Structure and high‐resolution thermogravimetry of liquid‐crystalline copoly(p‐oxybenzoate‐ethylene terephthalate‐p‐benzamide)

Thermotropic liquid‐crystalline copoly(ester‐amide)s consisting of three units of p‐oxybenzoate (B), ethylene terephthalate (E) and p‐benzamide (A) were studied by proton nuclear magnetic resonance at 200 and 400 MHz, wide‐angle X‐ray diffraction, and high‐resolution thermogravimetry to ascertain their molecular and supermolecular structures, thermostability and kinetics parameters of thermal decomposition in both nitrogen and air. The assignments of all resonance peaks of [¹H]NMR spectra for the copoly(ester‐amide)s are given and the characteristics of X‐ray equatorial and meridional scans are discussed. Overall activation energy data of the first major decomposition have been evaluated through three calculating techniques. The thermal degradation occurs in three steps in nitrogen and air. The degradation temperatures are higher than 447 °C in nitrogen and 440 °C in air and increase with increasing B‐unit content at a fixed A‐unit content of 5 mol%. The temperatures at the first maximum weight‐loss rate are higher than 455 °C in nitrogen and 445 °C in air and also increase with an increase in B‐unit content. The first maximum weight‐loss rates range between 11.1 and 14.5%min⁻¹ in nitrogen and between 11.9 and 13.5%min⁻¹ in air. The char yields at 500 °C in both nitrogen and air range from 45.8 to 54.3 wt% and increase with increasing B‐unit content. But the char yields at 800 °C in nitrogen and air are quite irregular with the variation of copolymer composition and testing atmosphere. The activation energy and Ln (pre‐exponential factor) for the first major decomposition are usually higher in nitrogen than in air and increase slightly with an increase in B‐unit content at a given A‐unit content of 5 mol%. The activation energy, decomposition order, and Ln (pre‐exponential factor) of the thermal degradation for the copoly(ester‐amide)s in two testing atmospheres, are situated in the ranges of 210–292 kJmol⁻¹, 2.0–2.8, 33–46 min⁻¹, respectively. The three kinetic parameters of the thermal degradation for the aromatic copoly(ester‐amide)s obtained by high‐resolution thermogravimetry at a variable heating rate are almost the same as those by traditional thermogravimetry at constant heating rate, suggesting good applicability of kinetic methods developed for constant heating rate to the variable heating‐rate method. These results indicate that the copoly(ester‐amide)s exhibit high thermostability. The isothermal decomposition kinetics of the copoly(ester‐amide)s at 450 and 420 °C are also discussed and compared with the results obtained based on non‐isothermal high‐resolution thermogravimetry. © 1999 Society of Chemical Industry     

Hermetic Thermal Behavior of 3,4‐Diaminofurazan (DAF)

Hermetic thermal behavior of 3,4‐diaminofurazan (DAF) was studied by DSC method with special high‐pressure hermetic crucibles. The complete exothermic decomposition process of DAF can be provided. The extrapolated onset temperature, peak temperature, and enthalpy of decomposition at a heating rate of 10 K min⁻¹ are 238.7 °C, 253.0 °C, and −1986 J g⁻¹, respectively. Self‐accelerating decomposition temperature and critical temperature of thermal explosion of DAF are 232.3 and 253.1 °C, respectively. Specific heat capacity of DAF was determined with a micro DSC method and the molar heat capacity is 140.78 J mol⁻¹ K⁻¹ at 298.15 K. Adiabatic time‐to‐explosion of DAF is about 90 s. The thermal stability of DAF is good.     

Metal adhesive properties of polyamides having the 2,3‐bis(1,4‐phenylene)quinoxalinediyl structure

Polyamides were synthesized by interfacial polycondensation of 2,3‐bis(4‐chloroformylphenyl)quinoxaline (BCFPQ) and several aliphatic diamines using a phase transfer catalyst, and their adhesive property for stainless steel was investigated. The inherent viscosity of the obtained polyamides ranged from 0.37 to 1.24 dL g⁻¹. The glass transition temperatures of the polyamides ranged between 154 and 201°C, and their thermal decomposition temperatures were above 450°C. The polyamides were soluble in several organic solvents, including m‐cresol, N‐methyl‐2‐pyrrolidone (NMP), and formic acid. The adhesive property for stainless steel was examined by a standard tensile test. One member of the series, polyamide P8, derived from BCFPQ and 1,8‐octanediamine, displayed high tensile strength with values of 232 kgf cm⁻² at 20°C, 173 kgf cm⁻² at 120°C, and 137 kgf cm⁻² at 180°C. Thus, the tensile strength of P8 decreased at 180°C, but the decrease was much smaller than that of an epoxy resin in wide use as a metal adhesive. Heat distortion temperature, measured by thermal mechanical analysis, of P8 was 191°C. This suggested that P8 possessed high thermal resistance in metal adhesives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1366–1370, 1999     

The β‐δ‐Phase Transition and Thermal Expansion of Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine

Phase behavior of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) is investigated by X‐ray powder diffraction (XRD). The XRD patterns at elevated temperature show that there is a co‐existing temperature range of β‐ and δ‐phase during the phase transition process. Additionally, mechanical forces can catalyze the conversion from δ‐ back to β‐phase. Based on the diffraction patterns of β‐ and δ‐phase at different temperatures, we calculate the coefficients of thermal expansion by Rietveld refinement. For β‐HMX, the linear coefficients of thermal expansion of a‐axis and b‐axis are about 1.37×10⁻⁵ and 1.25×10⁻⁴ °C⁻¹. A slight decrease in c‐axis with temperature is also observed, and the value is about −0.63×10⁻⁵ °C⁻¹. The volume coefficient of thermal expansion is about 1.60×10⁻⁴ °C⁻¹, with a 2.2% change from 30 to 170 °C. For δ‐HMX, the linear coefficients of thermal expansion of a‐axis and c‐axis are found to be 5.39×10⁻⁵ and 2.38×10⁻⁵ °C⁻¹, respectively. The volume coefficient of thermal expansion is about 1.33×10⁻⁴ °C⁻¹, with a 2.6% change from 30 to 230 °C. The results indicate that β‐HMX has a similar volume coefficient of thermal expansion compared with δ‐HMX, and there is about 10.5% expansion from β‐HMX at 30 °C to δ‐HMX at 230 °C, of which about 7% may be attributed to the reconstructive transition.     

Synthesis,Crystal Structure,and Thermal Behaviors of 3‐Nitro‐1,5‐bis(4,4′‐dimethylazide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP)

The energetic material, 3‐nitro‐1,5‐bis(4,4′‐dimethyl azide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP), was firstly synthesized by means of Click Chemistry using 1,5‐diazido‐3‐nitrazapentane as main material. The structure of NDTAP was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy; mass spectrometry, and elemental analysis. The crystal structure of NDTAP was determined by X‐ray diffraction. It belongs to monoclinic system, space group C2/c with crystal parameters a=1.7285(8) nm, b=0.6061(3) nm, c=1.6712(8) nm, β=104.846(8)°, V=1.6924(13) nm³, Z=8, μ=0.109 mm⁻¹, F(000)=752, and D_c=1.422 g cm⁻³. The thermal behavior and non‐isothermal decomposition kinetics of NDTAP were studied with DSC and TG‐DTG methods. The self‐accelerating decomposition temperature and critical temperature of thermal explosion are 195.5 and 208.2 °C, respectively. NDTAP presents good thermal stability and is insensitive.     

Properties of CP: Coefficient of Thermal Expansion,Decomposition Kinetics,Reaction to Spark,Friction and Impact

The properties of pentaamine (5‐cyano‐2H‐tetrazolato‐N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook‐off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear and isothermal heating, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 68.95 MPa and analyzed over a dynamic temperature range of −20 °C to 70 °C. Differential scanning calorimetry, DSC, was used to monitor CP decomposition at linear heating rates of 1–7 °C min⁻¹ in perforated pans and of 0.1–1.0 °C min⁻¹ in sealed pans. The kinetic triplet was calculated using the LLNL code Kinetics05, and predictions for 210 °C and 240 °C are compared to isothermal thermogravimetric analysis (TGA) experiments. Values are also reported for spark, friction, and impact sensitivity.     

New polymer syntheses. IX. Synthesis and properties of new conducting polyazomethine polymers containing main chain cycloalkanone and pyridine moieties

Novel polyazomethines containing cycloalkanones or pyridine moieties were synthesized by the polycondensation of 2,5‐bis(m‐aminobenzylidene)cyclopentanone (BMAP, IV), 2,6‐bis(m‐aminobenzylidene)cyclohexanone (BMAH, V), 2,6‐bis(p‐aminobenzylidene)cyclohexanone (BPAH, VI), and 2,6‐bis(m‐aminostyryl)pyridine (BMAS, VIII) diamines with terephthalaldehyde in EtOH at 25°C. These polymers were yellow to orange in color, had reduced viscosities up to 1.42 dL/g, and had electric conductivities as high as 10⁻¹¹–10⁻¹² S cm⁻¹. All the polyazomethines were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid. However, they were readily hydrolyzed in concentrated H₂SO₄. X‐ray diffraction diagrams showed that the crystallinities of the polyazomethines were low. These azomethine polymers showed high thermal and thermooxidative stability and exhibited no appreciable decomposition up to 400°C in air. The electronic spectra of the polymers indicated a large bathochromic shift of the π–π* absorption band (∼360 nm) that was due to the presence of CN bonds in the polymer main chain. Doping with iodine dramatically raised the conductivity and produced dark brown to black colored semiconductive polymers with a maximum conductivity on the order of 10⁻⁷ S cm⁻¹. Furthermore, the morphology of selected examples of the four polyazomethines was examined by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1218–1229, 2000     

Chemical Kinetics of the Thermal Decomposition of NTO

The kinetics of thermal decomposition of 3‐nitro‐2,4‐dihydro‐3H‐1,2,4‐triazol‐5‐one (NTO) in the temperature interval from 200 °C to 260 °C was investigated using a glass Bourdon gauge. The overall decomposition reaction includes two distinct stages: the fast first‐order decomposition and the subsequent autocatalytic reaction. The importance of the first stage increases with increasing decomposition temperature and decreasing loading density of the Bourdon gauge (m/V). A period of preliminary heating, at a lower temperature, strongly influences the autocatalytic stage when the decomposition is carried out at a higher temperature. In the temperature domain 200–220 °C, the Arrhenius constants of the decomposition reaction are found to be close to the values usually observed for nitrocompounds: E=173 kJ/mol and log₁₀ k≈12.5 (s⁻¹). It is shown that a simple model of NTO decomposition based on an autocatalytic reaction of the m‐th order can describe the course of the decomposition at high temperature but the m number appears to be excessively high, up to 4. A new model of the decomposition is developed, including an initial monomolecular reaction, decomposition of the crystalline substance, and an autocatalytic reaction of NTO dissolved in liquid decomposition products. This model gives the common order of autocatalysis, m=1.     

Synthesis and Characterization of 1,5‐Dinitro‐2,6‐bis(trinitromethyl)‐3a,4a,7a,8a‐tetrahydro‐[1,4]dioxino[2,3‐d:5,6‐d′]diimidazole (DNTNDI)

The polynitro imidazole derivative 1,5‐dinitro‐2,6‐bis(trinitromethyl)‐3a,4a,7a,8a‐tetrahydro‐[1,4]dioxino[2,3‐d:5,6‐d′]diimidazole (DNTNDI) was synthesized through nitration of 2‐(dinitromethylene)‐1H‐imidazol‐4‐ol in HNO₃/Ac₂O followed by cyclization of the di‐enol. It was characterized by NMR, IR, elemental analysis, and single‐crystal X‐ray diffraction analysis. Compound DNTNDI crystallizes in the orthorhombic space group P2(1)2(1)2(1). The thermal decomposition was studied with thermogravimetry/derivative thermogravimetry (TG/DTG) in a nitrogen atmosphere with a heating rate of 5 K min⁻¹. The TG/DTG analysis indicated that DNTNDI has 97.64 % mass loss between 127 °C and 173 °C by undergoing exothermic decomposition. The density of DNTNDI was determined as 1.906 g cm⁻³ at 293 K with an Ultrapycno 1000 Pycnometer. The denotation velocity and denotation pressure of DNTNDI were calculated as 9325 m s⁻¹ and 40 GPa by applying the LOTUSES (version 1.4) code, respectively. The oxygen balance of DNTNDI is 0 and its oxygen content amounts to 51.78 %, which is superior to that of new generation of chlorine‐free oxidizer ammonium dinitramide (ADN).     

Glycidyl Azide Polymer Crosslinked Through Triazoles by Click Chemistry: Curing,Mechanical and Thermal Properties

Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3‐dipolar cycloaddition reaction to form 1,2,3‐triazole network. The properties of GAP‐based triazole networks are compared with the urethane cured GAP‐systems. The glass transition temperature (T_g), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher T_g in comparison to the GAP‐urethane system (T_g−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)‐based theoretical calculations implied marginal preference for 1,5‐addition over 1,4‐addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP‐triazole and the mechanism of decomposition was elucidated using pyrolysis GC‐MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol⁻¹) against that of azide (317 kJ ⋅ mol⁻¹) and better mechanical properties of the GAP‐triazole renders it a better propellant binder than the GAP‐urethane system.     

Structural and Thermal Characterization of A Novel High Nitrogen Energetic Material: (NH4)2DNMT

1,4‐Dihydro‐5H‐(dinitromethylene)‐tetrazole ammonium salt ((NH₄)₂DNMT), a high nitrogen energetic compound, was synthesized and structurally characterized by single‐crystal X‐ray diffraction. The thermal behavior of (NH₄)₂DNMT was studied with DSC and TG‐DTG methods. The kinetic equation of the thermal decomposition reaction is: dα/dT=10^13.17/3β(1−α)⁻² exp(−1.388×10⁵/RT). The critical temperature of thermal explosion is 182.7 °C. The specific heat capacity of (NH₄)₂DNMT was determined and the molar heat capacity is 301 J mol⁻¹ K⁻¹ at 298.15 K. The adiabatic time‐to‐explosion of (NH₄)₂DNMT was calculated to be 277 s. The detonation velocity and detonation pressure were also estimated. All results showed that (NH₄)₂DNMT presents good performance.     

Characterisation of the Major Synthetic Products of the Reactions Between Butanone and Hydrogen Peroxide

The reactions between butanone and hydrogen peroxide, both catalysed and un‐catalysed, were investigated and spectral and sensitiveness data reported. The major product of the un‐catalysed reaction, 2‐hydroxy,2‐hydroperoxybutane, displayed a Figure of Insensitiveness (F of I) of 10, Temperature of Ignition (T of I) of 132 °C, and initiated when 128 N of frictional force or an electrostatic discharge (ESD) of 4.5 J was applied. Differential scanning calorimetric analyses revealed an onset of decomposition at 128 °C, peak maximum of 140 °C, and decomposition energy of 203 J g⁻¹. The major product of the cooled (5 °C) acid catalysed reaction between butanone and hydrogen peroxide, 2,2′‐dihydroperoxy‐2,2′‐dibutyl peroxide, displayed a F of I of<10, T of I of 110 °C and initiated upon application of 5 N of friction or a 0.45 J ESD. Calorimetry showed a melt at 38.3 °C, an onset of exothermic decomposition at 127 °C and the evolution of 1292 J g⁻¹. The major product of the raised temperature (20 °C) acid catalysed synthesis, 1,4,7‐trimethyl‐1,4,7‐triethyl‐1,4,7‐cyclononatriperoxane, displayed F of I of<10 and initiated upon application of 5 N of friction or a 0.45 J ESD. Calorimetry revealed an onset to melting at 28.9 °C, an onset to thermal decomposition at 128 °C, and decomposition energy of 1438 J g⁻¹.     

The influence of cross‐linking reaction on the mechanical and thermal properties of polyarylene ether nitrile

The processing of cross‐linked polyarylene ether nitrile (PEN), which has a triazine rings structure, has been investigated under different reaction times and temperatures. In this study, the PEN films prepared by the tape‐casting formed the thermally stable triazine rings by catalytic cross‐linking reaction gradually, which was characterized by Fourier transform infrared spectroscopy. The chemical cross‐linking reaction occurred as the CN group absorption of PEN at 2221 cm⁻¹ decreased and a new absorption peak, at 1682 cm⁻¹, was observed, and the absorption peak intensity would be progressively larger, with the extension of the processing time. After the formation of cross‐linking networks, the cross‐linking degree and thermal and mechanical properties of the processed films were improved substantially, compared with the untreated films. The film with added ZnCl₂ as the catalyst was more rapidly cross‐linked, and its properties were better than that without catalyst at the same treatment conditions. The glass‐transition temperature (T_g) of PEN films processed at 350°C for 4 h (213.65°C) was higher than that of PEN films before the treatment (161°C), and the tensile strength was also improved significantly. The PEN was processed at 350°C for 2 h, whose initial decomposition temperature increases by about 10°C, compared with that of untreated film, at one time. The rheology behavior of the cross‐linked films was processed on dynamic rheometer to monitor and track the process of polymer cross‐linking reaction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal Decomposition of NTO: An Explanation of the High Activation Energy

Burning rate characteristics of the low‐sensitivity explosive 5‐nitro‐1,2,4‐triazol‐3‐one (NTO) have been investigated in the pressure interval of 0.1–40 MPa. The temperature distribution in the combustion wave of NTO has been measured at pressures of 0.4–2.1 MPa. Based on burning rate and thermocouple measurements, rate constants of NTO decomposition in the molten layer at 370–425 °C have been derived from a condensed‐phase combustion model (k=8.08⋅10¹³⋅exp(−19420/T) s⁻¹. NTO vapor pressure above the liquid (ln P=−9914.4/T+14.82) and solid phases (ln P=−12984.4/T+20.48) has been calculated. Decomposition rates of NTO at low temperatures have been defined more exactly and it has been shown that in the interval of 180–230 °C the decomposition of solid NTO is described by the following expression: k=2.9⋅10¹²⋅exp(−20680/T). Taking into account the vapor pressure data obtained, the decomposition of NTO in the gas phase at 240–250 °C has been studied. Decomposition rate constants in the gaseous phase have been found to be comparable with rate constants in the solid state. Therefore, a partial decomposition in the gas cannot substantially increase the total rate. High values of the activation energy for solid‐state decomposition of NTO are not likely to be connected with a sub‐melting effect, because decomposition occurs at temperatures well below the melting point. It has been suggested that the abnormally high activation energy in the interval of 230–270 °C is a consequence of peculiarities of the NTO transitional process rather than strong bonds in the molecule. In this area, the NTO molecule undergoes isomerization into the aci‐form, followed by C3‐N2 heterocyclic bond rupture. Both processes depend on temperature, resulting in an abnormally high value of the observed activation energy.     

Chemical copolymerization of aniline with o‐chloroaniline: thermal stability by spectral studies

Poly(aniline‐co‐o‐chloroaniline) salts were synthesized by chemical copolymerization of aniline with o‐chloroaniline using three different acids. The polymer salt samples were heat treated at four different temperatures (150, 200, 275 and 375 °C) and the thermal stability of the polymer salts were studied by conductivity, electron paramagnetic resonance (EPR), infrared (IR) and electronic absorption spectral measurements. The conductivity of the copolymers could be controlled in a broad range from 10 S cm⁻¹ for homopolymer of aniline to 10⁻⁴ S cm⁻¹ for those of o‐chloroaniline. No structural changes took place up to 200 °C and this was confirmed from EPR, IR and electronic absorption spectra. No definite correlation exists between conductivity and spin concentration. © 2000 Society of Chemical Industry     

The Synthesis and Energetic Properties of 5,7‐Dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide (DNBTDO)

Energetic tetrazine‐1,3‐dioxide, 5,7‐dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide ( DNBTDO ), was synthesized in 45 % yield. DNBTDO was characterized as an energetic material in terms of performance (V_det 8411 m s⁻¹; p_{C J} 3.3×10¹⁰ Pa at a density of 1.868 g cm⁻³), mechanical sensitivity (impact and friction as a function of grain size), and thermal stability (T_dec 204 °C). DNBTDO exhibits a sensitivity slightly higher than that of RDX , and a performance slightly lower (96 % of RDX ).     

Preparation and Performance of a HNIW/TNT Cocrystal Explosive

A novel cocrystal explosive composed of 2,4,6,8,10,12‐hexanitrohexaazaiso‐wurtzitane (HNIW) and 2,4,6‐trinitrotoluene (TNT) in a 1 : 1 molar ratio was effectively prepared by solvent/nonsolvent cocrystallization adopting dextrin as modified additive. The structure, thermal behavior, sensitivity, and detonation properties of HNIW/TNT cocrystal were studied. The morphology and structure of the cocrystal were characterized by scanning electron microscopy (SEM) and single crystal X‐ray diffraction (SXRD). SEM images showed that the cocrystal has a prism type morphology with an average size of 270 μm. SXRD revealed that the cocrystal crystallizes in the orthorhombic system, space group Pbca, and is formed by hydrogen bonding interactions. The properties of the cocrystal including sensitivity, thermal decomposition, and detonation performances were discussed in detail. Sensitivity studies showed that the cocrystal exhibits low impact and friction sensitivity, and largely reduces the mechanical sensitivity of HNIW. DSC and TG tests indicated that the heterogeneous exothermic decomposition of the cocrystal occurs in the temperature range from 170 °C to 265 °C with peak maxima at 220 °C and 250 °C and significantly increases the melting point of TNT by 54 °C. The cocrystal has excellent detonation properties with a detonation velocity of 8426 m s⁻¹ and a calculated detonation pressure of 32.3 MPa at a charge density of 1.76 g cm⁻³, respectively. Moreover, the results suggested that the HNIW/TNT cocrystal not only has unique performance itself, but also effectively alters the properties of TNT and HNIW. Therefore, the cocrystal formed by HNIW and TNT could provide a new and effective method to modify the properties of certain compounds to yield enhanced explosives for further application.     

Investigation on the Thermal Expansion and Theoretical Density of 1,3,5‐Trinitro‐1,3,5‐Triazacyclohexane

The CTE and the theoretical density are important properties for energetic materials. To obtain the CTE and the theoretical density of 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), XRD, and Rietveld refinement are employed to estimate the dimensional changes, within the temperature range from 30 to 170 °C. The CTE of a, b, c axis and volume are obtained as 3.07×10⁻⁵ K⁻¹, 8.28×10⁻⁵ K⁻¹, 9.19×10⁻⁵ K⁻¹, and 20.7×10⁻⁵ K⁻¹, respectively. Calculated from the refined cell parameters, the theoretical density at the given temperature can be obtained. The theoretical density at 20 °C (1.7994 g cm⁻³) is in close match with the RDX single‐crystal density (1.7990 g cm⁻³) measured by density gradient method. It is suggested that the CTE measured by XRD could perfectly meet with the thermal expansion of RDX.     

Thermal stability and dynamic mechanical behavior of exfoliated graphite nanoplatelets‐LLDPE nanocomposites

The objective of this research was to investigate thermal stability and dynamic mechanical behavior of Exfoliated graphite nanoplatelets (xGnP™)‐Linear Low‐Density Poly Ethylene (LLDPE) nanocomposites with different xGnP loading content. The xGnP‐LLDPE nanocomposites were fabricated by solution and melt mixing in various screw rotating systems such as co‐, counter‐, and modified‐corotating. The storage modulus (E′) of the composites at the starting point of −50°C increased as xGnP contents increased. E′ of the nanocomposite with only 7 wt% of xGnP was 2.5 times higher than that of the control LLDPE. Thermal expansion and the coefficient of thermal expansion of xGnP‐loaded composites were much lower than those of the control LLDPE in the range of 45–80°C (299.8 × 10⁻⁶/°C) and 85–100°C (365.3 × 10⁻⁶/°C). Thermal stability of the composites was also affected by xGnP dispersion in LLDPE matrix. The xGnP‐LLDPE nanocomposites by counter‐rotating screw system showed higher thermal stability than ones by co‐rotating and modified‐co‐rotating system at 5 wt% and 12 wt% of xGnP. xGnP had a great effect on high thermal stability of xGnP‐LLDPE composites to be applied as tube and film for electrical materials. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Preparation and properties of thermally conductive photosensitive polyimide/boron nitride nanocomposites

A new thermally conductive photoresist was developed. It was based on a dispersion of boron nitride (BN) nanoflakes in a negative‐tone photosensitive polyimide (PSPI) precursor. 3‐Mercaptopropionic acid was used as the surfactant to modify the BN nanoflake surface for the dispersion of BN nanoflakes in the polymer. The thermal conductivity of the composite films increased with increasing BN fraction. The thermal conductivity of the PSPI/BN nanocomposite was up to 0.47 W m⁻¹ K⁻¹ for a mixture containing 30 wt % nanosized BN filler in the polyimide matrix. Patterns with a resolution of 30 μm were obtained from the PSPI/BN nanocomposites. The PSPI/BN nanocomposites had excellent thermal properties. Their glass‐transition temperatures were above 360°C, and the thermal decomposition temperatures were over 460°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011