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Thermal and morphological studies of chemically prepared emeraldine‐base‐form polyaniline powder Abstract In this study, emeraldine base (EB)‐form polyaniline (PANI) powder was chemically prepared in 1M HNO3 aqueous solution. The thermal characteristics and chemical structures of this powder were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). A polarizing optical microscope was also used to examine the crystalline morphology of this sample. The results indicated that the EB‐form PANI powder had a discernible moisture content. Moreover, in the first run of DSC thermal analysis, the exothermic peak at 170–340°C was due to the crosslinking reaction occurring among the EB‐form PANI molecular chains. FTIR and XRD examinations further confirmed the chemical crosslinking reaction during thermal treatment. TGA results illustrated that there were two major stages for weight loss of the EB‐form PANI powder sample. The first weight loss, at the lower temperature, resulted from the evaporation of moisture. The second weight loss, at the higher temperature, was due to the chemical structure degradation of the sample. The degradation temperature of the EB‐form PANI powder was around 420–450°C. The degradation temperature of emeraldine salt (ES)‐form PANI powder was lower (around 360–410°C) than that of the EB form (around 420–450°C). From the TGA results, I roughly estimated that 2.74 aniline repeat units, on average, were doped with 1 HNO3 molecule in the ES‐form PANI. I found a single crystalline morphology of EB‐form PANI, mostly like a conifer leaf. More complex, multilayered dendritic structures were also found. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2142–2148, 2003
Wiley - Tập 89 Số 8 - Trang 2142-2148 - 2003
pH responsive polymers with amino acids in the side chains and their potential applications ABSTRACT Design and synthesis of pH responsive polymeric materials has become an important subject in academia as well as in industrial field in recent years due to their applications in diverse field including controlled drug delivery, biomedical applications, membrane science, sensors and actuators, oil recovery, colloid stabilization, etc. Efforts have been made to incorporate stimuli‐responsive biomolecules in synthetic polymers to develop pH responsive “smart” non‐biological hybrid macromolecules with high water solubility, enhanced biocompatibility, bio‐mimetic structure and properties. This review is focused on the recent advances in side‐chain amino acid‐based pH responsive polymers synthesis and potential application aspects of these macromolecular architectures in drug and gene delivery, and other fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 41084.
Wiley - Tập 131 Số 20 - 2014
Déhydrochloruration du PCV en utilisant une correction pour des conditions isothermes
Wiley - Tập 18 Số 9 - Trang 2861-2863 - 1974
Thermal stabilization of polyvinyl chloride by group II metal laurates<sup>1,2</sup>
Wiley - Tập 13 Số 6 - Trang 1247-1252 - 1969
Characterization of polyvinyl alcohol/gelatin blend hydrogel films for biomedical applications Abstract In the present investigation, attempt was made to prepare blend hydrogel by esterification of polyvinyl alcohol with gelatin. The blend hydrogel was further converted into films by the conventional solution‐casting method. These films were characterized by FTIR, DSC, and X‐ray diffraction studies. The refractive index and viscosity of different composition of the blends were measured in the solution phase of the material. The mechanical properties of the blend films were measured by tensile test. Swelling behavior of the blend hydrogel was also studied. The FTIR spectrum of the blend film indicated complete esterification of the free carboxylic group of gelatin. The DSC results indicate that the addition of gelatin with PVA changes the thermal behavior like melting temperature of PVA, which may be due to the miscibility of PVA with gelatin. The interaction of gelatin with PVA molecule changes the crystallite parameters and the degree of crystallinity. The crystallinity of the blend film was mainly due to gelatin. The comparison of viscosity indicated an increase in the segment density within the molecular coil. The results revealed the changes observed in the properties of the gel, and it enhances the gel formation at viscoelastic phase of the material. The blend film had sufficient strength and water‐holding capacity. The results obtained indicated that the blend film could be used for various biomedical applications such as wound dressing and drug‐delivery systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Wiley - Tập 109 Số 5 - Trang 3431-3437 - 2008
Glyceryl methacrylate hydrogels Abstract Hydrophilic three‐dimensional polymer networks (hydrogels) were prepared from glyceryl methacrylate (2,3‐dihydroxypropyl methacrylate). The solubility of poly(glyceryl methacrylate) in water permits the preparation of transparent hydrogels containing variable amounts of water at the equilibrium stage. This is accomplished by varying the degree of swelling at the time of network formation, and by varying the density of crosslinks. The temperature dependence of swelling of the hydrogels in water and in 0.9% sodium chloride solution, was determined. There exists a linear relationship between the refractive index and the per cent of water in the hydrogel. These hydrogels are potentially useful in ophthalmology.
Wiley - Tập 9 Số 9 - Trang 3161-3170 - 1965
Hydrogels from 2‐hydroxyethyl methacrylate and propylene glycol monoacrylate Abstract Hydrophilic three‐dimensional polymer networks (hydrogels) were prepared from 2‐hydroxyethyl methacrylate (HEMA) and propylene glycol monacrylate (PGMA). By wet crosslinking, hydrogels which maintain their original shape and volume relatively well, compared with the dry‐cross‐linked polymer networks, were obtained. The maximum amount of water which can be maintained in transparent hydrogels depends on the hydrophilicity of the monomers, e. g., about 40% for HEMA gels, about 50% for PGMA gels, and 40–50% for HEMA–PGMA copolymer gels depending on the monomer composition. When the water content exceeds this maximum in transparent gels (homogeneous hydrogels), they become opaque and/or spongy (heterogeneous hydrogels). Effects of the amount of crosslinking agent and the initial dilution of the monomer solution upon the swelling behavior of hydrogels were investigated. The temperature dependence of the swelling of these hydrogels and the water permeation through them were also studied.
Wiley - Tập 9 Số 7 - Trang 2425-2435 - 1965
Some practical aspects of preparing polymeric hydrogels via γ‐irradiation
Wiley - Tập 28 Số 7 - Trang 2451-2454 - 1983
Flame‐retardant expandable polystyrene foams coated with ethanediol‐modified melamine–formaldehyde resin and microencapsulated ammonium polyphosphate ABSTRACT Melamine–formaldehyde resin was modified by ethylene glycol to decrease the amount of free formaldehyde and extend the storage time. The modified resin (EMF) was further used to prepare microencapsulated ammonium polyphosphate (MCAPP). The structures of both EMF and MCAPP were well characterized. Afterward, EMF and MCAPP were mixed and coated on the surface of pre‐expanded polystyrene particles to prepare flame‐retardant expandable polystyrene foams (EPS). Both water resistance and impact strength were enhanced by the presence of MCAPP, and the flammability of the samples was also significantly improved. For the sample containing 75 phr MCAPP, the limiting oxygen index value was increased to 31.4% with a V‐0 rating in the UL‐94 vertical burning test. Cone calorimeter tests showed that the peak heat release rate of the sample declined sharply to 172.7 kW/m2 , which is 81.6% lower than that of neat EPS. The smoke production of EPS foams during combustion was suppressed by the presence of MCAPP, and the thermal stability was also improved. Scanning electron microscopy showed that the char layer of the flame‐retardant sample after combustion became compact with negligible voids or cracks, which could further form an isolation barrier to prevent both heat and flame transfer. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46471.
Wiley - Tập 135 Số 28 - 2018
The flammability of expandable polystyrene foams coated with melamine modified urea formaldehyde resin ABSTRACT Urea formaldehyde resin (UF) was modified by introducing melamine during the condensation in order to reduce the amount of free formaldehyde and increase the solid content. The melamine modified UF (MUF) was firstly mixed with intumescent flame retardant (IFR) and then coated on the surface of pre‐expanded polystyrene (PS) particles to prepare flame retardant expandable PS (EPS) foams. The flammability of EPS foam samples was characterized by limiting oxygen index (LOI), UL‐94 vertical burning and cone calorimeter tests, and the results indicated that the peak heat release rate was significantly reduced from 406 to 49 kW/m2 and LOI value could reach 36.3 with V‐0 rating in UL‐94 test after coated with IFR. The smoke density test indicated that the maximum smoke density was decreased by the addition of IFR. Thermal analysis suggested that the thermal stability and char formation were significantly improved by the presence of coated flame retardants. The residual char observation revealed that MUF and IFR were beneficial to form integrated char layers with hollow stents, which could be the main reason for the improvement of flame retardant properties. The mechanical properties of flame retardant EPS foams can still meet the standard requirements for industrial applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44423.
Wiley - Tập 134 Số 5 - 2017
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