Matrix-Material Fabrication Technique and Thermogravimetric Analysis of Banana Fiber Reinforced Polypropylene Composites

From the environmental consideration,it would be very interesting to use natural fibers such as banana,jute or coir as reinforcement materials instead of artificial fibers or any kind of synthetic materials.Natural fibers have many advantages over synthetic ones.Polypropylene banana fiber composites(PPBC)are prepared using untreated and alkali-treated banana fibers at 10-25%by weight of the fiber loading.The thermal properties of polypropylene natural fiber composites are very important for technological uses.Thermogravimetric measurements show that the incorporation of banana fiber into PP enhances the thermal stability of composites containing treated fibers,in comparison with untreated fibers.A composite of biodegradable polypropylene(PP)reinforced with short banana natural fibers was prepared by melt blending followed by a hot press molding system.The thermal properties of matrix materials were studied using thermogravimetric analyzers TGA units.It is observed that the introduction of short banana fibers slightly improved the thermo oxidative stability of PP-banana composites.Physical and chemical changes occurred through dehydration,phase transition,molecular orientation,crystallinity disruption,oxidation and decomposition,and incorporation of several functional groups.Systematic investigations of the thermal behavior of polymers in gas,vacuum or inert atmosphere give the knowledge of how change takes place in polymers.To understand such changes thermogravimetric analysis(TGA)and thermal analysis(TG)were performed.It is observed reinforcement of short banana fiber leads to little improvement in the thermooxidative stability of PPBC.Due to the enhancement of thermo-mechanical properties,such composites may be used as building materials namely roof materials,selling materials and many other engineering applications.

Non-isothermal oxidation and ignition prediction of Ti-Cr alloys

The non-isothermal oxidation behavior and oxide scale microstructure of Ti-Cr alloy （0≤w（Cr）≤25%） were studied from room temperature to 1723 K by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The influencing mechanism of chromium on the oxidation resistance of Ti-Cr alloys was discussed. The results show that the oxidation resistance of the alloys decreases with Cr below a critical chromium content wC and increases above wC; above 1000 K, the oxidation kinetics obeys parabolic rule and titanium dominates the oxidation process; after oxidation, the oxygen-diffusing layer is present in the alloy matrix, the oxide scale is mainly composed of rutile whose internal layer is rich in chromium, and chromium oxides separated out from TiO2 near the alloy-oxide interface improve the oxidation resistance. Ignition of metals and alloys is a fast non-isothermal oxidation process and the oxidation mechanism of Ti-Cr alloys during ignition is predicted.

THERMAL DEGRADATION OF POLY(ARYLENE SULFIDE SULFONE)/NMETHYLPYRROLIDONE CRYSTAL SOLVATE

The thermal degradation of poly（arylene sulfide sulfone）/N-methylpyrrolidone （PASS/NMP） crystal solvate was studied by thermogravimetric analysis （TGA） and was compared with pure PASS in order to determine the way in which the formation of the crystal solvate affected the thermal properties of the polymer. The activation energy of the solid state process was determined using Kissinger＇s method, which does not require knowledge of the reaction mechanism （RM）, to be 174.18 kJ/mol which was lower than that for pure PASS （E = 214 kJ/mol）. The study of master curves together with interpretation of integral methods, allows confirmation that the thermal degradation mechanism for PASS in the crystal solvate system is a decelerated Rn type, which is a solid-state process based on a phase boundary controlled reaction, in the conversion range considered. Whereas, the pure PASS follows a decelerated Dn thermodegradation mechanism in the same conversion range.

Synthesis and Properties of Chiral Polyurethane Elastomers Using Tartaric Acids

The polyaddition of isocyanate and polyol to form polyurethane elastomers has rarely been applied to the construction of chiral polyurethane elastomers. Hence, the introduction of chiral units via polyaddition remains a challenging subject in polymer chemistry. In this study, the synthesis of chiral polyurethane elastomers using an aromatic isocyanate, polyols (polyether and polyester polyols), and L(+)-, D(&#8722)-, or meso-tartaric acid by a one-shot method is investigated. The polymers are characterized using FTIR and NMR spectroscopy, and their thermal properties are investigated by TGA, DMA, and DSC analyses. The optical activities of the polymers are confirmed by rotation. The use of chiral tartaric acids is essential to obtain the desired chiral polyurethane elastomers.

An Investigation of Thermomechanical Behavior of Tunisian Luffa Sponges’ Fibers

This work is realized in the context of valorizing natural and local resources, in particular, luffa plant fruit (luffa sponge). The raw fibers of the luffa sponge have a short lifetime. Hence, when they are chemically treated, it constitutes a solution is prepared to limit their degradation in the long term and to improve their mechanical characteristics. Therefore, this paper studies the effect of the chemical treatment on the mechanical properties of the luffa sponge’s fibers (fibers of luffa Sponge). The chemical process consists of dipping a brunch of luffa in various concentrations of sodium hydroxide (NaOH) at different time intervals and at different temperature conditions. The luffa sponge’s fibers were mechanical. Characterized before and after the treatment, mechanically (micro traction test). It has been shown that an optimum of 61% increase in mechanical properties (tensile strength) has been reached in the following conditions: treatment with 1% concentration for 90 min at 50°C.

Thermogravimetric analysis of bamboo-tar under different heating rates based on distributed activation energy model

Carbon fiber is a kind of new polymer material with excellent mechanical properties and being applied widely.The process of carbon fiber prepared by bamboo tar,including extraction,condensation,spinning,oxidation and carbonation,is influenced by the pyrolysis kinetics significantly.In this paper,the thermogravimetric analysis(TGA)of bamboo tar produced in the process of pyrolysis and gasification of the bamboo which is known as Phylostachys sulphurea,was analyzed by the distributed activation energy model(DAEM)to understand the kinetic properties and parameters of bamboo tar.The thermogravimetric analysis of bamboo tar which is used as the raw material of carbon fiber was conducted under 5 different heating rates(i.e.5,10,15,30 and 50℃/min,etc.)in nitrogen atmosphere.The results show that the activation energy of bamboo tar and the exponential factor increased significantly with the increase of the heating rate,and the low heating rate is advantageous to the extraction of bamboo tar solvent and the thermal polycondensation,which can provide scientific reference for the optimization of carbon fiber technology.The thermal weight results show that the temperature range of bamboo tar being decomposed rapidly is 213℃-410℃.The ranges of the activation energy were calculated by DAEM,which have small difference in comparisons with five heating rates when the conversion rate is at 0.1-0.6 and the average value of the activation energy is 119 kJ/mol.The stability range of the activation energy is enlarged when the conversion rate is greater than 0.6 and heating rate increases.

Preparation and Characterization of Mesophase Pitch via Co-Carbonization of Waste Polyethylene/Petroleum Pitch

The low-cost petroleum pitch and waste polyethylene （WPE） were used as raw materials to prepare the mesophase pitch by co-carbonization method and the forming mechanization of mesophase pitch was also investigated. Polarized microscopy, softening point, Fourier transform infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA） were used to characterize and analyze the properties and struc- ture of the mesophase pitch. The results showed that the carbonization yield of the modified pitch was high when 1-2 wt% WPE was added and the property of mesophase pitch （MP1-450-4 and MP2-450-4） prepared by thermal polymerization was excellent. Moreover, when the treatment temperature was above 420 ~C, the mesophase development of the modified pitch may be entire and 100% streamline texture mesophase can form. During the co-carbonization of WPEJpetroleum pitch, a large number of naphthenic structures and methylene bridges may be generated, which can improve the properties of the obtained mesophase pitch.

Influence of Size of Hematite Powder on Its Reduction Kinetics by H_2 at Low Temperature

The reduction kinetics and mechanisms of hematite ore with various particle sizes with hydrogen at low temperature were studied using the thermogravimetric analysis. At the same temperature, after the particle size of powder decreases from 107. 5μm to 2. 0 μm, the surface area of the powder and the contact area between the powder and gas increase, which makes the reduction process of hematite accelerate by about 8 times, and the apparent activation energy of the reduction reaction drops to 36.9 kJ/mol from 78. 3 kJ/mol because the activity of ore powder is improved by refining gradually. With the same reaction rate, the reaction temperature of 6.5 μm powder decreases by about 80 ℃ compared with that of 107. 5 μm powder. Thinner diffusion layer can also accelerate the reaction owing to powder refining. The higher the temperature, the greater is the peak of the reduction rate; at the same temperature, the greater the particle size, the smaller is the peak value of the reduction rate; both inner diffusion and interface chemical reaction play an important role in the whole reaction process.

Combustion characteristics of tannery sludge and volatilization of heavy metals in combustion

Incineration is considered one of the most readily available techniques for sewage sludge disposal, including tannery sludge, which often contains significant amounts of volatile heavy metals. The combustion characteristics and kinetic analysis of tannery sludge were investigated using thermogravimetric analysis (TGA) at a heating rate of 30 °C/min in 50–950 °C. In addition to confirming that tannery sludge has a high content of volatile material and ash, it was further discovered that almost all the zinc (Zn) in tannery sludge is volatilized at 900 °C. The degree of volatilization for heavy metals at 900 °C followed the order of Zn>Cd>Cu>Mn>Pb>Cr. Moreover, the volatilization of these heavy metals increased with temperature. It is thus concluded that, to avoid heavy metal volatization during incineration disposal, 800 °C is a reasonable incineration temperature.

Effects of Halloysite Nanotube Reinforcement in Expandable Graphite Based Intumescent Fire Retardant Coatings Developed Using Hybrid Epoxy Binder System

In this study, the effects of halloysite nanotubes （HNTs） reinforcement in expandable graphite based intumescent fire retardant coatings （IFRCs） developed using a polydimethylsiloxane （PDMS）/phenol BA epoxy system were investigated. Intumescent coating formulations were developed by incorporating different weight percentages of HNTs and PDMS in basic intumescent ingredients （ammonium polyphosphate/melamine/boric acid/expandable graphite, APP/MEL/BA/EG）. The performance of intumescent formulations was investigated by furnace fire test, Bunsen burner fire test, field emission electron microscopy （FESEM）, thermogravimetric analysis （TGA）, transmission electron microscopy （TEM）, and Fourier transform infrared analysis （FTIR）. The Bunsen burner fire test results indicated that the fire performance of HNTs and PDMS reinforced intumescent formulation has improved due to the development of silicate network over the char residue. Improved expansion in char residue was also noticed in the formulation, SH（3）, due to the minimum decomposition of char carbon. FESEM and TEM results validated the development of silicate network over char layer of coating formulations. A considerable mass loss difference was noticed during thermal gravimetric analysis （TGA） of intumescent coating formulations. Reference formulation, SH（0） with no filler, degraded at 300 ~C and lost 50% of its total mass but SH（3）, due to synergistic effects between PDMS and HNTs, degraded above 400 ~C and showed the maximum thermal stability. XRD analysis showed the development of thermally stable compound mulltie, due to the synergism of HNTs and siloxane during intumescent reactions, which enhanced fire performance. FTIR analysis showed the presence of incorporated siloxane and silicates bonds in char residue, which endorsed the toughness of intumescent char layer produced. Moreover, the synergistic effect ofHNTs, PDMS, and other basic intumescent ingredients enhanced the polymer cross-linking in binder system and improved fire resistive performance of coatings.

Effects of CuO Nanoparticles on Microstructure,Physical,Mechanical and Thermal Properties of Self-Compacting Cementitious Composites

In the present study,split tensile strength of self-compacting concrete with different amount of CuO nanoparticles has been investigated.CuO nanoparticles with the average particle size of 15 nm were added partially to self compacting concrete and split tensile strength of the specimens has been measured.The results indicate that CuO nanoparticles are able to improve the split tensile strength of self compacting concrete and recover the negative effects of polycarboxylate superplasticizer on split tensile strength.CuO nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca（OH）2 amount at the early ages of hydration.The increase of the CuO nanoparticles more than 4 wt% causes the decrease of the split tensile strength because of unsuitable dispersion of nanoparticles in the concrete matrix.Accelerated peak appearance in conduction calorimetry tests,more weight loss in thermogravimetric analysis and more rapid appearance of related peaks to hydrated products in X-ray diffraction（XRD） results all also indicate that CuO nanoparticles up to4 wt% could improve the mechanical and physical properties of the specimens.Finally,CuO nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.

In Situ TEM Observation of the Gasification and Growth of Carbon Nanotubes Using Iron Catalysts

We report the in situ transmission electron microscope (TEM) observation of the catalytic gasification and growth of carbon nanotubes (CNTs). It was found that iron catalysts can consume the CNTs when pumping out the precursor gas, acetylene, at the growth temperature, and reinitiate the growth when acetylene is re-introduced. The switching between gasification and growth of CNTs can be repeated many times with the same catalyst. To understand the phenomenon, thermogravimetric analysis (TGA) coupled with mass spectroscopy was used to study the mechanism involved. It was shown that the residual water molecules in the growth chamber of the TEM react with and remove carbon atoms of CNTs as carbon monoxide vapor under the action of the catalyst, when the precursor gas is pumped out. This result contributes to a better understanding of the water-assisted and oxygen-assisted synthesis of CNT arrays, and provides useful clues on how to extend the lifetime and improve the activity of the catalysts.

Lithium ion conduction and ion-polymer interaction in poly(vinyl pyrrolidone) based electrolytes blended with different plasticizers

Poly（ethylene oxide）, poly（vinyl pyrrolidone）（PEO/PVP）, lithium perchlorate salt（Li Cl O4） and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate（EC） based complex exhibits a maximum ionic conductivity value of the order of2.7279 10 4S cm 1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO（72%）/PVP（8%）/Li Cl O4（8%）/EC（12%） has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400–450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.

Thioether Functional Chain Extender for Thermoplastic Polyurethanes

In this study, a novel three functional chain extender （TATATRIOL） was synthesized from the reaction of 1,3,5- tri（prop-2-en-1-yl）-1,3,5-triazinane-2,4,6-trione （TATA） with 2-sulfanylethanol. Then new thermoplastic polyurethanes （TPUs） were synthesized by a one-step bulk polymerization from the reaction of 1,1＇-methanediylbis（4- isocyanatocyclohexane） （H12MDI）, a poly（ethylene adipate） based polyester polyol and a chain extender. Butane-l,4-diol （BD） and the newly synthesized monomer, TATATRIOL, were used as chain extenders. The effects of TATATRIOL on the properties of the TPU were investigated and compared to those of the TPU prepared with BD. The TPUs which derived from the sulfur containing chain extender displayed lower modulus and high elongation at break values than the analogous TPUs derived from BD. Moreover sulfur containing TPUs exhibited higher thermal stability.

Influence of preparation route and slip casting conditions on titania and barium titanate ceramics

Titania （TiO2） and barium titanate （BaTiO3） were synthesized using three different dicarboxylates, which included oxalate, malate and tartarate. These powders were characterized by X-ray powder diffraction, scanning electron micrographs, BET specific surface area and particle size distribution. Their properties depended to a great extent on the nature of the precursor. The titania and barium titanate powders obtained from the tartarate precursor were found to be good for slip casting. Slips of these oxides with different solids contents were prepared at different pH values using both distilled water and ethanol as the dispersing agent and also with and without deflocculant. The theological behaviors of the suspensions were then determined, and the slip, green and sedimentation bulk densities were measured. The minimum viscosities were observed at pH 8.2 for the TiO2-water and pH 10.2 for the BaTiO3-water system.