共查询到20条相似文献,搜索用时 15 毫秒
1.
E. Sacher 《Journal of Macromolecular Science: Physics》2013,52(2):441-448
There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier. 相似文献
2.
J. Belana P. Colomer M. Pujal S. Montserrat 《Journal of Macromolecular Science: Physics》2013,52(4-6):467-481
The relation between the temperature Tα of the dipolar relaxation, obtained by the technique of thermally stimulated currents (TSC) and the glass transition temperature Tg has been studied in amorphous poly(ethylene terephthalate) samples. The temperature Tα depends fundamentally on the polarization temperature Tp, the polarization time tp, and the heating rate v. For each heating rate a maximum Tα, TM, was obtained for an optimum polarization temperature Tpo. The value of Tpo is 70°C, independent of the heating rate, and very close to the glass transition temperature obtained by differential scanning calorimetry (69°C). The resulting value for TM coincides with Tpo in the limits of null heating rate and null isothermal polarization time, and, consequently, TM gives the value of the glass transition temperature for each heating rate as a function of the isothermal dipolar contribution on polarizing at the temperature Tpo. 相似文献
3.
The new technique of contact etching has been utilized to study the bulk morphology of polyethylene terephthalate by the echant, n-propylamine. A variety of films and fibers with different mechanical and thermal histories have been subjected to contact etching. The sample surfaces have been studied principally by scanning electron microscopy. A network superstructure with its characteristic dimension (thickness) of from 700 to 3000 Å, depending on sample history, has been observed. In the oriented samples the network superstructure aligns perpendicular to the direction of sample orientation. A simple model is proposed to describe the network superstructure which is believed to be moderately crystalline. 相似文献
4.
R. Mishra S. P. Tripathy K. K. Dwivedi D. T. Khathing S. Ghosh M. Müller 《辐射效应与固体损伤》2013,168(3):257-269
Abstract The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. Oxidative degradation leading to amorphisation of the polymer has been observed from spectral analysis. The thermal stability of the polymer was found to decrease due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated PET was found to be decreased due to electron bombardment. A decrease in crystallinity of the polymer has also been observed after irradiation. 相似文献
5.
Structural changes in glassy poly(ethylene terephtbalate) and their effects on its crystallization, melting, and various properties were studied. Quenched, annealed below Tg, crystallized, and drawn samples were studied using calorimetry, wide-and small-angle X-ray diffraction, mechanical spectroscopy, and stress-strain analysis. All results indicate some level of order in the glassy polymer which can be increased by annealing below Tg. This order still exists at tempertures above Tg and affects the properties of the polymer. 相似文献
6.
Li-Chen Hsu 《Journal of Macromolecular Science: Physics》2013,52(4):801-813
Poly(ethylene terephthalate) of number-average molecular weight of the order of 120,000 was prepared from commercial-grade material in the solid state with a gas chromatograph apparatus. Parameters studied were the catalyst, particle size, the molecular weight of the starting material, the reaction temperature and time, and the nature and flow rate of the carrier gas. 相似文献
7.
Alvarez C Nogales A García-Gutiérrez MC Sanz A Denchev Z Funari SS Bruix M Ezquerra TA 《The European physical journal. E, Soft matter》2005,18(4):459-465
The isothermal cold crystallization of poly(ethylene terephthalate)(PET) in
cryogenic mechanical alloyed blends of PET and Poly(ethylene naphthalene
2,6-dicarboxilate)(PEN) 1:1 by weight has been investigated by simultaneous
small and wide angle X-ray scattering (SAXS and WAXS) and dielectric
spectroscopy (DS). For transesterification levels higher than 23% the
blends tend to transform into a one-phase system and the crystallization of
PET is strongly inhibited due to the significant reduction of the PET
segment length. For lower levels of transesterification the blends are phase
separated and the overall crystallization behaviour can be explained
considering the confined nature of the PET domains in these blends. The
formation of a rigid amorphous phase in the intra-lamellar stack amorphous
regions is reduced in the blends due to a lower probability of stack
formation in the confined PET-rich domains. The more effective filling of
the space by the lamellar crystals in the blends provokes a stronger
restriction to the amorphous phase mobility of PET in the blends than in
pure PET. 相似文献
8.
Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy). 相似文献
9.
P. Slepi?ka A. ChaloupkaP. Sajdl J. HeitzV. Hnatowicz V. Švor?ík 《Applied Surface Science》2011,257(14):6021-6025
Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene terephthalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157 nm laser. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentration in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser. 相似文献
10.
Shaul M. Aharoni 《Journal of Macromolecular Science: Physics》2013,52(5-6):813-859
When mixtures of poly(ester carbonate) (PEC) and poly(ethylene terephthalate) (PET) containing up to two-thirds of the latter are melt extruded, they produce a single-phase amorphous “alloy.” This alloy is characterized by a sharp, single, composition-dependent glass transition temperature, Tg. When annealed below Tg, the alloy remains unaltered, but when annealed above its Tg, the alloy separates into minute pure-PET crystallites and an amorphous PEC/PET phase. The thermal and dynamic mechanical behavior, crystallization kinetics, and SAXS patterns all strongly suggest the PEC-rich alloys to be solid solutions in which the PET molecules are dispersed individually or in small aggregates containing only a few PET molecules each. Calculations of the interaction parameter and assumed interfacial layer thickness tend to support this suggestion. Use of appropriate solvents allows one to selectively dissolve the PEC and recover from the alloys both PET and PEC in the original purity and molecular weights. Diffusion constants of PET molecules through the amorphous alloys were obtained from studies of PET crystallization above Tg of the alloys. The magnitude of the constants are in the range of expectation. The mechanical properties of the amorphous alloys in the glassy state do not deviate greatly from simple additivity of the respective properties of the parent polymers. However, the melt viscosity of the PEC-rich alloys and their plateau modulus above T show drastic decreases from straight additivity. A qualitative, but not quantitative, explanation of these observations is offered. 相似文献
11.
Mutsumasa Kyotani Wiwik Pudjiastuti Akhtar Saeed 《Journal of Macromolecular Science: Physics》2013,52(3):197-215
Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and 1H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content. 相似文献
12.
A. S. Smolyanskii I. P. Shelukhov E. R. Klinshpont G. S. Zhdanov P. Yu. Apel A. Yu. Didyk V. K. Milinchuk 《Radiation measurements》1995,25(1-4):115-116
Low-temperature (77–300 K) RadioThermoLuminescence (RTL) investigations of Poly(Tetra FluoroEthylene) (PTFE) and Poly(Ethylene TerePhthalate) (PET) foils previously treated by different flux (Φ = 106–1011 cm−2) of Xenon ions with energy 1.1 MeV/nucleon have been showed an essential ion-induced changes in RTL of the both polymers under study. In PET as well as in PTFE significant changes of RTL light yield observed at the ion flux more than 109 cm−2. Variation of RTL light yield in PTFE accompanied by appearance of new TL temperature maxima on the glow curve. An existence of correlation between observed changes of molecular mobility in ion-irradiated polymer and optical (PET) and strength (PTFE) properties have been found. 相似文献
13.
Monika Konieczna Aneta Woźniak-Braszak Krystyna Hołderna-Natkaniec Jan Jurga 《Central European Journal of Physics》2011,9(2):466-471
The relaxation processes and the properties of polymer/ceramic nanocomposites have been studied by the 1H nuclear magnetic resonance methods. Nanocomposites of poly(ethylene terephthalate) PET and poly(phenylene sulfide) PPS with
0.25, 2.5 and 5% wt. barium titanate BT were prepared using a twin screw extruder and injection moulding machine. The spin-lattice
relaxation time T1, second moment M2 and the motional parameters as e.g. the activation energies in the nanocomposites were investigated. 相似文献
14.
《Physics letters. A》1997,235(5):557-561
Positron spectroscopy was used to study the free volume properties of glassy poly(ethylene terephthalate) as a function of temperature and aging time. The experimental results indicate that the glass transition temperature increases with increasing aging time. This is confirmed by differential scanning calorimetry measurements. From the aging time dependence of the intensity of the ortho-positronium (o-Ps) component I3 and the fractional free volume, we observe that the concentration of free volume holes and the fractional free volume show a continuous decrease at a fixed aging temperature, which suggests that structural relaxation and segmental rearrangement occur during physical aging. 相似文献
15.
Poly (ethylene terephthalate) (PET) is available worldwide and has a broad range of applications. However, its basic properties as a scintillation material that is undoped with fluorescent guest molecules are not completely known. Here, we optically characterise undoped PET for use in radiation detection. Light absorption is primarily below 350 nm, with an emission maximum at 385 nm. An effective refractive index, determined from the emission spectrum and the wavelength dependence of the refractive index, is 1.62, which is greater than that for the sodium D line (ND = 1.57). The density of PET is 1.33 g/cm3, and its stopping power for 1-MeV electrons is 1.72 MeV cm2/g. Distinct peaks generated by alpha particles from 210Pb and 241Am radioactive sources appear in PET light-yield distributions. The PET response to 5-6-MeV alpha particles is approximately one-eighth that for electrons. These results demonstrate that undoped PET has special attributes for alpha particle detection. This knowledge will enable better performance of radiation equipment based on PET and its blends with other aromatic ring polymers. 相似文献
16.
17.
Cold plasma-induced modification of the dyeing properties of poly(ethylene terephthalate) fibers 总被引:1,自引:0,他引:1
Antonino Raffaele-Addamo Ruggero Barni Francesco Orsini Laura Meda Bruno Marcandalli 《Applied Surface Science》2006,252(6):2265-2275
Surface modification of poly(ethylene terephthalate) (PET) fabrics induced by air radiofrequency (RF) plasma treatment has been investigated systematically as a function of plasma device parameters, to identify the plasma-polymer surface interactions prevailing under different operating conditions and leading to an increased color depth upon dyeing. Some tests have also been performed employing chemically inert argon as a feedstock gas. The dyeing properties of plasma-treated fibers were correlated to their topographical characteristics, determined by AFM analysis, and to their chemical surface composition, determined by XPS analysis, while the plasma-originated UV radiation was found to have no relevant effects in PET surface modification. The relative importance of plasma-induced surface processes, such as etching and grafting of polar species, is discussed in relation to their role in modifying PET dyeing properties. 相似文献
18.
The moisture barrier property of AlxOy coated poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and poly(carbonate) (PC), have been investigated. The differences in the morphology of the AlxOy sputtered grown on these substrate were investigated using atomic force microscopy (AFM). The initial growth of the AlxOy followed closely the topology of the substrate and an amplified roughness was observed. In the fully grown AlxOy, the comparative roughness followed that of the substrates. It has been found that a single layer AlxOy improved the moisture barrier of PET by an order of magnitude, PC by two orders of magnitude while no improvement was observed for PEN. UV-ozone treatment on PC further improved the moisture barrier, while no improvement was observed for PET and PEN. The comparative effects of the substrate surface roughness and surface energy on the moisture barrier are discussed. 相似文献
19.
G. Gorrasi L. Incarnato L. Di Maio D. Acierno V. Vittoria 《Journal of Macromolecular Science: Physics》2013,52(5):643-653
The transport properties of incompatible blends of poly(ethylene terephthalate) (PET) and a thermotropic liquid crystalline polymer (TLCP) composed of 40 mol% of PET and 60 mol% of p-hydroxybenzoic acid (Rodrun 3000) have been investigated using dichloromethane as permeant. Films, obtained by a blown film extrusion process, were analyzed and compared with the same samples stored 2 and 15 days at 60°C. With respect to the as-blown films, blends submitted to physical aging show a decrease in permeability by a percentage that increases with the amount of the LC phase present and a larger contribution derived from the polymeric matrix. The decrease of permeability is essentially attributed to a lowering of sorption because diffusional behavior for the different samples is the same. 相似文献
20.
E. Sacher 《Journal of Macromolecular Science: Physics》2013,52(4):739-743
Although the glass transition relaxation process is regarded as involving gross chain motions, the local mode [l] process is generally viewed a s involving independent motions of groups within a repeat unit [2,3]. The purpose of this note is to present an alternative model-in the case of poly(ethy1ene terephthalate), experimental evidence indicates that the local mode process involves the cooperative motions of several repeat units. 相似文献