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Individual Polymers (individual + polymer)
Selected AbstractsThermally stimulated depolarization study in polyvinylidenefluoride,polysulfone polyblend filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Pooja Saxena Abstract Thermally stimulated depolarization currents (TSDCs) in short- and open-circuit modes in polyvinylidenefluoride (PVDF),polysulfone (PSF) polyblend have been recorded. The TSDC thermograms of PVDF and PSF in short-circuit mode show two peaks, whereas the polyblend of the two polymers shows a single peak. With the increase in PSF weight percentage in the polyblend, the magnitude of TSDC peak current increased and the peak current position shifted toward the lower temperature side. The single peak in polyblend appears at 165°C ± 10°C, which is at higher temperature than the temperature of low-temperature peak for individual polymers. This suggests that this peak may be due to dipolar polarization. Subsequently, shifting of peak toward higher temperature side with increase in polarizing temperature indicates the space charge peak. This contradiction has been explained on the basis of induced dipole theory. The behavior of short circuit TSDC could be explained in terms of the heterocharge caused by dipole orientation and ionic homocharge drift, together with the injection of charge carriers from electrodes and their subsequent localization in surface and bulk traps. However, two oppositely directed TSDC peaks observed in open-circuit mode in all the polyblend samples could be considered as the result of superposition of two overlapped and oppositely directed peaks, one caused by relaxation of dipole polarization and the other by the space charge. Thus, we have compared TSDC measured in open- and short-circuit modes to distinguish between these two relaxation processes and separate them. There is only one broad peak observed in the short-circuit mode of the polyblend, which entirely corresponds to the relaxation of dipole polarization. Insertion of a dielectric gap in the open-circuit mode does not affect the dipole current, but the space charge component flowing in the opposite direction is added to the former. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Rheological and electrical properties of bentonite in anionic polystyrene sulfonate and nonionic poly(vinyl alcohol)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Bassem A. Mostafa Abstract The flow properties of bentonite were studied with a combination of anionic polystyrene sulfonate (molecular weight = 70,000 g/mol) and nonionic poly(vinyl alcohol) (molecular weight = 50,000 g/mol). This combination had a significant effect on clay suspensions depending on the sequence of the polymer addition. The addition of 50 mg/L anionic polystyrene sulfonate followed by 200 mg/L nonionic poly(vinyl alcohol) improved the rheological properties with a 7% bentonite suspension, especially at 20°C and after 24 h of aging. However, by the reversal of this addition sequence, the rheological properties of bentonite suspensions were reduced. The , potential of bentonite suspensions of the individual polymers at the same concentration was ,42 mV for polystyrene sulfonate and ,63 mV for poly(vinyl alcohol). The combined effect of anionic polystyrene sulfonate followed by nonionic poly(vinyl alcohol) noticeably changed the , potential (,95 mV). With the reversal of the addition sequence, this parameter did not change. Potential energy profiles were constructed to investigate the suspension stability. Potential energy profiles of polystyrene sulfonate added to bentonite suspensions and followed by poly(vinyl alcohol) produced high repulsion potential energy between clay surfaces, reflecting high suspension stability. By the reversal of this sequence, a significant reduction of the energy barrier was observed. On the basis of the rheological and electrical properties of this system, the addition of polystyrene sulfonate followed by poly(vinyl alcohol) provides a promising tendency for a 7% clay concentration to meet desirable drilling mud properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3886,3894, 2007 [source] Effect of ,-irradiation on the physical properties and dyeability of poly(vinyl butyral) blends with polystyrene and poly(ethylene glycol)POLYMER COMPOSITES, Issue 6 2008Horia M. Nizam El-Din Cast films of polymer blends essentially based on poly(vinyl butyral) (PVB) and equal ratios of polystyrene (PS) and poly(ethylene glycol) (PEG) were prepared from benzene and butyl alcohol solutions of the individual polymers. The effect of ,-irradiation on the thermal decomposition and tensile mechanical properties was investigated. Moreover, the effect of ,-irradiation on the dye affinity of PVB/PS and PVB/PEG for basic and acid dyestuffs was studied. The thermogravimetric analysis (TGA) study showed that the unirradiated PVB polymer films prepared in benzene displayed higher thermal stability than the same polymer films prepared in butanol. However, in all cases the thermal stability was found to increase with increasing ,-irradiation dose. On the other hand, PVB/PS blend possesses higher thermal stability than PVB/PEG, as shown from the determination of the weight loss (%) at different heating temperatures, the temperatures of the maximum rate of reaction and the activation energy. While, pure PS films showed the stress-strain behavior of brittle polymers, PVB/PS films showed the behavior of tough polymers with yielding properties. The results of dyeing clearly showed that the solvent type, blend composition, and irradiation dose are determining factors for the dye affinity for basic or acid dyes. For example, unirradiated PVB films prepared from butanol displayed a higher affinity for the basic and acid dyes than the same polymer prepared from the same benzene. However, PVB prepared from butanol showed higher affinity to the dyes than PS prepared from the same solvent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] On the effect of pressure on the shear and elongational viscosities of polymer meltsPOLYMER ENGINEERING & SCIENCE, Issue 7 2004Tomas Sedlacek The effect of pressure and temperature on the shear and elongational deformation rate,dependent viscosities has been experimentally investigated for several polymers (HDPE, LDPE, LLDPE, PP, PC, PMMA, and PS) on a capillary rheometer with a back-pressure device. Pressure, ,, and temperature, ,, coefficients have been determined through simultaneous fitting of the shear and extensional viscosity data by the modified White-Metzner model. The dependence of , and , on temperature and pressure, respectively, was investigated and it has been found that simple relationships exist between pressure and temperature sensitivity coefficients for individual polymers. Polym. Eng. Sci. 44:1328,1337, 2004. © 2004 Society of Plastics Engineers. [source] Processing behavior of polycarbonate/functionalized-ethylene copolymer blendsPOLYMER ENGINEERING & SCIENCE, Issue 12 2000Marcos L. Dias The melt blending of polycarbonate (PC) and ethylene-methacrylic acid copolymers (EFC) either in the acid form (EFC-H) or partially neutralized with sodium (EFC-Na) or zinc (EFC-Zn) was investigated. Torque monitoring of the blending showed that the polymers are capable of reacting generating new chemical species that increase the melt viscosity. As general behavior, the torque curves pass by a maximum that takes place before 30 min, the final torque being higher than that of the individual polymers. SEC analyses reveal that PC degradation also occurs and is stronger in the case of blends with EFC-Na that acts to catalyze PC degradation, promoting CO2 formation. FTIR studies on chloroform insoluble fractions of the PC/EFC-Zn blends showed that in addition to a very small number of carbonate groups, feature absorption bands of aromatic ester and hydroxyl groups appear in the new chemical species formed during the reactive processing. [source] | ||||||||||