Ethylene-co-vinyl Acetate Research Articles

Gamma radiation-induced grafting of C5 aliphatic petroleum resin onto ethylene-co-vinyl acetate copolymer for improving crude oil flowability

At present, ethylene-co-vinyl acetate (EVA) copolymers are the predominant choice among pour point depressants (PPDS) for enhancing the flowability of waxy crude oil. Still, they have shortcomings. Thus, this work aims to investigate the irradiation modification of a commercial EVA copolymer using C5 aliphatic petroleum resin (C5 PR) and its potential for utilization as a flow improver for crude oil. Results conclusively demonstrate the successful grafting of (C5 PR) onto EVA copolymer through gamma radiation, confirmed via grafting parameter characterization, FTIR, and 1H NMR spectroscopy. This modification significantly improved pour point results (ΔPPD = 24, 21, and 24 °C) for (EVA)0kGy, (EVA)50kGy, and (1EVA:1C5 PR)50kGy when treated with 3000 ppm of additives. Notably, the grafted EVA copolymers with C5 PR (1EVA:1C5 PR)50kGy outperformed non-modified EVA at a lower dosage of 1000 ppm. Also, irradiating EVA copolymer without insertion C5 PR resulted in EVA copolymer crosslinking, leading to a decrease in efficiency that could attributed to its accumulation. Furthermore, the crude oil’s rheological properties were substantially enhanced, evidenced by viscosity reductions of 60.8%, 51.3%, and 64.1% at 25 °C, and 55.2%, 18.7%, and 59.4% at 12 °C with the addition of 1000 ppm. Increasing the dosage to 3000 ppm led to even more remarkable viscosity decreases: 76.2%, 67.7%, and 78.2% at 25 °C, and 83.2%, 74.9%, and 84.7% at 12 °C for (EVA)0kGy, (EVA)50kGy, and (1EVA:1C5 PR)50kGy, respectively.

MORPHOLOGICAL, MECHANICAL, ORGANIC VAPOUR PERMEATION PROPERTIES AND BIODEGRADABILITY OF POLY(ETHYLENE-CO-VINYL ACETATE)/WASTE PISTACHIO SHELL-DERIVED CELLULOSE COMPOSITE MEMBRANES

Cellulose fibers have attracted interest as a suitable candidate for manufacturing composites. In the present work, cellulose derived from waste pistachio shell was used to prepare composite membranes with poly(ethylene-co-vinyl acetate (EVA) via solution casting, and their morphological, mechanical, organic vapour permeation characteristics and biodegradability were evaluated. Scanning electron micrographs showed that the voids in the EVA polymer were filled effectively by cellulose fibers. The mechanical testing of the composites revealed an improvement in Young’s modulus with the increase in cellulose loading. The permeation of polar and non-polar solvents through the membranes was studied and explained by molar size, molecular mass and polarity of the solvents. Nielson’s permeability equation as modified by Baradwaj was used to analyse the relative permeability of the membranes. Soil burial degradation experiments of the composite membranes showed a decrease in weight and tensile strength, revealing the biodegradability of the membranes.

Thermal separation of plastic components from waste crystalline silicon solar cells: Thermogravimetric characteristics and thermokinetics

ABSTRACT Thermal treatment is a mainstream technique to separate plastic components from waste crystalline silicon (c-Si) photovoltaic (PV) modules. In this study, the thermogravimetric analysis (TGA) was conducted for a better understanding of the characteristics of plastic components mainly poly(ethylene-co-vinyl) acetate (EVA) binder and polyfluoroethylene composite membrane (TPT) backsheet in waste c-Si PV panels through thermal treatment at four different heating rates (5-20°C·min−1) under nitrogen and air conditions, respectively. The thermal process of the EVA binder whether in a nitrogen or air atmosphere could be divided into two phases, which were 300-400°C and 400-515°C in nitrogen with the total weight loss reached 99.64%; the two phases in the air were 270-405°C and 405-570°C with the total weight loss was 99.68%. The thermal weight loss of TPT in nitrogen has only one phase occured between 380-520°C, and the weight loss rate is about 83%. There are two weight loss phases in the air atmosphere, which the first phase starts from 265°C to 485°C and the second phase ends at 635°C with a final weight loss reaching 97%. Furthermore, the Kissinger-Akahira-Sunose (KAS) method was chosed to calculate the pyrolysis kinetic parameters. The activation energy for EVA in nitrogen (261.16 kJ·mol−1) was higher than in air (209.04 kJ·mol−1), also the TPT in nitrogen (188.28 kJ·mol−1) higher than in air (172.21 kJ·mol−1). That indicated that the thermal decomposition of EVA binder was accelerated at first phase in nitrogen, but there is little difference in air atmosphere. Moreover, the activation energy of PVF of the TPT backsheet in the first phase was lower than that in the second phase. This study provides the fundamental basis to develop efficient thermal separation for the plastic components EVA and TPT in waste PV panels. Implications This study main aims to explore the thermal separation of plastic components of waste c-Si panels for heating treatment, so that developing an accurate heat treatment approach that is efficient to implement for the separation of secondary raw material i.e., glass and silicon wafer from end-of-life PV panels. Therefore, this research findings have significant implications for providing the basic data support for waste PV panels management recycling standards, specifications, or policy documents

Enhancing the activity of ECG Surface Electrodes with super p carbon black additive

The recent developments in the area of surface electrodes materials for biomedical devices such as ECG, EEG are unforeseeable. The role of novel materials in electrode development is highly required for futuristic applications in health and biomedical industry to fulfill the patients’ demand. The proposed project has emphasized on the uses of conductive materials Super p carbon black (SPCB) in electrodes, for enhancing the activity of surface electrodes to capture the better signal of the patients. A great challenge lies not only in fabrication of such materials but also in physical characterization of such conductive materials. In the recent era carbon based nano-materials like CNTs, Graphene, GO and rGO overruled on Ag/AgCl based on its better conductivity. The research work has focused on the electrode fabrication with a conventional slurry-based gel cast method by using Super p carbon black and polymer Ethylene Co Vinyl Acetate (EVA). Further the study has aimed on the quantitatively use of Super p carbon black conductive materials on the surface of the electrode and fictionalized it by using EVA. The electrode material was characterized by in-situ non- destructive conductivity study using the Electrochemical Impedance Spectroscopic (EIS) method. This Super p carbon black could be used directly on the surface of the electrode as inbuilt in a dry form to avoid the un-comfortableness of the patient and longevity of the electrode in various biomedical devices like ECG, EEG, etc.

A continuum large-deformation theory for the coupled modeling of polymer–solvent system with application to PV recycling

Nowadays recycling of photovoltaics (PV) using the solvent method is becoming a very hot topic as massive products deployed in the last century have approached the end of their service lifetime. The key problem in the recycling of end-of-life PV modules is the nondestructive recovery of precious silicon wafers for the manufacturing of new products. However, the attempt to comprehensively understand the polymer–solvent system in the PV recycling process is completely lacking. In this work, a thermodynamically consistent large-deformation theory is proposed to model the coupled behavior of this system. The development of continuum theory accounts for the solvent permeation, swelling and elastic deformation, as well as shrinking effects due to the initial crosslinking of ethylene-co-vinyl acetate (EVA). The crosslinking of EVA influences the stiffness of the polymer network, and interacts with the diffusive kinetics of solvents. Also, given the effects of mechanical constraint, the two-way coupling between the EVA deformation and solvent diffusion is established on the basis of thermodynamic arguments. The proposed modeling method is firstly applied to simulate the swelling experiments of cylindrical EVA samples in solvents Toluene, Tetrahydrofuran, and Octane, and good agreement has been achieved between the numerical prediction and available testing data. Then the second example demonstrates the capability of this modeling framework to describe the influences of initial crosslinking and mechanical constraints on the time history evolution of swelling and elastic deformation. Finally, the complete PV laminate in the 3D setting is modeled for the investigation of solvent penetration induced deformation in the silicon cell layer during the PV recycling process, and comparison has been made to showcase the spatial distribution of maximum principal stress of the silicon cell layers in solvents with different solubility parameters and molar volumes. With this computational tool at hand, it is possible to provide guidance to the design of suitable experimental procedures for the structure-intact recovery of silicon wafers in PV recycling with the solvent method.

Physical, mechanical, viscoelastic, and morphological properties of poly(lactic acid)/ethylene‐co‐vinyl acetate blend reinforced with silicon carbide nanoparticles

AbstractPhase morphology, mechanical properties, melting and crystallinity, as well as the dynamic viscoelastic properties of poly(lactic acid) (PLA)/ethylene‐co‐vinyl acetate (EVA) (80/20) blend containing 0–3 wt% nano‐silicon carbide (SiC) were studied. Morphological observations revealed the localization of nano‐SiC particles around the EVA droplets with the consequence of a fall in the size of EVA dispersed phase in the nanocomposites compared with the unfilled blends. The mechanical characterization results showed a gradual increase in the elastic moduli and yield stress with increasing nano‐SiC content in the nanocomposites, while the strain at break and Izod impact strength were steadily decreased. The nano‐SiC particles served as nucleating agents for crystallization of the PLA matrix from the molten state. The crystallinity of the PLA matrix in the nanocomposites was slightly reduced compared with that of the unfilled blend. The dynamic mechanical thermal analysis results showed a gradual increase in the glass transition temperature of PLA matrix together with a steady decline of damping capability as the nano‐SiC content in the nanocomposite was increased. The dynamic rheological data demonstrated enhanced complex viscosities and storage moduli of the nanocomposites in a direct proportion to the nanofiller loading, specially at the low‐frequency region. The changes occurred in the various properties of the fabricated nanocomposites were interpreted in terms of alteration in the phase morphology and the physical interactions of the nano‐SiC particles with the blend's components.

Molten-State Dielectrophoretic Alignment of EVA/BaTiO3 Thermoplastic Composites: Enhancement of Piezo-Smart Sensor for Medical Application.

Dielectrophoresis has recently been used for developing high performance elastomer-based structured piezoelectric composites. However, no study has yet focused on the development of aligned thermoplastic-based piezocomposites. In this work, highly anisotropic thermoplastic composites, with high piezoelectric sensitivity, are created. Molten-state dielectrophoresis is introduced as an effective manufacturing pathway for the obtaining of an aligned filler structure within a thermoplastic matrix. For this study, Poly(Ethylene-co Vinyl Acetate) (EVA), revealed as a biocompatible polymeric matrix, was combined with barium titanate (BaTiO3) filler, well-known as a lead-free piezoelectric material. The phase inversion method was used to obtain an optimal dispersion of the BaTiO3 within the EVA thermoplastic matrix. The effect of the processing parameters, such as the poling electric field and the filler content, were analyzed via dielectric spectroscopy, piezoelectric characterization, and scanning electron microscopy (SEM). The thermal behavior of the matrix was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry analysis (DSC). Thermoplastic-based structured composites have numerous appealing advantages, such as recyclability, enhanced piezoelectric activity, encapsulation properties, low manufacturing time, and being light weight, which make the developed composites of great novelty, paving the way for new applications in the medical field, such as integrated sensors adaptable to 3D printing technology.

Dependence of adhesion on degradation mechanisms of ethylene co-vinyl acetate encapsulants over the lifetime of photovoltaic modules

The long-term reliability of encapsulation has a critical impact on the overall cost and effectiveness of photovoltaic modules. An often overlooked but important element of this reliability concerns adhesive degradation of the encapsulant, which results in delamination. This work critically examines the degradation mechanisms – deacetylation, β-scission, and hydrolytic depolymerization – primarily responsible for adhesion loss in ethylene co-vinyl acetate (EVA) encapsulants to provide evidence and clarity regarding the contribution of these mechanisms to the adhesive degradation over the lifetime of a module. EVA samples obtained from mini-modules exposed in two sets of controlled, accelerated conditions – with and without ultraviolet (UV) radiation – are characterized to find specific evidence for the proposed degradation mechanisms. The mini-modules were exposed up to 10,000 h, which represents up to 15–20 years in the field. Results affirm that initially, deacetylation dominates the degradation before scission takes over, followed by hydrolytic depolymerization. Additional analysis highlights the climacteric interdependency between deacetylation and hydrolytic depolymerization as it relates to eventual delamination, where deacetylation products catalyze interfacial hydrolysis reactions. Furthermore, effects occurring at a given interface are isolated, explicitly providing evidence for how these mechanisms are nonuniform throughout the thickness of the EVA. Results demonstrate that the EVA that interfaces with the glass as opposed to the cell experiences increased levels of degradation, explaining why this initially stronger interface becomes the preferential interface for delamination after longer periods of exposure. Additionally, elevated temperatures alone are shown to induce limited migration of sodium ions across the glass/EVA interface.

Exploiting hydrogen bonding to enhance lidocaine loading and stability in a poly ethylene-co-vinyl acetate carrier matrix

Sustained release of lidocaine from poly ethylene-co-vinyl acetate (EVA) implants can significantly improve pain management outcomes; however, poor drug loading is a major limitation. Recently, myristic acid was found to improve drug loading in EVA by inhibiting the crystallization of lidocaine. Here, lidocaine’s interaction with myristic acid was studied by differential scanning calorimetry. Spectra of lidocaine-myristic acid mixtures were analysed using two-dimensional correlation (2DCOS) maps. Furthermore, spectroscopic analysis of EVA matrices containing lidocaine, alone and in combination with myristic acid, was also performed and drug release was evaluated in vitro. A eutectic was obtained on combining lidocaine and myristic acid at the molar ratio of 1:1 due to loss of myristic acid’s dimeric conformation resulting in hydrogen bonding of its COOH group with lidocaine’s amide I moieties. In EVA, hydrogen bonding between adjacent lidocaine molecules caused crystallization above a threshold concentration and could be inhibited by incorporation of myristic acid by eutectic formation. By altering the molecular confirmation and solid state properties of lidocaine in EVA, myristic acid reduces lidocaine crystallization, increases drug loading and influences drug release kinetics. Exploiting these interactions and promoting further hydrogen bonding through the addition of specific excipients presents a viable strategy to enhance and stabilise drug loading in polymer matrices for various applications.

Broadband microwave absorbing materials for green electronics based on poly (lactic acid)/ethylene‐vinyl acetate copolymer blends loaded with carbon nanotube

AbstractPartially bio‐based conducting polymer nanocomposites constituted by poly(lactic acid) (PLA)/ethylene‐co‐vinyl acetate (EVA) (50:50 wt%) blend loaded with different amounts of carbon nanotube (CNT) were prepared for developing microwave absorbing materials. The effect of EVA characteristics and the mixing conditions on the electrical conductivity was investigated. The higher conductivity value was achieved using PLA@CNT master batch and EVA with 28% of VA. In fact, this system presented electrical percolation threshold of 7 × 10−4 volume fraction and a conductivity value of 3 × 10−3 S/m with the addition of 0.9 wt% (0.58 vol%) of CNT. A minimum reflection loss of −29 dB (electromagnetic (EM) attenuation of around 99.9%) at 11.7 GHz and the bandwidth (<−10 dB) of 4.9 GHz was observed with the presence of 0.58 vol% of CNT, whereas RL value of around −39.4 dB (EM attenuation of around 99.99%) at 14.7 GHz and a bandwidth of 4.6 GHz was observed for the composite loaded with 0.25 vol% of CNT. Due to the outstanding microwave absorption properties and wide absorption bandwidth with low amount of CNT, these composites are promising candidates for flexible materials suitable for shielding electronic devices in a wide frequency range.

Study on the effect of WER and EVA on the performance and microstructure of cement mortars for a prefabricated residential floor

In this study, cement mortars were modified with ethylene-co-vinyl acetate (EVA) powder and water-based epoxy resin (WER) emulsion. This study aimed to investigate the effect of the content of the two polymers on the mechanical properties, abrasion resistance, and toughness of the mortar and to relate these properties to the microstructure of the mortar. We combined IPP(a combination of Stereo Light Microscopy and Image-Pro Plus image processing software) and the mercury intrusion porosimetry (MIP) to analyze the microscopic pore structure of polymer modified mortars. The microstructure of polymer modified mortars was studied by scanning electron microscopy (SEM). The results show that the use of alternating wet and dry curing regimes helps to improve the toughness of the modified mortar. Under this curing regime, the maximum flexural strength of the polymer modified mortar was 14.32 MPa and the maximum compressive strength was 90.52 MPa. The addition of polymer significantly improved the abrasion and impact resistance of the cement mortar, with a 28% reduction in abrasion volume from 116 mm3 to 83 mm3 and a 36% increase in impact strength from 13.92 J/cm2 to 18.97 J/cm2. Both polymers have the effect of filling capillary pores in the mortar, but there is a difference in the effect on large-size pores at high dosing levels. This work contributes to an in-depth understanding of the role of polymers in improving the performance of cement mortars, which enables rational development of polymer modified cementitious materials for prefabricated residential floors.

A comparative study of the application-based properties of hot melt adhesives (HMAs) formulated with different waxes

In this study, three chemically similar but morphologically different high melting hydrocarbon waxes having similar DSC peak melting temperatures were analysed, and the influence of their molecular architectures on hot melt adhesive (HMA) performance, was evaluated. Selected waxes included each of the following types: Fischer Tropsch wax (FT), by-product polyethylene wax (BPPE) and first intention polyethylene wax (FIPE). Both, ethylene-co-vinyl acetate (EVA) and metallocene catalysed polyethylene (mPE) based HMAs were formulated. The high chain linearity of FT wax resulted in faster crystallization and faster adhesive set times as well as higher peel adhesion, shear adhesion and IOPP heat resistance temperatures. Wax viscosities were in direct correlation with resultant HMA viscosities. EVA HMAs had longer set times and were more prone to thermal degradation upon prolonged exposure to elevated temperatures and was most pronounced for FIPE wax. Average traction force was dependent on the open time and wax/polymer combination with FT showing a smaller open time window for both EVA and mPE based HMAs.

EFFECTS OF LASER IRRADIATION ON ADHESIVE TRIBO-PERFORMANCE OF EVA/HDPE/MA-G-PE/OMMT BLENDED POLYMER NANOCOMPOSITES

Ethylene-co-vinyl acetate (EVA), high density polyethylene (HDPE) and their blends are being used in many engineering applications. In this work, an attempt was made to extend the conventional uses of EVA/HDPE blended polymer nanocomposites by laser treating their surface to automobile, aircraft, and similar industries, where tribological properties played an important role. Effects of laser irradiation on adhesive tribo-performances of maleic anhydride grafted polyethylene (MA-g-PE: 2phr) modified ethylene-co-vinyl acetate/high density polyethylene (EVA/HDPE: 70/30 wt. %) organ modified montmorillonite (OMMT: 4phr) blended polymer nanocomposite have been investigated. EVA/HDPE/MA-g-PE/OMMT polymer nanocomposite was irradiated by Ytterbium laser system (YSL-2000) at various scan speeds and power densities. As per ASTM G99 standard, tribo-performance attributes coefficient of friction and specific wear rate were evaluated using pin-on-disc machine against rotating EN31 steel disc of 60 HRC at different loads and speeds. Wear mechanisms of worn surfaces were analyzed using scanning electron microscopy (SEM) images. It was observed that coefficient of friction and specific wear rate were significantly affected by power density and load, while sliding distance and scan speed have marginal effects.

Thermal decomposition kinetics of melt-mixed ethylene-co-vinyl acetate – based bio-composites

Bio-composites of ethylene-co-vinyl acetate (EVA) with chitosan (CS) and chitosan-g-PANi (CS-PANi) have been developed by using a melt-mixing process by varying the composition of fillers. Investigations on the degradation mechanism of thermoplastics lead to insights of their performance at high temperatures. The decomposition kinetics of the bio-composites was determined by plotting thermograms at different heating rates. The model-free Flynn-Wall-Ozawa and Kissinger method has been used to estimate the energy of activation (Ea) of the developed composites. The activation energies of EVA/CS composites lie between 162 and 209 kJ/mol and EVA/chitosan-g-PANi composites within the range of 145–256 kJ/mol. The variation in activation energy across the extent of conversion levels denotes multistep kinetics of degradation. The calculated Ea has been found to be in good agreement with the literature reports.

Synchronization of thermal properties and constituents in Nanocomposite: Manufacturing, characterization, adjustable properties

AbstractThis is critical to maintain better thermal properties, especially thermal conductivity as well as low particle content along with organized particle dispersion in polymer nanocomposites. Thus, this study is designed to develop a nanocomposite containing a constant reinforcing load of binary particles (carbon and alumina) in the binary matrix of polypropylene (PP)/poly ethylene‐co‐vinyl acetate (EVA). The samples were prepared through the melt blending and hot pressing technique. Compared to pure PP/EVA matrix, the nanocomposites showed a shift in Fourier‐transform infrared spectroscopy peak and absorption intensity, which proves better interaction of nanoparticles with the matrix. The Scanning Electron Microscopy analysis showed the nanocomposite having carbon (C) and alumina (A) relative ratio 2:3 offered even structure with better distribution of nanoparticles compared to other nanocomposites. Also, Differential scanning calorimetry and Thermogravimetric analysis revealed that alumina‐rich binary nanoparticles reinforced composites offer an efficient improvement in thermal behavior. Moreover, the nanocomposite containing high alumina relative ratio (C: A = 2:3) gives a sharp shift in thermal conductivity of 1.57 W/m‐k from 1.2 W/m‐k of carbon‐rich nanocomposite (C: A = 3:2) and 0.16 W/m‐k of pure PP/EVA. However, these relative properties emphasize the important role of this nanocomposite as a programmable thermal material.

Highly toughened poly(lactic acid) (PLA) prepared through melt blending with ethylene-co-vinyl acetate (EVA) copolymer and simultaneous addition of hydrophilic silica nanoparticles and block copolymer compatibilizer

In this study, a highly toughened PLA was prepared through physical melt-blending with EVA at the presence of hydrophilic nanosilica and SEBS-g-MA block copolymer compatibilizer. The effect of nanosilica and compatibilizer on the morphology, mechanical properties, and linear rheology of the PLA/EVA blends was also investigated. According to TEM images, nanosilica was selectively located in the PLA matrix while some were placed on the interface between the two polymers as was also predicted by thermodynamic and kinetic analysis. Upon the addition of nanoparticles, the interfacial adhesion between the phases was enhanced and the average droplet size decreased. Interestingly, incorporation of SEBS-g-MA induced morphological changes as the spherical EVA droplets turned into a cylindrical shape. DSC results indicated that blending with EVA copolymer resulted in the reduction of crystallization of PLA matrix; however, the crystallinity increased at the presence of nanoparticles up to 5 wt%. The addition of compatibilizer considerably hindered the crystallization of the PLA phase. PLA/EVA blend containing optimum levels of nanosilica exhibited considerably enhanced tensile toughness, elongation at break, and impact strength. On the other hand, the simultaneous addition of nanoparticles and SEBS-g-MA led to synergistic toughening effects and the compatibilized blend containing nanosilica exhibited excellent impact toughness. For instance, the elongation at break of the compatibilized PLA/EVA blend containing the optimal content of nanosilica was increased from 7% to 121% (compared to neat sample). The notched Izod impact strength was also increased from 5.1 to 65 kJ/m2. Finally, the microstructure of the blends was assessed by rheological measurements.

Bio-based ethylene-co-vinyl acetate/poly (lactic acid) thermoplastic vulcanizates with enhanced mechanical strength and shape memory behavior

With the increasing attention to the shortage of petroleum resources and environmental pollution, it is more urgent to develop new type biomass-derived and bio-degradability polymer materials. In this study, a various of bio-based ethylene-co-vinyl acetate (EVA)/poly (lactic acid) (PLA) thermoplastic vulcanizates (TPVs) with enhanced mechanical strength and shape memory behavior were prepared. The Fourier transform infrared spectroscopy (FTIR), torque rheometer, swelling equilibrium experiments, and thermal gravimetric analysis (TGA) indicate that the EVA component is more aggressive to the active radicals than PLA component, and the improvement of gel content for EVA component is more than that of PLA component. The scanning electronic microscope (SEM) and transmission electron microscopy (TEM) show that the co-continuous structure of EVA/PLA/AD TPV could be well maintained when the TMPTA was introduced into the multicomponent system. Obviously, the results also exhibit that the improvement of mechanical strength and shape memory behavior for EVA/PLA/AD TPV could be attributed to the increased gel content, especially the gel content of EVA component, without changing the crystallization behavior of EVA/PLA/AD TPV.

Experimental Analysis of Dry Sliding Friction and Wear Behavior of OMMT Nanoclay Added EVA/HDPE/MA-g-PE Compatibilized Polymer Blends with Parametric Study of Influencing Factors

Abstract In this study, an attempt has been made to find out the possibility of extending the conventional engineering applications of Maleic Anhydride–grafted Polyethylene (MA-g-PE), compatibilized Ethylene-co-Vinyl Acetate (EVA), and High-Density Polyethylene (HDPE) polymer blends with the addition of Organo-Modified Montmorillonite (OMMT) nanoclay to sliding wear–resistant parts in the automobile, aerospace, and other similar industries. An experimental analysis of dry sliding friction and wear has been investigated for MA-g-PE (2 parts per hundred, i.e., phr) grafted EVA/HDPE (70/30 by weight %) blend with the addition of 0, 1, 2, 3, and 4 phr of OMMT nanoclay. According to ASTM G99, Standard Test Method for Wear Testing with a Pin-on-Disk Apparatus, specimens slid against an EN31 steel disk of 60 HRC using a wear and friction tribometer at different forces, sliding distances, and sliding velocities. Effects of forces and sliding distances on sliding friction coefficients and specific wear rates of polymer nanocomposites were evaluated. It was observed that the coefficient of friction decreased with the increase in forces and slightly varied with increments in sliding distance. On the other hand, the specific wear rate increased by increment in forces and decreased with the increase in sliding distance. Wear mechanisms and worn surfaces were analyzed using scanning electron microscopic images. Parametric study of influencing factors (polymer compositions, forces, sliding distances, and sliding velocities) was conducted using the Taguchi design of experiment and ANalysis Of VAriance (ANOVA). Taguchi was used to rank and optimize four influencing factors, viz., composition, force, sliding distance, and sliding velocity. ANOVA determined the statistical significance and percentage contribution of control factors.

Experimental and theoretical evaluation of mechanical, thermal and morphological features of EVA-millable polyurethane blends

Heterogeneous blends of millable polyurethane (MPU) and ethylene-co-vinyl acetate (EVA) elastomers have been prepared by conventional open mill mixing, and subsequently cured with DCP as curing agent. The prepared blends were characterized by TGA, DSC, XRD and DMA techniques. Mechanical and solvent transport features have been evaluated. Examination of EVA phase crystallization dynamics revealed that the 50:50 blend possessed a higher energy barrier during crystallization. When EVA became the minor or major phase, the system offers similar energy barrier features. Solvent transport mechanism has been found to shift towards non-Fickian for blends with EVA as the major phase. Mechanical properties have been found to be complementary to the observed crystalline features of the blends. A blend with EVA to MPU ratio 80:20 is highlighted as a soft and strong material, with enhanced solvent resistance features suitable as a matrix for different engineering applications.

Matrix-based controlled release delivery of acyclovir from poly-(ethylene co-vinyl acetate) rings

Up to 85% of the US adult population carries herpes simplex virus type-1 (HSV-1), with a smaller percentage (22%) infected with HSV-2. Herpesviruses can survive in lytic phase, when the viruses are actively replicating, or in latency, when the virus is functionally dormant in ganglia. Among drugs to treat these infections is acyclovir (ACV). ACV exhibits poor oral bioavailability and a short in vivo half-life; only about 10–15% of ingested drug enters the bloodstream and its half-life is about 3 h. With those disadvantages and the possibility of poor patient compliance, viral replication may not always be suppressed. To abrogate these shortcomings we propose local distribution via sustained drug release. We present a matrix-based antiherpetic ring, composed of poly(ethylene co-vinyl acetate), that releases ACV directly to the vaginal epithelium. A 30-day in vitro drug release trial showed that approximately 135 ± 20 μg/day of ACV was consistently released. Rings were nontoxic in cell culture and suppressed primary HSV-1 and HSV-2 replication. We expect these data form the basis for novel interventions in human health, where new prophylactics and therapeutics against genital herpes are truly needed.