Ethylene-vinyl Acetate Copolymer Film Research Articles

Creep lifetime of ethylene vinyl acetate co-polymer film after pre-load relaxation

Creep lifetime of ethylene vinyl acetate co-polymer film after pre-load relaxation

Investigation of polysilicon passivated contact's resilience to potential-induced degradation

We present clear evidence of excellent resilience to potential-induced degradation (PID) from polysilicon passivated contacts implemented on the rear of n-type solar cells. Under the stress conditions of −1000 V, 50 °C, 30% relative humidity with aluminum foil, no damage was caused to the passivated contact consisting of an ultrathin silicon oxide (SiOx) film and an n+-doped polysilicon (poly-Si) layer after 168 h. With +1000 V bias and under the same chamber conditions, the SiOx/poly-Si (n+) passivated contact showed a slight change that translated into about 1% module power loss after 168 h, which is significantly lower than the 5% threshold recommended by IEC 62804-1 PID test standard. Furthermore, the SiOx/poly-Si (n+) passivated contact, even when encapsulated with ethylene-vinyl acetate copolymer films having a low volume resistivity in the range of 5 × 1014 Ω⸱cm, exhibited good stability under high-voltage stress. The experimental results were also validated by a generic device simulation, where the SiOx/poly-Si (n+) stack was shown to be immune to the surface polarization effect. In addition, a promising cell-level solution (i.e., using a stack of aluminium oxide and silicon nitride) to the polarization-type PID for n-type passivated emitter rear totally diffused silicon solar cells was also demonstrated.

Nonlinear distortion of AC dissipation current waveform and space charge in EVA film

AC dissipation current waveform shows nonlinear distortion at AC high field, and this nonlinear distortion is supposed to be related to the behavior of space charge under AC field (AC space charge). We investigated the relationship between the nonlinear distortion of AC dissipation current waveform and AC space charge formation in ethylene–vinyl acetate copolymer film (EVA film). At low field, the capacitive current component was subtracted from the output signal of AC current, and then, the AC dissipation current waveform was obtained with the increase of applied AC field. As the result, the AC dissipation current waveform of EVA film showed nonlinear distortion at high field. In addition, the AC dissipation current waveform has a phase advanced from the phase of the applied AC field. The phase advance is considered to be caused by the increase of the capacitive current component due to space charge injection. We suggested that the nonlinear distortion and the phase advance of AC dissipation current waveform of EVA film were affected by the space charge injection. In addition, we developed a new evaluation method of the AC space charge injection layer based on the phase advance and the nonlinear deformation of the AC dissipation current waveform. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Preparation, characterization and properties of partially hydrolyzed ethylene vinyl acetate copolymer films for controlled drug release

In this study, partially hydrolyzed ethylene vinyl acetate (EVA) copolymers with three hydrolysis degrees (12.2%, 32.6% and 46.9%) were obtained by alkaline hydrolysis of EVA copolymer, characterized by Fourier-transform infrared spectroscopy (FTIR), 1H NMR and gel permeation chromatography (GPC). Paclitaxel-loaded and drug-free films based on the partially hydrolyzed EVA copolymers were fabricated. The swelling behaviors, crystallinities, mechanical properties of the fabricated films were investigated, and the effects of hydrolysis degree, film thickness and drug loading dose on in vitro drug release from the films were also investigated. In vitro swelling study showed that the swelling of partially hydrolyzed EVA films was greater than the EVA film and the film with higher hydrolysis degree swelled more intensively. X-ray diffraction (XRD) results exhibited that the crystallinity of the polymer increased with increasing hydrolysis degree. In paclitaxel-loaded EVA film, a part of paclitaxel was in crystalline form; while in paclitaxel-loaded partially hydrolyzed EVA films, paclitaxel was distributed in amorphous form or molecularly dispersed. In the in vitro drug release test, the film with higher hydrolysis degree and smaller thickness released paclitaxel more quickly. With higher drug loading dose, the drug release rate was larger. The partially hydrolyzed EVA films were applied for drug delivery systems for the first time, and demonstrated to have great capability of controlling drug release thanks to the adjustable hydrolysis degree.

Radiation Effects on Optical Properties of Ethylene Vinyl Acetate Copolymer Films

The optical properties of ethylene vinyl acetate (EVA) film have been studied. The effects of gamma irradiations on the optical spectrum of EVA films have been investigated using spectrophotometric measurements of reflectance and transmittance in the wavelength range 200–1100 nm. The absorption spectra were recorded in the UV–vis region for the unirradiated and irradiated films (from 0 to 50 kGy). Optical constants such as refractive index (n), extinction coefficient (K), and complex dielectric constant have been determined, as well as the optical dispersion parameters and high frequency dielectric constants. A large dependence of the fundamental optical constants on the irradiation dose was noticed. On irradiation, a higher refractive index was obtained as compared with that for unirradiated film. The dispersion parameters, such as E 0 (single‐oscillator energy), E d (dispersive energy), and M −1 and M −3 (moments), are discussed in terms of the single‐oscillator Wemple–DiDomenico model.

Surface photocrosslinking of ethylene-vinyl acetate copolymer films

Surface photocrosslinking of ethylene-vinyl acetate copolymer films

Reference electrode for potentiometric analyses in corrosive media

A new and simple reference electrode has been developed which can be used for electroanalytical measurements in corrosive media. The electrode has proven useful in HF acid solutions, in other systems of extreme pH conditions, in the presence of either oxidizing or reducing agents, and in mixed aqueous–organic media, as well. The electrode is based on a stainless-steel wire immersed in an HCl electrolyte, separated from the sample solution by an ion-exchange membrane. Sulfonated ethylene–vinyl acetate copolymer films, manufactured according to a patented procedure, were used as the membrane. The electroanalytical applications of the electrode are based on its constant potential value of –0.545 V versus SCE [–0.303 V versus standard hydrogen electrode (SHE)], which is maintained over the entire pH range and in a broad temperature domain (from 281 to 344 K), with a temperature coefficient of [(–6.85 ± 0.05)× 10–4 V K–1]. Some of the analytical applications are demonstrated.

Depression of sorption of volatile compounds into EVA film by electron beam irradiation

AbstractDecrease in solubility of volatile compounds (octan‐l‐ol, octanal, ethyl hexanoate, octane and d‐limonene) into a film liner was studied after electron beam irradiation up to 20 Mrad of ethylene vinyl acetate copolymer (EVA) film. The solubility coefficient decreased gradually during ageing despite no change immediately after the irradiation. In all films dosed with 5‐20 Mrad the sorption was depressed about 40% in comparison with the unirradiated one after 4 months. The behaviour was consistent with that of the decay of the radicals in the films. The enthalpy change in sorption (ΔH) was −18.0 kJ mol−1 for 5 Mrad ethylene vinyl acetate copolymer film compared with −48.1 kJ mol−1 for the unirradiated one. In a homologous series, sorption was significantly depressed with increasing carbon chain length of the volatile compound. The specific sorption depression effect was observed for low polarity compounds such as hydrocarbons, aliphatic esters and d‐limonene. The diffusion coefficient of the sorbed compounds increased about 1.6 times after 3 months when irradiated to 20 Mrad.

Effects of the number of carbon atoms of flavor compounds on diffusion, permeation and sorption with polyethylene films.

Sorption, permeation and diffusion of volatile compounds have been studies under a nitrogen stream containing an organic vapor with polyethylene (PE) films with massfraction crystallinity from 0.49 to 0.64 and ethylene vinylacetate copolymer film. The volatile compounds used were n-alkanes, aliphatic ethyl esters, n-aldehydes and n-alcohols containing 4-12 carbon atoms. The semilogarithmic plots of diffusion, permeation, solubility coefficient against the carbon number in any homologous series gave linear relationships up to the compounds with 10 carbon atoms. The slopes of straight lines for sorptions ranged from 0.43 to 0.58. This revealed that the sorption into PE film caused the marked changes in composition of flavor components. Furthermore, the effects of crystallinity and molecular structure of PE on diffusion, permeation and sorption were also discussed.