Ethylene Vinyl Acetate Films Research Articles

Energy Efficiency Improvement of Vanadium Redox Flow Battery by Integrating Electrode and Bipolar Plate

An integral electrode-bipolar plate assembly, which is composed of electrode, conductive adhesive film (CAF) and bipolar plate, has been developed and evaluated for application with a vanadium redox flow battery (VRB) to decrease contact resistance between electrode and bipolar plate. The CAF, made of EVA (ethylene-vinyl-acetate) material with carbon black or CNT (Carbon Nano Tube), is applied between the electrode and the bipolar plate to enable an integral assembly by adhesion. In order to evaluate the integral assembly of VRB by adhesive film, the resistivity of integral assembly and the performance of single cell were investigated. Thus, it was verified that the integral assembly is applicable to redox flow battery. Through resistance and contact resistance of bare EVA and CAF films on bipolar plate were changed. Among the adhesive films, CAF film coated with carbon black showed the lowest value in through resistance, and CAF film coated with CNT showed the lowest value in contact resistance, respectively. The efficiency of VRB single cell was improved by applying CAF films coated with carbon black and CNT, resulting in the reduced overvoltage in charging process. Therefore, the energy efficiency of both CAF films, about 84%, were improved than that of blank cell, about 79.5 % under current density at 40 mA cm−2. The energy efficiency of the two cells were similar, but carbon black coated CAF improved the coulomb efficiency and CNT coated CAF improved the voltage efficiency, respectively.

Risk Assessment of Agricultural Plastic Films Based on Release Kinetics of Phthalate Acid Esters.

Plastic films have become an integral part of fruit and vegetable production systems, but their release of phthalate acid esters (PAEs) is a threat to human health. The release kinetics of PAEs and measures of risk are still not well understood. We investigated 50 agricultural films, with concentrations ranging from 2.59 to 282,000 mg kg-1. The seven commercially available film types included were polyvinylchloride (PVC), metallocene polyethylene (mPE), ethylene vinyl acetate (EVA), polyolefin (PO), and three mulch films. Bis(2-ethylhexyl) phthalate (DEHP) was detected in most of films, and its release fitted well into the first-order kinetic model. The release rate of DEHP was negatively related to the film thickness. The potential carcinogenic risks of DEHP in the air of six kinds of plastic greenhouses to human health were estimated. We found that the carcinogenic risks associated with PVC and mPE greenhouse films warrant greater attention. Though EVA, PO greenhouse, and mulch films were lower risk, we advise keeping plastic greenhouses well ventilated during the first month of use to reduce direct human exposure to volatile PAEs.

Preparation and characterization of ultra-lightweight fly ash-based cement foams incorporating ethylene-vinyl acetate emulsion and waste-derived C-S-H seeds

Recycling of accumulated fly ash (FA) from the coal-burning power plant positively avoids the severe environment problems. Also, to achieve the energy-savings in building facades, the excellent fire-resistant and heat-insulating high-porosity fly ash-based foamed cement (ULFC) with dry density less than 160 kg/m3, was formulated in this work. Ethylene-vinyl acetate (EVA) emulsion was introduced into ULFC slurry, and a lab-made hardening accelerator named A-3 and waste-derived calcium silicate hydrate (C-S-H) seeds from the discarded cement foams were also developed and mixed to regulate the early hydration rate of this green FA-based binder incorporating FA up to 50 wt%. Results revealed that under the optimum preparation parameters, the dry density, compressive strength and heat conductivity of ULFC at 28 days can approach to 154.7 kg/m3, 0.47 MPa and 0.0514 W/(m·K), respectively. Morphological analysis elucidated that the polymeric EVA film solidified at the gas–solid interface and well-interwined with hardened cement stone to improve the compressive strength when the specimens was cured at a relative humility of 60–65%. Moreover, the foam stability of ULFC was promoted by the increased bubble confinement force with an incremental content of EVA. Also, an optimized air-void structure was observed in the sample containing synthetic C-S-H from X-CT due to its nucleation effect on the hydration of cement particles. From the energy consumption analysis in practical application, more than 50% energy consumed for heat supply was conserved in ULFC-embedded exterior wall.

A novel tool for assessing microbiomes in cultural heritage documents

This mini-review reports a novel way for exploring the world Cultural Heritage, in the absence of damage or contamination of the items under investigation, called the EVA technique. It is based on films of ethylene vinyl acetate (EVA) impregnated with strong anion and cation exchangers and hydrophobic resins, C8 and C18. When in contact with any surface these films can harvest nano-moles of macromolecules as well as metabolites, which can then be identified by standard instrumentation (e.g. mass spectrometry). Some applications related to microbial contaminations are reported, such as the findings of Koch bacterium in Chekhov’s shirt and in a letter by Orwell to a Russian journal editor as well as the Y. pestis and anthrax bacteria in the death registries of Milan’s lazaretto in the 1630 plague bout. Novel findings are offered too, such as the identifications of three different strains of Aspergillus in the Aleppo Codex and the detection of melanin (produced by A. niger) in the Dead Sea Scrolls. It is hoped that the present methodology could open the doors of museums, state archives and private collections for detecting biological traces left by artists, literates and men of culture in their masterpieces.

Silver nanowire loaded self-healing EVA films

In this study, ethylene vinyl acetate (EVA) transparent nanocomposite films, which heal easily with the inclusion of a low amount of silver nanowire (AgNw), were produced. For this purpose, first AgNw was homogeneously dispersed in the polymer solution and then, nanocomposite films were produced from the solutions by casting method. The thermal, mechanical and optical properties of the produced films were characterized. Self-healing properties of nanocomposite films were confirmed by optical microscopy and mechanical tests. Optical microscope results showed that the optimum recovery temperature was 130°C and the addition of a small amount (5% w/w) of AgNw reduced the recovery time of the scratch on EVA film reducing the healing time by 66.66% (from 15 minutes to 5 minutes). In addition, tensile test results supported the optical microscope results. DSC results showed that the regular crystal regions were formed in composite films due to the high thermal conductivity and nucleating agent effect of AgNw. On the other hand, DSC curves proved that the healing process was occurred via re-entanglement of the polymer chains by heat effect, while silver nanowire addition did not affect the mechanical strength and transparency of the films, significantly. AgNw-loaded-EVA-based self-healing transparent films can be used for applications such as tempered glass laminates, electrical cables, coatings, packages, especially to protect the product and reduce the cost of repair.

Luminescent down-shifting natural dyes to enhance photovoltaic efficiency of multicrystalline silicon solar module

The short wavelength photons (below 500 nm) of the solar spectrum are under-utilized in multicrystalline silicon (mc-Si) solar modules because of their high surface recombination losses. The application of luminescent down-shifting (LDS) materials is an effective way to utilize the short wavelength photons to enhance the efficiency of a mc-Si solar module. This study utilized four ‘natural’ dyes extracted from the wheat husk, rice husk, turmeric rhizomes (Curcuma longa L.), and Moringa Oleifera leaves for LDS application. These natural dyes showed absorption in the UV and blue range, and emission in the visible range which is effectively utilized by the silicon solar cell. Optimum concentrations of the natural dyes were incorporated in the front ethylene vinyl acetate (EVA) layers which were used to encapsulate bare Si cells into photovoltaic (PV) modules. The mc-Si PV modules which had the front encapsulation of EVA films containing the turmeric and moringa dyes showed relative enhancement of ~ 6.8% (±3.6) and ~ 9% (±4) respectively, in their efficiencies with respect to that of the corresponding bare silicon cells. The gains in the photovoltaic efficiency obtained with the turmeric and moringa dyes were found to be comparable to (or slightly greater than) the values reported in the literature using various Eu3+ based lanthanide complexes as LDS materials. Finally, the inclusion of natural LDS dyes in the encapsulating EVA layer would offer an economical and pro-environmental solution at high volume manufacturing to improve the utilization of short-wavelength photons.

EVA Technology and Proteomics: A Two-Pronged Attack on Cultural Heritage.

A novel way for exploring the world's cultural heritage in the absence of damage or contamination (such as removing pigments in paintings or chipping away pieces of bones) of the items under investigation is here reported, called the EVA technique. It is based on films of ethylene vinyl acetate (EVA) impregnated with strong anion and cation exchangers, admixed with hydrophobic resins, C8 and C18. When in contact with any surface these films can harvest nanomoles of macromolecules (proteins and DNA) as well as metabolites, which can then be identified by standard instrumentation. Some important applications are reported, such as the findings of the renal pathology and assumption of morphine in the original manuscript of Master I Margarita by Bulgakov, the presence of TBC bacterium in Chekhov's shirt and in a letter by Orwell, the Y.pestis and anthrax bacteria in the death registries of Milan's lazaretto in the 1630 plague bout, as well as ample traces of five metals in Kepler's manuscripts, suggesting his potential practice of alchemy. Also, in the pages of the Memoirs of Casanova, although the gonorrhea bacterium could not be found, spots of HgS could be measured, suggesting its use for curing the disease. A family of EVA films is described, enlarging its use to dedicated applications, such as the capture of drugs of abuse in the pages of famous writers and even in the paintings of fauvists. It is hoped that the present methodology could open the doors of museums, state archives, and private collections for detecting biological traces left by artists, literates, and men of culture in their masterpieces.

Early‐stage identification of encapsulants photobleaching and discoloration in crystalline silicon photovoltaic module laminates

AbstractCommercially different variants of ethylene‐vinyl acetate (EVA) encapsulants are available in the photovoltaic (PV) market. Photobleaching and discoloration are the two most commonly observed phenomena, and their initiation may be different for different encapsulants. To investigate the EVA encapsulant photobleaching and discoloration, solar cell laminates having different EVA films (UV‐transparent [T], UV‐cut [C], and combination of the two [TC]) were tested in Xenon test chamber. High temperatures are created in the laminates during the aging tests by using a thick insulation layer behind the backsheet. The UV fluorescence images and grayscale profile show clear signs of photobleaching and discoloration. It is found that the oxygen diffusion coefficient of the T sample is four and nine times slower than the TC and C samples, respectively, in the photobleached region. Fluorescence imaging and spectra and Raman spectra were taken before and after the accelerated test and indicate that discoloration causing fluorophores generation is higher after the photobleached region for transparent and combined EVAs, whereas higher at the center for UV‐cut EVA laminates. A colorimeter was used to measure the Yellowness Index of the samples before and after the accelerated aging test. This work will help in the early detection of photobleaching and discoloration of any encapsulant used in the PV modules. This method will also help to study the behavior of encapsulants in different climatic conditions like hot, cold, dry, humid, and their combinations by simulating the same in an accelerated weathering chamber by using the different insulation thickness.

Influence of Fragment Size on the Time and Temperature of Ethylene Vinyl Acetate Lamination Decomposition in the Photovoltaic Module Recycling Process

Photovoltaics is a commercially available and reliable technology with significant potential for long-term growth in nearly all global regions. Several research institutes and companies are working on recycling concepts for thin film modules and modules with crystalline cells. The establishment of recycling and reuse technologies appropriate and applicable to all photovoltaics (PV) modules is a key issue to be addressed as part of corporate social responsibility to safeguard the environment and to implement a fully material-circulated society without any waste. The copolymer ethylene-vinyl acetate (EVA) layer is a thermoplastic containing cross-linkable ethylene vinyl acetate, which is used to encapsulate the photovoltaic cells. The cells are laminated between films of EVA in a vacuum, under compression, and up to 150·°C. The encapsulant’s primary purpose is to bond or laminate the multiple layers of the module together. In the photovoltaic module recycling process, the second important step (after mechanical dismantling of the frame) is EVA lamination removal. In this study, different parameters of the thermal delamination method used during the recycling process were experimentally tested and compared, and the most ecological and economical one is proposed.

Mechanical, rheological and oxygen barrier properties of ethylene vinyl acetate/diamond nanocomposites for packaging applications

In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field emission scanning electron microscopy, contact angel measurement, rheometric mechanical spectroscopy, tensile test, differential scanning calorimetry, and thermogravimetric analysis were employed. The result showed a more uniform dispersion of modified NDs in the EVA matrix. Also, the oxygen permeability rate of EVA films in the presence of NDs was reduced remarkably. Furthermore, the mechanical characteristic and thermal stability of the EVA matrix were enhanced significantly in the presence of the modified NDs and the EVA/NDs nanocomposite films have this capability to use for the packaging applications.

Effect of vinyl acetate content on the photovoltaic‐encapsulation performance of ethylene vinyl acetate under accelerated ultra‐violet aging

ABSTRACTThe vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 °C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra‐red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48268.

Effect of Strain Rate on the Tensile Performance of Nonwoven EVA/Aramid Composite Fabrics

The present research work investigates the effect of strain rate on the tensile response of rectangular strips made of nonwoven ethylene-vinyl acetate (EVA)/aramid composite fabrics. The strips were manufactured in four layers with stacking sequence of different fiber angles, sandwiched between two EVA films. The performance of these composite fabrics was studied by means of tensile testing conducted at various loading speeds and different positioning angles of 0° and 45° to determine the effect of strain rate in real-life operating conditions. The fabrics demonstrate strain rate sensitivity in positioning angle 0° has decreasing performance with increasing test speed due to a progressively growing triggering mechanism affecting the material stretching. On the other hand, the fabrics exhibit consistency in their performance in positioning angle 45 due to their nonwoven nature which allows for frictionless yarn-to-yarn rotation.

The Influence of the EVA Film Aging on the Degradation Behavior of PV Modules Under High Voltage Bias in Wet Conditions Followed by Electroluminescence

The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p -type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, Vbias = +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.

Fabrication and performance investigation of the EVA/Ag coated hollow fiber

Ethylene-vinyl acetate (EVA) copolymer was adopted as the dielectric material to fabricate the dielectric/silver coated hollow fiber (HF) with a dynamic liquid-phase coating method. The corresponding EVA film thicknesses of the EVA/silver coated HFs fabricated with different coating velocities and concentrations of EVA solution were obtained by analyzing the measured loss spectra with theoretical calculations. The relationship between the thickness of EVA film and the fabrication parameters was concluded as a reference for the design and fabrication of such kind of HF. The material dispersion property of the EVA film coated inside the HF was also evaluated. Under the optimum fabrication condition we suggested, the EVA film showed high quality in smoothness and uniformity.

Measurement and modelling of water ingress into double‐glass photovoltaic modules

AbstractPolymer encapsulants are an essential component in photovoltaic (PV) devices, providing mechanical support, optical coupling, and electrical and physical isolation. However, moisture ingress into the module can degrade these polymers and subsequently the performance of the device. In this paper, we report experimental measurements of the temporal evolution of moisture content in ethylene‐vinyl acetate (EVA) encapsulant in a double‐glass PV module. Using physical properties of EVA as determined by water vapour transmission rate measurements, we simulate diffusion of water into the module using a finite element model. The model accounts for realistic geometry of our module and is used to simulate accelerated test conditions and outdoor operation in geographic locations. Using the calculated results, we propose two schemes using the accelerated test results to understand the behaviour of modules operating in humid climates. Finally, we show that the time needed to reach the saturation water concentration can be increased by as much as a factor of two by reducing the initial water content in EVA films.

Analysis of Mechanical and Thermal behaviors for Cross linked Ethylene Vinyl Acetate (EVA) Protective film employed for PV cells

Ethylene Vinyl Acetate (EVA) is typically being utilized as a protective film for photovoltaic (PV) cells. The cross linked EVA film is subjected to intense environmental conditions during their total life time. Which tends to affect the PV reliability. It is imperative to examine the mechanical and thermal properties to understand its fatigue and creep behaviors. In this study, the mechanical and thermal properties are evaluated for determining its reliability when EVA is crass-linked (VA 40%). The critical issue pertaining to PV module is the need for improvement in its life time with the proper choice of materials and its components. Thermal and mechanical analysis using DSC & DMA for cross-linked EVA is performed and the results are elucidated.

Preparation, characterization and application of EVA film containing Eu3+ complex with 1-tridecanecarboxylic acid ligand

In this study, on the basis of complex Eu(DBM)3Phen which was widely applied in polymer matrices, quaternary complex Eu(DBM)2Phen(TA) was synthesized by the introduction of 1-tridecanecarboxylic acid (TA). XRD analyses show that Eu(DBM)2Phen(TA) inclines to amorphization compared with Eu(DBM)3Phen which is crystal. Ethylene-vinyl acetate (EVA) film doped with Eu(DBM)2Phen(TA) was prepared by casting method. SEM and AFM analyses show that the compatibility of Eu(DBM)2Phen(TA) with EVA is better than that of Eu(DBM)3Phen with EVA. Under the same addition amount of Eu3+ complexes, visible light transmittance of Eu(DBM)2Phen(TA)/EVA film is obviously greater than that of Eu(DBM)3Phen/EVA film, and the fluorescence intensity of Eu(DBM)2Phen(TA)/EVA film is only slightly lower than that of Eu(DBM)3Phen/EVA film. With the optimum addition amount of Eu3+ complexes, the energy conversion efficiency of the polycrystalline silicon solar cell coated with Eu(DBM)2Phen(TA)/EVA film is improved to 12.14%, and in comparison, that of the solar cell coated with Eu(DBM)3Phen/EVA film is only 11.98%. Hence Eu(DBM)2Phen(TA)/EVA film has a potential prospect as luminescent down-shifting material.

Efficiency loss of thin film Cu(InxGa1−x)Se(S) solar panels by lamination process

Efficiency loss of thin film Cu(InxGa1−x)Se(S) (CIGS) solar panels by lamination process has been compromising the final output power in commercial products of solar modules, but few reports have been published on such issue, as the majority of the investigation is focused on the efficiency at the circuit level, i.e., before lamination process. In this paper, we studied the effect of lamination process to the efficiency loss of thin film CIGS solar panels. It was observed that the fill factor degradation dominated the efficiency loss with the small change of Voc and Jsc. Experiments showed that neither the temperature nor the pressure, nor the two combined in the lamination process is the root cause of the efficiency loss; instead, the ethylene vinyl acetate (EVA) layer as the encapsulation material which directly contacts the solar cell devices was the major factor responsible for the efficiency loss. It was found that the gel content of the cured EVA film after lamination was highly correlated to the efficiency loss. The higher the gel content, the higher the efficiency loss. The mismatch of coefficient of thermal expansion between the EVA film and the CIGS thin film resulted in compressive stress in the device layer after lamination process. The compressive stress is speculated to affect the lattice defects, but need to be confirmed with the measurement of capacitance voltage (CV) and drive level capacitance profiling (DLCP). Three-day sun soak was then carried out and it was observed that the fill factor recovered significantly and so did the efficiency. Experiments also showed that there was no impact of chemical erosion on the front electrode of transparent conductive oxide (TCO) films by chemicals released from the EVA films during lamination.

Correlation between Numerical and Experimental Tests of Laminated Glass Panels with Visco-elastic Interlayer

Present research is focused on numerical and experimental investigation of glass laminate structure consolidated with ethylene vinyl acetate film. The European wide industry standard for laminate glass panels is considered polyvinyl butyral interlayer film where ethylene vinyl acetate layer is particular out of autoclave manufacturing process related. Conducted numerical and experimental research worldwide rarely consider this type of polymer in lamination process even though in Baltic‘s this is industry standard. So far such glass laminate products are not mechanically characterised to the level that experimental results correlation with numerical predictions to give an engineers required confidence. Therefore current research initially characterise post cured ethylene vinyl acetate film then integration of viscoelastic material properties in numerical four point bending analysis and finally verification with non-contact measurements of natural frequencies to assess mechanical response of laminate glass panels. It was shown that by introducing non-linear viscoelastic behaviour of ethylene vinyl acetate film for depicting mechanical behaviour in 4-point bending the discrepancy between numerical and experimental results was less than 5% whereas assuming the interlayer as isotropic material only obtained discrepancy reached up to 50%.

스프레이코팅법에 의한 패시베이션 박막이 플렉시블 CIGS 태양전지의 특성에 미치는 영향

<TEX>$Cu(In,Ga)Se_2$</TEX> (CIGS) 휨성 태양전지의 셀을 보호하기 위하여 스프레이 코팅방법에 의해 수분과 공기로부터의 보호막을 형성하고 그 전기적, 광학적 특성을 평가하였다. 일반적으로 CIGS 휨성 태양전지의 소자층을 보호하기 위해서 EVA(ethylene-vinyl acetate) 필름을 라미네이션 장비를 통하여 여러 겹 보호막을 형성함으로써 복잡한 공정으로 인해 원가상승의 요인으로서 작용한다. 본 연구는 휨성 CIGS 태양전지의 보호막을 라미네이션 박막공정 대신에 간단한 스프레이 코팅공정을 통한 패시베이션(passivation) 박막층을 형성함으로써 CIGS 태양전지 무게의 경량화와 공정시간 단축 연구를 진행하였다. 패시베이션 박막층으로는 PVA(polyvinyl alcohol), SA(sodium alginate) 물질에 <TEX>$Al_2O_3$</TEX> 나노 입자를 첨가하여 유 무기 복합 용액을 사용하였다. 스프레이 코팅된 소자에 비해 에너지 변환 효율특성 62.891 gm/[<TEX>$m^2-day$</TEX>]의 비교적 양호한 습기 차단 특성을 나타내었다. In order to protect the solar cells from the moisture and oxygen, we evaluated the electrical and optical properties for the <TEX>$Cu(In,Ga)Se_2$</TEX> (CIGS) solar cells which were prepared by the spray coating method. Generally, the EVA (ethylene-vinyl acetate) films are laminated to protect the CIGS flexible solar cells, which results in a high cost process due to complicated devices. In this study, we tried to prepare the protection layers of the flexible CIGS flexible solar cells by using spray coating method instead of conventional laminating films in order to reduce the device weight as well as the process time. The CIGS solar cells with spray coating method showed an enhanced efficiency than the before treated sample (2.77% to 2.93%) and relatively proper water vapor transmission rate of the solar cells about 62.891 gm/[<TEX>$m^2-day$</TEX>].