Vinyl Acetate Matrix Research Articles

Влияние содержания технического углерода на вольт-амперные характеристики полимерных композитов

The influence of the concentration (C) of technical carbon (CB) on the current-voltage characteristics (CVC) of composites based on an ethylene vinyl acetate matrix has been studied. It has been established that in polymer composites with low (С = 5%) and high (С  25%) concentrations, the conductivity is practically independent of the electric field strength. In composites with CB concentrations corresponding to the percolation region, the presence of two pronounced segments of the CVC was found. After reaching a certain threshold field, a sharp increase in conductivity was observed. The behavior of the current-voltage characteristics of such composites in the region of high fields is described with good accuracy by the Fowler-Nordheim expression.

Incorporation of polyethylene fillers in all-polymer high-thermal-conductivity composites

This work presents a lightweight electrically insulating composite material for high thermal conductivity: all polymer composites created by mixing ultra-high molecular weight polyethylene flakes into a matrix of low-density polyethylene or ethylene vinyl acetate. The ultra-high molecular weight polyethylene flakes have a reported thermal conductivity of 40 W m−1 K−1, and when 30 volume percent is compounded in an ethylene vinyl acetate matrix, the thermal conductivity is measured to be 2.5 W m−1 K−1 at 52 °C and the notched impact strength is 350 J/m. The temperature stability of the polyethylene flakes is investigated using polarized Raman spectrometry and thermal conductivity measurements, and it is discovered that flakes compounded at temperatures of 115 °C and above show a dramatic drop in thermal conductivity due to melting and reduced polymer chain alignment. This study highlights the possibility of using high-thermal-conductivity polymer fillers in bulk composites for near-room-temperature applications.

Polyethylene/Ethylene Vinyl Acetate and Ethylene Octene Copolymer/Clay Nanocomposite Films: Different Processing Conditions and Their Effect on Properties

Polymer nanocomposites based on a layered clay used as nanofiller and copolymers ethylene and vinyl acetate matrix (EVA, the content of vinyl acetate (VA) component 19 wt% and 5 wt%) and ethylene octene copolymer (EOC, 17% and 45% of octene) were prepared. KO Buss kneader and double screw extruder were used. The MMT Na+ and four types of commercial products such as Nanofil N5 and N3000, Cloisite 93A and 30B were used as nanofillers—5 wt% in relation to the content of montmorillonite. The aim was to evaluate the influence of copolymer composition and processing on prepared nanocomposite properties. The morphology of samples was examined by means of X‐ray diffraction (XRD) and transmission electronic microscopy TEM. Furthermore, mechanical and especially barrier properties were observed. Despite the fact that the XRD and microscopy results have revealed that complete exfoliation did not take place in any case, mechanical properties as well as the permeability showed that used 5 wt% of clay was enough to achieve the improvement of properties. Cloisite 30B might be the most suitable for the polyethylene/EVA matrix. In case of EOC copolymer the nanofiller Nanofil N3000 and mainly Cloisite 93A seems to be more suitable. The better properties were achieved for the version of EVA with lower VA content and also for EOC 17, but not for each evaluated property. POLYM. ENG. SCI., 59:2514–2521, 2019. © 2019 Society of Plastics Engineers

Controlled Release of Mangiferin Using Ethylene Vinyl Acetate Matrix for Antioxidant Packaging

This study investigated the use of ethylene vinyl acetate (EVA) matrix in controlled release packaging. Mangiferin, having high antioxidant activity, was incorporated into the EVA matrix with different vinyl acetate (VA) contents. Mangiferin release rate increased with increasing VA content (or decreasing crystallinity). Linear relationship between mangiferin release rate and VA content was observed in the range of 18–40% VA. The diffusion coefficients of mangiferin released from the EVA matrices containing 12%, 18%, 25% and 40% VA were 0.482, 0.512, 2.81 and 2.88 (×10−14 m2/s), respectively. The enhancement factors of about 22-fold and sevenfold were observed in the 12% and 18% VA matrices, respectively, when using triethyl citrate as a plasticizer. EVA film containing 40% VA had the highest antioxidant activity (81.90% radical scavenging capacity, (RSC)) because the highest amount of mangiferin was released in the food simulant (84.66 µg/ml). Addition of mangiferin in the polymer matrices had no significant (p > 0.05) effect on thermal and barrier properties of the films but decreased tensile strength and Young's modulus. The results of this study demonstrated that EVA matrices with varying degree of VA could potentially be used to control mangiferin release rate for antioxidant packaging. Copyright © 2014 John Wiley & Sons, Ltd.

Properties and optimal manufacturing conditions of chicken feathers thermoplastic biocomposites

The aim of this study was the analysis and characterization of composites based on thermoplastics (ethylene vinyl acetate, polypropilene and high-density polyethylene) and chicken feathers. Several composite samples with a content of 20% v/v of chicken feathers have been studied to determine the optimal manufacturing conditions of temperature, mixing time, and mixing speed to achieve the best tensile properties. The results have shown that the addition of micronized chicken feather (20% v/v) to thermoplastic matrices increases stiffness and provides a more brittle behavior. Ethylene vinyl acetate matrix also shows an ability to participate in second-order intermolecular interactions with chicken feathers, providing better tensile properties (tensile strength and toughness) than polypropilene and high-density polyethylene. Optimal manufacturing conditions were found for a mixing time of around 5 min; a mixing speed of 50 r min−1; and temperature values of 160℃ in case of high-density polyethylene, 120℃ for ethylene vinyl acetate, and 170℃ for polypropilene. Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy analysis have been performed in order to provide further understanding of the compatibility and microstructural features that support the tensile properties of the materials.

Numerical Investigation of Heat Transfer of Silver-Coated Glass Particles Dispersed in Ethylene Vinyl Acetate Matrix

The effective thermal conductivity of silver-coated glass spheres dispersed in an ethylene vinyl acetate matrix was investigated numerically as a function of filler concentration. The finite-element method was carried out for modeling the thermal heat transport and to calculate the effective thermal conductivity of the composite for three elementary cells; simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC). The effect of the inclusion/matrix thermal contact resistance and the ratio of thermal conductivities of the filler-to-matrix material are also taken into account. The numerical results are compared with previously published experimental data and some theoretical models. The calculated values of the thermal conductivity of the SC model are in good agreement with the measured results for all the filler volume fractions. Numerical results for FCC and BCC models were found to be in good agreement with analytical models. The results show that the filler/matrix contact resistance has an important effect on the effective thermal conductivity.

Tensile, rheological properties, thermal stability, and morphology of ethylene vinyl acetate copolymer/silica nanocomposites using EVA-g-maleic anhydride

In this article, we present a study on the properties of ethylene vinyl acetate copolymer/silica nanocomposites prepared in absence and presence of EVA-g-maleic anhydride as a compatibilizer between silica nanoparticles and ethylene vinyl acetate matrix. A series of ethylene vinyl acetate/silica nanocomposites with different contents of silica nanoparticles were prepared by solution method. EVA-g-maleic anhydride with 0.5 wt% maleic anhydride groups was added to all ethylene vinyl acetate/silica nanocomposites. Fourier transform infrared, field emission scanning electron microscopy, rheology behavior, and thermogravimetry analysis were used to characterize the structure, morphology, rheological, and thermal properties of the nanocomposites, respectively. The Fourier transform infrared spectra and field emission scanning electron microscopy micrographs showed that the hydroxyl groups on the surface of silica nanoparticles interact with maleic anhydride groups in EVA-g-maleic anhydride and lead to a finer dispersion of individual silica nanoparticles in the ethylene vinyl acetate matrix. The rheological properties and thermal stability of ethylene vinyl acetate/silica nanocomposites were significantly increased after adding EVA-g-maleic anhydride into the nanocomposites. Mechanical properties including tensile strength and elongation at break of the nanocomposites were mainly affected by the content of silica nanoparticles. For the tensile strength as well as elongation at break of the nanocomposites, a maximum value was observed at the content of 0.5 wt% of silica nanoparticles. The addition of EVA-g-maleic anhydride into ethylene vinyl acetate/silica nanocomposites resulted in a further improvement of mechanical properties of the nanocomposites.

Electrical and Mechanical Properties of Ethylene Vinyl Acetate Based Composites

In this study various composites based on the commercial ethylene vinyl acetate polymer matrix and multiwalled carbon nanotubes were prepared by casting from solution in the form of thick films. The degree of dispergation of carbon nanotubes in the polymer matrix was examined by scanning electron microscopy. Electrical conductivity and mechanical properties of those composites were investigated. It was observed that the electrical conductivity of composites increases with an increase of multiwalled carbon nanotubes content. The mechanical properties of composites were only slightly changed when compared with properties of neat ethylene vinyl acetate matrix.

Thermophysical and Electrical Properties of Nanocomposites Based on Ethylene–Vinylacetate Copolymer (EVA) Filled with Expanded and Unexpanded Graphite

Over the last few years, conducting polymer/graphite nanocomposites have attracted considerable interest because of their exceptional electrical, thermal, and mechanical properties. Polymeric nanocomposites prepared from high aspect ratio layered graphite nanofillers achieve significant improvements in thermophysical and electrical properties at low filler concentrations, compared to conventional composites, without a significant increase in density. In this work, various aspects of the electrical and thermophysical behavior of nanocomposites are presented based on the ethylene–vinylacetate matrix filled with nanostructured expanded graphite and standard, (nano)/micro-sized graphite.

Release characteristics of quinupramine from the ethylene–vinyl acetate matrix

An ethylene–vinyl acetate (EVA) matrix containing quinupramine was prepared in an attempt to develop a controlled delivery system for quinupramine. Permeation studies of quinupramine through the EVA copolymer membrane were carried out using a two-chamber diffusion cell. The rate of drug permeation through the EVA membrane was proportional to the PEG 400 volume fraction. The release of quinupramine from the EVA matrix was examined using a modified Franz diffusion cell. A plasticizer was added to prepare the pore structure of the EVA matrix in order to increase the rate of drug release. The effects of PEG 400, membrane thickness, drug concentration, temperature, and plasticizer on drug release rate were investigated. The drug release rate from the EVA matrix increased with increasing PEG 400 volume fraction, temperature and drug loading dose. The activation energy for drug release was 5.91, 5.39, 4.68 and 4.52 kcal/mol for a loading dose of 0.5%, 1%, 1.5%, and 2%, respectively. Among the plasticizers used, diethyl phthalate showed the best results. The release of quinupramine from the EVA matrix follows a diffusion-controlled model, where the quantity released per unit area is proportional to the square root of time. The controlled release of quinupramine was achieved using the EVA polymer including a plasticizer.

Indicator Products: A New Tool for Lifetime Prediction of Polymeric Materials

The possible correlation between the degree of degradation in the polymer matrix and the release of indicator products was investigated. The degree of degradation was measured by following the molar mass changes by size exclusion chromatography, while indicator products were analyzed by gas chromatography-mass spectrometry. The degree of degradation in polyethylene and polyethylene vinyl acetate matrix after thermooxidation was found to be in correlation with the amount of dicarboxylic acids and lactones formed during aging, while the degree of degradation in photooxidized polyethylene could be predicted from the amount of dicarboxylic acids. The relative amount of lactones compared to the relative amount of dicarboxylic acids increased if the oxidation temperature was increased. However, the total amount of indicator products was in correlation with the remaining number average molar mass and the number of chain scissions caused by oxidation. The amount of butanedioic acid and butyrolactone correlated well with the total amount of dicarboxylic acids and lactones, respectively. Thus, instead of the whole compound classes, butanedioic acid or butyrolactone alone could be used as indicators of oxidation. The detected correlation offers a novel tool for making lifetime predictions and studying the long-term properties of polymeric materials.

Enhanced transdermal delivery of atenolol from the ethylene–vinyl acetate matrix

To enhance transdermal delivery of atenolol, ethylene–vinyl acetate (EVA) matrix of drug containing penetration enhancer was fabricated. Effect of penetration enhancer on the permeation of atenolol through the excised rat skin was studied. Penetrating enhancers showed the increased flux probably due to the enhancing effect on the skin barrier, the stratum corneum. Among enhancers used such as glycols, fatty acids and non-ionic surfactants, polyoxyethylene 2-oleyl ether showed the best enhancement. For the controlling transdermal delivery of atenolol, the application of EVA matrix containing permeation enhancer could be useful in the development of transdermal drug delivery system.

Evaluation of the morantel sustained release trilaminate in the control of parasitic gastroenteritis in first season grazing cattle.

A novel intraruminal bolus developed for the sustained delivery of the anthelmintic morantel tartrate was evaluated in the seasonal control of parasitic gastroenteritis in first season grazing calves. The morantel sustained release trilaminate is a trilaminate sheet consisting of a central lamina of a morantel tartrate/ethylene vinyl acetate matrix coated on both sides with a thin impermeable layer of ethylene vinyl acetate. A symmetrical pattern of circular perforations punched through the device controls the release of morantel. Administration of the trilaminate to calves significantly reduced their faecal egg output compared with untreated controls and thus reduced pasture larval contamination. Clinical parasitic gastroenteritis was prevented in the treated calves and there were significant reductions in their worm burdens compared with the untreated control calves both during and at the end of the grazing season. The control of parasitic gastroenteritis resulted in a significantly greater (P less than 0.0001) weight gain, of 45 kg, by the treated calves.

Therapeutic effect of human fibroblast interferon on premalignant lesions arising in oral mucosa: A pilot study

Human fibroblast interferon (HuIFN- β) was topically administered to 20 premalignant lesions histopathologically showing epithelial dysplasia such as leukoplakia and lichen planus which arose in the oral mucosa. HuIFN- β was prepared in the water-soluble gel form containing 2% carboxymethylcellose, 45% glycelin, 0.1 M citrate buffer (pH 4.5) and 0.2% SDS as stabilizing agents. This preparation was found to be effective for herpetic gingivostomatitis and zostal lesions arising along the intercostal nerve. Thus, the HuIFN- β preparation (10 4 to 5 × 10 3 IU) was applied to the oral mucosal lesion for 1 h twice a week. The lesion with topical administration of HulFN- β was covered tightly with the mucosal bandage which was coated with carboxymethylcellulose, glycelin and CaCl 2 on vinyl acetate matrix. The 14 oral lesions with erosion or ulcer formation accompanied by severe pain by touch, had complete remission after approximately 10 successive applications of this preparation. Although subjective symptoms such as irritation pain in the other 6 patients with severe hyperkeratotic lesion subsided, white coatings and streaks could not be completely removed by this therapy. No other side-effects excluding slight pain and reddish swelling which occurred intermittently during HuIFN- β administration were observed.