Ethylene Vinyl Acetate Samples Research Articles

Enhancing mouthguard longevity: Impact of surface treatment against aging from brushing and disinfectant exposure.

The study aimed to assess the surface characteristics of sports mouthguards under mechanical stresses during cleaning, either by brushing or immersion in disinfectant solutions. Ethylene-vinyl acetate samples, 4 mm thick, were randomly assigned to cleaning methods: control (C-no cleaning), brushing with water (B.W), brushing with neutral liquid soap (B.S), brushing with toothpaste (B.T), immersion in distilled water for 10 min (I.W), immersion in 2.25% sodium hypochlorite solution for 10 min (I.SH), and immersion in sodium bicarbonate solution for 5 min (I.SB). All cleaning methods were applied for 28 days. Surface roughness average (Ra) and wettability were measured at baseline for the control group (n = 9), and after cleaning for all the other groups. One-way ANOVA with Tukey tests (5% significance) indicated significant differences among groups (p < .05). The I.SB group had higher surface roughness than B.S and B.T (p < .05). B.W showed the lowest wettability, significantly lower than B.T, I.W, and I.SB (p < .05). I.SB exhibited the highest wettability, significantly different from sodium hypochlorite, neutral liquid soap, brushing with water, and control groups (p < .05). The sodium bicarbonate immersion group (I.SB) demonstrated greater statistical variation, displaying higher susceptibility to aging compared to brushing with neutral liquid soap. Cleaning mouthguards with a toothbrush, water, and neutral liquid soap emerged as the most promising method, causing minimal surface changes in the material.

The effect of the simulated aging by thermocycling on the elastic modulus of ethylene-vinyl acetate brands and stress/strain development during an impact: An in vitro and 3D-FEA analysis.

Mouthguards are used to prevent dental trauma and orofacial injuries. The aim of this study was to evaluate the influence of ethylene-vinyl acetate (EVA) aging by thermocycling on elastic modulus, stress, strain and shock absorption ability of different ethylene-vinyl acetate brands used for mouthguards. Thirty EVA samples with a dimension of 70 × 10 × 3 mm were obtained from four commercial brands (Bioart®, Erkodent®, Polyshok® and Proform®). Fifteen samples were submitted to 10,000 cycles (5°C-55°C) in a thermocycling machine with an immersion time of 30 s and a transfer time of 5 s. The samples were submitted to a uniaxial tensile test in a universal testing machine to calculate the elastic modulus. Data were statistically evaluated by two-way ANOVA and Holm-Sidak test. A three-dimensional model of the anterior maxilla was created using Rhinoceros 5.0. A 3 mm custom-fitted mouthguard was simulated. The three-dimensional volumetric mesh was generated using the Patran software (MSC Software) with isoparametrics, 4-noded tetrahedral elements and exported to Marc/Mentat (MSC Software) as element number 134. A non-linear dynamic impact analysis was performed in which a rigid object struck the central incisor at a speed of 5 m/s. The stresses were evaluated by the modified von Mises criteria and the strains were also recorded. Statistically significant differences were observed for elastic modulus values (p < .001). Mean and standard deviation values (MPa) without thermocycling were: Bioart (34.5 ± 0.9), Erkodent (15.0 ± 0.4), Polyshok (17.3 ± 0.4), Proform: (20.6 ± 0.8); and with thermocycling: Bioart (25.4 ± 0.8), Erkodent (10.7 ± 0.5), Polyshok (13.3 ± 0.6), Proform (13.1 ± 0.6). The thermocycling process reduced stress and strain levels regardless of the mouthguard materials. Shock absorption ability calculated based on the strain values was increased with thermocycling process. The thermocycling process, regardless of the commercial brand, reduced the stress/strain and increased the shock absorption ability of mouthguards.

Ethylene-vinyl acetate detector exposed to gamma radiation and evaluated via principal component regression

Ethylene-vinyl acetate (EVA) is the flexible plastic material commonly used in industries. The EVA samples, in green, white and black colors were irradiated with absorbed doses of 0.01 kGy up to 10.0 kGy using a 60Co Gamma Cell-220 system, and the Fourier Transform Infrared (FTIR) spectrophotometry technique was used for evaluating the samples. This work aimed to investigate EVA samples in measurements with gamma radiation, analyzing the linearity through the Principal Component Regression (PCR) method and its sensitivity. For sensitivity and linearity, the green samples showed the best results, followed by white and black EVA samples. The PCR method inflated gradually the number of principal components, then reducing the residuals between the measured and calculated values, consequently obtaining maximum linearity of 1.000 for all EVA samples. In conclusion, the FTIR was adequate for the acquisition of absorbance spectra, the linearity via PCR and sensitivity showed good results indicating that the EVA detectors can be useful in radiation measurements.

Combined UV-irradiation and pyrolysis-GC/MS approach for evaluating the deterioration behavior of ethylene vinyl acetate

Ethylene vinyl acetate (EVA), commonly used to encapsulate photovoltaic (PV) modules, deteriorates on prolonged exposure to sunlight. In this work, fresh and deteriorated EVA samples prepared by UV irradiation (500 W m−2) over different periods (0–168 h) are characterized by conventional elemental analysis, microscopic observations, Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetry. To the best of our knowledge, this is the first work to employ pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and micro-UV irradiation combined Py-GC/MS (UV/Py-GC/MS) to investigate the deterioration behavior of EVA, using in-situ identification of gases liberated during UV irradiation, such as H2O, CO2, ketones, acetic acid, and lactones. In addition, the deterioration of the thermal stability on aging is confirmed using evolved gas analysis-mass spectrometry (EGA-MS). UV/Py-GC/MS revealed that acetaldehyde, acetone, acetic acid, γ-butyrolactone, succinic anhydride, and cyclobutanone are produced during UV irradiation. In addition, Py-GC/MS identified cyclopentanone, citraconic anhydride, γ-valerolactone, and cyclobutanone from the UV deteriorated EVA samples, which suggested the presence of ketone and lactone structures in the deteriorated EVA. This work establishes the combined usage of UV irradiation and Py-GC/MS as a promising method to investigate UV deterioration behavior in greater detail. These findings may contribute to a superior understanding of the breakdown of PV modules by the deterioration of EVA, and lead to the development of UV-resistant encapsulating materials.

Comparative investigation and analysis of delaminated and discolored encapsulant degradation in crystalline silicon photovoltaic modules

Delamination and discoloration are the most commonly observed encapsulant degradations in crystalline silicon photovoltaic (PV) modules under field conditions. In this work, a comparative analysis of brown discoloration and front side grey appearing delamination of ethylene vinyl acetate (EVA) has been presented, to understand their basic effects and modes of degradation. For this purpose, both type of degraded EVA samples from field-aged PV modules have been investigated, for finding the difference in their spectral response, chemical constituents, structural change, and impact on module electrical performance. These investigations have been performed using quantum efficiency (QE) measurement, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, electrical analysis was performed using PSpice circuit simulator. The distinct effect of discolored and delaminated EVA degradations, on incident radiations was identified mainly in absorption and reflection loss respectively, under different wavelengths. Also, the impact of these degradations on module performance, due to mismatch loss within the module has been presented. The chemical constituent investigation, supported presence of delamination in grey degraded sample due to absence of interfacial adhesive agent, in contrast to discolored sample. Findings from the structural investigation, corroborated a decrease in crystalline behaviour of both degradations. Furthermore, impressions from etched silicon cell were observed only in delaminated sample, which can be the reason of its grey appearance and more reflection. This work highlights the comparative effects and impact of dominant EVA degradations in terms of their characteristic aspects, which can be instrumental in improvement of EVA formulation.

Damp Heat Induced Degradation of Silicon Heterojunction Solar Cells With Cu-Plated Contacts

Damp heat exposure is one of the most stringent environments for testing the durability of solar cells in packaged modules. Damp heat stresses and induces a variety of degradation modes in solar cells and modules: for example, moisture-induced corrosion of electrodes and interconnections, deterioration of polymeric materials, and/or thermally activated diffusion processes. To screen for these and other potential degradation modes, we subject one-cell modules containing silicon heterojunction (SHJ) solar cells with Cu-plated contacts to extended damp heat tests at 85 °C/85% relative humidity. SHJ cells were laminated with two common encapsulants: ethylene vinyl acetate (EVA) and polyolefin elastomer (POE), and two constructions: glass–backsheet and glass–glass. We observe degradation in all components of solar cell maximum power $(P_{{\rm{MP}}})$ : current, voltage, and fill factor, and find evidence of increased carrier recombination and nonideal diode behavior with increasing stress. For glass–backsheet constructions, EVA samples generally degrade more than POE by a factor of approximately 1.5x $P_{{\rm{MP}}}$ , and the different encapsulants produce different degradation patterns. Similar trends are observed in glass–glass modules, but to a lesser degree. In a different experiment, we observe a decrease in effective minority carrier lifetime of nonmetallized SHJ precursors measured after damp heat. This implies that some degradation unrelated to the contacts is to be expected and confirms the observation of increasing recombination.

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.

FTIR Investigation of EVA Chemical Bonding Environment and Its Impact on Debond Energy

The chemical makeup of ethylene vinyl acetate (EVA) interfaces in photovoltaic (PV) modules is probed via Fourier-transform infrared spectroscopy (FTIR) to determine the impact of the EVA formulation on the adhesion degradation. EVA samples laminated with glass particles are used to demonstrate the effect of damp heat exposure on the glass-EVA interface, showing that increasing silane content increases chemical stability. Delamination interfaces created in one cell modules demonstrate a high correlation between the siloxane bonding at the silicon cell-EVA interface and the debond energy. A significant decrease in debond energy after UV exposure is also shown to be due in part to decreasing siloxane bond density at the interface. However, FTIR results indicated contributions to the adhesion beyond the chemical interface, and a basic tensile test indicates increasing bulk mechanical properties with increasing silane. These results demonstrate the importance of the EVA formulation on its adhesion performance and long-term reliability. Furthermore, it is shown that FTIR is a capable technique for assessing and quantifying chemical mechanisms within PV modules. These results can then be used to more effectively model module lifetimes and to better design polymer systems for PV modules.

Development of EVA-SEBS based wax fuel for hybrid rocket applications

An attempt has been made in the present study to obtain the suitable wax based fuel that could be used in the practical hybrid rocket applications. It is known that wax has high regression rate compare to other polymeric fuels and is a most suitable hybrid fuel but suffers with poor mechanical properties. Thus, additives such as EVA (Ethylene Vinyl Acetate) and SEBS (Styrene-Ethylene-Butylene-Styrene Copolymer Grafted with 2% Maleic Anhydride) have been utilized to enhance its mechanical properties. Apart from the mechanical properties, regression rate, combustion efficiency and sliver loss studies have also been conducted. Various combinations of wax with EVA and SEBS samples have been prepared. Among these fuels developed, wax mixed with the combination of 10% SEBS and 5% EVA had shown significant improvement in the mechanical properties (maximum tensile strength was 4.26 MPa and percentage elongation was 24.6%). These properties are within the range to be utilized as a solid fuel in practical applications. Regression rate studies on the fuels developed in the present study had shown that the wax with SEBS based fuels obtained higher regression rate than wax with EVA based fuels. The wax fuel with combination of 10% SEBS and 5% EVA had shown the best regression rate characteristics along with mechanical properties that required for practical applications. The increment in combustion efficiency was observed with addition of polymeric additives to wax. With the addition of 20% EVA to wax the combustion efficiency improved from 63% to 72%. The burnt profiles from injector end to the nozzle end were more uniform with wax-SEBS fuel grains than pure wax fuel grains. Hence, the sliver loss is expected to be lower with wax-SEBS fuel.

The impact of electron beam irradiation on Low density polyethylene and Ethylene vinyl acetate

Improvement of measured gel content, hardness, tensile strength and elongation at break of Ethylene vinyl acetate (EVA) have confirmed positive effect of electron beam irradiation on EVA. Results obtained from both gel content tests show that degree of cross-linking in amorphous regions is dependent on dose. A significant improvement in tensile strength of neat EVA samples is obtained upon electron-beam radiation up to 210 kGy. Similarly, hardness properties of Low-density polyethylene (LDPE) improvewith increasing electron beam irradiation. This article deals with the impacts of electron beam (EB) irradiation on the properties of LDPE and Ethylene-Vinyl Acetate (EVA) as the two common based formulations for wire and cable applications.

Shock-absorption properties of functionally graded EVA laminates for footwear design

The shock-absorbing performance of single ethylene-vinyl acetate (EVA) foams and functionally graded laminates of these foams were evaluated with simulated gait experiments. Mechanical properties such as the hardness and density were measured, along with the viscoelastic behavior. The shock-absorbing performance was found to be dependent on the cellular structure, namely the density, elastic modulus, and loss tangent of the single EVA foams. However, for the laminated samples, there were slight variations in the shock-absorption efficiency for samples with the same density. The graded materials showed higher shock-absorption efficiency compared with non-graded single materials with the same density. In addition, laminates with elastic modulus values slightly higher than those of the single EVA samples showed higher shock-absorption efficiency. Finally, since laminates with varied properties were produced, a design concept for a suitable functionally graded material is presented for footwear applications.

DNA Coatings from Byproducts: A Panacea for the Flame Retardancy of EVA, PP, ABS, PET, and PA6?

One of the most important challenges for thermoplastic polymers is to find flame retardants (FRs) capable of efficiently protecting them. At the same time, these desired FRs should be environmentally sustainable, cheap, and suitable for most of the polymers employed on the industrial scale. Obviously, it is almost impossible to design such a universal FR to be used for polymers having different chemical structures. We have recently demonstrated the efficiency of a deoxyribose nucleic acid (DNA) coating as a FR solution for cellulose and ethylene-vinyl-acetate (EVA) copolymer. Pursuing this research, in the present study we investigate the FR effect of different DNA amounts on 3 mm EVA samples in order to optimize its cost/effectiveness ratio. FR performances were evaluated with a cone calorimeter under 35 and 50 kW/m2. Then, the optimized DNA amount was tested on EVA samples having different thicknesses (namely, 1 and 6 mm) in order to establish whether a correlation between DNA amount and sample mass exi...

Non-Destructive Determination of Ethylene Vinyl Acetate Cross-Linking in Photovoltaic (PV) Modules by Raman Spectroscopy

Vibrational spectroscopy was found to be a suitable method for the determination of the degree of cross-linking of ethylene vinyl acetate (EVA) polymers. Spectral changes in the Raman spectra of EVA with increasing lamination time (which equals increasing degree of cross-linking) were mainly detected in the CH vibrational regions, namely, in the relative intensities of the characteristic CH3 and CH2 bands. These spectral regions were chosen for a chemometric evaluation where a calibration was performed with the Raman spectra of reference EVA samples and the results obtained from corresponding thermal analysis (differential scanning calorimetry) and Soxhlet extraction data. These datasets were subsequently used to non-destructively determine the progress of cross-linking in EVA foils, embedded in various mini-modules by Raman microscopy. Thus, we could show that Raman spectroscopy is a highly interesting method for quality control in the production of photovoltaic (PV) modules. However, this approach is valid only for a given grade of EVA, meaning a demand for a new calibration when changing the supplier or the type of EVA used. In addition, the applicability of infrared spectroscopy for the determination of the degree of cross-linking was tested. A good correlation of the decrease in intensity of the characteristic cross-linker infrared bands with increasing progress of the cross-linking was found, as determined by reference methods. However, this analytical method requires taking samples of the EVA foils and is, thus, unsuitable for the non-destructive determination of the degree of cross-linking of the EVA encapsulated within a PV module.

An Experimental Study on Surface Discharge Characteristics of Different Types of Polymeric Material under AC Voltage

Surface discharge is a common electrical discharge that normally occurs on the surface of outdoor insulators and also causes the failure in the electrical insulation system. One of the causes of surface discharge is the presence of high voltage stress. Experimental works had been carried out to examine the surface discharge characteristics on polymeric samples as insulation material. The IEC (b) electrode configuration had been used to investigate the surface discharges phenomena of different types of polymeric materials with controlled of air relative humidity (RH). In these experimental works, three types of polymeric sample were selected, namely high-density polyethylene (HDPE), ethylene-vinyl acetate (EVA), and polystyrene (PS), respectively. The characteristics of the discharge are critically depending on the types of polymer. Surface discharges intensity, number of discharge occurrence, and surface morphology of each polymeric material were also investigated. Comparisons of these electrical characteristics were conducted among the samples. Results from the experiment showed that the EVA samples experienced severe degradation as compared to HDPE and PS samples.

Electron-beam irradiation of low density polyethylene/ethylene vinyl acetate blends

Abstract In this work, the properties of electron-beam irradiated low density polyethylene (LDPE), ethylene vinyl acetate (EVA) and blends were investigated. EVA addition had an enhancement effect on crosslinking of irradiated LDPE/EVA blends. The measured gel content increase of the blends and the improvement of thermal elongation, tensile strength, elongation at break, thermal aging and heat deformation, have confirmed the positive effects of electron-beam irradiation on the blend properties. The crystallinity of the blends decreased with irradiation. The gel content and hot set tests showed that the degree of crosslinking in the amorphous regions was dependent on the dose and blend composition. Increasing the EVA content resulted in tighter network structures. A significant improvement in the tensile strength of the neat EVA samples was obtained upon electron-beam irradiation up to 210 kGy. The irradiated LDPE/EVA blends showed improved tensile strength and elongation at break, when compared to LDPE. The enhanced irradiation crosslinking of the LDPE/EVA blends was proportional to the good compatibility and the increasing degree of the amorphous region’s content of the LDPE/EVA blends. The possible degradation mechanism of LDPE/EVA blends was discussed quantitatively with a novel method step analysis process of irradiated LDPE/EVA blends in the thermal gravimetric analysis (TGA) technique. It was found, with measuring thermal conductivity (k) and specific heat capacity (Cp) of the blends, that the k values of the LDPE samples at a prescribed temperature range decreased with increasing irradiation. An increase in the crystallinity led to an increase in the k values and a decrease in the Cp values of the LDPE samples. Irradiation below 150 kGy decreased the Cp (at 40°C) and k in average values, whereas increasing the EVA made enhanced the Cp and k values of LDPE/EVA blends at each irradiation. The surface resistance and volume resistivity (VR) of the blends reached a maximum at a 170 kGy irradiation and 30 wt% of EVA. Increasing the amount of EVA contents resulted in enhancement of the dielectric loss factor for the irradiated blends.

Near-infrared spectropolarimeter using an acousto-optic tunable filter

The long chain of a polymer molecule often has intrinsic linear birefringence and/or dichroism, which lead to macroscopic properties when the molecules have a preferred orientation under nonequilibrium conditions, such as flow of a polymer melt. Measurements of properties, including linear birefringence, in a polymer melt can in turn lead to valuable insights into its structure, morphology, and rheology. We demonstrate that a spectropolarimeter based on an acousto-optic tunable filter can measure linear birefringence in real time during the manufacture of polymers, at hundreds of wavelengths, within 5 min, and thus provides more information than use of a spectrometer or laser-based polarimetry alone. In this work, optical properties of different molten ethylene vinyl acetate samples were measured with a spectropolarimeter based on an acousto-optic tunable filter and a photoelastic modulator in the near infrared. Regression models of the results indicate good correlation between the melt indices of the samples and the measured spectra.

Quality control of EVA encapsulant in photovoltaic module process and outdoor exposure

The objective of this work is to understand the physical and chemical properties of the standard cure copolymer ethylene-vinyl-acetate (EVA), used as encapsulant, during photovoltaic module encapsulation process and also in field exposure of Algerian Sahara as specific desert climate. EVA samples are characterized by gel content measurements (crosslinking test), dielectric spectroscopy as function of temperature and frequency, thermally stimulated current (TSC), UV–visible–near infrared transmittance spectrometry to detect the quality of the material. Results show a decrease in most properties of EVA in natural field exposure due principally to the specificity of the region characterised by hot and dry climate.

Calibration Models for the Vinyl Acetate Concentration in Ethylene-Vinyl Acetate Copolymers and its On-Line Monitoring by Near-Infrared Spectroscopy and Chemometrics: Use of Band Shifts Associated with Variations in the Vinyl Acetate Concentration to Improve the Models

The present study investigates calibration models for the vinyl acetate (VA) concentration in ethylene-vinyl acetate (EVA) copolymers and its on-line monitoring by near-infrared (NIR) spectroscopy and chemometrics. The key point in the present study is to make use of band shifts associated with concentration changes in the vinyl acetate (VA) for the improvement of the models. NIR spectra of EVA in melt and solid states were measured by a Fourier transform near-infrared (FT-NIR) on-line monitoring system and a FT-NIR laboratory system. Some of the bands in the NIR spectra for both states show significant shifts with the variations in the VA concentration. The peak shifts induced by the VA concentration changes are larger in the solid-state EVA than those in the melt-state EVA. We have developed calibration models for the VA concentration in the solid-state EVA and investigated how to improve the calibration models. The factor analysis of partial least squares (PLS) regression has suggested that the wavenumber shifts caused by the VA concentration changes affect the calibration models for the VA concentration in EVA. From the analysis, it has been proposed that the wavenumbers in the spectrum of one sample in nine EVA samples (VA concentration range: 0-41.1%) are shifted for the improvement of the calibration models, and the effects of the proposed method have been confirmed by using the PLS calibration models for the VA concentration in the solid EVA samples. As the next step, the effects of the wavenumber shift method have been explored for the calibration models for the VA concentration in the melt-state EVA. After that, the discrimination method using the score plots of PLS and the application sequence for the on-line monitoring to use the proposed wavenumber shift method were studied. The simulation results using the discrimination and wavenumber shift methods have shown that those methods are very effective to improve the predicted values of the calibration models for the on-line monitoring of the VA concentration in the melt-state EVA.

The effect of high-energy electron beam irradiation and content of ATH upon mechanical and thermal properties of EVA copolymer

Mechanical and thermal properties of ethylene vinyl acetate (EVA) mixed with various amounts of alumina trihydrate (ATH), irradiated with 5 MeV electron beam at dose range varied from 38 to 190 kGy, have been studied. A small amount (1%) of triallyl cyanurate has been used as a radiation sensitizer. It has been found that (i) EVA samples with various contents of ATH are crosslinked, (ii) crosslinking increases with irradiation dose, (iii) the mechanical properties of samples improve by irradiation and (iv) decomposition of samples takes place at two stages and due to irradiation, decomposition temperatures shift to higher values. These studies were carried out in order to obtain a suitable compound for wire and cable insulation.

Forces transmitted through a laminated mouthguard material with a Sorbothane insert.

Sorbothane is a visco-elastic polyurethane that has been used in sports and orthopaedic applications because of its shock-absorbing properties. The aim of this laboratory study was to evaluate the effect of an intermediate layer of Sorbothane on the peak force transmitted through two thermoplastic ethylene vinyl acetate (EVA) sheets as used in the construction of a custom-made sports mouthguard. The EVA sheets were tested at room temperature after thermal lamination under pressure, either without (control) or with a Sorbothane intermediate layer of 1.1 or 2.65 mm thickness. A piezo-electric transducer was used to measure the peak force transmitted through each sample from a free-falling steel ram. The peak force recorded was significantly less for laminated EVA samples with a Sorbothane intermediate layer than for controls of comparable thickness. We conclude that a Sorbothane intermediate layer between heat-cured laminated EVA sheets, as used in the fabrication of a custom-made sports mouthguard, may dissipate significantly the force of impact resulting from a blow to the teeth and jaws.