Thermogravimetry Analysis Analysis Research Articles

A novel green nanocomposite for EOR: Experimental Investigation of IFT Reduction, wettability Shift, and nanofluid stability

A stable nanofluid (NF) is crucial for success of nano-enhanced oil recovery (nEOR) processes. However, this represents a significant challenge as nanoparticles (NPs) tend to agglomerate under high salinity and NP concentration adversely affecting the oil recovery. New nanomaterials including functionalized nanoparticles also known as nanocomposites (NC) can help to overcome these issues. In this paper, first, we reported synthesis, characterization, and performance evaluation of a novel hydrophobic CuO-SiO2-Montmorillonite-K+-Thiazine NC for the first time. The NC was characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), X-Ray Diffraction (XRD), Thermogravimetry Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). SEM analysis showed that the NC is composed of uniformly distributed NPs. EDAX results confirmed presence of Cu, SiO2, O2, and Cl in the NC. XRD analysis indicated that SiO2 is the dominant phase in the crystal lattice and responsible for adsorption capacity of the NC. TGA analysis showed that the NC will be thermally stable in typical reservoir temperatures (∼80°C). FTIR results confirmed presence of Si-O, Cu-O, Si-O-Si, Al-O-Si, Al-OH, and OH bonds in the NC. In the second phase of this research work, the novel NC was used to investigate recovery of a Kazakhstani paraffinic heavy crude oil from Berea sandstone with focus on IFT reduction, oil recovery, wettability alteration, and stability analysis of the NFs. NFs were prepared with NC concentrations of 250, 500, and 1,000 ppm using moderate salinity (MS), low salinity (LS), and distilled water (DW). The results showed that the optimal NF (250 ppm LS) exhibited a high zeta potential value (−65.5 mV) indicating a high stability which is superior to all of the previously reported NCs. This high stability is attributed to use of thaizine as a source of natural surfactant. The optimum NF also altered the wettability of the sandstone by 77.6% and the contact angle (CA) was reduced from 117.9° to 26.4° making the system strongly water wet. The nanoclay has significantly facilitated the wettability alteration. The optimum NF also reduced the IFT by 92.3% from 27.42 mN/m to 2.11 mN/m. An incremental oil recovery of 20% was also achieved in the tertiary or EOR stage of oil. A comparison with the NCs reported in the literature confirmed the excellent performance of this novel NC in terms of NF stability, IFT reduction, and wettability alteration. The novel NC has a great potential for nEOR and other oilfield and environmental applications.

Fabrication and characterization of microencapsulated dimethyl adipate phase change material with melamine-formaldehyde shell for cold thermal energy storage in coating

Abstract Microencapsulated phase change material (MPCM) was synthesized by using the in-situ polymerization technique. Dimethyl adipate (DMA) and melamine-formaldehyde were used as core and shell material for polymerization respectively. Sodium laureate sulphate (SLS) is used as a surfactant. The thermal properties were characterized by using a differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). Fourier transform infrared spectroscopy (FT-IR) was used to confirm the chemical structure. The morphology of microcapsules was studied by using, scanning electron microscopy. DSC result of MPCM has been observed to melt at 10.09 °C with melting latent enthalpy 88 J/g and crystallizes at 4.69 °C with crystallization latent heat 89.50 J/g. TGA analysis confirms increases in the thermal stability of MPCM. The decorative coating was prepared with 0, 5, 10, 15, and 20 % MPCM loading, and the prepared paint was tested for pencil hardness, gloss, and stain resistances. The thermal energy transfer rate was used to measure how much time coated panel took to reach the equilibrium temperature of 25 °C. Coating with 20 % MPCM loading revealed good thermal storage capacity but other general coating properties deteriorate.

Photocatalytic degradation of orange II dye via high pore volume polymorph zirconium-doped titania under visible light irradiation

A series of mixed-phase Zr-doped TiO2 was utilized for the photocatalytic degradation of orange II dye. These materials were synthesized through a sol–gel technique by varying the amounts of zirconium in the photocatalysts. These materials were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), Raman spectroscopy, thermogravimetry analysis (TGA), and X-ray photoelectron spectroscopy (XPS) among others. XRF and XPS data showed that the elemental composition of the photocatalysts consists of zirconium, titanium, and oxygen. In addition, XRD and Raman spectroscopy confirmed the existence of anatase and rutile phases of TiO2. The TGA analyses showed that the undoped TiO2 was the most stable, with no significant weight loss during the heating range. Furthermore, the materials can effectively degrade orange II dye solution up to 7 cycles through asymmetric cleavage of the azo bond.

Efficient nitro-aromatic sensor via highly luminescent Zn-based metal-organic frameworks

Highly stable zinc-based luminescent metal-organic framework (LMOF) [(Zn2-(NDC)2(bpy)·Gx) where NDC-2,6-naphthalene dicarboxylic acid, bpy - 4,4' bipyridine, and G - guest solvent molecules] is synthesized via solvothermal method at different synthesizing temperatures (120, 150 and 180∘C) for the detection of nitro-aromatics. Sample structure and presence of ligands is confirmed by X-ray diffraction and FTIR measurements, respectively. The photoluminescence properties of synthesized LMOF samples show the strong emission intensity in ethanol at 376 nm when it is excited at 240 nm. The detection limit is calculated using fluorescence quenching for the various nitro-analytes (2,4-DNP, 2-Nitrotoulene, 4-Nitrophenol, and Nitrobenzene) revealed that it is least for the sample synthesized at 150∘C with the maximum percentage in fluorescence decay. The thermal stability of as-synthesized samples is analysed using thermogravimetry analysis (TGA) which reveals that sample synthesized at 150∘C is the most stable sample. The TGA analysis also shows that on further heating from 526∘C to 980∘C decomposition of zinc metal and formation of zinc oxide takes place. FE-SEM confirms the cuboidal morphology with an average particle size of 12.62 nm, corroborated by the TEM analysis. The fluorescence quenching mechanism is explained on the basis of dipole-dipole and π-stacked interactions between the MOF and nitro-aromatics that play a prominent role in the sensing of nitro-analytes. Synthesized MOF samples show excellent recyclability in fluorescence quenching even after the fourth cycle, i.e. more than 95% and is sensitive to detect nitro-aromatics even upto 0.284 µM, and the results can generalize the explosive sensor technology and sensing various nitro-based pollutants.

Synthesis, Characterisation, and Electrochemical Impedance Spectroscopy Study of Green and Sustainable Polyurethane Acrylate from Jatropha Oil Using a Three Step Process

Bio-based polymer is a promising candidate to substitute conventional petroleum-derived polymer as it is sustainably produced from renewable resources, which helps reduce the production process’ carbon footprint. It also helps reduces humankind’s dependability on fossil fuel-based feedstock. In this work, a sustainable jatropha oil-based polyurethane acrylate (PUA) was successfully prepared and synthesised using a 3-steps process; epoxidation (formation of an epoxy group), hydroxylation (addition of–OH group to opened ring), and acrylation (addition of acrylate group into polyol). The yellowish PUA prepared has a gel consistency, which is sticky and slightly runny. The PUA was characterised by using wet chemical tests such as oxirane oxygen content (OOC), acid value (AV), hydroxyl number (OHV) and iodine value. OOC value for the PUA synthesised was 4.23 % at the 5 hr reaction time. At the same time, the Epoxidised jatropha oil (EJO) used to prepare polyol records a hydroxyl number of hydroxyl 185.81 mg KOH/g and an acid value of 1.06. The polyol prepared was mixed with 2, 4-toluene-diisocyanate (TDI) and Hydroetyhlmethacrylate (HEMA) to produce PUA. The PUA was characterised by thermogravimetry analysis (TGA) and electrochemical impedance spectroscopy (EIS). TGA analysis shows that the polymer is stable up to 373 K, whereas the EIS analysis records an ionic conductivity of (5.60±0.03) × 10-6 S cm-1. This polymer’s great thermal stability properties make it suitable for outdoor application where high temperature due to sun exposure is common. Furthermore, PUA prepared gel-like properties to make it a suitable candidate for preparing a gel polymer electrolyte.

Facile preparation of highly dispersed copper promoted cobalt catalyst supported on alumina nanospheres

Co/Cu catalyst supported on alumina nanospheres were prepared by two methods. First, Al2O3 nanospheres were successfully prepared by sol – gel method. Next, the prepared alumina nanospheres were impregnated with cobalt and copper metals by wet impregnation method. The physico – chemical properties of the catalyst were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Thermogravimetry analysis (TGA) and Differential Scanning Calorimetry analysis (DSC). The calculated crystallite size of the catalyst was found to be around 4.3 nm by using XRD analysis. Morphological studies revealed good dispersion and spherical structure and the particles diameter ranges around 62.67 nm. The prepared catalyst was thermally stable up to 750 °C was confirmed by TGA analysis. Further, DSC studies showed that the occurrence of the crystallization process in catalyst with an exothermic peak.

Synthesis and characterization of dialdehyde cellulose/amino‐functionalizedMCM‐41 core‐shellmicrospheres as a new eco‐friendly flame‐retardant nanocomposite

AbstractUsing proper flame‐retardant materials when constructing buildings or fabricating devices is the most important fire safety guidelines. The halogen and phosphorus‐based compounds are among the most effective flame retardants. However, most of these compounds are recognized to have a harmful effect on human body and the environment during combustion. In this context, we designed and synthesized a new eco‐friendly flame‐retardant nanocomposite by combining dialdehyde cellulose (DAC) and amino‐functionalized mesoporous silica MCM‐41 (N‐M41). Spherical N‐M41 nanoparticles have been successfully prepared in one‐pot reaction using tetraethyl orthosilicate and (3‐aminopropyl)triethoxysilane (APTES), and then coated with different amounts of DAC through Schiff base reaction between the carbonyl group of DAC and NH2of APTES. The resulted DAC@N‐M41 nanocomposite was characterized by XRD, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, differential thermal analysis (DTA) and thermogravimetry analysis (TGA). TEM micrographs revealed that this nanocomposite was made up of core‐shell nanospheres structure with narrow size distribution (ca. 140 nm). DTA and TGA analysis revelated that the presence of silica within the nanocomposite can effectively increase the char yield, decrease the heat release, and improve the fire performance of the prepared nanocomposite. A mechanism of the reduction in flammability of this nanocomposite has been proposed.

Synthesis of a Solid Superacid and Its Application in Flame-Retardant Poly(vinyl chloride) Material.

TiO2/PO43– solid superacid was synthesized by using the precipitation immersion method and characterized by means of X-ray diffraction (XRD) and an energy-dispersive spectrometer; it was added into flexible poly(vinyl chloride) (PVC) composites as a flame retardant. The smoke suppression and flame retardance of TiO2/PO43– accompanied by Sb2O3 were investigated through the limiting oxygen index (LOI), cone calorimetry test, and thermogravimetry analysis (TGA). The results indicated that the LOI value of PVC/Sb2O3/(TiO2/PO43–) reached to 32.3%, which is higher by 6% than that of neat PVC (26.3%). In addition, Sb2O3/(TiO2/PO43–) greatly reduced the peak heat release rate and total heat release simultaneously in comparison to using Sb2O3 separately, suggesting a significant synergistic effect between TiO2/PO43– and Sb2O3 on improving the flame retardancy of the PVC. Further, results of TGA and differential thermal analysis showed that the thermal stability of the composites was greatly improved. For the Fourier transform infrared analysis, Sb2O3/(TiO2/PO43–) leads to a large amount of functional group surplus, which specifically indicates that its carbon residue increases. The surface of the char formed after combusting of the PVC compounds was observed through scanning electron microscopy. It is found that the solid superacid can promote decomposition, pyrolysis, and cross-linking of PVC into the compact and continuous char layer on the surface of the material, which improved the flame retardancy and smoke suppression of PVC.

Thermal energy storage properties and thermal reliability of PEG/bone char composite as a form-stable phase change material

Bone char (BC) is a promising porous material that can be used for preparing a form-stable composite phase change material (PCM). In this paper, form-stable polyethylene glycol (PEG 6000)/BC composite PCMs were prepared by impregnation method. The PEG was used as the phase change material, and two different particle sizes of BC (0.8–1 mm: BC-1; 0.25–0.8 mm: BC-2) were acted as the supporting materials. The phase composition and chemical structure of the composite PCMs (PEG/BC-1 and PEG/BC-2) were characterized using X-ray diffraction and Fourier transformation infrared. The results indicated that the PEG can be well impregnated into BC pores with good compatibility. Thermal properties and thermal stability of the composite PCMs were determined by differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). DSC results showed that the maximum impregnation percentage for PEG into BC-1 and BC-2 was 38.77 and 43.91%, respectively, without melted PCM seepage from the composites. The TGA analysis revealed that the composite PCMs had good thermal stability above their working temperature range. The thermal cycle test of 100 melting–freezing cycles showed that the composite PCMs have good thermal reliability and chemical stability. The form-stable composite PCMs can be used as thermal energy storage material for waste heat storage and solar heating system.

Liquid metal gallium laden organic phase change material for energy storage: An experimental study

This paper presents the experimental study on the thermophysical behavior, thermal cyclic characteristics and energy storage performance of liquid metal (LM) laden in organic solid-liquid phase change material (PCM) for energy storage. In this view, Gallium (Ga) is added into D-Mannitol (DM) with a weight fraction of 0.1% and 0.5% by dispersion technique using a ball mill. Repeated melting/freezing cycle was carried out for 350 cycles and the samples were characterized using Differential Scanning Calorimetry (DSC), Thermogravimetry Analysis (TGA) and Fourier Transform Infrared (FTIR). The DM/Ga composite PCM showed enhanced thermal conductivity of ∼8.4%, ∼27.8% for 0.1 and 0.5 wt % Ga as compared to pure DM. XRD studies reveal that the pure DM exhibited β polymorphic phase while TGA and FTIR analysis confirm the thermal reliability and chemical stability of composites in the temperature range of 50–200 °C. Non isothermal crystal kinetic study proved that the addition of Ga increased the crystallization rate due to heterogeneous nucleation effect and leads to the reduction in subcooling temperature of the PCM. The experimental setup results to test the charging and discharging performance of the composite PCM revealed that the total time for one complete cycle reduced from 97.48 min for pure DM to 84.73 min and 63.92 min for DM-Ga composite with 0.1 wt % and 0.5 wt % respectively. Based on the results obtained, D-Mannitol based composites could be recommended as potential PCM candidates for solar heat and industrial waste heat recovery application due to its high energy density capacity, thermal/chemical stability and good heat transfer performance.

A novel LiSnVO4 anode material for lithium-ion batteries

In this work, a new material LiSnVO4 has been prepared via sol-gel method utilizing ammonium metavanadate, acetates of tin and lithium as starting materials, and nitric acid and oxalic acid as complexing agents. The amount of starting materials used has been chosen so that the mole ratio of Li/Sn/V is 1:1:1. The sol-gel precursor has been sintered at 700 °C for 6 h. Based on thermogravimetry analysis (TGA) analysis, the formation mechanism suggested the product to be LiSnVO4. Energy-dispersive X-ray analysis (EDX) reveals the ~1:1 ratio of Sn:V. EDX results agree reasonably with the formation mechanism from TGA analysis that the Sn:V ratio is 1:1. Results from X-ray photoelectron spectroscopy (XPS) indicate that the oxidation states of Li, Sn, and V are +1, +2, and +5, respectively. Since there is no ICDD data available to match the XRD diffractogram of the material obtained, CMPR and powder diffraction data interpretation and indexing program (POWD) softwares have been used to predict the crystal structure system to be tetragonal (similar to that of SnO2). A fabricated LiSnVO4//Li cell can deliver a large initial irreversible discharge capacity of 1270 mAh g−1 and reversible capacity of 305.4 mAh g−1 at the end of second cycle, which drops to 211 mAh g−1 at the end of 53rd cycle. The capacity retention is 69 % with respect to the second discharge capacity.

Synthesis of Platinum Nanoparticles from K2PtCl4 Solution Using Bacterial Cellulose Matrix

Platinum (Pt) nanoparticles have been synthesized from a precursor solution of potassium tetrachloroplatinate (K2PtCl4) using a matrix of bacterial cellulose (BC). The formation of Pt nanoparticles occurs at the surface and the inside of the BC membrane by reducing the precursor solution with a hydrogen gas reductant. The Pt nanoparticles obtained from the variations of precursor concentration, between 3 mM and 30 mM, and the formation of Pt nanoparticles have been studied using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and thermogravimetry analysis (TGA). Based on X-ray diffraction patterns, Pt particles have sizes between 6.3 nm and 9.3 nm, and the Pt particle size increases with an increase in precursor concentration. The morphology of the Pt nanoparticles was observed by SEM-EDS and the content of Pt particles inside the membrane is higher than that on the surface of BC membranes. This analysis corresponds to the TGA analysis, but the TGA analysis is more representative in how it describes the content of Pt particles in the BC membrane.

Influences of gamma irradiation on structure, thermal stability and thermal energy storage properties of form stable phase change materials

AbstractForm stable phase change materials (PCMs) were prepared from high density polyethylene (HDPE), poly(ethylene-co-vinyl acetate) (EVA), organophilic montmorillonite (OMT) and paraffin. The influences of gamma irradiation on the structure, thermal stability and thermal energy storage properties of form stable PCMs were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM), thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC). The XRD results indicated that the morphological structure of intercalation for form stable PCMs would not be appreciably varied by gamma irradiation. The SEM images showed that the intermolecular cross-linking induced by gamma irradiation made the three-dimensional network structure more compact and the interface more illegible. The results of TGA analyses indicated that the thermal stability of form stable PCMs after gamma irradiation was higher than that of the corresponding PCMs before gamma irradiation, and the enhancement slightly ...

Preparation and Characterization of a Form-Stable Phase Change Materials Composed by UF, Paraffin and Expanded Perlite

A kind of form stable phase change material (PCM) based on expanded perlite, paraffin, urea formaldehyde hybrids is prepared by using vacuum-impregnation process. This kind of form stable PCM is made of paraffin as a dispersed phase change material and expanded perlite as a supporting material, and urea-formaldehyde resins as membrane materials to be applied to the porous surface of expanded perlite(EP). The structure of urea-formaldehyde resins(UF) being prepared is characterized by Fourier Transform Infrared Spectrophotometer(FT-IR). Hybrids’ thermal stability, latentheat and morphology are characterized by the thermogravimetry analysis(TGA), differential scanning calorimeter(DSC) Method and scanning electronic microscope(SEM), respectively. The FT-IR and SEM curves show that urea-formaldehyde resins have already been formed. The TGA analysis indicates that the form-stable phase change material has very good thermostability under working atmosphere. The application of DSC not only studies the appropriate curing time of UF，but also indicates that the form-stable PCM that has been prepared has more stable thermal energy storage performance than the traditional one.

The promotion effect of catalytic activity by Ru substitution at the B site of La1−x Sr x Cr1−y Ru y O3−z for propane steam reforming

A series of La1−x Sr x Cr1−y Ru y O3−δ (0.1 ≤ x ≤ 0.5, 0.05 ≤ y ≤ 0.15) materials was prepared by the sol–gel method to develop alternative catalysts for propane steam reforming. Catalyst characteristics were evaluated using physicochemical methods including X-ray diffraction, Brunauer–Emmett–Teller methods, H2 temperature-programmed reduction, and thermogravimetry analysis (TGA). Effects of the amount of ruthenium (Ru) and strontium and the steam-to-carbon ratio (S/C) were investigated. An increase in Ru content led to increased propane conversion and H2 yield, especially below 700 °C. Dramatic enhancement of catalytic activity was observed with La0.8Sr0.2Cr0.85Ru0.15O3 under 600 °C, achieving propane conversion over 79% between 600 and 800 °C with maximum propane conversion and H2 yield of 98.3% and 63.3%, respectively. Also, good resistance to carbon formation for the La0.8Sr0.2Cr0.85Ru0.15O3 catalyst was confirmed by long-term testing and TGA analysis.

Microstructure Characterisation of Ag<sub>2</sub>O<sub>3</sub>-Bi<sub>2</sub>O<sub>3</sub> Composite Cathodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs)

Porous Ag-Bi2O3 composite cathodes on stainless steel (SS) substrate, an excellent mixed-ionic conductor that can be used as cathode material for the intermediate temperature solid oxide fuel cell (IT-SOFC) has been developed using the slurry painting method. Characterisation of the composite cathode includes the thermal analysis, morphology, and porosity of the porous cathode. Thermal analysis of the dried slurry was conducted in order to determine the heating schedule for eliminating the organic components using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). The TGA and DSC analyses confirmed the organic vehicle was fully decomposed below 418oC and the formation of composite cathode oxide phase took place beyond 600oC. The microstructure of the thermally treated cathode was analysed using SEM and XRD. The SEM results showed that the grain size of the cathode increased with the increase of temperature during thermal treatment and the X-ray diffraction (XRD) analyses confirmed the presence of δ-Bi2O3 phase on the cathode. Porosity was obtained using the Archimedes method. The Ag2O3-Bi2O3 cathode on stainless steel substrates was found to have a porosity of 53%, 51%, 39% and 28% upon 1, 2, 3, and 4 coatings, respectively, as well as thermal treatment at 800°C for 1 hour.

Synthesis and Characterization of Fe2MoO4 as a Precursor Material for Mo Alloying in Steel

The objective of the present thesis is to optimize the electric arc furnace (EAF) practice from an environmental view point. Two aspects that meet the requirements of the secondary steelmaking industries today, viz. Mo alloying with maximum retainment of the alloying element in molten steel and optimization of foaming by carbonate addition with a view to optimize the energy need of the process. Both these aspects would also have a significant impact on the process economy. Iron molybdate (Fe2MoO4) has been synthesized from commercial grade materials and proposed as a new potential precursor for steel alloying with Mo. The thermal stabilities of different molybdates, viz. Fe2MoO4, CaMoO4 and MgMoO4, were studied using thermogravimetry analysis (TGA). It was found that Fe2MoO4 is the most stable one and doesn’t evaporate in Ar atmosphere when heating up to 1573 K. The synthesis of Fe2MoO4 requires high temperature (1373 K) and long holding time (up to 16 hours). In a view of this, the possibilities for in-situ formation of Fe2MoO4 and CaMoO4 from their precursor mixtures were studied with the aid of high-temperature X-ray diffraction (XRD) and TGA analysis. Laboratory and industrial trials on steel alloying with Mo were conducted using precursor mixtures as sources of Mo. It was found that the mixture, which contains FeOx, MoO3 and C (Fe2MoO4 precursor), can provide the Mo yield up to 98 % at both the laboratory as well as industrial trials. The Mo yields even in the case of C+MoO3 and C+MoO3+CaO mixtures were around 93 % in these trials. The higher yield for the MoO3+C+FeOx mixture was attributed to the stabilization of Mo in the precursor (marked by the decrease in the Gibbs energy of Mo) and the readiness to dissolve in the steel bath. The heat effect of the slag foaming with carbonates addition was studied at 1623 and 1673 K with the aid of thermal analysis technique with a new crucible design. Experiments were conducted by adding limestone and dolomite pieces of defined shapes (together with iron sinkers) in molten slag and monitoring the temperature changes accompanying the decomposition of carbonates. It was found that the decomposition energies for dolomite and limestone for the studied slag composition are in the range 56-79 % of theoretical values, which is linked to the energy saving effect of slag foaming. No influence of sample shape on decomposition energy was found both for limestone and dolomite. The kinetics of slag foaming by limestone particles was studied at 1773 K with the aid of X-ray imaging system. A model was proposed to describe the decrease in foam height with time on the basis of CaO shell formation during decomposition reaction. The energy impact of limestone and raw dolomite addition was examined in a 100-ton EAF. It was found that, in the case of addition of carbonates after the scrap is completely molten; the endothermic heat effects for limestone and dolomite (2255 and 2264 kJ/kg respectively) were only 70 % from theoretical values. This is indicative of the resistance to heat transfer due to increased foaming.

Preparation, characterization and thermal properties of PMMA/ n-heptadecane microcapsules as novel solid–liquid microPCM for thermal energy storage

This study is focused on the preparation, characterization and thermal properties of microencapsulated n-heptadecane with polymethylmethacrylate shell. The PMMA/heptadecane microcapsules were synthesized as novel solid–liquid microencapsulated phase change material (microPCMs) by emulsion polymerization method. The chemical and thermal characterization of the microPCMs were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The diameters of microPCMs were found in the narrow range (0.14–0.40 μm) under the stirring speed of 2000 rpm. The spherical surfaces of microPCMs were smooth and compact. The DSC results show that microPCMs have good energy storage capacity. Thermal cycling test showed that the microPCMs have good thermal reliability with respect to the changes in their thermal properties after repeated 5000 thermal cycling. TGA analyses also indicated that the microPCMs degraded in three steps and have good thermal stability. Based on all results, it can be considered that the PMMA/heptadecane microcapsules as novel solid–liquid microPCMs have good energy storage potential.

High temperature resistant tailor‐made poly(meth)acrylates bearing adamantyl group via atom transfer radical polymerization

AbstractThis investigation reports preparation of tailor‐made poly(meth)acrylates bearing adamantyl group using atom transfer radical homo and copolymerization via initiator as well as via monomer approach. The ATRP of methyl methacrylate was investigated using different initiators having adamantyl group (like AdMBr or AdBr) as well as conventional EBiB initiator and CuBr as catalyst in combination with PMDETA as ligand. It was observed that the incorporation of the bulky adamantyl group increased the rate of polymerization. The polymerization proceeded through first‐order kinetics and molecular weights increased linearly with conversion, close to the targeted molecular weights. The living nature of the end‐group was confirmed by MALDI‐TOF‐mass spectrometry and chain extension experiment. The homopolymerization of adamantyl methyl acrylate (AdMA) and its copolymerization with MA was successfully carried out using methylbromopropionate (MBrP) as initiator and CuBr/dNbpy as the catalyst. Interestingly, the resultant poly(meth)acrylates bearing the adamantyl group had excellent thermal stability and much better thermal stability than the similar polymers without adamantyl group as evidenced from thermogravimetry analysis (TGA) and isothermal TGA studies. Importantly, incorporation of adamantyl group “adamantly” increases rate of polymerization, thermal stability, and glass transition temperature of the polymers. All the polymers were characterized by NMR, MALDI‐TOF‐MS, DSC, and TGA analysis. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7101–7113, 2008

Preparation, thermal and flammability properties of a novel form-stable phase change materials based on high density polyethylene/poly(ethylene-co-vinyl acetate)/organophilic montmorillonite nanocomposites/paraffin compounds

The paraffin is one of important thermal energy storage materials with many desirable characteristics (i.e., high heat of fusion, varied phase change temperature, negligible supercooling, self-nucleating, no phase segregation and cheap, etc.), but has low thermal stability and flammable. Hence, a novel form-stable phase change materials (PCM) based on high density polyethylene (HDPE)/poly(ethylene-co-vinyl acetate) (EVA)/organophilic montmorillonite (OMT) nanocomposites and paraffin are prepared by twin-screw extruder technique. The structures of the HDPE–EVA/OMT nanocomposites and the form-stable PCM are evidenced by the X-ray diffraction (XRD), transmission electronic microscopy (TEM) and scanning electronic microscope (SEM). The results of XRD and TEM show that the HDPE–EVA/OMT nanocomposites form the ordered intercalated nanomorphology. The form-stable PCM consists of the paraffin, which acts as a dispersed phase change material and the HDPE–EVA/OMT nanocomposites, which acts as the supporting material. The paraffin disperses in the three-dimensional net structure formed by HDPE–EVA/OMT nanocomposites. The thermal stability, latent heat and flammability properties are characterized by thermogravimetry analysis (TGA), dynamic Fourier-transform infrared (FTIR), differential scanning calorimeter (DSC) and cone calorimeter, respectively. The TGA and dynamic FTIR analyses indicate that the incorporation of suitable amount of OMT into the form-stable PCM increase the thermal stability. The DSC results show that the latent heat of the form-stable PCM has a certain degree decrease. The cone calorimeter shows that the heat release rate (HRR) has remarkably decreases with loading of OMT in the form-stable PCM, contributing to the improved flammability properties.