Search Results (89)

In the process of extracting and transporting waxy crude oil, pipeline blockages resulting from wax deposition significantly impede production efficiency and lead to substantial economic losses. Ethylene vinyl acetate copolymer (EVA) is a widely used chemical wax inhibitor; however, its performance is influenced by multiple factors, including its molecular structure, concentration, and the carbon number distribution of the wax system. A systematic elucidation of its mechanism of action and associated phase changes is therefore necessary. In this study, differential scanning calorimetry (DSC) was employed to systematically investigate the thermal behavior of a wax system with a broad carbon number distribution (C5–C50). The objectives were to analyze the influence of EVA concentration, vinyl acetate (VA) content, and molecular weight on the phase transition parameters, to elucidate the wax inhibition mechanism, and to construct a phase prediction model based on the Flory–Huggins theory. The results demonstrate that the wax appearance temperature (WAT), phase transition temperature, and phase transition enthalpy of the wax systems increase monotonically with carbon number. Furthermore, the addition of EVA was found to significantly reduce both the WAT and the amount of wax precipitated. The optimal structural parameters were identified as a VA content of 10%, a number average molecular weight of 20,000, and an optimal concentration of 800 ppm. The medium-carbon wax system (C16–C30) was found to be the most sensitive to the EVA response. The established phase model exhibited high predictive accuracy, with a mean relative error of less than 4%, a root mean square error (RMSE) of 0.32%, and a coefficient of determination (R²) of 0.987, thereby providing preliminary insights and a practical tool for optimizing EVA wax inhibitor formulations under simplified conditions and guiding their potential engineering applications. Full article

In this study, the effect of temperature on thermal-assisted glass delamination was investigated using two treatment conditions differing in the set temperature of the process (100 °C vs. 140 °C). Thermogravimetric Analysis (TGA) confirmed that ethylene-vinyl acetate (EVA) remains thermally stable up to about 280 °C, with degradation onset near 300 °C, ensuring that both treatments operate below decomposition. Differential Scanning Calorimetry (DSC) analysis identified an endothermic transition attributable to the melting of crystalline regions in EVA within the thermal range of 35–65 °C, indicating enhanced polymer chain mobility at elevated temperatures. This endothermic transition corresponds to the melting of polyethylene crystallites within the EVA copolymer and should not be interpreted as a glass transition, since the Tg of EVA is typically located at approximately −30 to −35 °C. Fourier Transform Infrared (FTIR) analysis verified preservation of ester functional groups, confirming the absence of chemical degradation. The morphological analysis performed via Scanning Electron Microscopy (SEM) revealed a clear temperature-dependent morphology of EVA after thermal-assisted delamination. At 140 °C, enhanced polymer softening and viscous flow led to smoother surfaces and more uniform interfacial separation, whereas at 100 °C, limited mobility resulted in heterogeneous, fragmented residues and predominantly cohesive failure. These results highlight that optimizing temperature is key to balancing effective delamination with residue minimization, supporting more sustainable PV recycling. Full article

This study addresses the brittleness, poor bonding, and low crack resistance of ordinary Portland cement (OPC) grouting materials by incorporating an ethylene-vinyl acetate (EVA) copolymer. The enhancement mechanisms and engineering applicability of EVA-modified cement grouts were systematically investigated. Using EVA contents from 0% to 20%, macro-scale tests covering fluidity, rheology, bleeding rate, and compressive strength were conducted, along with microstructural analyses (SEM, XRD, FT-IR). Results indicate that with 12% EVA, the 28-day compressive strength reached 21.03 MPa, reflecting a 68% increase over the unmodified grout. Most favorable amount of EVA promoted the formation of C–S–H gel, filled microcracks, and enhanced structural densification, whereas excessive EVA content led to the formation of a polymer film that hindered hydration and reduced strength. Furthermore, EVA effectively improved the rheological behavior of the grout, with the Vipulanandan model demonstrating superior accuracy over the Bingham model in characterizing its non-Newtonian flow. This study systematically established a quantitative–qualitative correlation between EVA content, nonlinear rheological behavior (characterized by advanced models), microstructure evolution (porosity, C–S–H, polymer film) and final macromechanics and durability. Full article

Ethylene–vinyl acetate (EVA) copolymers are widely used in packaging, films, foams, and adhesives because of their softness and optical clarity; however, their relatively low mechanical strength limits broader applications. In this study, a scalable masterbatch strategy was developed to reinforce EVA by introducing TEMPO-oxidized cellulose nanofibers (T-CNFs), pre-encapsulated within an ethylene–vinyl alcohol (EVOH) matrix. EVOH acted as a compatibilizer, establishing robust hydrogen bonding with T-CNFs (evidenced by a 2.73-fold increase in the hydrogen bonding index) and thereby promoting their uniform dispersion and strong interfacial adhesion in the hydrophobic EVA phase. The resulting nanocomposites demonstrated significant improvements in mechanical performance, achieving a maximum 1.54-fold increase in tensile strength and a 1.42-fold increase in Young’s modulus compared to neat EVA. These findings highlight a practical route to produce bio-based, mechanically enhanced EVA nanocomposites with potential for industrial-scale applications. Full article

As a non-invasive diagnostic technique, evolved gas analysis (EGA) holds significant value in assessing the insulation conditions of critical equipment such as power cables. Current analytical methods face two major challenges: insulation materials may undergo multiple aging mechanisms simultaneously, leading to interfering characteristic gases; and traditional approaches lack the multi-label recognition capability to address concurrent fault patterns when processing mixed-gas data. These limitations hinder the accuracy and comprehensiveness of insulation condition assessment, underscoring the urgent need for intelligent analytical methods. This study proposes a deep convolutional neural network (DCNN)-based multi-label classification framework to accurately identify the gas generation characteristics of five typical power cable insulation materials—ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), silicone rubber (SR), polyamide (PA), and cross-linked polyethylene (XLPE)—under fault conditions. The method leverages concentration data of six characteristic gases (CO₂, C₂H₄, C₂H₆, CH₄, CO, and H₂), integrating modern data analysis and deep learning techniques, including logarithmic transformation, Z-score normalization, multi-scale convolution, residual connections, channel attention mechanisms, and weighted binary cross-entropy loss functions, to enable simultaneous prediction of multiple degradation states or concurrent fault pattern combinations. By constructing a gas dataset covering diverse materials and operating conditions and conducting comparative experiments to validate the proposed DCNN model’s performance, the results demonstrate that the model can effectively learn material-specific gas generation patterns and accurately identify complex label co-occurrence scenarios. This approach provides technical support for improving the accuracy of insulation condition assessment in power cable equipment. Full article

This work proposes a coating approach for obtaining flame-retardant ethylene–vinyl acetate (EVA) and ethylene–butyl acrylate (EBA) copolymer-based materials. Nanocomposite films of EVA and EBA were first produced by cast extrusion, with two types of layered double hydroxides (LDHs) differing in the aspect ratio used as nanofillers. Subsequently, the films were applied as a coating to the corresponding neat copolymer substrate, and the combustion behavior of the so-obtained samples was evaluated through cone calorimeter tests. Despite the small amount of nanofillers (0.5 wt.% considering the whole specimen), the application of the coatings significantly improved the time to ignition compared to the pristine copolymers, while the shape of the heat release rate curves and the relative peak values remained relatively unchanged. The effect of the embedded nanofillers in delaying the ignition was more effective for the EVA-based systems than for the EBA ones (showing an increment of 30% and 12%, respectively, compared to the uncoated samples), likely due to the more homogeneous dispersion of the LDHs obtained in the first case. The obtained results demonstrate the effectiveness of the coating approach, since it allows the flame-retardant action to be concentrated on the surface of a polymer system, where combustion specifically takes place, while minimizing the required amount of flame retardant. Full article

Single-type viscosity reducers often fail to meet the application requirements of specific oilfields for high-viscosity heavy oils. This study focused on Henan heavy oil, systematically investigating the viscosity reduction performances of oil-soluble viscosity reducers, emulsifiers, and their composite systems. Experimental results indicated that the oil-soluble ethylene-vinyl acetate copolymer (EVA) achieved optimal efficiency at a concentration of 500 ppm, with a viscosity reduction rate of 44.2%. Among the screened emulsifiers, acrylonitrile-ethylene-styrene (AES) exhibited the highest viscosity reduction rate (99.9%), which basically complied with relevant industrial application standards. When EVA and AES were compounded, the resulting composite reducer showed a significantly higher viscosity reduction rate than single EVA, and the stability of the formed oil-in-water (O/W) emulsion was further enhanced. The synergistic mechanism was clarified as follows: EVA first disrupts the aggregation of heavy components (resins and asphaltenes) and modifies wax crystal morphology, creating a favorable microfoundation for subsequent emulsification; AES then promotes the formation of stable O/W emulsions, ultimately achieving a “1 + 1 > 2” synergistic viscosity reduction effect. Furthermore, the potential action mechanism of the EVA-AES composite system was verified using multiple characterization techniques. This study provides a valuable reference for the selection and practical application of heavy oil viscosity reducers in oilfield operations. Full article

The article presents the results of a study of the possibility of using heat-treated ethylene-vinyl acetate copolymer (EVA) as a thermoplastic modifier in a photosensitive composition based on tert-butyl acrylate (tBA). The use of such a modifier in 3D printing compositions is important for improving their physical and mechanical properties at low temperatures. An attempt was also made to use EVA as a polymer chain brancher. The molecular structure of the components and their compositions, rheology, curing kinetics, and phase organization of photocured systems were studied using FTIR and NMR spectroscopy, spectrophotometry, rheometry, Photo-DSC, and scanning electron microscopy. It was found that heat treatment of EVA allows the formation of single C=C bonds in macromolecules, which are necessary for a potential crosslinking agent with tBA. It was shown that EVA effectively functions as a thickener and modifier: with an increase in the modifier concentration, the nature of the composition flow changes from Newtonian to pseudoplastic, the rate of the photochemical polymerization reaction decreases, and the degree of conversion of the system decreases. However, the formation of a heterogeneous phase structure and the absence of a continuous spatial network of chemical bonds prevent the use of EVA simultaneously as a functional additive and crosslinking agent. Full article

To enhance the overall performance of asphalt pavements and promote the efficient utilization of solid waste resources, this study innovatively incorporates recycled polyethylene (PE) particles and recycled ethylene-vinyl acetate copolymer (EVA) particles, each compounded with waste cooking oil (WCO), to modify base asphalt. Systematic tests were conducted to evaluate the physical and rheological properties of the composite modified asphalt. Additionally, Fourier transform infrared spectroscopy (FTIR) and thin-layer chromatography with flame ionization detection (TLC-FID) were used to analyze the microstructures and internal components of the modified asphalt. The results indicate that the optimal mixing ratio for the WPA is 5% WCO, 5% EVA, and 5% PE. With the incorporation of these modified materials, the asphalt’s high-temperature and low-temperature properties, as well as its rutting and fatigue resistance, are enhanced to some extent. Furthermore, the modification significantly improves the rheological properties of the asphalt across the full temperature range. Additionally, the modified materials lead to changes in the internal composition of the asphalt: the content of lighter components decreases, while the content of heavier components increases. These changes in the internal composition are the primary cause of the observed improvements in the rheological properties of the asphalt. Full article

Fabric veneer panels were prepared using ethylene-vinyl acetate copolymer film (EVA) as the intermediate layer and poplar plywood as the substrate. Eight fabrics with different compositions were selected for evaluation to screen out fabric materials suitable for poplar plywood veneer. The fabrics were objectively analyzed by bending and draping, compression, and surface roughness, and subjectively evaluated by establishing seven levels of semantic differences. ESEM, surface adhesive properties, and peel resistance tests were used to characterize the microstructure and physical–mechanical properties of the composites. The results show that cotton and linen fabrics and corduroy fabrics are superior to other fabrics in performance, and they are suitable for decorative materials. Because the fibers of the doupioni silk fabric are too thin, and the fibers of felt fabric are randomly staggered, they are not suitable for the surface decoration materials of man-made panels. The acetate veneer surface gluing performance was 1.31 MPa, and the longitudinal peel resistance was 20.98 N, significantly exceeding that of other fabric veneers. Through the subjective and objective analysis of fabrics and gluing performance tests, it was concluded that, compared with fabrics made of natural fibers, man-made fiber fabrics are more suitable for use as surface finishing materials for wood-based panels. The results of this study provide a theoretical basis and process reference for the development of environmentally friendly decorative panels, which can be expanded and applied to furniture, interior decoration, and other fields. Full article

This study investigated the effects of electron beam radiation on the room-temperature and high-temperature mechanical properties of two ethylene-vinyl acetate (EVA) copolymers, designated EVA 206 and EVA 212. These copolymers had varying vinyl acetate (VA) contents (6 wt.% and 12 wt.%), with the same melt flow index of 2.0 g/10 min. Samples were irradiated at doses ranging from 60 to 180 kGy. The impact of electron beam irradiation on the creep, frequency sweep, and stress–strain behaviors of the ethylene-vinyl acetate copolymers was evaluated using a dynamical mechanical analyzer (DMA). Crystallinity was measured using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Creep compliance was quantitatively analyzed using four-parameter and six-parameter models. While crosslinking had minimal influence on the room-temperature properties, it significantly affected the behavior at 150 °C. With increasing irradiation dose, creep compliance decreased, while the shear modulus, viscosity, and shear stress at a strain of 0.03 increased, indicating enhanced resistance to deformation. Crosslink density also increased with irradiation dose. EVA 212 with a higher vinyl acetate content exhibited a higher resistance to creep and better high-temperature mechanical properties across all measurements. Full article

The properties of EVA copolymers with various vinyl acetate (VA) contents were compared, with EVA 206 (6 wt.% VA) and EVA 212 (12 wt.% VA) having the same melt flow indices of 2 g/10 min. The impact of electron irradiation at levels of 60, 120, and 180 kGy was studied. Four testing methods were employed as follows: wide-angle X-ray diffraction (WAXD); differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA), using a high-temperature frequency sweep at 150 °C; and gel content analysis. The amount of crystalline phase was determined by WAXD and DSC. Copolymers with a higher VA content (EVA 212) had lower crystallinity. The increase in the amorphous phase allows for the greater movement of radicals, enabling them to react and form cross-links. The effects of the VA content, radiation dose, and frequency on dynamic mechanical properties were investigated by DMA. The DMA analysis focused on the shear storage modulus $G^{\prime }$, damping factor $\tan \delta$, and complex viscosity ${\eta }^{*}$. After irradiation, the damping factor $\tan \delta$ decreased with an increasing VA content, indicating improved elasticity and a higher degree of cross-linking. A gel content analysis was used to calculate the parameters of the Charlesby-Pinner and Charlesby–Rosiak equations, which help with the determination of the relationship between cross-linking and chain scission. The ratio of cross-linking to scission $G\left(X\right)/G\left(S\right)$ was higher for the EVA with a higher VA content (EVA 212). Due to a higher VA content (12 wt.%), EVA 212 exhibits more efficient network formation. Full article

Poly(L-lactic acid) (PLLA) was blended with an ethylene-vinyl acetate (EVA) copolymer, which is generally recognized as a phase-separated system. The interactions between these polymer species were examined via spherulite observation. The PLLA/EVA blend was concluded to be a partially miscible system. The onset temperature for the crystallization of PLLA, as the crystalline polymer, systematically changed when PLLA was blended with EVA at various ratios. The glass transition behavior of EVA was almost absent in the thermogram when the PLLA:EVA blend ratio was greater than 2:1. The spherulite size distribution of PLLA became finer as the PLLA:EVA ratio was changed from 3:1 to 2:1 to 1:1, and observing spherulites was difficult when the blend ratio was 1:2. Because the nucleation position was different each time during the repeated melting/crystallization of spherulites, this system exhibited homogeneous nucleation. In addition, in a plot of the spherulite size versus the crystallization time, the inclination angle changed between the PLLA/EVA = 3:1 and 2:1 blends, and the critical ratio at which the crystallization behavior changed was estimated. Full article

Using solid waste-based materials, such as recycled building aggregate (RCA), preparing 3D-printed materials can reduce costs but increase the water–cement ratio of the printed material, which reduces its mechanical performance. In order to solve the problem of mechanical properties decline caused by an increase in the w/c ratio, this experiment found that adding calcined salt mud (CSM) to the printing materials and changing the water-to-cement ratio from 0.37 to 0.4 CSM can ensure that the compressive strength of the printing materials remains basically unchanged. Moreover, through TG, SEM, and other microscopic data, it can be seen that calcium hydroxide in CSM can not only participate in the synergistic reaction of ethylene/vinyl acetate copolymer (EVA) and dust ash (DA), produce more NaOH, and promote the hydration of granulated blast furnace slag (GBFS) but also promote the formation of ettringite together with SO₄²⁻ in solution, optimizing pore size distribution. Full article