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One of the hindering issues for the long‐term reliability of the photovoltaic (PV) modules is the degradation of poly(ethylene‐co‐vinyl acetate) (PEVA)—a popular encapsulant material. As a globally accepted practice, PEVA is required to have the vinyl acetate (VA) content between 28–33% by weight for encapsulation application in the PV modules. Recent studies have indicated stability improvements in the bare encapsulant layer when the VA content is reduced up to 18%. However, effect of UV aging on the PEVA films encapsulated using these VA contents have not been studied at the module level. Therefore, in this work, we have fabricated mini‐modules containing PEVA films that contain 18, 24 or 33% VA content and have subsequently been subjected to UV aging (1000 hours at 340 nm wavelength and 65°C). The assessment of the durability at both the mini‐module and materials level has been made using various characterization techniques such as current–voltage characteristics, adhesion strength measurement, fluorescence imaging and spectra, FTIR, Raman spectra, volume resistivity and TGA. ΔYI for the free‐standing films of PEVA18, PEVA24 and PEVA33 after 1000 hours of UV aging was slightly less than the ΔYI values for the corresponding laminated films of PEVAs in mini‐PV modules after similar hours of aging. This work shows for the first time that increasing the VA content in PEVA increases the fluorescence intensity and contour size in the encapsulated polymer after UV aging. FTIR analysis indicates deacetylation of PEVA33 which resulted in discoloration (increased ΔYI) and has adversely affected the adhesion strength and power output after UV aging. Compared to PEVA33, the modules containing PEVA18 and PEVA24 are resilient against UV aging for all the properties. Hence, this study recommends using PEVA with 24% VA content as an encapsulant as it presents best combination of the adhesion strength and the environmental stability. [ABSTRACT FROM AUTHOR]

The characteristics of a poly(ethylene-co-vinyl acetate) (PEVA) film formed by spin coating process and ion beam (IB) irradiation was investigated with irradiation times. A physicochemical analysis was used to analyse the suitability of the PEVA film as a uniform liquid crystal (LC) alignment layer. Atomic force microscopy (AFM) revealed an increased surface roughness after IB irradiation. X-ray photoelectron spectroscopy (XPS) analysis showed IB irradiation broke the polymer branches and increased the oxygen concentration and bonding on the surface. These derived the strong Van der Waals forces and dipole-dipole interactions between the PEVA surface and LCs. The IB irradiation generated surface anisotropy on the PEVA film and unidirectional LC alignment was achieved. Polarised optical microscopy (POM) and pre-tilt angle measurements were carried out to show the uniform LC alignment. The transmittance curve exhibited a high optical performance. These results show the promising capabilities of IB irradiated PEVA film as an alignment layer in LC displays. [ABSTRACT FROM AUTHOR]

• PEVA films of 18, 24, 33 and 40% vinyl acetate content have been prepared and cured. • Films have been accelerated damp-heat aged at 85°C & 85% R.H. for 1000 and 2000 h. • Tensile strength after aging for 18 and 24% VA content was higher than 33 & 40% VA. • Same trend was seen for thermal stability and degree of crosslinking. • Inadequate transmittance after DH aging discourages PEVA18 as an encapsulant. • Better encapsulation response against DH aging may result if VA % is reduced to 24%. The most common encapsulant used in the photovoltaic (PV) modules is poly (ethylene-co-vinyl acetate) (PEVA). The characteristics of PEVA can be varied by modulating its vinyl acetate (VA) content. According to the general consensus within the PV industry, PEVA as an encapsulant should have VA content between 28 and 33%. Degradation of PEVA films due to environmental stressors like humidity, temperature and solar radiation in the field aged modules is not uncommon. Moreover, degradation of PEVA encapsulant implies a concomitant loss in the electrical performance of the PV modules. VA content modulation especially outside the most commonly used and accepted range has been tried in this study to improve the damp heat aging resistance of PEVA films. PEVA films containing 18, 24, 33, and 40% VA content with the necessary additives have been fabricated and cured at 150 °C under vacuum and subsequently subjected to accelerated damp-heat (85°C and 85% RH) aging according to IEC 61215 standard for 1000 and 2000 h. Tensile strength, thermal stability and degree of crosslinking have been found to be greater for PEVA containing lower VA content (18 and 24%) and diminished for PEVA with higher VA content (33 and 40%) due to DH aging. However, inadequate % transmittance and relatively high stiffness after 2000 h of DH aging discourages PEVA18 as an encapsulant. Moreover, PEVAs with higher VA content (33 and 40%) have been degraded significantly after 2000 h of DH aging resulting in significant loss in transmittance and mechanical integrity. Therefore, the results of this investigation encourage the PV industry to reduce the VA content in PEVA down to 24% for better encapsulation response against DH aging. [ABSTRACT FROM AUTHOR]

Partial eigenvalue assignment (PEVA) is a milestone in the field of structural dynamics control, for which the system models based on finite-element analysis have larger dimensions. The solution for PEVA has early seminal contributions, but today, other relevant advances have been offered by researchers in this interdisciplinary field. This work aims to demonstrate the construction of a new method to solve PEVA in linear time-invariant systems to guarantee the regional stability of the reassigned eigenvalues. The theoretical review of PEVA and D -stability are shown to support the development of an algorithm that involves linear matrix inequalities and left-eigenvectors parametrization. To verify the efficiency of the algorithm, tests were performed on numerical examples borrowed from the literature. Furthermore, the solution's quality is illustrated through location plots and eigenvalue comparison tables. [ABSTRACT FROM AUTHOR]

This work describes a novel approach to produce high quality release paper at lower cost than traditional methods. The anti-adhesive properties of release paper require the use of expensive machine glazed kraft or “Glassine” paper as the paper base. A series of polymer coatings including polyvinyl alcohol, carboxymethyl cellulose, polyethylene vinyl acetate, and polystyrene were chemically synthesized and coated onto a low cost pulp paper base. Surface roughness (Sa) and smoothness coefficients (k) were determined by atomic force microscopy (AFM), and the interactions between the polymer coating and base paper were investigated by Raman spectroscopy. Studies show the use of polyethylene vinyl acetate (PEVA) as a pre-coating layer on low cost pulp paper exhibits similar anti-adhesive properties as higher cost paper bases. In low margin markets such as the production of release paper, decreases in cost are critical to industry survival.

The aim of this study was to modify or replace the PEVA foil (polyethylenevinylacetate) currently used in the Czech Army as a construction material for the NBC protective disposable suit JP-90 (a part of the OM-90 protective mask set). This material shows inadequate protective properties; therefore, barrier coatings based on melamine, Parylene (polyparaxylylene) and various types of SiO were applied to its surface by vacuum technologies. The selected samples coated with polymer matrix barrier nanocoatings were continuously evaluated for resistance to permeation by highly toxic chemicals warfare agents (CWAs) and industrial pollutants at the Military Technical Institute of Protection (MTIP) in Brno. In addition, the microstructure of selected samples was assessed before and after the exposure to pollutants. The nanocoatings thus prepared were characterised in terms of surface morphology (SEM), chemical structure (FTIR), and oxygen transmission rate (OTR) at the Faculty of Chemistry, Brno University of Technology. Sulphur mustard (HD) was used to test the sample resistance to permeation. Cyclohexane and subsequently 1,6-dichlorhexane were used as substitute testing substances for HD; however, the latter proved to be more advantageous. The resulting OTR values are presented, along with the permeation by toxic substances, both for the initial uncoated and the barrier-layers-coated PEVA foil. The results show a difference in the mechanism of vapour permeation of CWAs and toxic volatile organic solvents (VOCs). [ABSTRACT FROM AUTHOR]

UC781 is potent, hydrophobic, non-nucleotide reverse transcriptase inhibitor (NNRTI) against the human immunodeficiency virus (HIV). UC781 is currently being investigated for use as a potential HIV microbicide. A study in rhesus macaques demonstrated that a 100-mg UC781-loaded silicone elastomer vaginal ring released limited amounts of UC781 into the vaginal fluid and tissue after 28 days. The reason for this was due to the hydrophobic nature and limited aqueous solubility of UC781. This study describes the manufacture of UC781-loaded polyethylene vinyl acetate (PEVA) vaginal rings, which have an improved in vitro release rate of UC781 when compared to UC781-loaded silicone elastomer vaginal rings. The study demonstrates that the UC781 in the PEVA rings is mostly in its amorphous form due to the rings being manufactured above UC781's melting point. Furthermore, the rings do not show any signs of UC781 degradation, such as the presence of UC22. [ABSTRACT FROM AUTHOR]

The alignment characteristics of liquid crystals (LCs) on poly(ethylene-co-vinyl acetate) (PEVA) films via ion-beam (IB) irradiation at incidence angles of 15°, 45°, or 75° were investigated. Uniform and homogeneous LC alignment were achieved with a PEVA film IB-irradiated at an incidence angle of 45°. Physicochemical modification progressed by IB irradiation were examined by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The AFM results show that the plasma argon ions penetrated and thereby increased the surface roughness and decreased kurtosis of the PEVA. The XPS results suggest that chemical reconstruction of the PEVA film induced the van der Waals forces and dipole-dipole interactions with the LCs. These transformations resulted in uniform LC alignment at 45° IB incident angle, as confirmed by polarized optical microscopy and pre-tilt angle measurements. The 45° incidence-angle IB-irradiated PEVA film also showed high transmittance in the visible light region. A twisted nematic LC cell based-on the PEVA film showed successful electro-optical performance as stable switching behavior and fine operation characteristics. These results indicate that IB irradiation is an effective method for uniform LC alignment and the 45° incidence-angle IB-irradiated PEVA film can be adopted for LC alignment in future LC display applications. • Uniform LC alignment was achieved on PEVA surface via manipulating ion beam irradiation angle. • Physicochemical modifications of the PEVA surface were investigated by AFM and XPS analysis. • Ion beam with 45° incidence induced reinforced and anisotropic surface for uniform LC alignment. • IB irradiated PEVA layer displayed suitable electro-optical performances for TN-LCD system. • IB treated PEVA film is a promising alternative for stable and remarkable LC alignment layers. [ABSTRACT FROM AUTHOR]

This work describes a method for analyzing polymer concentration in solution using density. The method can be applied to any polymer/solvent combination given certain experimental conditions; however, this study is specific to commercial samples of poly (n-butyl methacrylate) (PBMA) or poly (ethylene-co-vinyl acetate) (PEVA), two polymers of interest to Cordis Corporation. The test method was validated with respect to ICH requirements of linearity, accuracy, precision, range, etc.[1,2] The kinetic dissolution of PBMA or PEVA in tetrahydrofuran (THF) was evaluated as a practical analysis of Cordis process parameters. The results are provided as examples of the test method application. [ABSTRACT FROM AUTHOR]

Electrospun fiber mats are explored as drug delivery vehicles using tetracycline hydrochloride as a model drug. The mats were made either from poly(lactic acid) (PLA), poly(ethylene-co-vinyl acetate) (PEVA), or from a 50:50 blend of the two. The fibers were electrospun from chloroform solutions containing a small amount of methanol to solubilize the drug. The release of the tetracycline hydrochloride from these new drug delivery systems was followed by UV–VIS spectroscopy. Release profiles from the electrospun mats were compared to a commercially available drug delivery system, Actisite® (Alza Corporation, Palo Alto, CA), as well as to cast films of the various formulations. [Copyright &y& Elsevier]

• Uniform alignment of liquid crystals on the PEVA surface was achieved by ion beam irradiation. • Physicochemical characteristics of PEVA surface was investigated by AFM and XPS analysis. • Ion beam induced significant chemical modification on the surface for uniform LC alignment. • IB irradiated PEVA film is a promising alternative for stable and remarkable LC alignment layers. The post-processing of a poly(ethylene-co-vinyl acetate) (PEVA) film by ion-beam (IB) irradiation is described herein for use as a liquid crystal (LC) alignment layer. Various film curing temperatures are investigated in order to achieve a stable film prior to IB irradiation, and a uniform and homogeneous LC alignment with superior optical transparency is obtained at a curing temperature of 130 °C. The chemical and morphological effects of IB irradiation are further examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the surface morphology exhibits a random pattern, the IB irradiation is found to modify the chemical characteristics of the PEVA surface by simultaneously inducing van der Waals forces and strong dipole-dipole interactions with the LCs, thus leading to unidirectional LC alignment. In addition, LC cells are fabricated from the IB-irradiated PEVA films, and the LC alignment state is confirmed by polarized optical microscopy and pre-tilt angle measurements. Further, the high transparency of the deposited PEVA film compared to that of ITO-coated glass is demonstrated via transmittance measurement. In view of this superior performance, the IB-irradiated PEVA film is a promising alternative for advanced LC displays. [ABSTRACT FROM AUTHOR]

This work describes a novel approach to produce high quality release paper at lower cost than traditional methods. The anti-adhesive properties of release paper require the use of expensive machine glazed kraft or "Glassine" paper as the paper base. A series of polymer coatings including polyvinyl alcohol, carboxymethyl cellulose, polyethylene vinyl acetate, and polystyrene were chemically synthesized and coated onto a low cost pulp paper base. Surface roughness (Sa) and smoothness coefficients (k) were determined by atomic force microscopy (AFM), and the interactions between the polymer coating and base paper were investigated by Raman spectroscopy. Studies show the use of polyethylene vinyl acetate (PEVA) as a pre-coating layer on low cost pulp paper exhibits similar anti-adhesive properties as higher cost paper bases. In low margin markets such as the production of release paper, decreases in cost are critical to industry survival. [ABSTRACT FROM AUTHOR]

The effect of thermal treatments, on the benzene vapor sensitivity of polyethylene (co-)vinylacetate (PEVA)/graphene nanocomposite threads, used as chemiresistive sensors, was investigated using DC resistance measurements, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). These flexible threads are being developed as low-cost, easy-to-measure chemical sensors that can be incorporated into smart clothing or disposable sensing patches. Chemiresistive threads were solution-cast or extruded from PEVA and <10% graphene nanoplatelets (by mass) in toluene. Threads were annealed at various temperatures and showed up to 2 orders of magnitude decrease in resistance with successive anneals. Threads heated to ≥80 °C showed improved limits of detection, resulting from improved signal-noise, when exposed to benzene vapor in dry air. In addition, annealing increased the speed of response and recovery upon exposure to and removal of benzene vapor. DSC results showed that the presence of graphene raises the freezing point, and may allow greater crystallinity, in the nanocomposite after annealing. SEM images confirm increased surface roughness/area, which may account for the increase response speed after annealing. Benzene vapor detection at 5 ppm is demonstrated with limits of detection estimated to be as low as 1.5 ppm, reflecting an order of magnitude improvement over unannealed threads.