of both ZnO NPs and PAI.

Effect of CeH2.29 on the microstructures and hydrogen properties of LiBH4-Mg2NiH4 composites

A composite of LiBH4-Mg2NiH4 doped with 10wt% CeH2.29 was prepared by ball milling followed by dynamic interspace vacuum treatment at 573 K. The introduction of CeH2.29 caused a transformation in the morphology of Mg from complex spongy and lamellar to uniformly spongy, resulting in refined particle size and abundant H diffusion pathways. This LiBH4-Mg2NiH4 + 10wt% CeH2.29 composite exhibited excellent hydrogen storage properties. The starting temperature of rapid H absorption decreased to 375 K in the doped composite from 452 K for the unmodified material, and the onset decomposition temperature of its hydride was reduced from 536 K to 517 K. In addition, the time required for a hydrogen release of 1.5wt% (at 598 K) was 87 s less than that of the un-doped composite.

New Energetic Derivatives of 1-Amino-3-Nitroguanidine

Two new energetic derivatives of 1-amino-3-nitroguanidine were synthesized. The furoxan moiety and 2,4,6-trinitrophenyl moiety were introduced to the nitroguanidine frame. The resulting compounds 3-methyl-4-((2-(N′-nitrocarbamimidoyl)hydrazono)methyl)-1,2,5-oxadiazole-2-oxide (1, C5H7N7O4) and N′-nitro-2-(2,4,6-trinitrobenzylidene)hydrazinecarboximidamide (2, C8H6N8O8) were characterized by infrared (IR) spectroscopy, multinuclear nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), as well as elemental analysis. The structure of 1 was confirmed by X-ray diffraction. Both compounds possess good thermal stability with the decomposition onset temperature above 180°C. Their sensitivity and explosive properties were investigated by experimental and theoretical methods.

Novel CuCo2O4/graphitic carbon nitride nanohybrids: Highly effective catalysts for reducing CO generation and fire hazards of thermoplastic polyurethane nanocomposites

Novel spinel copper cobaltate (CuCo2O4)/graphitic carbon nitride (g-C3N4) (named C-CuCo2O4) nanohybrids with different weight ratios of g-C3N4 to CuCo2O4 were successfully synthesized via a facile hydrothermal method. Then the nanohybrids were added into the thermoplastic polyurethane (TPU) matrix to prepare TPU nanocomposites using a master batch-melt compounding approach. Morphological analysis indicated that CuCo2O4 nanoparticles were uniformly distributed on g-C3N4 nanosheets. Thermal analysis revealed that C-CuCo2O4-7 (proportion of g-C3N4 to CuCo2O4 of 93/7) was an optimal nanohybrid for the properties improvement of TPU. Incorporation of C-CuCo2O4-7 into TPU led to significant improvements in the onset decomposition temperature, temperature at maximal mass loss rate and char yields. The heat release rate and total heat release of TPU/C-CuCo2O4-7 decreased by 37% and 31.3%, respectively, compared with those of pure TPU. Furthermore, the amounts of pyrolysis gaseous products, including combustible volatiles and carbon monoxide (CO), were remarkably reduced, whereas, non-flammable gas (carbon dioxide) increased. Excellent dispersion of C-CuCo2O4-7 in TPU host was achieved, due to the synergistic effect between g-C3N4 and CuCo2O4. Enhancements in the thermal stability and flame retardancy were attributed to the explanations that g-C3N4 nanosheets showed the physical barrier effect and catalytic nitrogen monoxide (NO) decomposition, and that CuCo2O4 catalyzes the reaction of CO with NO and increased char residues.

Thermal degradation mechanism of polycarbonate/organically modified montmorillonite nanocomposites

There were contradictory results about the effect of clay on polycarbonate (PC) thermal stability in previous reported papers. For ascertainment of the actual role of clay, PC nanocomposites were prepared by direct melt-mixing PC with hexadecyl trimethyl ammonium chloride modified montmorillonite (OMT). The results of X-ray diffractometry, transmission electron microscopy, and high-resolution electron microscopy experiments present the formation of uniformly intercalated structure. Thermogravimetric analyses show the onset decomposition temperature of PC/OMT nanocomposites is earlier 65°C than neat PC. The mechanism of PC thermal decomposition effected by OMT was discussed in detail. It reveals that OMT can catalyze thermal degradation of PC macromolecular chains and decrease thermal stability of the nanocomposites. POLYM. COMPOS., 37:2301–2305, 2016. © 2015 Society of Plastics Engineers

Stille cross‐coupling applied to get higher molecular weight polymers: Synthesis, optoelectronic, Voc properties, and solar cell application

ABSTRACTConjugated polymers are highly desirable for the photovoltaic applications. We report the synthesis, characterization, optoelectronic properties, and solar cell application of two polymers, namely, poly[(9,9‐didodecylfluorene‐2,7‐diyl)‐alt‐(2,2′:5′,2″‐terthiophene‐5,5″‐diyl)] (P1) and poly[(1,4‐bis(dodecyloxy)benzene‐2,5‐diyl)‐alt‐(2,2′:5′,2″‐terthiophene‐5,5″‐diyl)] (P2). The polymers were synthesized via Stille cross‐coupling reaction, and were characterized by the gel permeation chromatography, nuclear magnetic resonance, Fourier transform infrared, UV–vis, thermogravimetric analysis, and cyclic voltammetry analyses. The two copolymers are processable due to their good solubility in organic solvents (tetrahydrofuran, CHCl3, toluene, chlorobenzene, and o‐dichlorobenzene). The optical band gaps (UV–vis, film, and Egopt) of the P1 and P2 are 2.04 and 2.00 eV, respectively. The density functional theory output structures showed that S…O space interaction is likely responsible for the higher planarity of P2. The polymers showed low HOMO energy levels (P1: −5.33 eV, P2: −5.05 eV). The EHOMO for P1 is close to the EHOMO (−5.4 eV) of an ideal polymer, which is an important, rare, and main origin of the observed higher Voc (801–808 mV). The onset decomposition temperatures (Td) for the P1 and P2 are 418°C and 365°C, respectively. The polymer solar cell based on the P1: C60 (1: 1) and P2: C60 (1: 1) blend showed a power conversion efficiency (PCE) of 0.94 and 0.71%, respectively. The composite polymer : PC60BM = 1 : 2 increased PCE of the P1 (1.65%) and P2 (1.09%) under AM 1.5 illumination (100 mW/cm2). The study provided important examples to design donor–donor (D–D) polymers for the photovoltaic applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42147.

Preparation and enhanced properties of Fe3O4 nanoparticles reinforced polyimide nanocomposites

Polyimide (PI) nanocomposite reinforced with Fe3O4 nanoparticles (NPs) at various NPs loadings levels of 5.0, 10.0, 15.0, and 20.0wt% were prepared. The chemical interactions of the Fe3O4 NPs/PI nanocomposites were characterized using Fourier Transform Infrared (FT-IR) spectroscopy. X-ray Diffraction (XRD) results revealed that the addition of NPs had a significant effect on the crystallization of PI. Scanning electron microscope (SEM) and the atomic force microscope (AFM) were used to characterize the dispersion and surface morphology of the Fe3O4 NPs and the PI nanocomposites. The obtained optical band gap of the nanocomposites characterized using Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV–Vis DRS) was decreased with increasing the Fe3O4 loading. Differential scanning calorimetry (DSC) results showed a continuous increase of Tg with increasing the Fe3O4 NPs loading. Some differences were observed in the onset decomposition temperature between the pure PI and nanocomposites since the NPs and the PI matrix were physically entangled together to form the nanocomposites. The contact angle of pure PI was larger than that of Fe3O4/PI nanocomposites films, and increased with increasing the loading of Fe3O4. The degree of swelling was increased with increasing the Fe3O4 loading and the swelling time. The dielectric properties of the nanocomposite were strongly related to the Fe3O4 loading levels. The Fe3O4/PI magnetic property also had been improved with increasing the loading of the magnetic nanoparticles.

Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

ABSTRACTFreeze‐dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363‐55D (P55D)] by a solvent casting method to fabricate CNC‐reinforced nanocomposites. This study demonstrated that the addition of small amounts (1–5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass‐transition temperature, but the onset decomposition temperature was shifted from 286 to 327°C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (εf) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that εf was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41970.

Investigations on the thermal stability and decomposition mechanism of an amine-functionalized ionic liquid by TGA, NMR, TG-MS experiments and DFT calculations

Amine-functionalized ionic liquids (ILs) have potential applications for CO2 capture. The CO2 capture process is generally operated at a relatively high temperature for a long term, so determining the thermal stability of amine-functionalized ILs is important. In this study, the thermal stability of an amine-functionalized IL 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was investigated by thermogravimetric analysis (TGA), thermogravimetric mass spectroscopic analysis (TG-MS), 1H nuclear magnetic resonance (NMR) experiments and density function theory (DFT) calculation. Amine-functionalization was found to reduce the thermal stability of [aEMMIM][BF4] compared to the non-functionalized counterpart. Besides that, we found that [aEMMIM][BF4] favors a unimolecular substitution nucleophilic (SN1) decomposition reaction rather than bimolecular nucleophilic substitution (SN2) reaction. Vaporization and elimination processes are negligible due to amine functionalization. Moreover, an operational temperature, Toper, is proposed for evaluating the thermal stability of ILs. Results show that Toper of [aEMMIM][BF4] only reaches 138°C, much less than that of the onset decomposition temperature, Tonset (284°C). Evaluating thermal stability of amine-functionalized ILs by Toper is more practical than by Tonset.

Synthesis and Characterization of Poly(vinyl pyrrolidone)/Reduced Graphene Oxide Nanocomposite

Poly(vinyl pyrrolidone) (PVP)/reduced graphene oxide (RGO) nanocomposites were synthesized by reducing graphene oxide in the polymer matrix at different temperatures. The effects of the GO content on the properties of the nanocomposites were investigated by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The degree of dispersion of GO in the PVP matrix was examined by field-emission scanning electron microscopy. The results showed that both GO and RGO were well dispersed in the PVP matrix. Under low filler content, the improvement of onset decomposition temperatures of PVP nanocomposites was not obviously observed, but the amounts of residual char of the PVP nanocomposites were clearly increased. In addition, the decomposition temperature peak values of the PVP nanocomposites were increased, while the peak was broadened.

Thermal stability of nanostructured TiZrSiN thin films subjected to helium ion irradiation

The phase stability, upon vacuum annealing up to 1000°C, of nanostructured (Ti,Zr)1−xSixN thin films is investigated by X-ray diffraction analysis as a function of Si content (0.13⩽x⩽0.25) and prior irradiation with He ions (40kV). The quaternary TiZrSiN thin films were deposited by reactive magnetron sputtering from elemental targets at the substrate temperature of 600°C. It was found that the increase in Si content, x, results in the transformation of structure from nanocrystalline (x=0.13, grain size of 11nm) to nanocomposite state (0.19<x⩽0.25, grain size of 5nm). The phase composition of the films changes from single-phase, cubic c-(Ti,Zr)N columns with (111) preferred orientation to dual-phase system consisting of c-(Ti,Zr)N crystallites and amorphous SiNy. Irradiation with He ions at the doses of 2×1016 and 5×1016cm−2 does change the phase composition of the films. It is found that the onset temperature for phase decomposition decreases from 1000°C to 800°C with increasing Si content for unirradiated films. The formation of a secondary ZrN phase is observed concomitantly with increased broadening of the (200) c-(Ti,Zr)N diffraction peak. For irradiated films, the subsequent annealing at 1000°C leads to decomposition of the c-(Ti,Zr)N solid solution into TiN- and ZrN-rich phases as well as crystallization of hexagonal Si3N4 phase.

Improvement of interaction between pre-dispersed multi-walled carbon nanotubes and unsaturated polyester resin

Efforts are being given to the development of well-dispersed nanoparticle-reinforced polymer nanocomposites in order to tailor the material properties. In this perspective, well dispersion of multi-walled carbon nanotubes (MWCNTs) in unsaturated polyester resin (UPR) was prepared using pre-dispersed MWCNTs in tetrahydrofuran solvent with ultrasonication method. Then the well-dispersed MWCNTs reinforced UPR nanocomposites were fabricated through solvent evaporation. Fourier-transform infrared spectroscopy indicates a good interaction between matrix and MWCNTs. This along with homogeneous dispersion of nanotubes in matrix has been confirmed by the field emission scanning electron microscopy. At low shear rate, the value of viscosity of UPR is 8,593 mPa s and that of pre-dispersed MWCNT–UPR suspension is 43,491 mPa s, showing implicitly a good dispersion of nanotubes. A notable improvement in the crystallinity of UPR from 14 to 21 % after MWCNTs inclusion was observed by X-ray diffractometry. The mechanical properties, such as tensile strength, tensile modulus, impact strength, and elongation-at-break, of nanocomposite were found to be increased to 22, 20, 28, and 87 %, respectively. The estimated melting enthalpy per gram for composites as analyzed by differential scanning calorimetry is higher than that of UPR. The onset temperature of thermal decomposition in the nanocomposites as monitored by thermogravimetric analysis is found higher than that of UPR. Correlations among MWCNTs dispersion, nucleation, fracture morphology, and various properties were measured and reported.

Influence of Potassium Chloride on the Thermal Decomposition of Ammonium Nitrate

The thermal decomposition of ammonium nitrate (AN), activated carbon (AC), and potassium chloride (KCl) mixtures are investigated. The thermal properties were studied using differential scanning calorimetry (DSC) and the evolved gas was analyzed using thermogravimetry with mass spectroscopy (TG-DTA-MS). The time to maximum rate (TMRad) was then calculated using commercial thermal analysis software. DSC measurements of an AN/KCl mixture in a sealed sample pan showed a sharp exothermic decomposition and lower onset temperature than pure AN, whereas AN/KCl in an open pan exhibited an endothermic reaction. A mixture of AN/AC/KCl exhibited a lower onset temperature than both AN/AC and AN/KCl. TG-DTA-MS results revealed HCl gas was evolved from AN/KCl, which indicated the reaction of KCl with HNO3 dissociated from AN to form HCl, and the subsequent destabilization of AN and AN/AC by HCl. TMRad calculations showed that AN/KCl underwent a run-away reaction within one day under closed adiabatic conditions above 180°C.