Vinyl Acetate Content Research Articles

Respiratory functions and health risk assessment in inhalational exposure to vinyl acetate in the process of carpet manufacturing using Monte Carlo simulations

Vinyl acetate (VA) is a volatile compound and the main compound of the carpenter’s glue. VA causes upper respiratory tract irritation, cough, and hoarseness in occupational exposure. As Iran is one of the biggest carpet producers in the world, this study was carried out to determine the inhalational health risk for employees exposed to VA. To the best of our knowledge, this was the first health risk assessment and the first evaluation of the lung functions and respiratory symptoms in employees exposed to VA. In the six finishing shops of carpet manufacturing industry in Kashan city, Iran the cross-sectional studies were conducted in 2022. The subjects comprised of forty male employees exposed to VA and of forty non-exposed employees in the reference group. VA analyses in the workers’ breathing zones were performed based on the National Institute for Occupational Safety and Health (NIOSH) 1453 Method. VA concentrations were measured using Gas Chromatography-Mass Spectrometry (GC–MS). Inhalational risk assessment to VA was performed using the United States Environmental Protection Agency method and the Monte Carlo simulations. Respiratory functions were determined using the spirometry indices. In the exposed employees, considerably higher prevalence rates of pulmonary symptoms were observed in comparison with the control group. Statistical analysis showed a remarkable difference between lung function parameters measured in the case and the control groups. The VA Hazard Quotient (HQ) values for all working posts, except the quality control unit, were > 1 indicating the substantial inhalational non-cancerogenic risk. The sensitivity analysis revealed that the VA concentrations and exposure time had the most significant contribution in the uncertainty assessment. Therefore, it is recommended to decrease exposure to VA concentrations and to reduce the working time of exposed employees.

Simulation study on the co-polymerization of vinyl acetate between ethylene

Vinyl acetate-ethylene copolymer is an important chemical product, which is formed by the polymerization of vinyl acetate and ethylene, which involves complex reactions and lacks kinetic parameters. Based on the Density Functional Theory method, we constructed molecular models of vinyl acetate-ethylene propagation, ethylene–vinyl acetate propagation, vinyl acetate-vinyl acetate propagation and ethylene-methanol chain transfer. Based on the fitted kinetic parameters, we used process simulation aiming at the VAE product with 80% vinyl acetate content. We found that due to the continuous feeding of reactants and discharge of products, the side reactions have a little effect on the polymerization process, and the Polymer Dispersity Index of polymerization products is lower. In general, the batch operation is more conducive to chemical reactions requiring complete conversion, while the continuous operation is more suitable for the synthesis of products with stable quality due to the small relative molecular weight dispersion of polymerization products.

EVA-PVA binder system for polymer derived mullite made by material extrusion based additive manufacturing

Low processing temperature of preceramic polymers (PCPs) makes them attractive for material extrusion based additive manufacturing (MEX-AM), earlier called fused deposition modeling (FDM). Fabrication of bulk polymer derived ceramics is challenging due to gas evolution during crosslinking leading to pores and cracks in final product. Mixture of ethylene vinyl acetate (EVA) and polyvinyl alcohol (PVA) was successfully used to generate open porosity before crosslinking step. For 3D printing, a pellet extruder was used and a PVA binder content of 50 vol% was essential for succcessful solvent debinding process in water. The effect of PVA content and different EVA grades on printability and debinding behavior was studied. EVA with a lower melt flow index (MFI) showed better compatibility with PVA additive in terms of mixing and printing. EVA with higher vinyl acetate content seems to be more favorable for later thermal debinding processes because of its higher gas permeability.

Improvement in the reliability of photovoltaic mini-modules through modifying the structural composition of EVA encapsulant

The photovoltaic (PV) module manufacturers use ethylene vinyl acetate that contains 28 to 33% by weight vinyl acetate (VA) for the encapsulation application. However, it has been found in various field surveys that EVA degrades during its operation in the field. The resilience of ethylene vinyl acetate against environmental stressors can be enhanced by optimising its vinyl acetate (VA) content as has been seen in the few studies done on free-standing EVA films. However, no such comparative study has been carried out on EVA films placed in a module mimicking the actual structure of a PV module. Therefore, in this work EVA films containing 18, 24 and 33% VA content by weight are prepared with the necessary additives to fabricate mini-modules. These mini-modules have been subjected to damp-heat (DH) ageing for 1000 h at 85 °C temperature and 85% relative humidity (RH) according to IEC 61,215 standard. The power output, adhesion strength and volume resistivity reduce and YI increases for the modules containing EVA33 after ageing. However, no significant changes are observed for the above-mentioned properties for the modules containing EVA24 and EVA18. This study presents findings of 1000 h of DH ageing as per IEC standards for mini-modules containing different EVA films and observed that the films of EVA18 and EVA24 are resilient compared to EVA33. Moreover, the findings on mini-modules have a few differences with prior studies done on free-standing EVA the films.

Thermal, mechanical, rheological and morphological properties of compatible poly(lactic acid)/ethylene vinyl acetate blends

This paper examines the effects of poly (ethylene-co-vinyl acetate) (EVA) with 40% vinyl acetate content on thermal, mechanical, rheological, and morphological properties of polylactic acid (PLA) blends. Thermal analysis indicated improvement of crystallinity in the presence of more EVA. With 15% EVA, the impact strength of the binary blend increased significantly (37.80 KJ/m2) at an optimum elongation at break due to the compatibility of the blend and the formation of fibrils. In the presence of % EVA, complete phase separation with the formation of EVA droplets in the PLA continuous phase resulted in a reduction of impact strength and elongation at break. Changes in compatibility and morphology lead to variation in rheological properties. The complex viscosity (η*) decreased with increasing EVA content up to 10% EVA but slightly increased at 15% EVA due to optimum interphase interaction between components in the compatible blend. In the presence of more than 20% EVA, η* reduced again due to the occurrence of phase separation. The variations in the mechanical and rheological properties of PLA/EVA blends are directly related to the state of compatibility and morphology of the blends.

Quantitative Analysis of the Calcium Hydroxide Content of EVA-Modified Cement Paste Based on TG-DSC in a Dual Atmosphere.

The calcium hydroxide (Ca(OH)2) content is one of the main indices of cement hydration degree. In order to accurately determine the calcium hydroxide content of ethylene and vinyl acetate (EVA) copolymer-modified cement paste, a dual atmosphere thermogravimetric method (first in an oxidizing atmosphere and then in an inert atmosphere) was used to track the mass loss and change in enthalpy by TG-DSC (simultaneous thermogravimetry and differential scanning calorimetry). The results showed that using the dual atmosphere thermogravimetric method, the source of mass loss can be distinguished. The exothermic peaks in an oxidizing atmosphere show the oxidation reactions of EVA, while the endothermic peak in an inert atmosphere is due to the pyrolysis reaction of EVA and the decomposition of the calcium hydroxide. The influence of EVA on cement hydration was investigated. The results showed that the polymer powder can be dispersed in water, forming a kind of composite membrane. The test method of dual atmosphere thermogravimetry to measure the calcium hydroxide content of polymer-modified cement pastes is more accurate and convenient than those previously applied.

Vinyl acetate content influence on thermal, non-isothermal crystallization, and optical characteristics of ethylene–vinyl acetate copolymers

Vinyl acetate content influence on thermal, non-isothermal crystallization, and optical characteristics of ethylene–vinyl acetate copolymers

Thermal conductivity of ethylene-vinyl acetate copolymers with different vinyl acetate contents dependent on temperature and crystallinity

In this work, the thermal conductivity of a series of ethylene-vinyl acetate copolymers (EVAs) with different vinyl acetate (VAc) contents at different temperatures are measured by the transient hot line method. It is found that the thermal conductivity of a series of EVA samples with different VAc contents decreased smoothly with increasing temperature at temperatures from -20 to 80 °C. Meanwhile, the crystallinity and melting point of a series of EVA samples are determined by differential scanning calorimetry (DSC), and an empirical formula between the thermal conductivity of EVA and temperature and crystallinity is established by using a data-fitting method. The theoretical calculation of thermal conductivity obtained from this empirical formula is compared with the measured results, and the error is within 5%. Therefore, this empirical formula is for guidance for predicting the thermal conductivity of EVA samples with different VAc contents at different temperatures in the future.

Wax Inhibition by Ethylene-Vinyl Acetate Using United Atom Molecular Simulations

We used the TraPPE-UA [Martin, M. G.; Siepmann, J. I. J. Phys. Chem. B 1998, 102, 2569] scheme to investigate the inhibition of crystal growth in an octacosane matrix embedded with an ethylene-vinyl acetate (EVA) inhibitor. Through elucidating the phenomena of EVA-induced morphological transitions, we demonstrated that an EVA chain needs to possess suitable configurations with an optimal concentration of polar vinyl acetate (VA) side units, minimal distance between VA units subject to the constraint that VA units remain separate, and symmetrical location distributions of VA units to achieve the best inhibition performance. Furthermore, we revealed that the EVA inhibition was triggered by distortions of the EVA backbone section due to the strong affinity of VA components to neighboring molecules. We obtained an agreement with the experimental characterizations and provided an insight into the solution for the problem of paraffin crystallizations in crude oil pipelines.

A comparison of evolution of adhesion mechanisms and strength post damp-heat aging for a range of VA content in EVA encapsulant with photovoltaic backsheet

Ethylene vinyl acetate (EVA) is an effective encapsulant to adhere various layers in the photovoltaic (PV) module. In this study, we have fabricated EVA films containing different vinyl acetate (VA) content (18%, 24%, 33% and 40%) and laminated between two layers of backsheet (BS). These laminates have been subjected to damp-heat (DH) ageing at 85OC and 85% relative humidity (RH) for 1000 h to evaluate the change in adhesion strength at EVA/BS interface using the T-peel test. The adhesion strength for EVA containing 18% VA content has been found to improve but it deteriorates for EVA with 33 and 40% VA content after ageing. However, adhesion strength for EVA containing 24% VA content is found unaffected after ageing. The degree of cross-linking and VA content have been determined through gel content measurement and thermo-gravimetric analysis (TGA) respectively. The degree of cross-linking and VA content increases significantly in EVA18 but decreases in EVA40 due to DH ageing. The chemical changes have been examined by the Fourier transform infrared spectroscopy (FTIR) and the X-ray photoelectron spectroscopy (XPS). The failure mode (cohesive or delamination) at the interface and its correlation with the adhesion strength has been explored using XPS. The failure mode at the EVA18/BS interface alters from delamination type in pristine condition to the cohesive type due to DH ageing. However, the failure mode for EVA24 and EVA40 is found to be cohesive in both the pristine and aged condition.

Processing, Performance Properties, and Storage Stability of Ground Tire Rubber Modified by Dicumyl Peroxide and Ethylene-Vinyl Acetate Copolymers.

In this paper, ground tire rubber was modified with dicumyl peroxide and a variable content (in the range of 0–15 phr) of ethylene-vinyl acetate copolymers characterized by different vinyl acetate contents (in the range of 18–39 wt.%). Modification of ground tire rubber was performed via an auto-thermal extrusion process in which heat was generated during internal shearing of the material inside the extruder barrel. The processing, performance properties, and storage stability of modified reclaimed ground tire rubber were evaluated based on specific mechanical energy, infrared camera images, an oscillating disc rheometer, tensile tests, equilibrium swelling, gas chromatography combined with a flame ionization detector, and gas chromatography with mass spectrometry. It was found that the developed formulas of modified GTR allowed the preparation of materials characterized by tensile strengths in the range of 2.6–9.3 MPa and elongation at break in the range of 78–225%. Moreover, the prepared materials showed good storage stability for at least three months and satisfied processability with commercial rubbers (natural rubber, styrene-butadiene rubber).

Control Release and Diffusion-Reaction Kinetics of Genipin-Eluting Fibers Using an in Vitro Aneurysm Flow Model.

The minimally invasive treatment of intracranial aneurysms by endovascular coiling is attractive yet faces challenges related to the degradation of fibrin clots in the aneurysm sac over time. Fibrin gels cross-linked with genipin exhibit enhanced mechanical and chemical stability, but there are many unknowns related to best practices for delivery from endovascular devices and subsequent integration of cross-linkers with the nascent clot. Here, we describe the in vitro characterization of genipin-eluting polymer fibers prepared by coextrusion with poly(ethylene-co-vinyl acetate). Genipin incorporation and release from these fibers are characterized by various gravimetric and spectroscopic techniques. Genipin release adheres to Higuchi kinetics with Higuchi constants varying between (2.44 ± 0.83) × 10-7 and (8.41 ± 0.82) × 10-7 mol·h-0.5 depending on genipin loading and vinyl acetate concentration in the polymer matrix. The diffusion-reaction kinetics of genipin released from polymeric fibers within fibrin hydrogels was investigated using an in vitro aneurysm flow model. Spatiotemporal maps of genipin cross-linking density in fibrin gels produced by absorbance measurements suggest that genipin cross-link concentrations up to 9,993.87 ± 909.01 μM can be achieved. This work describes relevant diffusion-reaction parameters of genipin in fibrin gels and establishes the viability of genipin-eluting fibers as a platform for improving endovascular embolization of intracranial aneurysms.

Effect of pour point depressants and diluents on exergy destruction during pipeline transportation of crude oil

Exergy destruction in pipeline flow of crude oils mixed with pour point depressants (PPD) and diluents has been investigated. Ethylene vinyl acetate with vinyl acetate content of 18% and 28% (EVA-18 and EVA-28) and Polymethyl methacrylate (PMMA) with concentrations of 200 ppm, 1000 ppm and 1500 ppm were chosen as the PPDs for this purpose. Four different diluents were considered viz. n-hexane, cyclohexane, n-butanol and toluene representing paraffins, naphthenes, alcohols and aromatics respectively. The viscosity reduction was found out experimentally. Using these results for a hypothetical pipeline, the effect of API gravity of crude oil, pipeline diameter, Reynolds number, PPD concentration and diluent type on exergy destruction was investigated. These findings would help in making a prudent choice of PPD and diluents for efficient transportation of crude oil through pipelines.

Characterization of Low-Density Polyethylene and LDPE-Based/Ethylene-Vinyl Acetate with Medium Content of Vinyl Acetate

Low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA), which are non-polar and polar polymers, are immiscible and form a polyphase system. In this study, LDPE was mixed with 2.5%, 5%, 7.5%, 10%, 12.5% Ethylene-vinyl acetate (EVA-28) with a medium content of vinyl acetate (28% VA), respectively by injection molding machine and LDPE. Tensile strength and flexural strength were tested according to ASTM D638-02 standard and ISO 178 standard. The results showed that adding EVA-28 increased the elongation at break of the LDPE/2.5% EVA, LDPE/5% EVA and LDPE/10% EVA blend samples. In addition, the tensile and flexural strength of the LDPE/EVA blend decreases gradually as the EVA-28 content in the blend increases. The hardness decreases with the increasing EVA-28 content. EVA-28 spherical particles appeared scattered on the surface of the LDPE matrix, in the highest EVA-28 percent sample (12.5% EVA-28), the number of particles appeared to be quite a lot, and was dispersed quite evenly on the surface. The LDPE/EVA-28 blend achieved a higher elongation at the break than LDPE, in which 10% EVA-28 gives the highest elongation at break.

Structural, thermal, mechanical and viscoelastic properties of ethylene vinyl acetate (EVA)/olefin block copolymer (OBC) blends

In this study, ethylene vinyl acetate and olefin block copolymer (OBC) blends were prepared by melt-compounding. The effect of vinyl acetate (VA:12 and 28 wt%) and OBC (10–50 wt%) content on the morphological, thermal, and mechanical properties of EVA/OBC blends were studied in detail. Short-term flexural creep tests were also reported to investigate the time-dependent behavior of the blends. Non-isothermal crystallization results showed that, fractionated crystallization around 75C was observed in EVA (28%) blends. The creep study showed that the creep behavior of the blends significantly improves with the addition of OBC. The four-element Burgers model and the two parameter power law (Findley’s) model were fitted creep curves of the blends well. The addition of OBC promoted significant gains in terms of the mechanical and solid-state viscoelastic properties.

AtmosphericCO2/CH4permeability ofEVAcopolymer/SiO2composite membrane for biogas purification

AbstractThe CO2and CH4permeabilities of poly(ethylene‐co‐vinyl acetate) (EVA)/SiO2composite membrane were investigated at atmospheric pressure. The membranes were fabricated by compression molding and characterized by Fourier transformed infrared spectroscopy, differential scanning calorimetry, a universal testing machine, and a contact angle analyzer. The effect of vinyl acetate content (18–33 wt%) was evaluated for both single‐gas and mixed‐gas permeation systems. A non‐pressurized homemade‐permeation cell was used for the single‐gas permeation of CO2and CH4, while a tubular membrane was utilized for a continuous separation of CO2/CH4mixture. CO2flux was readily increased (from 0.7 to 2.0 ml/m2.s) with vinyl acetate content (18–33 wt%). The enhanced CO2permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO2/CH4) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO2as a filler (0.5–2.0 wt%) especially increased the membrane polarity and hence the CO2flux up to 6.0 ml/m2.s. However, the CH4flux was not affected by VA and SiO2contents.

Features of high-filled composites based on various brands of polyvinyl alcohol

Composites based on polyvinyl alcohol (PVA) and polysaccharides (PS) have significant potential for use as compostable packaging materials, as well as in various fields of crop production. PVS are produced by the industry of various brands that differ in molecular weight (MM) and the residual content of vinyl acetate (BA) groups, and as a result - the degree of hydrolysis. Depending on the brand of PVA and the nature of the filler, such properties of composites based on them as water resistance, strength, degree of bioconversion, etc.will differ significantly. The purpose of the work: a comprehensive assessment of the properties of high-filled composites based on PVA of various brands, differing in the degree of hydrolysis, and polysaccharides. Objects of research: composites obtained by direct combination of a 5% solution of PVA (grades 1799, VS-05, BP-05, KurarayPoval 3-83) and PS powder (wood microcellulose - MCD, corn native starch - KK), with and without the addition of a plasticizer (P) - glycerin, followed by dehydration in air or in a vacuum drying cabinet. Based on the presence of external defects after dehydration and the strength characteristics of the material, it was found that for PVA-1799 it is possible to achieve a filling degree of 80 vol.%, for a PVA BP-05, VS-05 KurarayPoval and 3-83-no more than 50 vol.% without plasticizer and up to 70 vol.% in the presence of a plasticizer. It is noted that when filling PVA with starch up to 50 vol.% dehydrated composites are transparent or semi-transparent, which gives them additional advantages as packaging materials (including film). For composites based on PVA-1799, it was found that the maximum water absorption (250% by weight) has a PVA filled with MCD (20: 80 vol.%), and the introduction of a plasticizer (5 vol.% ) significantly reduces the degree of water absorption (up to 150% by weight), which is not typical for this brand of PVA filled with CC (water absorption was about 50% by weight with and without plasticizer). Composites based on PVA grades VS-05, BP-05, KurarayPoval 3-83 dissolve in water at room temperature for 5-10 minutes. During the preliminary assessment of the biodegradation of the studied PVA-1799 composites, it was found that micro-cracks and areas with immobilized microbiota were observed in the polymer matrix during microscopy after 6 months of composting and soil testing, however, no significant damage to the integrity of the polymer of this brand occurred during the specified composting period, which emphasizes the complex nature of the biodegradation of PVA with high MM and low content of VA groups.

Ethylene vinyl acetate copolymer/Mg–Al‐layered double hydroxide nanocomposite membranes applied in CO2/N2 gas separation

AbstractSeries of ethylene vinyl acetate (EVA) copolymer/layered double hydroxide (LDH) nanocomposite membranes with 40 wt% vinyl acetate content (EVA/12AA–LDH) were prepared by solution blending and casting, and applied in membrane gas separation. The organically modification of LDH nanolayers (12AA–LDH) was manufactured by using 12‐aminododecanoic acid (12AA) as an intercalation agent via co‐precipitation method. The distance between the 12AA–LDH nanolayers was approximately 2.10 nm from calculation of the XRD diffraction pattern, which resulted from the successful intercalation of 12AA within the LDH. The result of CO2 adsorption isotherms shows that 12AA–LDH is much more attractive than the neat LDH, which enhances the performance in membrane separation. Furthermore, the exfoliated/intercalated morphology of 12AA–LDH/LDH structures within EVA matrix was prepared successfully and can be observed clearly by transmission electron microscopy micrographs. The gas permeation performance of the EVA/12AA–LDH nanocomposite membranes was measured, and the results show that the best selectivity of CO2/N2 increased to 20 with a CO2 permeability of 119.21 barrer for the composite membrane containing 1.0 wt% 12AA–LDH. This result not only attributed to the exfoliation of the 12AA–LDH nanolayers within the EVA matrix, but also the amino group of 12AA interacted more with CO2 compared with N2 and O2. This result illustrated that 12AA–LDH shows highly potential for use as an additive in CO2 capture membranes.

Copolymer composition tailored carbon nanotube network breakdown and piezoresistivity of ethylene-vinyl acetate electroconductive composites

Herein, the development of carbon nanotube-based electromechanical sensors with excellent sensing range and gauge factor is reported. Electroconductive composites (EPCs) of ethylene–vinyl acetate random copolymer (EVAc) with different ethylene (E) and vinyl acetate (VAc) segment ratios and different volume fractions of carbon nanotube (CNT) were prepared. The E/VAc ratio was found to significantly impact the AC impedance, electron tunneling, CNT-CNT structural breakdown, effective aspect ratio, and electromechanical behavior. The percolation threshold of CNT was lowest in EPCs with VAc 12%; interestingly, though, the effective aspect ratio, as determined from the micromechanical modeling, was considerably increased in EPC with VAc 40%. With an increase in VAc content, the electrical conductivity decreased; however, the electromechanical response improved significantly. Crystalline content, interfacial wetting, critical strain for the shear strain-induced structural breakdown of percolated CNT network, and effective aspect ratio were found to correlate with the superior electromechanics of EVAc/CNT EPC.

Investigation of Different Types of Biochar on the Thermal Stability and Fire Retardance of Ethylene-Vinyl Acetate Copolymers.

In this work, three biochars, deriving from soft wood, oil seed rape, and rice husk and differing as far as the ash content is considered (2.3, 23.4, and 47.8 wt.%, respectively), were compounded in an ethylene vinyl acetate copolymer (vinyl acetate content: 19 wt.%), using a co-rotating twin-screw extruder; three loadings for each biochar were selected, namely 15, 20, and 40 wt.%. The thermal and mechanical properties were thoroughly investigated, as well as the flame retardance of the resulting compounds. In particular, biochar, irrespective of the type, slowed down the crystallization of the copolymer: this effect increased with increasing the filler loading. Besides, despite a very limited effect in flammability tests, the incorporation of biochar at increasing loadings turned out to enhance the forced-combustion behavior of the compounds, as revealed by the remarkable decrease of peak of heat release rate and of total heat release, notwithstanding a significant increase of the residues at the end of the tests. Finally, increasing the biochar loadings promoted an increase of the stiffness of the resulting compounds, as well as a decrease of their ductility with respect to unfilled ethylene vinyl acetate (EVA), without impacting too much on the overall mechanical behavior of the copolymer. The obtained results seem to indicate that biochar may represent a possible low environmental impact alternative to the already used flame retardants for EVA, providing a good compromise between enhanced fire resistance and acceptable mechanical properties.