The effect of the addition of polypropylene-grafted SiO2 nanoparticle on the thermal conductivity of isotactic polypropylene

The thermal conductivity of Isotactic polypropylene (iPP)/silica particle (SiO₂, 26 nm) nanocomposite has been investigated. The untreated SiO₂ and iPP grafted onto SiO₂ were dispersed in the iPP (M _w = 2.5 × 10⁵) matrix. The molecular mass of the iPP-grafted chain, M _n, was precisely controlled to be 5.8 × 10³, 1.2 × 10⁴, and 4.6 × 10⁴. It was found that the thermal conductivities of graft-treated nanocomposites were higher than that of untreated SiO₂ composites. This implied that it is possible to achieve even higher thermal conductivity using the graft treatment. A thermal conductivity analysis conducted using a three-phase model, with considerations for thermal conductivity at interfacial layers, showed that the thermal conductivity of the interfacial layer increased significantly when a graft chain was incorporated. Moreover, the thermal conductivity per graft chain was proportional to the 1/2 power of the molecular mass ( \( M_{\text{n}}^{0.5} \) ). The results strongly suggest that the thermal conductivity pathway of interfacial layer was the main chain direction of iPP-grafted molecular chains.     

Preparation and characterization of epoxy–silica networks chemically bonded through aminophenyl-trimethoxysilane

Epoxy–silica hybrids with interfacial bonding using aminophenyl-trimethoxysilane (APTMOS) have been prepared by the sol–gel process. In a sequential polymerization procedure the amine groups present on the APTMOS were used to partially cure diglycidyl ether of bisphenol-A (DGEBA) whereas the methoxy groups created silica-network simultaneously, through the sol–gel process. Complete curing and cross-linking were carried out later using curing agent jeffamine D-400 at higher temperature. The nature of silica network structure chemically bonded with the epoxy chains was studied by Fourier transformed infrared spectroscopy and the morphology of the hybrid through scattering electron and atomic force microscopies. The visco-elastic properties of the resulting hybrids were measured through dynamical thermal mechanical analysis. The effect of inter-phase bonding of the resulting hybrids and their thermal mechanical properties are compared with the similar DGEBA epoxy matrix where un-bonded silica network was produced from tetraethoxysilane. The properties of the hybrids using APTMOS show considerable improvement in thermal mechanical properties and the coefficient of thermal expansion is reduced in contrast to the un-compatiblized system.     

Thermophysical properties of thorium–praseodymium mixed oxides

Thorium–Praseodymium mixed oxide solid solutions (Th_1?yPr_y)O_2?x (y = 0.15, 0.25, 0.4, 0.55) were prepared by co-precipitation method. These mixed oxides form single-phase fluorite solid solutions (fm3m). Heat capacity (C _p) measurements and lattice thermal expansion characteristics of these solid solutions were determined with differential scanning calorimeter in the temperature range of 298–800 K and high temperature X-ray diffractometer in the temperature range of 298–2,000 K, respectively. The C _p,₂₉₈ of (Th _1?yPr_y)O_2?x pertaining to the solid solutions with the compositions, y = 0.15, 0.25, 0.4, and 0.55, were found to be 65.2, 62.4, 60.1, and 57.1 J K^?1 mol^?1, respectively. The coefficients of lattice thermal expansion in the temperature range of 298–2,000 K of (Th_1?yPr_y)O_2?x for these solid solutions with the compositions y = 0.15, 0.25, 0.4, and 0.55 were found to be 16.97, 20.43, 25.63 and 30.82 × 10^?6 K^?1, respectively.     

Rheo-optical Fourier-transform infrared (FTIR) spectroscopy of polymers

Rheo-optical FTIR spectroscopy has been applied to monitor the onset, progress and decay of strain-induced crystallization in loading-unloading cycles of sulfur-crosslinked natural rubber at 300 K and 343 K. From the short-time spectroscopic data conclusions were also drawn with respect to the orientation of the average polymer and the polymer chains in the strain-induced crystal phase.     

IR and Py-GC/MS spectral simulation of polymer film by quantum chemical and quantum molecular dynamics calculations using the polymer models

We have simulated IR and pyrolysis gas chromatography mass spectrometry (Py-GCMS) spectra of six polymers (PE, PP, PS, PET, N6, PVDF) with the density-functional theory and quantum molecular dynamics calculations on model oligomers. In the former calculations, experimental harmonic frequencies of the polymers have been assigned from the simulated IR spectra. In the latter QMD calculations on thermal decomposition of polymer models, the approximated mass spectra of six (PE, PP, PS, PET, N6, PVDF) polymers were almost in good accordance with the experimental results in Py-GC/MS, although we adjusted the decomposition temperatures to 2240, 2520, and 2800 K as the average absolute deviation of 8%.     

Preparation,thermal property,and thermal stability of microencapsulated n-octadecane with poly(stearyl methacrylate) as shell

This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n-octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g^?1) and crystallization (94.8 J g^?1) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/n-octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n-octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential.     

Thermal decomposition of polymethylmethacrylate synthesized with anionic catalysts

TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.     

An experimental study on thermal decomposition behavior of magnesite

Thermal decomposition of magnesite is investigated by using a TG–MS. Different kinetic methods including Coats–Redfern, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose are used to investigate the thermal decomposition kinetics of magnesite. It was observed that the activation energy values obtained by these methods are similar. The average apparent activation energy is found to be about 203 kJ mol^?1. The raw magnesite and its decomposition products obtained at different temperatures are analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The concentration of functional groups, crystal structure and composition, and apparent morphology of decomposition products were studied in detail. The FTIR, XRD, and SEM analyses showed that magnesite was completely decomposed at 973 K to form MgO.     

Two-dimensional analysis of the SAXS of partially oriented polymers*)

The Small-angle X-ray scattering (SAXS) patterns of oriented LDPE (λ=1...5.7) were fitted by calculating the small-angle intensity for a structure consisting of a linear paracrystalline lattice built up by finite lamellar or cylindrical crystallites. The resulting data of the superstructure were compared with corresponding values from wideangle X-ray scattering. It is shown that it is impossible to get quantitative information about the superstructure of oriented polymers by using SAXS alone. Nevertheless, the qualitative transition of the crystals during orientation can be explained very well.     

Thermal behaviour of a modified encapsulation agent

Thermal behaviour of heptakis-6-iodo-6-deoxy-beta-cyclodextrin (HIDBCD) under inert and oxidative conditions was investigated by TG/DTG/DTA, FTIR, and using the hyphenate technique TG–FTIR. Due to the fact that thermal behaviour of HIDBCD was not studied before, we set our goal in the investigation of thermal degradation process in a dynamic air atmosphere vs. nitrogen atmosphere at a heating rate of 10 °C min^?1, up to 500 °C, respectively, 600 °C. It was found that the degradation process in air occurs in a single step, with a total mass loss of 99.9 %. The results of TG/DTG/DTA–FTIR indicated that the thermal behaviour of this cyclodextrin can be divided into three stages and more information was provided about the reaction sequences and the relevant products of reaction.     

Extraction and chemical investigation of jute (Corchorus olitorius,Linn.) seed protein

Studies were made on the protein solubility of deoiled jute (Corchorus olitorius, Linn.) seed in aqueous solution over various pHs and in different concentrations of NaCl at pH 8.0. Chemical analysis of the seed protein showed 16 amino acids, of which 9 were essential. Gel filtration on Sephadex G-200 revealed the presence of four components, and their molecular weights were determined by two standard methods. Extractable jute seed proteins in salt solution were separated into six fractions electrophoretically (SDS-PAGE). The molecular weights of the six fractions were found to be 118,000; 103,000; 96,000; 67,500; 48,500; and 15,000.     

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL^?1 and a dynamic range as wide as from 0.001 to 100 ng mL^?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.

The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.     

Largely enhanced molecular orientation and mechanical property of injection-molded high-density polyethylene parts via the synergistic effect of polyamide 6 in situ microfibrillar and intense shear flow

The high-density polyethylene (HDPE)/polyamide 6 (PA6) in situ microfibrillar composites (HAM-C) were fabricated by the “extrusion-hot stretch-quenching” technique, in which PA6 microfibrillar had diameters lying in the range 0.55 to 1.05 μm. Then the HAM-C and pure HDPE were processed by multi-melt multi-injection molding (MMMIM). The effect of PA6 in situ microfibrillar and secondary melt penetration on the crystalline morphologies and mechanical properties was investigated using a variety of characterization techniques including differential scanning calorimetry (DSC), rheological experiments, scanning electron microscopy (SEM), synchrotron two-dimensional small-angle X-ray scattering (SAXS), and tensile testing. It was found that PA6 microfibrillar not only acted as a heterogeneous nucleation agent, but also prolonged the relaxation time of HDPE matrix by suppressing the mobility of HDPE molecular chains. It was revealed, from observing the morphologies, that the presence of PA6 microfibrillar not only facilitated the formation of transcrystalline superstructures on its surface, but also induced much more oriented crystals nearby as a result of the amplified local shear field. Furthermore, SAXS results confirmed that the degree of orientation of the injection-molded HAM-C part (HAM-M) was largely enhanced. Finally, the tensile testing showed that the tensile strength and Young’s modulus of the HAM-M sample were enhanced by 38.8 and 54.6 %, respectively, when compared with pure HDPE parts. This work provides a promising way to tailor the crystalline structure of the injection-molded parts.     

Synthesis of nanosized BaZrO3 from oxalate precursor

Nanosized barium zirconate (BaZrO₃) is prepared from its oxalate precursor, barium zirconyl oxalate (BZO). The decomposition of BZO precursor was studied by thermogravimetry, differential thermal analysis, fourier transform infra red spectroscopy (FTIR), and X-ray diffraction (XRD) techniques. FTIR and XRD study reveals that BZO precursor calcined at 1173 K for 2 h gives nanosized perovskite type cubic BaZrO₃ powder. The transmission electron microscope study shows that BaZrO₃ particles prepared at 1173 K is nearly spherical in shape with diameter of 40–75 nm. Particle size study was carried out to investigate particle size distribution of BaZrO₃ particles. Band gap of BaZrO₃ was estimated from UV–visible spectroscopy data. Impedance measurement study shows that dielectric constant of BaZrO₃ prepared in this work is 31.69 at 10 kHz.     

Thermal analysis of polymorphism

The combined techniques of thermomicroscopy, differential scanning calorimetry (DSC), thermomicrophotometry (TMP), and micro-Fourier transform infrared spectroscopy (FTIR) are essential for the unequivocal detection of polymorphism. The polymorphism ofp-hexadecylaminobenzoic acid (HABA), a pharmaceutical intermediate, is presented to illustrate the need to use a multitechnique approach. While DSC can record thermally induced processes, it is not a specific technique and it alone cannot distinguish polymorphic transformations from other events connected with enthalpy changes. Thermomicroscopy usually provides confirmation of polymorphism by direct observation of polymorphic forms and transformations, but not all transformations result in visual changes in structure. Micro-FTIR, combined with thermomicroscopy, confirms the chemistry of these thermal changes and provides more specific information on changes in molecular structure.     

Physical structure and thermal behavior of ethylcellulose

The physical structure and properties of ethylcellulose (EC) powders of different molecular weights were examined. A molecular weight in the range of 20–144 kDa with a large polydispersity was determined. EC thermal analysis revealed a glass transition at ~130 °C and a melting temperature at ~180 °C. Glass transition temperatures increased with polymer molecular weight. Wide angle (WAXS) analysis detected an amorphous broad peak at q = 1.5 Å^?1 and a distinct Bragg’s peak at 12.6 Å, which seems to be related to a supramolecular ordered structure of the polymer. These observations were confirmed using high temperature powder X-ray diffraction analysis where the crystalline peak disappeared above the melting temperature of the polymer. Ultra-small angle (USAXS) results were fitted to the Bouacage fractal unified model and fractals with an average size of 100–600 nm with a relatively smooth surface were predicted. This prediction was confirmed by transmission electron microscopy (TEM) images. According to our results, the EC polymer has a semi-crystalline structure, with crystalline domains within an amorphous background.     

Insight into the thermal decomposition of kaolinite intercalated with potassium acetate: an evolved gas analysis

The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.     

Preparation,characterization, and properties of novel category of processable thermally stable poly(ether ether imide)s

New poly(ether ether imide)s were synthesized based on an aromatic diamine containing pyridine and four ether groups. Diamine was designed to induce desirable properties to final polymer such as flexibility and processability in addition to thermal stability. The diamine was synthesized via a three-step procedure. Firstly, 1-fluoro-4-nitrobenzene was reacted with hydroquinone to obtain a nitrophenol compound. Next, the catalytic reduction was performed to convert nitro to amino group. Finally, the resulted aminophenol was reacted with 2,6-dichloropyridine and the diamine was synthesized. Polycondensation reactions of the diamine with three dianhydrides led to the preparation of novel poly(ether ether imide) films. All prepared materials and polymers were completely characterized. Thermal stability and glass transition temperature of polyimides were measured and compared. Mechanical properties and cross-section morphology of films were also investigated. Poly(ether ether imide)s revealed unique balance of physical and thermal properties including very high flexibility along with outstanding thermal stability.     

Electroactive shape memory effect of radiation cross-linked SBS/LLDPE composites filled with carbon black

The poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer and linear low-density polyethylene (LLDPE) were blended and irradiated by γ rays to prepare shape memory polymer (SMP). Different weight fractions of conductive carbon black (CB) were filled into SMP to form a novel electroactive shape memory CB/SBS/LLDPE composite. The CB reinforced radiation cross-linked SBS/LLDPE blends for the improvement of the mechanical weakness and conductivity of SBS/LLDPE bulk and for wide practical engineering uses. The electroactive shape memory CB/SBS/LLDPE composites were investigated by electrical properties, mechanical, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electroactive shape memory effects. It is found that the tensile strength, storage modulus, and resistance against mechanical and thermal mechanical cycle loading in the developed composites increased due to the role of reinforcement of CB. The melting temperatures and volume resistance of the composites decreased with the increment of CB for excellent electrical conductivity of CB. The electroactive shape memory effects of developed CB/SBS/LLDPE composites were affected by CB weight fractions and applied voltage, while good shape recovery could be obtained in the shape recovery test. When the CB fraction is more than 5 wt%, full recovery can be observed after tens of seconds and shape recovery speed increased with CB fractions and voltage increasing. However, the shape recovery rate decreases slightly with increment of cycle times.