Properties Of Ethylene Vinyl Acetate Copolymer Research Articles

Fabrication of ethylene-vinyl acetate copolymer/polyamide/modified sepiolite composite with improved physical properties via e-beam irradiation

The effects of silanized sepiolite (SP) and electron beam (e-beam) irradiation on the physico-mechanical properties of ethylene-vinyl acetate copolymer (EVA)/ternary polyamide (tPA) composites were studied. SP was silanized with vinyltriethoxysilane (VTES) to enhance the dispersion and compatibility of the inorganic filler into the EVA/tPA matrix. The crosslinking of EVA/tPA by e-beam irradiation was carried out ranging from 50 to 250 kGy. The prepared composite films were characterized for change in morphology, mechanical properties, crosslinking effect on crystallinity and swelling using various established analytical techniques. Experimental results indicated that tensile strength of irradiated composite EVA/tPA/m-SP5 (70/30/5) was 3 times higher than that of virgin composite film at an absorbed dose of 250 kGy. The storage modulus of EVA/tPA/m-SP5 (70/30/5) composite film was significantly increased with the increase of absorbed dose. However, melting and crystallization temperature of EVA/tPA composites slightly decreased with the increase of absorbed dose. Moreover, the modification of SP with VTES and irradiated composite films were subjected to oil swelling studies.

Coupling Dynamic Covalent Bonds and Ionic Crosslinking Network to Promote Shape Memory Properties of Ethylene-vinyl Acetate Copolymers.

Dynamic crosslinking networks based on Diels–Alder (DA) chemistry and ionic interactions were introduced to maleic anhydride modified ethylene-vinyl acetate copolymer (mEVA) via in situ melt processing. The dual dynamic crosslinking networks were characterized by temperature-dependent FTIR, and the effects on the shape memory properties of mEVA were evaluated with dynamic mechanical thermal analysis and cyclic tensile testing. A crosslinking density was achieved at 2.36 × 10−4 mol·cm−3 for DA-crosslinked mEVA; as a result, the stress at 100% extension was increased from 3.8 to 5.6 MPa, and tensile strength and elongation at break were kept as high as 30.3 MPa and 486%, respectively. The further introduction of 10 wt % zinc methacrylate increased the dynamic crosslinking density to 3.74 × 10−4 mol·cm−3 and the stress at 100% extension to 9.0 MPa, while providing a tensile strength of 28.4 MPa and strain at break of 308%. The combination of reversible DA covalent crosslinking and ionic network in mEVA enabled a fixing ratio of 76.4% and recovery ratio of 99.4%, exhibiting an enhanced shape memory performance, especially at higher temperatures. The enhanced shape memory and mechanical performance of the dual crosslinked mEVA showed promising reprocessing and recycling abilities of the end-of-life products in comparison to traditional peroxide initiated covalent crosslinked counterparts.

Effects of electron beam irradiation and multi-functional monomer/co-agents on the mechanical and thermal properties of ethylene-vinyl acetate copolymer/polyamide blends

The effect of electron beam (e-beam) irradiation on the mechanical and thermal properties of ethylene-vinyl acetate copolymer (EVA)/ternary copolyamide (tPA) blends was studied. The crosslinking of EVA/tPA induced by e-beam irradiation was carried out over a dose range from 50 to 250 kGy with tripropylene glycol diacrylate (TPGDA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPEHA) as crosslinking co-agents. With increasing irradiation dose, the gel contents of EVA/tPA containing the co-agents increased more significantly than that of EVA/tPA. After electron beam irradiation of 250 kGy, the gel content of EVA/tPA with 3 phr TPGDA reached 81%, much higher than 22% for EVA/tPA without any co-agent. The irradiated EVA/tPA/TPGDA (70/30/3) also exhibited high tensile strength and oil-resistance properties. The addition of TPGDA and the irradiation dose are two crucial factors affecting the mechanical properties of the EVA/tPA blend.

Investigation of the effect of titanium dioxide and clay grafted with glycidyl methacrylate by gamma radiation on the properties of EVA flexible films

Many studies report that nanocomposites obtained by dispersion of a small amount nanofiller into the polymer have remarkable improvements achieved in the mechanical and physical properties. However, in order to achieve this great improvement in properties, it is necessary that the nanofillers be dispersed homogeneously into the polymeric matrix. Often this dispersion is difficult to achieve due to the high interfacial energy of the nanoparticles present. This study reports the effect of gamma irradiation induced graft of glycidyl methacrylate (GMA) onto the surface of TiO2 and Clay nanofillers to improve their dispersion into the EVA matrix. The physical and mechanical properties of Ethylene-vinyl acetate copolymer (EVA) flexible films with these nanoparticles were studied. EVA nanocomposite with adding of the different amount of TiO2 and modified montmorillonite clay grafted and un-grafted with glycidyl methacrylate (GMA) using gamma irradiation have been prepared by melt extrusion. The nanocomposite flexible films were produced using a flat die extrusion process. The PGMA-grafted nanofillers were characterized by XRD and TEM analysis. The flexible films were characterized by Tensile tests, ATR–FTIR, UV–VIS, XRD, TG, and FE-SEM analysis to understand the nature of the interaction between the nanofillers and EVA matrix. The results showed that the addition of PGMA-grafted TiO2 and Clay nanofillers into EVA matrix improved the bonding between the nanofillers and matrix. It was also found that the PGMA-grafted nanofillers could be well dispersed into an EVA matrix in contrast to that of un-grafted. The tensile strength and modulus of the resulting EVA/TiO2-PGMA enhanced in comparison to that of un-grafted TiO2. The EVA/Clay-PGMA had slightly decreased tensile strength comparable to that of EVA/Clay but had considerably improved elastic modulus. In addition, the flexible films based on TiO2 exhibited high UV–Vis light absorption with energy gap shifted to the visible region. The results demonstrated that TiO2 and Clay nanofillers grafted with GMA by gamma radiation can be used to prepare EVA flexible films with improved bonding between the nanofillers and matrix and, consequently, enhanced properties for food and cosmetic packaging application.

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.

The effect of high-dispersion fillers on adhesive and frictional properties of ethylene-vinyl acetate copolymer

The adhesive strength of adhesive joints between metal surfaces has been improved considerably by modifying an adhesive based on a copolymer of ethylene with montmorillonite vinyl acetate. It as been proved that the static (adhesive joint) and dynamic (frictional interaction) adhesion modes are correlated. It has been shown that the surface potential found by a modified Kelvin-Zisman method increases with increasing adhesion of the metal-polymer joint.

Interaction between Agrochemical Contaminants and UV Stabilizersfor Greenhouse EVA Plastic Films

Abstract. Research was conducted to evaluate how solar radiation, agrochemical contamination, and different light stabilizer systems influence the mechanical properties of ethylene-vinyl acetate copolymer (EVA/C) based films suitable for crop protection. Three independent outdoor trials were performed at the experimental field of the University of Bari (Italy) in 2006, 2007, and 2008. During each trial each film type was installed in the field as new covering of two low tunnels: one of the tunnels was periodically sprayed inside with agrochemicals containing sulfur, chlorine and iron, while the other one, not sprayed, was used as control. Besides, artificial photoaging tests were carried out on the films in laboratory. The research showed that the different light stabilizer systems influenced the mechanical behavior of the films in the presence of the progressively absorbed agrochemicals. An improved resistance to the agrochemicals was recorded for the EVA/C films stabilized with aminoether type hindered amine light stabilizer (NOR-HALS) and ultra violet filter.

Synthesis and performance of three flame retardant additives containing diethyl phosphite/phenyl phosphonic moieties

Three novel intumescent flame retardants (IFRs) containing phosphorus and nitrogen based on Schiff bases, poly(phosphonate ester(s)) (designated as PAB, PEB, and PPB), were synthesized and characterized. Thermal stability and flammability properties of ethylene-vinyl acetate copolymer (EVA)/30% IFRs blends were investigated by thermogravimetric analysis (TGA), limited oxygen index (LOI), vertical burning test (UL-94) and microscale combustion calorimetry (MCC). The results from UL-94 showed that EVA/IFRs blends all could reach V-2 rating. The addition of PAB into EVA reduced the PHRR value by 31%, and the LOI value increased from 19 to 24. Scanning electron microscope (SEM) observation results indicated that the existence of the cohesive charred layer on the surface of the residue was responsible for the improvement of the flame retardancy of EVA.

Flammability and Mechanical Properties of EVA Composites Containing Ammonium Polyphosphate Microcapsules

Flame retardant and mechanical properties of ethylene-vinyl acetate copolymer (EVA) composites containing ammonium polyphosphate (APP) and its microcapsules, MFAPP with a shell of melamine–formaldehyde resin and EPAPP with a shell of epoxy resin, were evaluated in EVA. The results indicate that APP after the microencapsulation leads to an increase in LOI in EVA compared with APP. When dipentaerythritol is added into the EVA composites containing APP microcapsules, a further improvement in flame retardancy of the composite is observed. Moreover, thermal decomposition behavior and mechanical properties of the EVA composites are investigated.

CORRELATION BETWEEN AGROCHEMICALS, SOLAR RADIATION AND MECHANICAL PROPERTIES OF GREENHOUSE PLASTIC FILMS

A research was carried out in order to evaluate how agrochemicals contamination and solar radiation influence the mechanical properties of ethylene-vinyl acetate copolymer (EVA) films. The films, manufactured adding several different combinations of light stabilizers, were subjected to natural and artificial weathering and to three agrochemicals commonly used during the cultivation practices. Two sets of field trials were carried out from 2006 to 2007 at the experimental centre of the University of Bari (Italy). The films, installed on steel arches of low tunnels, were periodically sprayed with the agrochemicals containing iron, chlorine and sulphur. For control the same films, mounted over other low tunnels, were not sprayed. Stress and strain at break of the film samples, taken at fixed time intervals in the field and after exposure in an artificial ageing chamber, were measured. Tests were conducted to evaluate the chemical contaminants absorbed by the films. Solar radiation falling on the films under the test was continuously measured and recorded by means of a pyranometer and a CR10x Campbell data logger. The results of the tests showed that the different light stabilizers influenced the behaviour of the films in presence of the sprayed agrochemicals. The experimental data were investigated evaluating the cumulative solar radiation, the kind of anti-UV additive and the absorbed contaminants. Concerning the agrochemicals which were absorbed by the films, values up to 6800 ppm of sulphur were recorded during the tests. The research allowed the identification of suitable additives in relation with used agrochemicals. The tests showed that an improved resistance to the agrochemicals was recorded for the EVA film stabilized with NOR-HALS plus UV filter.

Viscosity of Blends of Pectins of Various Origins with Ethylene-Vinyl Acetate Copolymers

The rheological properties of ethylene-vinyl acetate copolymers of various compositions in blends with pectins of various origins (pectins recovered from apple pulp, watermelon peel, and citrus fruits) were studied. The degrees of swelling of blend films in water were measured.

Monolayer properties of ethylene-vinyl acetate copolymers

Monolayer properties of ethylene-vinyl acetate copolymers

Study of thermoelastic properties of ethylene-vinyl acetate copolymer

The thermoelastic properties of the random ethylene-vinyl acetate copolymer crosslinked with dicumyl peroxide were investigated. It was found that the relationships between equilibrium stress and temperature showed a discontinuity in the temperature range 38–42°C which was due to the crystalline character of the samples. The value of energetic contribution fu/ f is negative at elongations ranging from 1.1 to 2.1 while it assumes a relatively high value at greater elongations. The values of relative energetic contribution fu/ f change with elongation and are in agreement with the values of fu/ f calculated from shear modulus for the region of medium elongations in the investigated range. The character of the relationship between f u or fu/ f and elongation indicates that a change in the intra- and inter-molecular interaction energies occurs in the case of uniaxial strain of the investigated copolymer.

The Principle of Superposition of Time, Temperature and Concentration in Dynamic Properties of Ethylene-Vinyl Acetate Copolymers

The dynamic mechanical tests of samples of ethylene-vinyl acetate copolymers with various contents of vinyl acetate monomer (VAc) ranging from 0 to 25.3wt% made at varying temperatures from 5°C to 80°C at frequencies ranging from 1 to 100 cycles/sec., and their dynamic tensile modulus E', E were obtained. These were made the data for examining each sample with respect to its principle of superposition of time and temperature. It was found that the larger the melt index of the sample was the wider was the scatter of these data in it. The shift distance log aT was larger than those given from WLF equation. The values of log aT2 computed from the following equation gave good straight lines on a plot of log aT2 vs. 1/T;logaT=(1-φ)logaT1+φlogaT2where log aT and log aT1 represent respective shift distance obtained from experiment and from WLF equation, and in present trial, φ was assumed to represent volume fraction of crystalline part of each sample. Time-concentration principle was also examined with a convenient assumption that one monomer composition in the copolymer act as a diluent or a low molecular plasticizer. It seemed that the principle of superposing time and concentration was formally applicable to the data of copolymer by regarding the content of one monomer composition as concentration.