TGA Result Research Articles

Faradaic number as a criterion for the promotion effect of external electric field on the heterogeneous oxidative cracking of liquefied petroleum gas on ZSM-5 supported catalyst

The oxidative cracking of liquefied petroleum gas (LPG) in the presence of CO2 as oxidant, under a novel catalytic reaction system, with an electric field, was studied over a series of CrHZSM-5, HZSM-5 and NaZSM-5 catalysts. This research is the first report for olefin production with the synergetic effect of zeolite catalysts and external electric field. The prepared catalysts were characterized by XRD, SEM, FTIR, BET, NH3-TPD, H2-TPR and TGA techniques and an impedance analyzer with a potentiostat. Different parameters such as temperature, input electrical current, gap distance, amount of metal loading, oxidant, and GHSV were investigated. The activity was greatly increased by a weak electric field. The XRD pattern showed that the structure of the treated catalysts remained intact while BET results indicated the surface and micropore areas decreased after metal loading on HZSM-5. TPR data exhibited the reduction phenomenon of the catalysts. NH3-TPD analysis determined that Cr/HZSM-5 catalyst has more strong acid sites compared to NaZSM-5 and HZSM-5. According to TGA result, in the presence of an electric field, coke formation is decreased. Electrical conductivity played an important role in the reaction. Faradaic number was used to show the promotion effect of electric field. The results showed the electrons provided by external electric field, metal loading, and catalyst support were drastically promoted LPG to light olefins at 625 °C and 12 mA, which led to 42.58 and 92.12% ethylene yield and conversion, respectively, and 335.07 Faradaic number.

Preparation and characterization of aqueous phase self-dispersed CB/PSSS composites

Aqueous phase self-dispersed CB/PSSS composites were prepared by KH570-modifed CB and p-styrene sulfonate sodium (SSS) via in-situ polymerization. SEM and TEM results indicated that CB/PSSS composites were amorphous with a core-shell structure and had around 10nm copolymer. TGA result indicated that the grafting rate of CB/PSSS composites was 13.3wt%. Particle size analysis results showed that the mean particle size of CB/PSSS composites was 175.9nm diameters with zeta potentials −38.4mV. The CB/PSSS composites showed excellent self-dispersing properties in aqueous phase without extra treatment. This research gives an opportunity to solve the deposition problem during transport and storage process.

Degradation Test of Natural Rubber/Chitosan Composite

Degradable materials from 20wt% chitosan loading and natural rubber (CS/NR) were prepared by solution casting without surface treatment to study their thermal and mechanical properties after degradation test in aging condition. The test was done in an acrylic degradation box with 600 W light and high humidity for accelerate degradation condition. Samples included high ammonia concentrated latex (HA) with no filler, fresh latex (FL) with no filler, HA with chitosan filler, FL with chitosan filler, and natural rubber with shrimp shell filler to compare the result with chitosan filler. After degradation test, thermal properties from TGA both before and after degradation showed that the fillers effected on these composite materials. TGA result of CS/NR composite with aging at temperature 100 °C for 10 h and 20 h showed that chitosan slightly effected on thermal stability of composites when compare to natural rubber. SEM images were compared before and after degradation of HA and FL with no filler, chitosan filler, and shrimp shell. It was clearly seen that the samples degraded as the shape and size were changed. Tensile testing values showed that longer aging time could lead to the degradation in CS/HA and lower the tensile strength.

Synthesis, characterization and electrical property of MWCNT-ZnS nanocomposite embedded in polyaniline

PANI/MWCNT-ZnS nanocomposites with different contents of ZnS wt.% have been synthesized by the chemical oxidative in situ polymerization reaction of aniline in the presence of multi-walled carbon nanotube (MWCNT). TEM, XRD, RAMAN and TGA studies have been done for the structural and thermal characterizations of the samples. The particle sizes of ZnS nanoparticles have the values in the range from 3.21 to 5.08 nm. XRD spectrum reveals the co-existence of MWCNT, ZnS in PANI matrix, where ZnS forms a hexagonal structure. TGA result shows that nanocomposite becomes more thermally stable with increase in ZnS content. The dc electrical transport property of PANI/MWCNT-ZnS nanocomposites has been investigated within a temperature range 77 K ⩽ T ⩽ 300 K. The dc conductivity follows a 3D variable range hopping (VRH) model. A large magnetoconductivity change (23.1%) is observed for 2 wt.% ZnS content in PANI/MWCNT-ZnS, which is explained by the wave function shrinkage model.

Facial preparation of superhydrophobic and superoleophilic textiles by depositing nano-SiO2 for oil–water separation

In this study, a facile one-step dip-coating approach was reported for the fabrication of superhydrophobic and superoleophilic cotton fabrics for oil–water separation. By depositing the hydrophobic nano-SiO2 on the micro-scale cotton fabric surface, the combination of the nano-SiO2 and the micro-roughness cotton fabric created a micro/nano-binary surface roughness and presents superhydrophobicity and superoleophilicity. SEM, EDS, and TGA result shows that the treated cotton fabric was completely covered by the nano-SiO2 particles when the nano-SiO2 particles was about only 3.6 wt% of the pristine cotton fabric. The separation efficiency of the fabricated superhydrophobic and superoleophilic fabric was calculated up to 98.3 wt%. The one-step production technique described here is realizable for industrial use, relatively mild processing conditions, and large-scale fabrication.

Synthesis of a novel phosphorus-containing benzoxazine-monomer and its polymer alloys based on bismaleimides

To improve the flame resistance properties and thermal properties of bismaleimides (BMI) resin, a reactive phosphorus-contained benzoxazine monomer (PBOZ) was synthesized based on a phosphorus-containing compound 10-(2, 5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(ODOPB), and its chemical structure was characterized by infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). The novel PBOZ monomer was then used to blend with BMI (PBOZ-BMI), and the flame resistance of PBOZ-BMI resin was evaluated by the vertical flame test and the limited oxygen index (LOI) test. The results showed that the PBOZ-BMI exhibits better flame resistance. The thermal properties of cured PBOZ-BMI resins were investigated by differential scanning calorimeter (DSC) and thermogravimetry (TG). DSC results showed that the curing temperatures of PBOZ-BMI resins decreased with suitable content of PBOZ in comparison with BMI. The TGA result showed that the onset decomposition temperatures and the char yields also increased with the suitable addition of PBOZ. These conclusions can further confirms that the flame resistance of PBOZ-BMI enhanced as its thermal properties increase.

Enhanced magnetoconductivity and electrical property of MWCNT-CdS nanocomposite embedded in polyaniline

PANI/MWCNT-CdS nanocomposites with different content of CdS wt.% has been synthesized by the chemical oxidative in-situ polymerization reaction of aniline in the presence of multi-walled carbon nanotubes (MWCNT). TEM, XRD, FTIR, and TGA studies were done for the structural and thermal characterization of the samples respectively. The particle size of CdS nanoparticles distributes in between 2.7 and 4.8 nm. XRD spectrum reveals that the co-existence of MWCNT, CdS in PANI matrix, where CdS forms a hexagonal structure. TGA result shows that nanocomposite becomes more thermally stable with the increase in CdS content. The dc electrical transport property of PANI/MWCNT-CdS nanocomposites has been investigated within a temperature range 77 ≤ T ≤ 300 K. The dc conductivity follows a 3D variable range hopping (VRH) model. A large magnetoconductivity change (19%) is observed for 2 wt% CdS content in PANI/MWCNT-CdS, which is explained by the wave function shrinkage model.

Investigating the Properties and Hydrolysis Ability of Poly-Lactic Acid/Chitosan Nanocomposites Using Polycaprolactone.

Poly-lactic acid (PLA) has been widely applied in the medical field (in biomedicines such as medical capsules, surgical sutures and suture wounds) owing to its high biodegradability, good biocompatibility and ability to be dissolved in common solvents. Chitosan (CS) is an abundant polysaccharide and a cationic polyelectrolyte present in nature. In this study, the combination of PLA and CS has been used to form PLA/CS nanocomposites having the advantages of both the original components. To enhance the dispersibility and compatibility between PLA and CS in the PLA/CS nanocomposites, polycaprolactone (PCL) is added as a compatibilizer. The Fourier Transform Infrared spectroscopies prove the existence of the interactions of PCL with PLA and CS. A more regular dispersion of CS of 200-400 nm particle size, is observed in the PLA matrix of the PLA/CS nanocomposites containing PCL, through the Field Emission Scanning Electron Microscopy images. The appearance of one glass transition temperature (T(g)) value of PLA/CS/PCL nanocomposites occuring between the T(g) values of PLA and CS in DSC diagrams confirms the improvement in the compatibility between PLA and CS, due to the presence of PCL. The TGA result shows that PCL plays an important role in enhancing the thermal stability of PLA/CS/PCL nanocomposites. The hydrolysis of PLA/CS/PCL nanocomposites in alkaline and phosphate buffer solutions was investigated. The obtained results show that the PLA/CS/PCL nanocomposites have slower hydrolysis ability than the PLA/CS composites.

Ethylene/1-Hexene Copolymerization over Different Phases Titania-Supported Zirconocene Catalysts

Ethylene/1-hexene copolymerization was performed over titania-supported zirconocene/dMMAO catalysts. Effects of titania having different phases on the catalytic activity and polymer properties were investigated. It was found that anatase titania exhibited the highest catalytic activity, and afforded copolymer with high 1-hexene incorporation among other titanias. According to TGA result, the stronger interaction between dMMAO and titania for anatase phase led to the highest catalytic activity, because the stronger interaction between cocatalyst and support would prevent the leaching of cocatalyst. Additionally, based on EDX mapping, a good dispersion of dMMAO over support surface is another reason for an increase in the catalytic activity. SEM analysis indicated that no significant change in polymer morphology was found for all supported catalysts. The incorporation of 1-hexene determined by 13C NMR suggested that titania which possessed high amount of [Al]dMMAO over support surface showed high ability to incorporate 1-hexene. The random copolymers were produced in all systems.

Effect of propyleneimine external cross-linker on the properties of acrylate latex pressure sensitive adhesives

Acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). These PSA polymers were then cross-linked with trifunctional propyleneimine external cross-linker (SAC-100) to study the cross-linking reaction between carboxylic group of the polymer chain and cross-linking agent. It was found that cross-linking provided a significant influence on the film formation process based on the result of SEM analysis. In addition, with the increase of SAC-100 content, the gel content of the polymer increased significantly, while molecular weight between cross-link points (Mc) and the sol molecular weight (Mw, Mn) of the polymer decreased remarkably. The TGA result showed that the addition of the external cross-linker can enhance the thermal stability of the latex film. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncross-linked counterparts. Besides, dynamic mechanical analysis (DMA) was also used to evaluate the viscoelastic properties of the acrylate emulsion PSA film.

Synthesis of Cotton from Tossa Jute Fiber and Comparison with Original Cotton

Cotton fibers were synthesized from tossa jute and characteristics were compared with original cotton by using FTIR and TGA. The FTIR results indicated that the peak intensity of OH group from jute cotton fibers occurred at 3336 cm−1whereas the peak intensity of original cotton fibers occurred at 3338 cm−1. This indicated that the synthesized cotton fiber properties were very similar to the original cotton fibers. The TGA result showed that maximum rate of mass loss, the onset of decomposition, end of decomposition, and activation energy of synthesized cotton were higher than original cotton. The activation energy of jute cotton fibers was higher than the original cotton fibers.

Silver nanoparticles with 4,4′-dicyanamidobiphenyl ligand: Synthesis, photoluminescent and electroluminescent properties and DFT calculations

In this research, a new complex of 4,4′-dicyanamidobiphenyl (bpH2) ligand, Ag(bpH) has been synthesized and characterized by FT-IR, UV–Vis spectroscopies, and elemental analysis. The morphology and size of complex were determined by the scanning electron microscopy (SEM) image. The diameter of the complex was about 61nm and the nanoparticles were spherical. TGA result indicated that this complex was thermally stable. Also, photoluminescent and electroluminescent properties of Ag(bpH) were reported. The blue–green light emission was observed by fabricating double-layer devices using Ag(bpH) as electron-transport and NPB as hole-transport material. In addition, this complex was optimized by B3LYP/LANL2DZ method. The calculated FT-IR and UV–Vis data are in better agreement with the experimental results. In addition to DFT calculations, natural bond orbital (NBO) was also performed at the same level of theory.

Al<sub>2</sub>Ca를 함유한 A356 합금에서의 다양한 열처리 조건에 따른 공정 Si 개량화 거동

This study is focused on the effect of Al2Ca as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at 540oC and 170oC, respectively. Although A356 alloy, which Al2Ca was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that Al2Ca added A356 alloy has a certain improvement in oxidation resistance.

Dispersion and Degradation of Polycarbonate/MWCNT Nanocomposites with Melt Extrusion

Polycarbonate/Multi-wall Carbon Nanotubes (PC/MWCNT) nanocomposites with 0.55% and 0.77% of MWCNT were prepared by twin-screw compounding extruder. The morphology and dispersion were characterized by SEM. The Raman analysis confirmed the good interaction between carbon nanotubes (CNTs) and Polycarbonate (PC). The TGA result showed that the PC/MWCNT nanocomposites degraded in two time extrusion (TTE) as compared to one time extrusion (OTE), which was attributed to the temperature effect. Inspite of degradation, TTE nanocomposite showed good dispersion of MWCNT in PC.

Polypyrrole‐silk electro‐conductive composite fabric byin situchemical polymerization

ABSTRACTThis article describes the preparation of polypyrrole‐silk composite fabric byin situchemical polymerization of pyrrole.In situpolymerization process has been optimized by employing Box‐Behnken response surface design. The effect of process parameters on surface resistivity of the fabric has been statistically analyzed. Most significant process parameter and interaction effects have been identified. Thermal, electrical, and morphological properties of the composite fabric have been studied. Surface resistivity of the fabric obtained is 636.33 Ω. The fabric composite shows a linerV–Icharacteristic like an Ohmic conductor. An exponential rise of surface temperature of the fabric is observed by the application of DC voltage across it. Optical microscopic and SEM studies reveal uniform and even coating of polypyrrole on silk surface. FTIR studies indicate a possible chemical interaction between polypyrrole and silk. The polypyrrole‐treated composite fabric exhibits enhanced thermal stability as is evidenced from DSC and TGA result. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41336.

Synthesis of High Generation Dendronized Polymers and Quantification of Their Structure Perfection

The sixth generation (g = 6) dendronized polymer (DP) PG6 was synthesized on a 2 g scale with Pn ∼ 500 in 60% chemical yield and with a coverage degree of 87–90% using a recently developed “n + 2” approach from its structurally virtually perfect, deprotected g = 4 congener dePG4. This synthesis represents the first fully reliable access to a g = 6 representative of this DP series and was therefore used for the synthesis of two higher generation representatives, the g = 7 and g = 8 DPs, PG7 and PG8, which are the highest g DPs ever reported. The structure perfection of the obtained DPs was analyzed by the conventional UV-labeling method and compared with the results from TGA, with which the amount of cleaved-off Boc-protecting groups was quantified. The accuracy of the TGA method was assessed as ±3% by using a Boc-containing dendron and well-characterized low generation DPs as reference. For the high generation DPs obtained by “n + 2” approach the TGA results confirmed the UV-determined coverages. For PG7, the TGA result slightly exceeds the error range (3.3%), which may suggest a possible overestimation of the coverage determined by UV quantification. AFM imaging shows a so far uncommon inhomogeneous appearance for PG7 and PG8, which may be a result of structural defects in both DPs.

Study on the rheological behaviors of UHMWPE/CA‐MMT nanocomposite

In our previous study, we have prepared a novel antibacterial ultra‐high molecular weight polyethylene/chlorhexidine acetate‐montmorillonoid (UHMWPE/CA‐MMT) composites and examined its crystallization process and kinetics [1]. In this work, the rheological behaviors of pure UHMWPE, UHMWPE/MMT, UHMWPE/CA, and UHMWPE/CA‐MMT were characterized. The results showed that MMT can increase the viscosity of the polymer composites and CA can act as a plasticizer in the composites. Compared with UHMWPE/CA, UHMWPE/CA‐MMT had lower η*, G′, and G″. The TGA result indicated that CA‐MMT has higher thermostability than CA. Hence, CA‐MMT has the lower thermal decomposition ratio at high temperature than CA when it is blended with polymer. The TGA result could be used to explain that UHMWPE/CA‐MMT composites had better plasticizer effect than UHMWPE/CA composites. POLYM. COMPOS., 36:47–50, 2015. © 2014 The Authors Polymer Composites published by Wiley Periodicals, Inc.

New high performance waterborne organic–inorganic hybrid materials from UV curing

The third generation glycerol based hyperbranched polyester (HBPE-3G) was synthesized by reacting glycerol and 2,2-bis(hydroxymethyl)propionic acid in a stoichiometric molar ratio. This polyester was used as preparation for waterborne hyperbranched UV cured polyurethane–silica hybrid coatings. The acrylic terminated waterborne coatings were prepared by modifying some of the hydroxyl groups HBPE-3G to acidic groups by reacting with maleic anhydride. The remaining hydroxyl groups were reacted with NCO terminated acrylate. Then the prepolymer was neutralized with triethyl amine and dispersed in water. The waterborne hybrid formulations were prepared by mixing 3, 5 and 10% of trimethoxysilylpropyl methacrylate (TMSPM) into the acrylic terminated waterborne coatings. The films were casted and cured under UV light. The various film properties were studied by XRD, AFM, TGA and DMTA instruments. TGA result suggests that the onset degradation temperature and final mass residue increase with increasing TMSPM concentration. DMTA results show that the storage modulus and glass transition temperature increase for the hybrid formulations with increasing TMSPM concentration. The structural characterization of the hybrid coatings was performed using FTIR spectroscopy. The tensile test demonstrated that the mechanical properties improve with the increasing TMSPM content. Surface morphology was studied by atomic force microscopy (AFM). AFM study revealed that TMSPM was crosslinked homogenously through the polymer matrix. The TGA and DMTA data suggest that higher thermal stability and glass transition temperature (Tg) for the TMSPM hybrid films compared to their pure counterparts were obtained with increasing the TMSPM content.

Preparation and Characterization of SiCOH Film Using a New Precursor Trimethoxy [2-(oxabicyclo [4.1.0] hept-3yl) Ethyl] Silicane

The SiCOH film has been prepared by using a new precursor of trimethoxy [2-(7-oxabicyclo [4.1.hept-3-yl) ethy silane via sol-gel and spin-coating methods. The resulting films were characterized by SEM, TGA, AFM, FTIR, nanomechanical testing, and electrical measurements. The TGA result shows that the SiCOH film has good thermal stability, and no obvious thermal decomposition can be observed before 400°C. After being annealed at 350°C for 2 hours, the resulting SiCOH film exhibits a smooth surface (RMS=0.222nm), and a significant reduction of CHn groups in the film. Further, the film exhibits a novel high k value of 15.6, a leakage current density of 2.72 × 10-6 A/cm2 at 1 MV/cm, and good mechanical properties of Er ~ 12.61 GPa and H ~ 3.80 MPa.

Synthesis and characterization of polyaniline/Ag–Pt nanocomposite for improved antibacterial activity

Polyaniline, polyaniline/Ag–Pt nanocomposite and bimetal (Ag–Pt) colloidal solution were chemically synthesized and characterized by UV–vis, XRD, FT-IR, TGA, HRSEM with EDAX and HRTEM techniques. The results reveal that there was a strong interaction between Ag–Pt nanocomposite and polyaniline chains. This interaction makes only small changes in the backbone chain of polyaniline/Ag–Pt nanocomposite when compared with polyaniline. TGA result revealed greater thermal stability of the composite. HRSEM images showed pebble like morphology for polyaniline/Ag–Pt nanocomposite. The average grain size of Ag–Pt nanoparticle was found to be 2–5nm, which is confirmed by HRTEM analysis. The polyaniline and polyaniline/Ag–Pt nanocomposite were tested for antibacterial activity. The composite showed improved inhibition efficiency with a maximum zone diameter of 30±1.25mm against Staphylococcus aureus. This is the first report on the synthesis and its antibacterial activity of polyaniline/Ag–Pt nanocomposite.