Differential Scanning Calorimentry Research Articles

One-step synthesis of polynitropyridine-based thermostable and low sensitive energetic materials

In this study, two energetic compounds based on a 3,5-dinitropyridine backbone linked by hydrazine and imine bridges were synthesized and fully characterized using elemental analysis, NMR (1H, 13C), IR, and differential scanning calorimentry (DSC). The crystal structures of 1,2-bis(3,5-dinitropyridin-2-yl)hydrazine (2) and N-(3,5-dinitropyridin-2-yl)-6,8-dinitro-[1,2,4]triazolo[1,5-a]pyridine-2-amine (3) were further determined using X-ray diffraction. Compounds 2 and 3 possess high thermal stability, with Td of 274 ​°C and 290 ​°C, respectively, both of which are higher than 250 ​°C. In addition, both compounds have desirable insensitive properties IS ​> ​40 ​J, FS ​> ​360 ​N) and are more insensitive than HNS and PYX (HNS: IS ​= ​5 ​J, FS ​= ​240 ​N; PYX: IS ​= ​10 ​J, FS ​= ​360 ​N). Moreover, the detonation properties of compounds 2 and 3 (2: vD ​= ​7862 ​m·s−1, p ​= ​25.4 ​GPa; 3: vD ​= ​8024 ​m·s−1, p ​= ​26.9 ​GPa) are both higher than that of HNS (vD ​= ​7612 ​m·s−1, p ​= ​24.3 ​GPa). These results indicate that both compounds have promising prospects as thermostable and insensitive explosives.

Dual controlled release effect of montmorillonite loaded polymer nanoparticles for ophthalmic drug delivery

Montmorillonite based polymeric nanoparticles was designed to effectively deliver adequate concentrations of drug to the ocular site after topical administration for treatment of glaucoma. In vitro and in vivo studies were carried out to evaluate their drug delivery performances. Betaxolol hydrochloride (BH) intercalated montmorillonite (Mt-BH) was successfully encapsulated into the Eudragit®PO (Mt-BH NPs) via an opportunely emulsification-solvent evaporation technique as indicated by Fourier transform infrared, differential scanning calorimentry, and the nitrogen sorption and desorption isotherms. The resulting nanoparticle system showed the mean particle diameters of 82 ± 8 nm and positive ζ potentials, with encapsulation efficiency of 77 ± 1% and drug-loading rate of 8 ± 2%. Interestingly, in vitro release profile of Mt-BH NPs exhibits an initial burst of surface-bound BH, followed by a slow release of BH due to polymer erosion, and a further drug release after the particle completely breakdown. About 80% were released after 10 h. The designed drug delivery system showed little irritation and well tolerance of nanoparticles in a chorioallantoic membrane assay. The new Eudragit®PO polymer nanoparticles system reported here is expected to be useful in ophthalmic application.

Effects of β-nucleating agent and graphene oxide on the crystallization and polymorphic composition of isotactic polypropylene / graphene oxide composites for bridge pavement

To control the polymorphic and crystallization behavior of β-nucleated isotactic polypropylene / graphene oxide (β-iPP/GO) composites for bridge pavement, the roles of β-nucleating agent (β-NA) concentration and GO content in the polymorphic crystallization behavior, morphology and crystallization kinetics were studied by means of differential scanning calorimentry (DSC), wide-angle X-ray diffraction (WAXD), scanning electronic microscopy (SEM). Results revealed that with the increase of β-NA concentration, the crystallization temperature, the percentage of β-phase βc and relative degree of crystallinity Xc increased evidently. Moreover, the crystallite sizes decreased, and the crystallization activation energy △E decreased, reflecting the strong nucleation effect of the β-NA to the composites; On the other hand, as the GO content increased, the crystallization temperatures and relative degree of crystallinity Xc also increased slightly. Interestingly, GO exhibited strong α-nucleation effect, which was not favorable for formation of β-phase. When the GO content was 2.0 wt%, unusual small banding patterned crystals were observed. In general, to control the polymorphic behavior and morphology of the β-iPP/GO composites, both β-NA concentration and GO content were very important factors.

Thermal expansion and the heat capacity of nanocrystalline and coarse-crystalline silver sulfide Ag2S

The thermal expansion and the heat capacity of coarse-crystalline and nanocrystalline silver sulfide Ag2S were studied by dilatometry and differential scanning calorimentry for the first time in the temperature range 290–970 K. It is found that the thermal expansion coefficient and the heat capacity of nanocrystalline silver sulfide in this temperature range are higher than those in the case of the coarse-crystalline sulfide. It is revealed that the transformation of α-Ag2S acanthite to β-Ag2S argentite and β-Ag2S argentite to γ-Ag2S phase are the first-order phase transitions; the temperatures and the enthalpies of these transformations have been determined.

Synthesis and Characterization of Soluble Cardo Poly(ester-imide)s Derived from 9,9-Bis[4-(3,4-dicarboxybenzoyloxy)phenyl]fluorene

ABSTRACTA novel fluorenyl cardo dianhydride-9,9-bis[4-(3,4-dicarboxybenzoyloxy)phenyl]fluorene (BDPF) was synthesized and characterized. A series of fluorenyl cardo poly(ester-imide)s (FCPEIs) were prepared by the polycondensation of BDPF with m-phenylene diamine, 4,4′-oxydianiline (4,4′-ODA), 3,4′-oxydianiline (3,4′-ODA), 2,2-bis[4-(4-amino -phenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and 1,6-hexamethylenediamine. Most of the FCPEIs exhibited excellent solubility in common organic solvents such as 1,2-dichlorobenzene (o-DCB), chloroform, tetrahydrofuran, N,N-dimethylacetamide (DMAc), dimethyl sulfoxide, N-methyl-2-pyrrolidinone, etc. Intrinsic viscosities of FCPEIs in DMAc, for instance, ranged from 0.29–0.52 dL/g. The glass transition temperature of these polymers was between 199°C and 283°C by differential scanning calorimentry, and the 5% weight loss temperature of all polymers exceeded 400°C in air.

Synergistic effect of methyl phenyl silicone resin and DOPO on the flame retardancy of epoxy resins

A series of flame-retarded epoxy resins (EPN) loaded with methyl phenyl silicone resin (Si603) and DOPO (9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) have been prepared. The morphology of these EPN composites were characterized by differential scanning calorimentry (DSC). The mixed epoxy systems all exhibit single glass transition temperature which indicates a homogeneous morphology of these mixed epoxy systems. The thermal stability and flammability of these EPN composites were investigated with limiting oxygen index, UL 94 vertical burning, and themogravimetric analysis tests (TG). The results showed that the DOPO and Si603 system had excellent flame retardancy and antidripping properties for EPN. The TG curves suggested that there was a distinct synergistic effect of DOPO and Si603, and this effect greatly promoted the char formation of the EPN composites and hence improved the flame retardancy. Additionally, the structure and morphology of char residues were studied with Fourier transform infrared and scanning electron microscopy.

Dynamic crystallization and melting behavior of β-nucleated isotactic polypropylene with different melt structures

In the previous work, we reported that the β-selectivity, morphology and tensile behavior of isotactic polypropylene (iPP) can be efficiently tuned by the combination of controlling the melt structure status (namely, creation ordered structure by tuning the fusion temperature Tf) and the addition of β-nucleation agent (β-NA, tradename WBG-II, concentration 0.01 wt%), which was called “Ordered Structure Effect” (OSE). This study further investigates the dynamic crystallization and melting behavior of β-iPP with a different melt structure status by differential scanning calorimentry (DSC) and non-isothermal crystallization kinetics. The results revealed that under all the cooling rates studied (2, 5, 10, 20 and 40 °C/min), the crystallization temperature on the cooling curves increased gradually with the decrease of Tf; meanwhile, when the Tf was in the temperature range of 168–186 °C where the OSE occurs (defined as Region II), the crystallization activation energy ΔE was found to be evidently lower, compared with that when the Tf was higher than 186 °C or lower than 168 °C. The results of the subsequent heating showed that the occurrence of the OSE can be observed at all the cooling rates studied; the location of the Region II was constant when the cooling rate varied. Low cooling rate encouraged the formation of more β-phase triggered by OSE. Moreover, the role of OSE on the β-α recrystallization was comparatively studied by tuning the end temperature of recooling (Tend) after held at Tf, and it was found that the OSE encouraged the formation of β-phase with high thermal stability at the low temperature part of Region II, while enhancing the β-crystal with relatively low thermal stability at the high temperature part of Region II.

Curing Kinetics Analysis and Properties Researches of Cyanate Composites

The powdery nitrile butadiene rubbers (P-NBRs) are employed to improve the comprehensive properties of the bisphenol A dicyanate ester (BADCY). The addition of P-NBRs affecting on the curing kinetics of the composites is analyzed and characterized by gelation test, differential scanning calorimentry (DSC) and Fourier transformed infrared spectroscopy (FTIR). And the contents of P-NBRs affecting on the mechanical and dielectric properties of the P-NBRs/BADCY composites are also investigated. Results show that the addition of P-NBRs has little influence on the cure activation energy. The mechanical properties of the P-NBRs/BADCY composites are optimal with 5 wt% P-NBRs. The dielectric constant values of the P-NBRs/BADCY composites are increased with the increasing addition of P-NBRs.

Synthesis of Copolymers Based on Benzene and Biphenyl and their Characterization by XRD and DSC

In this work the crystalinity and the thermal transitions of soluble and insoluble in chlorobenzene polyphenylene copolymers (synthesized by oxidative cationic polymerization) were studied. All copolymers had a degree of crystallinity between 44.6 and 66.7 %. With Differential Scanning Calorimentry (DSC) measurements it was found that the copolymers exhibited endothermic peaks in the region 268 up to 286 oC. These peaks in the case of soluble polyphenylenes were attributed to the melting of their crystallites, whereas in the case of insoluble polyphenylenes were attributed to liquid crystal transitions.

Synthesis and thermal energy storage properties of the polyurethane solid–solid phase change materials with a novel tetrahydroxy compound

Based on the phase change theory, a novel tetrahydroxy compound (THCD) was designed and prepared. Depending on the spatial structure of the tetrahydroxy compound, a form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was synthesized via employing PEG as soft segments, while multi-benzene ring structure made by 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound as hard segments. The composition and structure of THCD and TPUPCM, the TPUPCM’s the weight average molecular weight and number average molecular weight, dissolving and melting abilities, phase change behaviors, thermal performances and crystalline morphology were investigated by Fourier transform infrared spectrometer, 1H nuclear magnetic resonance spectrometer, multiangle laser light scattering apparatus, differential scanning calorimentry, dynamic mechanical thermal analysis, thermogravimetry analysis system, wide-angle X-ray diffraction, polarizing optical microscopy. The results show that the solid–solid phase change material owns excellent phase change properties and a broad processing temperature range. The heating cycle phase change enthalpy is 137.4J/g, and the cooling cycle phase change enthalpy is 127.6J/g. The started decomposition temperature and the maximum decomposition temperature are at 323.5 and 396.2°C, respectively. Furthermore, the solid–solid phase change material is dissolvable, meltable and can be processed directly, and has great potential applications in thermal energy storage.

Preparation and performance of a novel thermoplastics polyurethane solid–solid phase change materials for energy storage

Phase change materials (PCMs) are a series of functional materials with storing and releasing energy properties. PCMs are able to adjust and control the environment around them through storing and releasing energy during phase change process. Based on the phase change theory, bis(1,3-dihydroxypropan-2-yl)4,4′-methylenebis(4,1-phenylene)dicarbamate, a novel tetrahydroxy compound, was designed and synthesized. Depending on the spatial structure of the tetrahydroxy compound, the form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was prepared. In the molecular structure of TPUPCM, polyethylene glycol was employed as the soft segments, and the hard segments were made up of 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound made up multi-benzene ring structure. The composition and structure, crystalline morphology, phase change behaviors, thermal performances and mechanical properties for tetrahydroxy compound and TPUPCM were investigated by using fourier transform infrared spectrometer (FT-IR), 1H nuclear magnetic resonance spectrometer (1H NMR), wide-angle X-ray diffraction (WAXD), polarizing optical microscopy (POM), differential scanning calorimentry (DSC), thermogravimetry analysis system (TGA) and Instron 5566 tensile tester. The TPUPCM's the weight average molecular weight, number average molecular weight, dissolving and mechanical abilities were also tested. The results show that the solid–solid phase-change material possesses excellent phase-change properties and an applicable temperature range. The heating cycle phase-change enthalpy is 137.4J/g, and the cooling cycle phase-change enthalpy is 127.6J/g. The decomposition of TPUPCM starts and reaches a maximum at 323.5°C and 396.2°C, respectively. Furthermore, the solid–solid phase-change material is dissolvable, meltable and can be processed directly, and has potential applications in thermal energy storage.

Phase behaviour, microstructure, and percolation of poly(ethylene glycol) filled by multiwalled carbon nanotubes and organophilic montmorillonite

This work studies phase behavior, microstructure and percolation of the poly(ethylene glycol) (PEG), filled by multiwalled carbon nanotubes (MWCNTs), organo-modified montmorillonite (OMMT), and their mixtures, using differential scanning calorimentry (DSC), X-ray diffraction (XRD), electrical conductivity, and analysis of microscopic images. The DSC and XRD data showed a noticeable decrease of PEG crystallinity with increase of nanofiller content. Filling of PEG by MWCNTs was accompanied by a percolation threshold at ≈0.1 wt%, and the estimated electrical conductivity exponent ( t = 1.77 ± 0.07) was typical for the random percolation networks. The similar threshold behavior, but with higher percolation threshold ≈0.5–1.0 wt%, was observed for PEG filled by OMMT. The observed effect of OMMT-enhanced dispersion of MWCNTS in PEG at a high level of loading by nanoparticles offers good prospects for simultaneous improvement of the electrical and mechanical properties of PEG-based composites.

Straw based particleboard bonded with composite adhesives

Environmentally friendly particleboard was prepared with wheat straw, an inexpensive material. The particleboard was produced by a mixing process, using a composite adhesive comprised of urea-formaldehyde (UF) adhesives and EPU. The performance of the board was evaluated by measuring internal bonding strength (IB), thickness swelling, modulus of rupture (MOR), modulus of elasticity (MOE), and formaldehyde emission. The experimental results showed that maximum of dry and wet internal bonding strength, modulus of rupture, modulus of elasticity were 0.45MPa, 0.18MPa, 31.80MPa, and 5043MPa, respectively. The thickness swelling (TS2h) and thickness swelling (TS24h) were 3.9% and 10.7%, respectively. The composite adhesives and particleboards were measured by differential scanning calorimentry (DSC), dynamic mechanical analyzer (DMA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) measurements. The results indicated that the composite adhesive of UF/EPU could contribute to excellent mechanical, thermal, and water-resistant properties of the wheat straw particleboards.

A Luminescent Ionic Liquid Crystal: [C12mim]4[EuBr6]Br

Abstract[C12mim]4[EuBr6]Br·CH3CN (2) was obtained at –15 °C by reacting europium bromide with [C12mim]Br (1‐dodecyl‐3‐methylimidazolium bromide) in acetonitrile. 2 crystallizes in the triclinic space group P$\bar {1}$ (No. 2) with two formula units in the unit cell. The structure is characterized by double layers of [C12mim] cations with interdigitated alkyl chains which are separated by anion layers formed by [EuBr6] octahedra and Br···CH3CN units. Upon warming to room temperature 2 looses acetonitrile to form the room temperature ionic liquid crystal [C12mim]4[EuBr6]Br (1). The temperature dependent structural behavior has been characterized by differential scanning calorimentry and hot‐stage polarizing optical microscopy. In the temperature range of –3 to 98 °C 1 adopts a smectic liquid crystal phase. At 77 K 1 shows a strong red emission with a lifetime of 2.6 ms. Analysis of the emission spectrum yields a quantum efficiency of 0.45.

Synthesis, thermal property and hydrolytic degradation of a novel star-shaped hexa[p-(carbonylglycinomethylester)phenoxy]cyclotriphosphazene

A novel star-shaped cyclotriphosphazene substituted by glycinomethylesterphenoxy and its intermediates are synthesized from hexachlorocyclotriphosphazene (HCCP). The structures are characterized by 1H NMR, 13C NMR, 31P NMR, FTIR and elemental analysis. Their thermal properties are clarified by thermogravimetric analysis (TGA), differential scanning calorimentry (DSC) and FTIR, while hydrolytic degradation behaviour is studied with UV-vis spectrophotometer and by measuring the weight loss, and the phosphorus content of residue. According to hydrolysis behaviour of hexa[p-(carbonylglycinomethylester)phenoxy]cyclotriphosphazene (HGPCP) under different conditions, it is easy to hydrolyze in hydrochloric acid (pH 1.0) than in phosphate buffer (pH 7.4) at 37°C. And the sample hydrolytic degradation still remains at the stage of side groups’ break. The TGA data show that the thermal stability of the hexa[p-(aldehyde)phenoxy]cyclotriphosphazene (HAPCP), hexa[p-(carboxyl) phenoxy]cyclotriphosphazene (HCPCP) and HGPCP is so high that their char residues are 75%, 47% and 47% at 800°C, respectively, probably due to cross-linking between molecules.

DIELECTRIC PROPERTIES OF POROUS Si3N4-SiO2-BN COMPOSITES

Porous Si 3 N 4- SiO 2- BN composites were prepared by adding starch as both pore former and consolidator. Bruggeman effective-medium model, Maxwell-Garnett model and logarithmic model were used to describe and predict the dielectric constant of porous Si 3 N 4- SiO 2- BN ceramics. Relative dielectric constant of porous Si 3 N 4- SiO 2- BN composites decreases with the increase of apparent porosity within limits, and these models can forecast the change of the dielectric constant of the porous ceramics quite well. The minimum relative dielectric constant is 2.5 at the apparent porosity of 0.555 at room-temperature. The relationship between dielectric constant and temperature were investigated. It was found dielectric constant varied a lot with the increase of temperature, and Debye relaxation theory was employed to explain the variation of the dielectric constant with temperature increment. But the Debye relaxation theory can not explain the reason of variation of dielectric constant at the temperature range from 300°C to 900°C. To ascertain the cause of changes of dielectric constant at this temperature region, differential scanning calorimentry (DSC) measurement was performed. In this temperature region, phase transition behavior occurs at nearly 300°C in the porous composites. The new phase probably has a tidy large dielectric constant, and the dielectric constant increases sharply.

Study on Preparation of SiO2/Epoxy Resin Hybrid Materials by Means of Sol-Gel

Silicon dioxide/epoxy resin hybrid material was prepared by means of Sol-Gel based on epoxy resin, tetraethyl orthosioate (TEOS), [H2N(CH2)3Si(OC2H5)3](KH-550), Methyltetrahydrophthalic anhydride (MeTHPA), dimethyl phthalate (DMP-30) and (HOCH2CH2)N. The contents of TEOS, KH-550 and reacting temperature influencing on the properties of hybrid materials were studied. The behaviors of the hybrid materials were characterized by differential scanning calorimentry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform-infrared ray (FT-IR) spectroscopy. The results showed that the properties of the material was optimal at approximately 3% TEOS, 2% KH-550, reacting at 60°C, and the mechanical and thermal properties were significantly improved compared with the pure epoxy resin. The dimension of SiO2 particles was about 20 nm, and distributed homogeneously in the system.

Dissolution, Solubility, XRD, and DSC Studies on Flurbiprofen-Nicotinamide Solid Dispersions

Flurbiprofen-nicotinamide solid dispersions were prepared by the fusion method. The solid dispersions were evaluated for dissolution rate. The drug-carrier interaction in the liquid and solid states were studied by using phase solubility analysis, phase diagram, X-ray diffraction (XRD), and differential scanning calorimentry (DSC). Solid dispersions gave fast and rapid dissolution of flurbiprofen compared with the pure drug and the physical mixture. Phase diagram and DSC indicated that flurbiprofen and nicotinamide form a eutectic mixture. The aqueous solubility of flurbiprofen was enhanced in the presence of nicotinamide.

Vibration welding of nylon 6 to nylon 66

AbstractVibration welding of dissimilar nylons is a promising technique for assembling complex components made of different polymers. The effects of pressure and meltdown on the tensile strength of nylon 6 (PA 6) to nylon 66 (PA 66) vibration welds were determined in this study using an experimental design and three weld geometries. Weld strengths were generally improved by increasing meltdown and decreasing weld pressure. The weld strength was also shown to vary with the position of the lower melting material for T‐welds. Using differential scanning calorimentry and fracture surface analyses, it is concluded that for all geometries, higher weld strengths can be achieved when both materials are melted. Polym. Eng. Sci. 44:760–771, 2004. © 2004 Society of Plastics Engineers.

Effect of Morphology on the Electrical Transport Properties of Polyaniline Films for Electronic Applications

AbstractAlthough it is well known that the oxidation state of polyaniline is an important characteristic, there are few reports of its influence on the development of morphology and electrical properties in fibers and films. In this work, differential scanning calorimentry is used in conjunction with measurements of temperature dependence of conductivity and thermoelectric power to elucidate the intimate relationship between structure and properties. By increasing the amount of chemical reduction of polyaniline solutions, films are prepared which exhibit a thermal transition between 300 and 385 °C, indicative of melting. Increasing the chemical reduction also increases the conductivity of iodine doped films. The most reduced film exhibited a semiconductor transport mechanism, while the other films could be modeled with a quasi-one dimensional variable range hopping mechanism. The temperature dependence of conductivity also showed increasing order for increasing reduction, consistent with the DSC results.