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Sodium alginate (SA) was blended with varying amounts of poly(ethylene glycol) (PEG) viz., 10, 20, 30, 40 and 50 wt % by using water as a solvent. The obtained SA/PEG blends have been characterized for thermal behavior by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and surface morphology by scanning electron microscopic (SEM) methods. DSC analysis indicates the increase in glass transition temperature (Tg) of the blends with an increase in PEG content in the blend, which is due to chain entanglement. TGA results reveal the enhancement of thermal stability of SA/PEG blends in terms of the onset of degradation and percentage of weight loss. SEM photomicrographs shows the two phase morphology. This result indicates the immiscible nature of the SA/PEG blends. 相似文献
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The meta kaolin (MK) clay particulate filler with different weight ratios viz., 0, 5, 10, 20 and 30 wt% were incorporated into castable polyurethane (PU)/polystyrene (PS) (90/10) interpenetrating polymer network (IPN). The effects of MK particulate filler loading on the mechanical and thermal properties of PU/PS (90/10) IPN composites have been studied. From the tensile behavior, it was noticed that a significant improvement in tensile strength and tensile modulus as an increase in MK filler content. Thermogravimetric analysis (TGA) data reveals the marginal improvement in thermal stability after incorporation of MK filler. TGA studies of the IPN composites have been performed in order to establish the thermal stability and their mode of thermal degradation. It was found that degradation of all composites takes place in two steps. Degradation kinetic parameters were obtained for the composites using three mathematical models. Tensile fractured composite specimens were used to analyze the morphology of the composites by scanning electron microscopic (SEM) technique. 相似文献
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A series of different weight ratios of guar gum viz. 5, 10, 20 and 30 were incorporated into polyurethane/polyacrylonitrile (PU/PAN, 50/50) semi interpenetrating polymer networks (SIPNs) using polyethylene glycol-400, 4,4′-diphenyl methane diisocyanate, acrylonitrile, benzoyl peroxide and new metallic catalyst. The obtained polymer composites were subjected to biodegradation studies using specific fungi Aspergillus niger. The composites are characterized for physico-mechanical properties like density and tensile behaviour of the specimens before and after biodegradation. The positron annihilation lifetime spectroscopy (PALS) was used to monitor the content of free volume before and after biodegradation. The extent of degradation was examined by change in tensile behaviour and surface morphology. The influences of fungi on mechanical and morphological behaviour of filled IPNs are found to be interesting. The free volume changes in the composite systems correlates well with the mechanical properties. 相似文献
4.
H.N. Chandrakala B. Ramaraj Shivakumaraiah Siddaramaiah 《Journal of Physics and Chemistry of Solids》2014
We investigated the influence of lithium potassium zirconate (LiKZrO3) nanoparticles on the electrical properties and structural characteristics of poly(vinyl alcohol) (PVA) films. PVA/LiKZrO3 nanocomposite films were prepared by casting of aqueous solutions with varying LiKZrO3 content (0.5, 1.0, and 2.0 wt.%). The dielectric constant (ε′), dielectric loss (ε″), AC conductivity (σac), dielectric loss tangent (tan δ), and electric modulus (M′ and M″) of the nanocomposite films were measured over a range of frequencies at ambient temperature. The results show increases in σac and M′ with frequency, whereas ε′, ε″, and tan δ decreased with increasing frequency. The films were also characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) techniques. DSC and XRD revealed the nature of LiKZrO3 nanoparticle interaction with the PVA matrix. TGA analysis revealed an increase in thermal stability of the nanocomposites with increasing nanoparticle concentration. Scanning electron microscopy confirmed uniform dispersion of LiKZrO3 nanoparticles in the PVA matrix. 相似文献
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Bhojya Naik H. S. Siddaramaiah Ramappa P. G. 《Journal of Thermal Analysis and Calorimetry》1999,55(3):841-849
The complexes of cobalt(II) with dothiepin (DOT) hydrochloride have been studied for kinetics of thermal degradation by thermogravimetric
analysis (TG) and derivative thermogravimetric studies (DTG) in a static nitrogen atmosphere at a heating rate of 10° C min−1. A general mechanism of thermal decomposition is advanced involving dehydration and decomposition process for both organic
and inorganic ligands. The thermal degradation reactions were found to proceed in three steps having an activation energy
in the range 6.75–170 kJ mol−1. Thermal decomposition kinetics parameters were computed on the basis of thermal decomposition data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Polyaniline‐carboxylic acid functionalized multi‐walled carbon nanotube (PAni/c‐MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c‐MWNTs were dispersed in SDS emulsion then the aniline was polymerized by the addition of ammonium persulfate in the absence of any added acid. SDS forms the functionalized counterion in the resulting nanocomposites. The content of c‐MWNTs in the nanocomposites varied from 0 to 20 wt%. A uniform coating of PAni was observed on the c‐MWNTs by field‐emission scanning electron microscopy (FESEM). The PAni/c‐MWNT nanocomposites have been characterized by different spectroscopic methods such as UV‐Visible, FT‐Raman, and FT‐IR. The UV‐Visible spectra of the PAni/c‐MWNT nanocomposites exhibited an additional band at around 460 nm, which implies the induced doping of the MWNTs by the carboxyl group. The FT‐IR spectra of the PAni/c‐MWNT nanocomposites showed an inverse intensity ratio of the bands at 1562 and 1480 cm?1 as compared to that of pure PAni, which reveals that the PAni in the nanocomposites is richer in quinoid units than the pure PAni. The increase in the thermal stability of conductivity of the nanocomposites was due to the network structure of nanotubes and the charge transfer between the quinoid rings of the PAni and the c‐MWNTs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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In the present investigation, authors made an attempt to study the sliding wear behavior of polypropylene/ultrahigh molecular weight polyethylene (PP/UHMWPE, 90/10) blends loaded with 30% carbon short fibers (CSF) as reinforcement and nanoclay as filler material. The nanocomposites have been prepared with varying amounts viz., 0, 1, 2 and 3 wt% of nanoclay. The composites were prepared by melt mixing at 60 rpm extruder speed and compression moulding at 180°C. From all the composites, 6 mm diameter and 25 mm length sliding wear specimens were prepared. Sliding wear loss, specific wear rate and coefficient of friction were investigated by using computerized pin-on–disc machine at normal applied loads of 20, 30 and 40 N; at a sliding velocity of 1.5 m/s and at two abrading distances viz., 200 and 300 m. The wear behavior data reveals that 3 wt% nanoclay filled composite exhibits higher wear resistance and lowest specific wear rate as compared to other nanocomposites. Also morphological study was carried out for wear out surfaces of all the composites using scanning electron microscopy (SEM). 相似文献
8.
Polyurethane (PU) has been prepared by using polyether polyol (jagropol oil) and 1,6- hexamethylene diisocyanate (HMDI) as a cross-linker. The organically modified montmorillonite clay (MMT) is well-dispersed into urethane matrix by an in situ polymerization method. A series of PU/MMT nanocomposites have been prepared by incorporating varying amounts of nanoclay viz., 1, 3, 5 and 6 wt %. Thermogravimetric analysis (TGA) of the PU/MMT nanocomposites has been performed in order to establish the thermal stability and their mode of thermal degradation. The TGA thermograms exhibited the fact that nanocomposites have a higher decomposition temperature in comparison with the pristine PU. It was found that the thermal degradation of all PU nanocomposites takes place in three steps. All the nanocomposites were stable up to 205°C. Degradation kinetic parameters of the composites have been calculated for each step of the thermal degradation processes using three mathematical models namely, Horowitz–Metzger, Coats–Redfern and Broido's methods. 相似文献
9.
B. G. Soares Fernando G. SouzaJr A. Manjunath H. Somashekarappa R. Somashekar Siddaramaiah 《Pramana》2007,69(3):435-443
Small angle X-ray scattering data have been recorded for the blends of styrene butadiene, styrene copolymer/polyaniline using
the beamline of the LNLS (Laboratorio Nacional de Luz sincroton-Campinas, Brazil). Employing one-dimensional Hosemann’s paracrystalline
model, we have simulated the meridional reflections of these blends in order to compute the long periodicity and hence to
find the variation with concentrations of the blends. Within the region of available experimental data we observe that there
is a linear relationship between long periodicity and concentration of blends. These parameters are compared with physical
measurements like tensile strength to find the structure-property relation in these blends.
相似文献
10.
Semi-interpenetrating polymer networks (SIPNs) of polyurethane (PU) and poly(methyl methacrylate) (PMMA) in different weight ratios viz., 90/10, 70/30, 60/40 and 50/50 were prepared. The SIPNs were characterized for physico-mechanical properties like density, tensile strength and elongation at break. Thermal stability of IPNs was measured using thermogravimetric analysis (TGA). From the TGA thermograms it was noticed that all IPNs are stable up to 325 °C and undergo three-step thermal degradation in the temperature ranges 251-400, 378-508 and 445-645 °C for first, second and third steps, respectively. Thermal degradation kinetic parameters like activation energy (Ea) were calculated using Broido, Coats-Redfern and Horowitz-Metzger models. The values obtained by Broido and Horowitz-Metzger methods showed concurrency, whereas Coats-Redfern method showed relatively lower values. Surface morphology measured using scanning electron microscope (SEM) showed two-phase morphology for all the IPNs. 相似文献
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