Dielectric and optical properties of a poly(ethylene terephthalate) membrane in the temperature interval 150–400 K

In this study, the dielectric and optical properties of poly(ethylene terephthalate) (PET) membranes were examined. The dielectric measurements were carried out in the temperature interval 150–400 K and in the frequency range 20 Hz–60 kHz. We analyzed in detail the temperature dependences of the dielectric permittivity and dielectric loss (tan δ) at various test frequencies. The relaxation tan δ peak, which appeared in the temperature range 150–300 K, was identified as the secondary β relaxation. The increase in tan δ at temperatures higher than 300 K could be explained as approaching the α relaxation. Optical measurements were performed in the UV–visible region from 200 to 400 nm at various temperatures between 150 and 400 K. The values of the direct and indirect band gaps were calculated at various temperatures. These values were lower for higher temperatures. An absorption peak was observed at a wavelength around of 285 nm at temperatures lower than 300 K. Such insight into the dielectric and optical responses of PET track membranes in a wide temperature range is particularly important when this material is used as a matrix for the semiconductor structure in the development of optoelectronic or microfluid devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42834.     

CdS impregnated cellulose nanocrystals/PVDF composite flexible and freestanding films: Impedance spectroscopic studies

Nanocrystalline CdS impregnated cellulose nanocrystals (CdS‐Cellulose) were embedded in polyvinylidene fluoride (PVDF) matrix and free‐standing flexible films of CdS‐cellulose/PVDF nanocomposite were made by sol‐gel technique. Effect of CdS loadings in cellulose embedded in the host matrix (PVDF) on the impedance properties was studied critically for the above samples. Dielectric constants were studied as a function of frequencies (1–100 kHz) at room temperatures. The dielectric constant increased significantly in CdS‐cellulose/PVDF nanocomposite than that for pristine PVDF film. The higher values of dielectric constant as well as dielectric loss were obtained at lower frequencies. This may be caused due to contributions arising out of space charge, dipole, and electronic polarizations. At higher frequencies, only dipole and electronic polarization were seen to contribute significantly. The nature of the Cole‐Cole plots could be seen to deviate significantly from one impedance semicircular arc before diverging after a frequency of 3,158, 2,147, and 1,925 Hz for CdS‐cellulose/PVDF nanocomposite with increased loading of CdS. POLYM. ENG. SCI., 58:1419–1427, 2018. © 2017 Society of Plastics Engineers     

Wavelet Analysis of Particle Concentration Signals in an Acoustic Bubbling Fluidized Bed

The time series of fluid catalytic cracking (FCC) particle concentrations were measured by an optical fiber probe under conditions of different sound pressure levels and sound frequencies in an acoustic bubbling fluidized bed (? 140 mm × 1600 mm). The results show that the minimum fluidization velocity had a minimum value when the sound wave frequency was 150 Hz. Under the same sound frequency, the fluidization velocity decreased as the sound pressure level increased. The particle concentration signals in an acoustic fluidized bed were also analyzed by means of wavelet analysis. On the basis of discrete wavelet transform, an original signal was resolved into five detailed scale signals. By using wavelet energy analysis, it was found that the peak frequency of the scale 3 or 4 detail wavelet signals represents the bubbling frequency and the peak amplitude for the bubble size. The results indicate that the bubbling frequency and bubble size decreased with increasing sound pressure level at a given frequency. In addition they decreased with increasing sound frequency ranging from 50–150 Hz, but further increased with increasing sound frequency ranging from 150–500 Hz.     

Thickness dependence of ac electrical conductivity and dielectric behavior of plasma polymerized 1, 1, 3, 3–tetramethoxypropane thin films

AC electrical conductivity (σ_ac), dielectric constant (?′), and dielectric loss tangent (tan δ) of plasma polymerized 1, 1, 3, 3‐tetramethoxy‐propane (PPTMP) thin films of thicknesses 100, 150, and 200 nm prepared by plasma polymerization technique using a capacitively coupled glow discharge reactor have been investigated in the frequency range of 30–10⁶ Hz. It is observed that σ_ac increases as frequency increases with a higher slope in the medium frequency (<10⁵Hz) region in the PPTMP thin films of three thicknesses. These observations suggest that the conduction may be dominated by hopping of carriers between the localized states. The general trend of ?′ is to increase with increasing thickness, ?′ remains independent of frequency upto about 10⁴Hz and then falls rapidly. The dependence of tanδ with frequency for PPTMP thin films of different thicknesses showed small relaxation peak at the very low frequencies (<10²Hz) and then it decreases slightly with a broad minimum at 10³ Hz and again increases. Cole–Cole plot reveals that Debye type of mechanism is operative in the experimental frequency range. POLYM. ENG. SCI., 58:1342–1345, 2018. © 2017 Society of Plastics Engineers     

Dielectric and dynamic mechanical measurements of poly(4-methyl pentene-1)

The α-relaxation process of poly(4-methyl pentene-1) was studied by dielectric and dynamic mechanical means. The complex dielectric constant was determined at nine discrete frequencies from 100 to 10,000 Hz and over a temperature range of ?50–90°C. The complex dynamic mechanical Young's modulus was determined over the audiofrequency range of 10–22,000 Hz and a temperature range of 21–76°C, from which a master curve was constructed. The relaxation process was studied by comparing the activation energies and width of the dispersion curves. The results of a logarithmic frequency vs. reciprocal temperature plot of the loss peak maxima show that both the dielectric and mechanical curves are roughly linear but have different slopes. From the slopes the activation energies were determined. For the dielectric data an activation energy of 39 kcal/mol was obtained, whereas for the mechanical data a value of 106 kcal/mol was found. The width of the dispersion curves was determined by using a Cole–Cole empirical fit. The width of the dielectric dispersion curve is narrower by as much as a factor of 3 than the mechanical dispersion curve. It is concluded that the energy to cause the large scale molecular motion involved in the α-relaxation is lower when excited by an alternating electric field than by an alternating stress field. Also the number of repeat units involved is smaller in the dielectric case than in the mechanical case.     

Charge distributions of aerosol dioctyl sebacate particles charged in a dielectric barrier discharger

The collection efficiencies of submicron aerosol particles using a two-stage, dielectric barrier discharge (DBD) type electrostatic precipitator have been reported previously [Byeon et al. (2006). Collection of submicron particles by an electrostatic precipitator using a dielectric barrier discharge. Journal of Aerosol Science, 37, 1618–1628]. In this paper, the charge distributions of aerosol dioctyl sebacate (DOS) particles, which had a mobility equivalent diameter of 118, 175, and 241 nm and were charged in a DBD charger, were examined using a tandem differential mobility analyzer (TDMA) system at applied voltages of 9–11 kV and frequencies of 60–120 Hz. The mean number of elementary charges for positively or negatively charged particles increased slightly with increasing applied voltage or frequency. However, the number of elementary charges increased significantly with increasing particle size. At any applied voltage and frequency, the charge distributions of these particles of these sizes indicated asymmetric bipolar charging. The positive-to-negative charge ratios were 10.4, 4.7, and 3.0 for particle sizes of 118, 175, and 241 nm, respectively, at a DBD voltage and frequency was 9 kV and 60 Hz, respectively. Fluorometric analysis showed that average positive-to-negative charge ratios were 11.5, 4.9, and 3.7 for particle sizes of 118, 175, and 241 nm, which agrees well with the TDMA results. Further fluorometric analyses with larger particles (514 and 710 nm) and higher frequencies (1 and 2 kHz) showed that the positive-to-negative charge ratio reached almost unity with increasing particle size or frequency.     

Light wavelengths of LEDs to improve the color discrimination in Ishihara test and Farnsworth Panel D‐15 test for deutans

This study was performed to determine significant light wavelengths to improve color discrimination ability of subjects with deutan. We conducted both the Ishihara test and the Farnsworth Panel D‐15 test for subjects with deutan and normal color vision. Seven different LED lights from 450 to 660 nm and an additional D65 white lamp were utilized to change the lighting conditions, including the wavelength and intensity. The results of the Ishihara test and D‐15 test showed that color identification of deutans was markedly improved with the longer wavelength LEDs regardless of the intensity of the additional D65 lamp. Notably, the error rates of deutans in the Ishihara test were <25% for LED wavelengths of 630 and 660 nm. In the case of subjects with normal color vision, the D65 lamp abolished the errors in the Ishihara test, regardless of the LED wavelength. Addition of the D65 lamp also decreased the number of crossings in the D‐15 test. These results suggested that illumination by LED light with longer wavelengths, such as 630 and 660 nm, may provide deutans with greater red‐green discrimination ability in both the Ishihara test and the Farnsworth Panel D‐15 test. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 424–430, 2017     

Photodegradation of polymer materials containing flame-cut agents

Photodegradation of incombustible materials [polystyrene (PSt) and polypropyrene (PP) containing 2 wt% of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol-A (TBA) as a flame-cut agent] were studied using Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm, UV-visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA. Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymers containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260–280 and 300 nm for PP or PSt–TBA samples and PP or PSt–DBDE samples, respectively. © 1993 John Wiley & Sons, Inc.     

Photooxidative degradation of polyethylene containing flame retardants by monochromatic light

Photodegradation of incombustible polymer materials [high-density (HD) and low-density (LD) polyethylene (PE) containing 0.5 to 2.0 phr of decabromodiphenyl ether (DBDE) or tetrabromobisphenol A (TBA) as a flame retardant] were studied using an Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm. Ultraviolet and Fourier transform infrared (FTIR) spectra were taken to estimate the chemical changes caused by photoirradiation. Molecular weight change was followed by gel permeation chromatography (GPC) measurements. It was found that the photostability of PE samples was reduced by the addition of flame retardants. The threshold wavelengths of photodegradation are 320 nm and 360 nm for PE–TBA samples and PE–DBDE samples, respectively. Main-chain scission is favored when the irradiation was carried out with the light of wavelength 300 nm for HDPE–DBDE and HDPE–TBA samples. The most effective irradiation wavelengths for crosslinking are found to be 300 nm and 280 nm for LDPE–DBDE and LDPE–TBA samples, respectively. 1995 John Wiley & Sons, Inc.     

Rheological properties of teak wood flour reinforced HDPE and maize starch composites

Teak wood flour reinforced high density polyethylene and maize starch composites were prepared by using maleic anhydride grafted polyethylene as a compatibilizer. The mechanical properties (tensile and flexural) of all the composites increased after addition of 10%–40% teak wood flour into HDPE matrix. The complex viscosity (η*) was higher for all the composites at the low frequency, but decreased with increasing frequencies indicating a shear thinning behavior of the composites. The storage modulus and loss modulus increased for the composites compared to the HDPE at low frequencies. Damping factor peak of HDPE and composites showed high below 1 Hz, but the peak start decreasing with increasing above 1 Hz. The relaxation behavior of HDPE and the composites after incorporating teak wood flour, maize starch, and compatibilizer was obtained by Han plot. Biodegradability was enhanced with the incorporation of teak wood flour, maize starch into the composites. Appreciable water uptake and the thickness swelling for the composites indicating it's potential for interior, automobile and packaging applications.     

Preparation of poly(vinyl alcohol) films with promising physical properties in comparison with commercial polyethylene film

Poly(vinyl alcohol) (PVA) films with different thicknesses (0.08, 0.2, 0.23, 0.42 mm) were prepared by a casting technique. The transmission and the absorption of the PVA films were measured as functions of the wavelengths. PVA film with a thickness of 0.42 mm showed zero transmission in the wavelength range of 190–350 nm. The transmission spectrum of a commercial polyethylene film with a thickness of 0.21 mm was compared to the transmission spectrum of PVA film with a thickness of 0.42 mm. A correlation was found between the two transmission spectra in the region 190–350 nm and a 20% increase in the transmission of the PVA film in comparison with the transmission of commercial polyethylene in the region 350–1500 nm. The near‐infrared region of the transmission of commercial polyethylene was increased by 15% with respect to the transmission of the PVA film. The stress–strain measurements were done for PVA and commercial polyethylene films. The Young's modulus and the strength at break for PVA films are higher by two orders of magnitude than those for commercial polyethylene film. The strain at break for commercial polyethylene is 17% lower than that for PVA film. Radiation effects on the optical properties of PVA and commercial polyethylene films were investigated. The PVA and commercial polyethylene films were irradiated with a xeon arc lamp at 3.5–5 W/cm². The optical properties for PVA and commercial polyethylene films were studied after irradiation. The obtained results showed that PVA film with a thickness of 0.42 mm gave promising properties which could be used in technological applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1219–1226, 2002     

Glycidyl methacrylate as a new host material for laser dyes

This article reports on the laser action of pyrromethene 597 and pyrromethene 567 doped in the novel solid polymeric matrix glycidyl methacrylate. Mirrorless lasing was observed when samples with diameters of 10 mm and lengths of 20 mm, with different dyes concentrations, were transversely pumped at 532 nm. The influence of the dye concentration on the laser measurements included the peak wavelengths, output energies, conversion efficiencies, and laser gains. Relatively high lasing efficiencies (up to ～ 60%) were obtained from these new polymeric materials with very good photostability, where a decrease of only 65% in the initial laser output energy was observed after pumping by 60,000 shots of 15 mJ at 10 Hz. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 59–63, 2007     

超细颗粒在声场流化床中的流化特性

在内径为130mm的声场流化床中,以原生纳米级SiO2超细颗粒为物料,在声压水平为0～140dB、声波频率为0～500Hz范围内系统地考察了声波对超细颗粒流化特性的影响。结果表明：当声波频率为100～150Hz、声压大于130dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,显著地改善纳米SiO2颗粒的流化质量。在频率一定的情况下,声压越高,超细颗粒的临界流化速度越低,流化质量越好。当频率低于100Hz或高于150Hz时,随着频率的进一步降低或增加,超细颗粒的临界流化速度都增大,甚至又出现节涌和沟流。声波的效果减弱甚至消失。     

Effects of ultrasonic irradiation on the morphology of chemically prepared polyaniline nanofibers

Polyaniline (PANI) nanofibers were chemically prepared through ultrasonic irradiated polymerization with varying ultrasonic power, frequency, and reaction temperature. It was found that PANI nanofibers with smoother surfaces and uniform diameters can be achieved by increasing the ultrasonic power or the reaction temperature in the studied ranges; a higher reaction temperature was also beneficial for producing PANI nanofibers with larger aspect ratios. With the ultrasonic power set to 250 W, although the polymer prepared at higher frequencies showed higher purity as well as smoother surfaces than those at lower frequencies, the one prepared at 50 kHz with uniform diameters of about 80 nm and lengths of about 700 nm performed best. With the ultrasonic power and frequency fixed and aniline polymerization carried out between 0 and 75°C, PANI nanofibers exhibiting larger aspect ratio and less agglomeration were obtained under a higher reaction temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic mechanical analysis of particulate‐filled epoxy resin

The dynamic mechanical properties of epoxy composites filled with different amounts of quartz powder were investigated. The storage modulus and loss tangent were measured at frequencies between 7.8 and 323 Hz from room temperature up to 460 K. The influence of the filler content on the temperature and frequency behavior of the dynamic mechanical properties is discussed and explained in terms of models presented in the literature. In particular, the dependence of the composite damping with the quartz content is explained with regard to damping due to particle–particle and polymer–particle interaction. Also, the glass‐transition temperature as a function of filler content was obtained and was related to the results obtained for the apparent activation energies of the α relaxation, which were estimated with the Williams, Landel, and Ferry equation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 883–892, 2003     

Large‐field color matching functions

Color‐matching functions (CMFs) were derived with the Maxwell method for 10 subjects using two field conditions: (1) horizontally bisected circular 10° and (2) vertically bisected rectangular 102° (wide) × 50° (high). The primary set was composed of 453–533–601 nm components with a mean full‐width at half maximum of 18.3 nm; the reference field was illuminated with daylight fluorescent lamplight. Field size had a significant effect on the shape of the resulting CMFs. Under the large‐field conditions subjects were less sensitive to shorter wavelengths as characterized with the b? function and had higher sensitivities to the longer wavelengths as characterized with the r? function. © 2005 Wiley Periodicals, Inc. Col Res Appl, 31, 18–29, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20170     

Effects of frequency on electrical fatigue behavior of ZnO-modified Pb(Mg1/3Nb2/3)0.65Ti0.35O3 ceramics

This work aims to study the effects of frequency on the electrical fatigue behavior of ZnO-modified Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ (PMNT) ceramics. Changes in microstructures, ferroelectric and piezoelectric properties of the ceramics at bipolar electrical fatigue frequencies of 5, 10, 50 and 100 Hz were observed. The thickness of damaged surface of the ceramics decreased with increasing frequency. The degradation of properties of the ceramics fatigued at low frequency was greater than those fatigued at high frequency. The degradation by electrical fatigue at lower frequencies, 5 and 10 Hz, could be caused by the effects of both field screening and domain pinning, while at higher frequencies the fatigue was mainly a result of the field screening effect. The fatigue properties of ZnO-modified PMNT ceramics was compared to Pb-based and Pb-free ferroelectric ceramics. It was found that the fatigue endurance of ZnO-modified PMNT ceramic was greater than that of hard PZT ceramic but less than that of Pb-free ferroelectric ceramic.     

Applications of wittig reactions in dibenzo 18‐crown‐6‐ether substituted phenylenevinylene oligomer—synthesis,photo luminescent,and dielectric properties

Novel phenylenevinylene oligomer substituted dibenzo 18‐crown‐6 ether ring (DB‐OPV) was synthesized using dibenzo 18‐crown‐6 with terephthaldicarboxaldehyde via Wittig reaction. Formation of the oligomer was confirmed by spectral (FT‐IR, ¹H and¹³C‐NMR), gel‐permeation chromatography and elemental analysis. The morphology of the oligomer film of one‐dimensional and three‐dimensional architectures was observed using atomic force microscopy. The oligomer showed excellent photoluminescence with bluish green emission maxima at shorter wavelengths of 505 nm. Stability of the oligomer was analyzed using UV spectroscopy with varying time and temperature. The dielectric properties such as dielectric constant and loss factor for the oligomer have also been studied with respect to change of frequency (50 Hz–5 MHz) and temperature (30–60°C). The value of dielectric constant decreased with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. The value of dielectric constant increased with increasing temperature which is due to greater freedom of movement of the dipole molecular chains within the oligomer at high temperature © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

双组分颗粒声场流态化的实验研究

在内径为56 mm的玻璃声场流化床中,以5~10 nm未改性和有机改性的SiO2为实验物料主体颗粒,Fe3O4(粒径小于0.053 mm)为客体颗粒,在声压级为90~105 dB时系统考察了声场频率、声场强度和主客体颗粒不同配比关系对超细颗粒流化行为和聚团尺寸的影响。结果表明,当声场频率处于50 Hz,声压级大于100 dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,减小聚团尺寸,显著改善超细颗粒的流化质量。声场频率一定,声场强度越大,颗粒团聚体的直径越小。客体颗粒的添加比例存在一适宜范围。     

Colour matching using LEDs as primaries

In our metameric experiment, the colour of a filtered incandescent lamp was matched with the additive mixture of three LEDs in a Lummer–Brodhun‐type visual photometer. Two sets of primaries were used, one had their dominant wavelengths at 467, 533, and 600 nm; the other set had dominant wavelengths at 478, 552, and 635 nm. These values correspond approximately to the characteristic wavelengths of the Prime and Non‐Prime Colour spectral regions defined by W. A. Thornton. 1 Both the light of the incandescent lamp and that of the LED clusters were seen monocularly in a centrally divided bipartite field at a visual angle of 2°. The luminance of the matching fields was in the order of 20 cd/m² to provide sufficient gamut for the LED mixture. Ten young observers with normal colour vision participated in the experiment. The emission spectra of the viewing fields were measured with an array‐type spectroradiometer, and two sets of colour‐matching functions were used to calculate the chromaticity of the matching stimuli: the CIE 1931 standard colorimetric observer and the Judd–Vos modification of the colour‐matching functions. We found that the Judd–Vos modification of the CIE 1931 standard observer represents more accurately the real observers in the evaluation of our results. No systematic differences between the use of the two sets of LEDs were detected in contradiction to Thornton's findings. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 360–364, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20044