Ethylene Vinyl Acetate Copolymer Research Articles

Ethylene–Vinyl Acetate Copolymer and Resin-Stabilized Asphaltenes Synergistically Improve the Flow Behavior of Model Waxy Oils. 1. Effect of Wax Content and the Synergistic Mechanism

Both polymeric pour point depressants (PPDs) and asphaltenes can improve the flowability of waxy oils. However, the effect of polymeric PPDs together with asphaltenes on the flowability of waxy oils is not clear. In this paper, the synergistic effect of ethylene–vinyl acetate (EVA) PPD (100 ppm) and resin-stabilized asphaltenes (0.75 wt %) on the flow behavior of model waxy oils (10–20 wt % wax content) was investigated through rheological tests, DSC analysis, microscopic observation, and asphaltenes precipitation tests. The results showed that the asphaltenes disperse well in the xylene/mineral oil solvent as small aggregates (around 550 nm) with the aid of resins. The EVA or asphaltenes alone moderately improve the flow behavior of waxy oils by changing the wax crystals’ morphology from long and needlelike to a large, radial pattern or fine particles, respectively. The wax precipitation temperatures (WPTs) of waxy oils are also slightly decreased by adding EVA or asphaltenes, meaning that the cocrystall...

Preparation of LDPE/EVA/PE-MA, Nano Clay Blend Composite in the Stage Potassium Sorbate (KS) and Garlic Oil (GO) as an Antimicrobial Substance

In this study the using of antimicrobial substances and nanoparticles can increase the shelf living and on the other hand, keep from the addition of preservatives in food products. This material for putting in parcels is taken into account one of the active putting into technology. In this undertaking, low-density polyethylene was selected because of elasticity, transparency, low melting point and simple reversible process. After that, ethylene vinyl acetate copolymer (EVA), needing payment to adhesion condensation getting in the way of and product transparence properties and the polyethylene graft copolymer with maleic anhydride (PE-G-MA) as a thing making adjustment was used in the first stage. At the second was added to mixture LDPE/EVA/PE-MA. At the third stage, the Clay nanoparticles (NC) was used in the rules to make of a mixture having in it GO. Brabbndr twin-screw extruder was used to process the examples. The mechanical testing, sending (power and so on) electron microscopy (TEM), X diffraction (XRD), water absorption, water vapor, permeability, oxygen permeability and microbial permeability of films produced was taken. The outcome of the above test showed that mechanical properties of the mixture LDPE/EVA/PE-MA than clear LDPE has got well. On the other hand, the mixture having in it GO had the nearest properties to the said mixture and films having in it GO+NC got well mechanical properties, too. The outcome XRD, TEM put into orders for computer the sheet structure. The physical properties of water absorption showed that films having in it GO and GO+NC hare lower water absorption made a comparison to other examples. The outcome of water vapor and oxygen permeability tests indicated that films having in it GO+NC hare more getting in the way of properties than other examples. at last, the outcome of microbial test that was guided for a month, showed that examples having in it antimicrobial substances hare oppose against the growth of small-scale- organisms, in the event that, the motion picture existence without of antimicrobial substances against the growth of micro-organisms did not play or amusement any stopping effect.

Poly (Ethylene-Co-Vinyl Acetate) Blends for Controlled Drug Release

Ethylene vinyl acetate copolymer (EVA) was blended with polyvinyl acetate polymer (PVAc) to form EVA/PVAc blends. Paracetamol was used as a drug model in the investigated blends. Different weight ratios of the two polymers in the blend were investigated, these are (100/0, 80/20 50/50, 20/80, 0/100 w/w EVA/PVAc). The concentration of the drug was kept constant. The micro structure, as well as crystallinity and chemical composition of these blends were investigated. The scanning electron microscopy (SEM) has been conducted for blends before and after release. Crystallization behavior of EVA was investigated as well as X-ray diffraction (XRD) of the blends. Besides FTIR spectrum of the samples and equilibrium swelling and deswelling of the blends has been carried out.

Effect of redispersible polymer powder on setting time of thin-bed mortars

The aim of work is to describe and to complement the existing knowledge on the effect of redispersible polymer powder on the setting time of cement mortar as measured by means of ultrasonic apparatus. The mortars were simple mixtures of filler in the form of quartz sand, Portland cement CEM I 42.5 R as binder and methyl hydroxyethyl cellulose. The mortar additives were two commercially available redispersible polymer powders in an amount of 0-5% of total weight. The chosen polymers had different chemical structure: styrene-acrylic copolymer (SA), vinyl acetate-ethylene copolymer (ET), and minimum film forming temperature (MFFT). The amount of water was constant and equal to 20% of the total weight of the mortar. Conclusions: - even the small amount of redispersible polymer powder added to the cement mortar has a significant influence on mortar’s initial and final setting time and this effect strongly depends on the percentage of the additive, - the chemical structure of the studied redispersible polymer powders did not influence the behaviour of the whole chemical system, - the further studies on technical properties, such as mechanical strength and permeability are planned in order to find more information on the structure of hardened mortar.

Deep drawing of cylindrical cups using polymer powder medium based flexible forming

A novel flexible forming process—polymer powder medium based flexible forming (PPFF)—was presented in this research. Cylindrical cups with inner diameter of 8 mm were formed using rigid mould deep drawing and PPFF process, respectively. The blank material was pure copper C1100 with a thickness of 0.4 mm which was annealed at 450°C for 1 h in vacuum condition. The deep drawing experiments were carried out at room temperature under dry friction condition. Ethylene-vinyl acetate copolymer (EVA), poly vinyl chloride (PVC) and ultra-high molecular weight polyethylene (UHWPE) were used. The influence of polymer powder type and weight on deep drawing force and limiting drawing ratio (LDR) were investigated. The results showed that the cylindrical cups were well formed by using PVC. The LDR reached 2.1 by using PVC, higher than rigid mould. The surface quality was also good, with the thinning rate much smaller than rigid mould forming.

Preparation of Highly Tough Ethylene Vinyl Acetate (EVA) Heterogeneous Cation Exchange Membranes and Their Properties of Desalination

A manufacturing method has been devised to prepare novel heterogeneous cation exchange membranes by mixing ethylene vinyl acetate (EVA) copolymers with a commercial cation exchange resin. Optimum material characteristics, mixture ratios and manufacturing conditions have been worked out for achieving favorable membrane performance. Ion exchange capacity, electrical resistance, water uptake, swelling ratio and tensile strength properties were measured. SEM analysis was used to monitor morphology. Effects of vinyl acetate (VA) content, melt index (MI) and ion exchange resin content on properties of heterogeneous cation exchange membranes have been discussed. An application test was carried out by mounting a selected membrane in a membrane capacitive deionization (MCDI) system to investigate its desalination capability. 0.92 meq/g of ion exchange capacity, 8.7 Ω.㎠ of electrical resistance, 40 kgf/ ㎠ of tensile strength, 19% of swelling ratio, 42% of water uptake, and 56.4% salt removal rate were achieved at best. VA content plays a leading role on the extent of physical properties and performance; however, MI is important for having uniform distribution of resin grains and achieving better ionic conductivity. Overall, manufacturing cost has been suppressed to 5-10% of that of homogeneous ion exchange membranes.

Thermal Mechanical and Dielectric Studies on Thin Films of Ethylene Vinyl Acetate Copolymer with Varying Concentration of Vinyl Acetate

The Ethylene vinyl acetate, a copolymer of polyethylene (EVA) has been used for the preparation of thin films for the investigation. The films are prepared by room temperature using solvent casting method through varying the percentage of vinyl acetate content in EVA as 18%, 58% and 88%. Chloroform is used as a solvent for ethylene vinyl acetate, high-speed stirring resulting the homogenous dispersion of the molecules. The resultant thin films of EVA with 18%, 58% and 88% of VA are characterized under different characterization techniques. The Fourier Transform Infrared Spectroscopy (FTIR) confirms the functional groups present in the EVA films of varying concentrations of VA. Thermo Gravimetric Analysis (TGA) is carried out to confirm the Thermal Stability of the films with increase in VA content. The improvement in mechanical properties like Tensile Strength, Flexural Strength and Toughness with increase in vinyl acetate content is confirmed through mechanical studies. The dielectric properties are studied for all the three concentrations of vinyl acetate in EVA, which shows constant result on the value of dielectric constant at higher the vinyl acetate in EVA as 88%.

Development of directed regulation of rheological properties of fire retardant composite materials of ethylene vinyl acetate copolymer

The object of research is rheological processes of viscous flow of non-combustible polymeric composite materials. One of the most problematic issues arising in the processing of polymer composite materials is an increased viscosity, which requires an increase in shear stresses to achieve a given speed. In order to solve this problem, a method has been developed for the directed regulation of the rheological characteristics of polymer compositions by injecting a modifier into their composition. The influence of the modifier on the viscous flow processes of fire retardant materials of an ethylene with vinyl acetate copolymer and fire retardant fillers, has been studied. In the studies, an ethylene vinyl acetate copolymer is used. The content of vinyl acetate is 18 % and 28 %; MFI 2.5 g/10 min and MFI 5 g/10 min. Modifier is aminosilane. Fillers are fire retardants: aluminum trihydroxide with an average particle diameter of 1.5 μm and 3.0 μm; magnesium hydroxide with an average particle diameter of 3.0 μm and 3.7 μm; hydromagnesite with an average particle diameter of 1.4 μm. Using the method of capillary viscometry, the following characteristics are determined: melt flow index, shear stress, shear rate, effective viscosity and viscous flow activation energy. The melt flow index decreases with the use fire retardant fillers with a smaller average particle diameter. The melt flow rate of the polymer composition using fire retardant filler- of different chemical nature and dispersity increases with the modifier injection. For aluminum trihydroxide 2–8 times, for magnesium hydroxide 2.2–3 times, for hydromagnesite 2.0–2.2 times. The shear stress and the effective viscosity, on the contrary, decrease when the modifier is injected into the polymer composition. The obtained results allow to increase the productivity during processing of the developed materials due to the decrease of such parameters as viscosity, shear stress, increase in the melt flow parameters and shear rate. This, in turn, will positively affect the reduction of energy costs and the production time of cable products. The results will be useful in the development of formulations of polymer compositions for cable products and the directed regulation of technological parameters during their processing.

Effect of fire retardant fillers on thermophysical properties of composite materials of ethylene-vinyl acetate copolymer

The influence of composite materials of ethylene-vinyl acetate copolymer that do not maintain combustion and fire-retardant fillers on thermophysical processes was explored. Ethylene-vinyl acetate copolymer was used in the studies. The content of vinyl acetate is 18 % and 28 %; MFI is 2.5 g/10 min. and MFI is 5 g/10 min. Fire retardant fillers included aluminum oxide trihydrates with average diameter of particles of 1.5 µm and 3.0 µm; magnesium oxide dihydrates with average diameter of particles of 3.0 µm and 3.7 µm and hydromagnesite with average diameter of particles of 1.4 µm. Using the method of thermogravimetric analysis and differential scanning calorimetry TGA/DSC, temperatures of vitrification, melting and decomposition, crystallinity degree, specific thermal capacity, and activation energy were determined. It was found that temperatures of physical transformations (temperatures of vitrification, melting, and decomposition) of polymer compositions that do not maintain combustion depend on properties of ethylene-vinyl acetate copolymer. They increase with decreasing of fluidity indicator of copolymer of ethylene vinyl acetate. EVA 1 has lower values of the indicator of melt fluidity and content of vinyl acetate than EVA 2. During an increase in content of fire retardant fillers, temperatures of physical transformations are shifted in the direction of increasing: vitrification temperature increases from – 85 °C to 53 °C, melting temperature – from 68 °C to 90 °C. At the same time, crystallinity degree decreases from 8.8 % to 1.0 % and specific thermal capacity increases from 0.4 to 8.6 J/gK. This is due to formation of supermolecular structure of the derived compositions. The influence of the polymeric matrix, composition and dispersity of fire retardant fillers on thermal-physical characteristics of polymeric compositions was determined. In case of using a polymer matrix with lower MFI and fire retardants fillers with smaller average diameter of particles, temperature characteristics are shifted towards higher temperatures than in the case of selection of polymer matrix with large MFI and fire-retardant fillers with a larger diameter of particles. Obtained results will be useful during development of formulations of polymer compositions that do not maintain combustion for cable products, considering their thermophysical characteristics.

Investigation of rheological properties of light colored synthetic asphalt binders containing different polymer modifiers

Light colored synthetic asphalt (LCSA) binders were prepared by using aromatic oil, petroleum resin and various polymer modifiers. The polymers used included styrene-butadiene-styrene block copolymers (SBS), ethylene-vinyl acetate copolymer (EVA) and polyethylene (PE). The modification effects of single and combined polymers were investigated. Fluorescence microscopy analysis confirmed the well dispersion of polymer phase and the compatibility of the binder. Fundamental research into rheological behaviors was conducted by using viscosity test, dynamic shear rheological test and bending beam test. Test results showed that LCSA had a high viscosity at construction temperatures and strong frequency/temperature dependence on rheological properties. Polymer modification was identified by the master curves of phase angle and rheological black diagrams. BBR results demonstrated that LCSA binders were susceptible to low temperature and aging. Data analysis indicated that LCSA binders prepared by using SBS, EVA and the combination of SBS plus EVA showed considerable performance for practical application.

Non-destructive monitoring of ethylene vinyl acetate crosslinking in PV-modules by luminescence spectroscopy

This work reports on the prospects of using luminescence spectroscopy as a non-destructive method for the characterization of ethylene vinyl acetate copolymer (EVA) crosslinking in photovoltaic (PV) modules. Luminescence has the potential to be easily applied in-line for monitoring purposes, e.g. during manufacturing. We investigate the correlation of luminescence, Raman spectroscopy and differential scanning calorimetry with the EVA crosslinking. We show that all these methods, including the luminescence method, show a good correlation with the hold time during the lamination process. Furthermore, time-dependent luminescence measurements are introduced. These make use of the fact that the luminescence decreases upon the ultraviolet irradiation during the measurement. In contrast to steady-state luminescence, this facilitates measurements that are inherently less dependent on possible interfering signal artifacts, as these may occur in industrial PV modules due to other components of the PV module.

Effect of nanocomposite of attapulgite/EVA on flow behavior and wax crystallization of model oil

ABSTRACTNanocomposites of attapulgite (ATT)/ethylene vinyl acetate copolymer (EVA) were prepared with organically modified ATT covering in EVA. Organically modified ATT was prepared using KH550 and organic acid. The effect of nano-hybrid on the flow behavior of model oil containing 15 wt% wax was evaluated. The wax crystallization and crystal morphology of the model oil at low temperature were observed by polarizing optical microscopy (POM). The results indicated that the nano-hybrid with long-chain organic acid-modified ATT exhibited a better effect compared with the nano-hybrid with short-chain organic acid-modified ATT, pure EVA. In addition, it is interesting to note that EVA (VA = 32%)/stearic acid-modified ATT composite polymeric pour-point depressant (PPD) S-AtPPD(32) provided better cold-flow improvement for the model oil than EVA (VA = 32%)-modified nano-SiO2 composite PPD N-SiPPD (32) with a low dose, which resulted in a regular, bar-shaped, and uniform arrangement of wax morphologies. The pour point of the model oil was reduced from 30°C to −1°C when doped at 200 ppm S-AtPPD(32).

Advances in the research of polymeric pour point depressant for waxy crude oil

ABSTRACTIn the pipeline transportation of waxy crude oil when the temperature of the waxy crude oil drops lower than the wax appearance temperature (WAT), wax precipitates continuously from oil phase, which brings a series of negative impacts on pipeline performance and even causes complete blockage under severe conditions in recent decades, polymeric pour point depressants have a very important practical application in depressing the pour point and improving the fluidity of waxy crude oil, thus reducing the cost of waxy crude oil pipeline transportation. The most commonly used types of the polymeric pour point depressants include ethylene-vinyl acetate (EVA) copolymers, comb copolymers, and nano-hybrid pour point depressants. In this paper, the structural character, interactive types, and the action mechanism of the polymeric pour point depressants are reviewed with their application and research progress introduced.

Thermal conductivity, morphology and mechanical properties for thermally reduced graphite oxide-filled ethylene vinylacetate copolymers

Systematic variation of copolymers (Poly (ethylene-covinylacetate)) composition provide an opportunity to change matrix polarities and thus explore their effects on the polymer/filler interactions and composite properties. The main objective of this work is to study the effect of vinyl acetate (VA) content on the extent of exfoliation and dispersion of thermally reduced graphite oxide (TrGO), as well as its impact on the thermal conductivity and mechanical properties of the resultant composites. The use of ethylene vinyl-acetate (EVA) copolymers of different (0–40 wt%) vinyl acetate content with similar melt viscosities allowed us to keep the processing conditions constant and quantitatively compare the thermal conductivity and mechanical properties of composites with different matrix polarities. Composites with conductive graphite (GT) and multiwalled carbon nanotubes (MWCNT) were also prepared and examined for comparison. Melt dispersion of TrGO in EVA copolymers was quantified using a range of characterization techniques: transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray scattering measurements. Electron microscopy and X-ray diffraction revealed highly exfoliated morphology of TrGO throughout the entire matrix, while GT remained multi-layer even after melt processing. Nanocomposites reinforced with TrGO showed significantly improved thermal conductivities and mechanical properties combined with low rheological percolation thresholds comparable to those achieved using MWCNT and GT. We propose a formalism to assess the thermal conductivity and mechanical properties of graphene nanocomposites based upon the interfacial excess energies of EVA copolymers.

Dielectric relaxation behavior of exfoliated graphite nanoplatelets filled ethylene vinyl acetate copolymer and ethylene propylene diene terpolymer blend

Exfoliated graphite nanoplatelets(xGnP) filled 50:50 blend of ethylene vinyl acetate copolymer(EVA) and ethylene propylene diene terpolymer (EPDM) composites were prepared by solution casting followed by compression moulding method. The microstructure, dielectric characteristics and conducting behaviour were investigated as function of xGnP loading and frequency range of 102 to 5 × 106Hz. Dielectric constant increases with increase in xGnP loading and showed maximum value at 10 phr loading and then decreases with increase in xGnP loading. The enhancement of dielectric constant is due to Maxwell–Wagner–Sillars (MWS) interfacial polarization between the exfoliated graphite nanoplatelets and EVA/EPDM polymer blend interfaces. From Nyquist plot it is observed that with increase in xGnP loading beyond 6 wt% semicircles are obtained which become prominent above 8 wt% loading. AC conductivity values increases with increase in xGnP loading and a percolation threshold of 6 wt% was observed for EVA-EPDM (50:50) blend system which is much lower than the EVA-xGnP as well as EPDM-xGnP systems. The non-linear current–voltage(I–V) characteristics below the percolation threshold is obtained which is due to tunnelling and at higher xGnP loading, a liner I–V characteristic is due to direct contact between the xGnP nanoplatelets.

A PTX/nitinol stent combination with temperature-responsive phase-change 1-hexadecanol for magnetocaloric drug delivery: Magnetocaloric drug release and esophagus tissue penetration

An antitumor drug/esophagus stent combination can palliatively relieve malignant esophageal stricture and exert local chemotherapy to cancer. It is vital for effective treatment of cancer to control drug release and facilitate drug penetration into deep tissue after the combination is placed in the malignant strictured esophagus part. In this study, we firstly designed and prepared a novel antitumor drug/esophagus stent combination: a magnetocaloric nitinol stent coated with a bilayered film that consisted of one ethylene-vinyl acetate copolymer (EVA) layer as drug blocking layer and one EVA layer containing 10% paclitaxel (PTX) and 30% temperature sensitive phase-change fatty alcohol (1-tetradecanol, 1-hexadecanol or 1-octadecanol). The drug release and penetration into rabbit esophagus wall from the combination were investigated. It was found that, under an alternating electromagnetic field at a power of 0.1 kW, the combination was heated to 43 °C, the PTX was faster and more released from the combination, as well as the amount of PTX in esophagus tissue or its deep muscle tissue penetrated from the combination was much higher than that without alternating electromagnetic field. The pathological data showed that the combination was biocompatible and safe after placement in rabbit esophagus even under an alternating electromagnetic field. Overall, the PTX could be magnetocalorically released and effectively penetrated into esophagus wall from the PTX/nitinol stent combination.

Enhanced mechanical, conductivity, and dielectric characteristics of ethylene vinyl acetate copolymer composite filled with carbon nanotubes

We report high mechanical, dielectric, and thermal performance of carbon nanotubes (CNT) reinforced ethylene vinyl acetate (EVA) composites, fabricated using conventional melt extrusion processing. CNT have extremely high stiffness, electrical conductivity, and surface area, ensuring strong interactions with the polymer and effective reinforcement. The addition of CNT to EVA leads to an extremely high yield strength and Young’s modulus of the composites. The EVA composite produced, containing 5 wt% CNT, exhibited an almost 3-fold increase in Young’s modulus and a 2.2-fold improvement of yield strength compared to neat EVA. However, the composite maintained high deformation properties—a ductility of 1300%. Scanning electron microscopy analysis evidences the agglomeration of the CNT in the EVA/CNT composites. The EVA/CNT composites gained excellent electrostatic discharge properties—a surface resistivity in the range of 108 Ω/square. The observed thermal conductivity of the composites was increased by about 30% without losing the electrically insulating performance.

A New Insight in Determining the Percolation Threshold of Electrical Conductivity for Extrinsically Conducting Polymer Composites through Different Sigmoidal Models.

The electrical conductivity of extrinsically conducting polymer composite systems passes through a transition state known as percolation threshold. A discussion has been made on how different Sigmoidal models (S-models), such as Sigmoidal–Boltzmann (SB), Sigmoidal–Dose Response (SD), Sigmoidal–Hill (SH), Sigmoidal–Logistic (SL), and Sigmoidal–Logistic-1 (SL-1), can be applied to predict the percolation threshold of electrical conductivity for ethylene vinyl acetate copolymer (EVA) and acrylonitrile butadiene copolymer (NBR) conducting composite systems filled with different carbon fillers. An interesting finding that comes from these observations is that the percolation threshold for electrical conductivity determined by SB and SD models are similar, whereas, the other models give different result when estimated for a particular composite system. This similarity and discrepancy in the results of percolation threshold have been discussed by considering the strength, weakness, and limitation of the models. The percolation threshold value for the composites has also been determined using the classical percolation theory and compared with the sigmoidal models. Moreover, to check the universal applicability, these Sigmoidal models have also been tested on results from some published literature. Finally, it is revealed that, except SL-1 model, the remaining models can successfully be used to determine the percolation threshold of electrical conductivity for extrinsically conductive polymer composites.

Preparation and Evaluation of Modified Ethylene–Vinyl Acetate Copolymer as Pour Point Depressant and Flow Improver for Jianghan Crude Oil

The ethylene–vinyl acetate copolymer (EVA) was modified by alkali-catalyzed alcoholysis. The alcoholized EVA (EVAL) was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR). Moreover, the influence of modified polar groups of EVA on the crystallization process of wax was investigated through differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results showed that EVAL had better performance than EVA in reducing the pour point and the viscosity of crude oil. EVAL could change the wax crystal habit and obviously lower the wax precipitation amount of crude oil. In addition, EVAL with stronger polarity could provide greater electrostatic repulsion force to wax crystals compared with EVA, which made the wax crystals have more difficulty to connect together and form a much looser network structure.

Dynamic stability of ethylene-vinyl acetate copolymer/crumb rubber modified asphalt

In this paper, the recovered waste packaging ethylene-vinyl acetate copolymer (EVA) and crumb rubber (CR) were used as polymer modifying agents to prepare EVA/CR modified asphalt, and the EVA/CR modified asphalt’s dynamic stability were studied. After characterized and analyzed with conventional physical performance test, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), it can be found that the macro and micro properties of modified asphalt in the process of modification modified asphalt evolved from an unstable state to a dynamic stable state and until to a completely final stable state after removed the shear force. The polymer particles gradually dispersed evenly in the modified asphalt and a cross-linked polymer network structure was formed during the shearing process, which were clearly showed through the fluorescence microscopy images. Finally, the interaction between the polymer modifying agents and base asphalt and its impact to the properties of the system were also analyzed combining macro, micro properties of modified asphalt and the morphology changes of modifier and asphaltenes. In addition, stabilization mechanism of EVA/CR modified asphalt was revealed through the former analysis.