Higher Vinyl Acetate Content Research Articles

Investigation of the Rheological Properties and Storage Stability of Waste Polyethylene/Ethylene-Vinyl Acetate-Modified Asphalt with Crosslinking and a Silicone Coupling Agent.

As the market for polyethylene consumption continues to expand, the amount of waste polyethylene is also increasing. Modifying asphalt with waste polyethylene (PE) is economical and environmentally friendly. The low-temperature performance and storage stability of PE-modified asphalt has long been an insurmountable problem. The high vinyl acetate (VA) content of ethylene-vinyl acetate (EVA) and PE blended into asphalt can improve the compatibility of PE and asphalt. It compensates for the high VA content of EVA brought about by the lack of high-temperature resistance to permanent deformation but is still not conducive to the stable storage of PE at high temperatures. The effect of furfural extraction oil, a crosslinking (DCP) agent, a silicone coupling agent (KH-570), and calcium carbonate (CaCO3) on the rheological properties and compatibility of PE/EVA-modified asphalt was investigated in this study. The conventional physical properties of PE/EVA-modified asphalt were tested after introducing furfural extraction oil, DCP, KH570, and CaCO3 to determine the correlations of these materials. In addition, frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS) were utilized to characterize the rheological properties and fatigue behavior. The results reveal that the addition of suitable ratios of furfural extract oil, DCP, KH-570, and CaCO3 to PE/EVA-modified asphalt produces a remarkable improvement in the viscoelastic characteristics and viscosity compared with PE/EVA-modified asphalt. Furthermore, fluorescence microscopy (FM) was utilized to evaluate the modification mechanism, which shows that PE/EVA undergoes significant crosslinking in asphalt, forming a three-dimensional network structure that dissolves in the asphalt. The storage stability of the PE-modified bitumen was fully determined, and its high-temperature rheology was substantially improved.

EVA-PVA binder system for polymer derived mullite made by material extrusion based additive manufacturing

Low processing temperature of preceramic polymers (PCPs) makes them attractive for material extrusion based additive manufacturing (MEX-AM), earlier called fused deposition modeling (FDM). Fabrication of bulk polymer derived ceramics is challenging due to gas evolution during crosslinking leading to pores and cracks in final product. Mixture of ethylene vinyl acetate (EVA) and polyvinyl alcohol (PVA) was successfully used to generate open porosity before crosslinking step. For 3D printing, a pellet extruder was used and a PVA binder content of 50 vol% was essential for succcessful solvent debinding process in water. The effect of PVA content and different EVA grades on printability and debinding behavior was studied. EVA with a lower melt flow index (MFI) showed better compatibility with PVA additive in terms of mixing and printing. EVA with higher vinyl acetate content seems to be more favorable for later thermal debinding processes because of its higher gas permeability.

Effect of EVA copolymer containing different VA content on the thermal and rheological properties of bio-based high-density polyethylene/ethylene vinyl acetate blends

The effect of ethylene vinyl acetate (EVA) concentration and vinyl acetate (VA) content of EVA on the mechanical, morphological, and rheological properties of bio-based high-density polyethylene (BioPE)/EVA blends was investigated. The blends were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and rheological measurements under oscillatory shear flow. The degree of crystallinity of BioPE decreased with the increase in the EVA concentration and was unaffected with the increase in the VA content. DMTA results showed a decrease in the storage modulus (E′) with the increase in EVA content and that the BioPE/EVA19 blends showed higher E′ values than BioPE/EVA28 blend. The impact strength substantially increased with the addition of EVA concentration above 5 mass% and was higher for the blends containing the highest VA content. The blends containing a higher content of VA exhibited the higher EVA dispersed phase domain size, which increased with the increase in EVA concentration. The complex viscosity increased with the increase in the EVA content, being higher for the BioPE/EVA blends containing higher VA content. The storage modulus increased, at low frequencies, with the increase in the EVA content and can be ascribed to the increase in the EVA dispersed phase domain size.

Enhancement of resistance against damp heat aging through compositional change in PV encapsulant poly (ethylene-co-vinyl acetate)

The most common encapsulant used in the photovoltaic (PV) modules is poly (ethylene-co-vinyl acetate) (PEVA). The characteristics of PEVA can be varied by modulating its vinyl acetate (VA) content. According to the general consensus within the PV industry, PEVA as an encapsulant should have VA content between 28 and 33%. Degradation of PEVA films due to environmental stressors like humidity, temperature and solar radiation in the field aged modules is not uncommon. Moreover, degradation of PEVA encapsulant implies a concomitant loss in the electrical performance of the PV modules. VA content modulation especially outside the most commonly used and accepted range has been tried in this study to improve the damp heat aging resistance of PEVA films. PEVA films containing 18, 24, 33, and 40% VA content with the necessary additives have been fabricated and cured at 150 °C under vacuum and subsequently subjected to accelerated damp-heat (85°C and 85% RH) aging according to IEC 61215 standard for 1000 and 2000 h. Tensile strength, thermal stability and degree of crosslinking have been found to be greater for PEVA containing lower VA content (18 and 24%) and diminished for PEVA with higher VA content (33 and 40%) due to DH aging. However, inadequate % transmittance and relatively high stiffness after 2000 h of DH aging discourages PEVA18 as an encapsulant. Moreover, PEVAs with higher VA content (33 and 40%) have been degraded significantly after 2000 h of DH aging resulting in significant loss in transmittance and mechanical integrity. Therefore, the results of this investigation encourage the PV industry to reduce the VA content in PEVA down to 24% for better encapsulation response against DH aging.

Improvement of mechanical toughness of poly(lactic acid) by addition of ethylene-vinyl acetate copolymer

We investigated the structure and properties of binary blends comprising poly(lactic acid) (PLA) as a matrix and ethylene–vinyl acetate copolymer (EVA), by considering the effect of the vinyl acetate (VAc) content in EVA. The interfacial tension with PLA was found to decrease with increasing the VAc content. Therefore, blends comprising EVA with a high VAc content have fine EVA particles, and exhibit marked mechanical toughness and good transparency. Although pure PLA is prone to brittle fractures, the addition of EVA leads to shear yielding, which is prominent when the matrix ligament thickness is shorter than a critical value. The cavitation process in the dispersed EVA particles is also responsible for the mechanical toughness, which is obvious in EVA with a high VAc content.

Influenceof Vinyl Acetate Content on the Surface Hydrophobic Recovery of Ethylene Vinyl Acetate Copolymer after Plasma Modification

AbstractIn this paper, two kinds of ethylene vinyl acetate copolymers (EVA) with different vinyl acetate (VA) contents were modified by plasma technique. The surface hydrophobic recovery and the nanostructure of the samples were evaluated by water contact angle measurement and positron annihilation lifetime spectroscopy, respectively. The water contact angle results indicated that higher VA content would result in faster hydrophobic recovery after plasma modification. The positron annihilation results indicated that two kinds of EVA samples exhibited similar o‐Ps lifetime, and EVA with higher VA content showed higher o‐Ps intensity. The results implied that the faster hydrophobic recovery after plasma modification should be contributed to the easier relaxation of chain segments for the EVA with higher VA content.

Evaluation of acoustic and dynamic behaviour of ethylene vinyl acetate panels

AbstractEthylene vinyl acetate panels, with high vinyl acetate content and a closed‐cell structure, were studied through various experimental techniques as a first approach to evaluate the vibrational and acoustic behaviour of ethylene vinyl acetate panels for building applications. Test specimens, with a variety of densities and thicknesses were tested to evaluate the influence of these two parameters on acoustic impedance, sound transmission loss, dynamic stiffness and attenuation of vibrations. The results obtained shows sound transmission loss values for frequencies up to 2500 Hz with a maximum of about 63.7 dB, the dynamic stiffness results presented a wide range, with a maximum value of 350 MN/m3 and a minimum value of 23.3 MN/m3.On the other hand the lack of pore in the surface produce a high acoustic impedance. It can be concluded that ethylene vinyl acetate presents appropriate characteristics, mainly as an acoustic and vibration isolating material, for floorings and light partitions.

Preparation and characterization of ethylene-vinyl acetate nanocomposites: enhanced flame retardant

Ethylene-vinyl acetate (EVA) nanocomposites with enhanced flame retardance were prepared by the sol–gel process in the melt. Two EVAs with different vinyl acetate (VA) contents and aluminium isopropoxide were used as organic and inorganic phases. The nanocomposites were prepared in a batch mixer under constant processing conditions and were analysed by several characterization techniques. Aluminium isopropoxide presented low activation energy, which allows the synthesis of the nanoparticles without a post step treatment. The reaction mechanism is proposed. Nanocomposites with smaller and well dispersed metal nanoparticles were produced with an EVA with higher VA content. EVA nanocomposites achieve the requirements for 94 V-0 classification. © 2013 Society of Chemical Industry

Optimization of engineering and solvent resistive behavior of high vinyl acetate content EVA‐modified poly(ethylene‐co‐1‐octene) interpenetrating network blends using taguchi orthogonal array

AbstractProcess parameters of poly (ethylene‐co‐vinyl acetate) (EVA)‐modified poly (ethylene‐co‐1‐octene) (POE)‐interpenetrating, double network blend was designed through Taguchi L9 orthogonal array as a novel approach for complete optimization of engineering and solvent‐swelling properties. Influence of different factors like EVA and peroxide concentrations, blending temperature, and blending time on gel content, tensile modulus, tensile strength, ultimate elongation were statistically calculated. Results showed good correlation between mathematical and physical inferences. Stress relaxation, hysteresis and other physico‐mechanicals like total elongation, solvent‐swelling, etc., were interestingly depended upon the nature of dominantly crosslinked phase instead of net crosslinking of the network hybrids. Sorption, on the other hand, depended on the hydrophobic‐hydrophilic property of the surfaces. The series of data produced finally helped to select the best process parameters under which a particular POE‐EVA blend composition yielded most balanced physico‐mechanicals. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Photo-oxidative degradation of poly(ethylene-co-vinyl acetate)/nisin antimicrobial films

The photo-oxidative behaviour of different antimicrobial blown films based on poly (ethylene-co-vinyl acetate) (EVA) was studied. In particular, two samples of EVA containing different level of vinyl acetate comonomer (namely 14% and 28%) were used as matrices while nisin at different concentrations was used as antimicrobial agent. The degradation was followed by analyzing the changes in the spectroscopic behaviour and of the elongation at break measured in tensile tests. Moreover, changes in the antimicrobial activity of the films were followed by measuring the inhibition halo in agar diffusion tests. The results indicate that nisin acts as an excellent UV stabilizer for both samples of EVA used and especially for the sample with the higher vinyl acetate content. The protective effect of nisin is accompanied by a progressive decrease of the antimicrobial properties as a function of the photo-oxidation time due to the photo-degradation of the additive, which causes the inactivation of the additive.

Foaming of EVA/starch blends: Characterization of the structure, physical properties, and biodegradability

AbstractFoams produced from blends of an ethylene‐vinyl acetate copolymer (EVA) with high VA (vinyl acetate) content (28%) and corn starch have been successfully fabricated using an improved compression molding technique. A detailed characterization of the structure and physical properties has been carried out. The results showed that the corn starch acts as filler for EVA, showing a good compatibility with the polyolefin. Different types of cellular structure (closed, partially interconnected, and fully interconnected) and cell sizes were obtained depending on the relative density and the amount of starch included in the composition. Besides, the addition of starch allows tailoring the physical properties of the composite foams. An increase in the starch content leads to an increase of the density, compressive strength, hardness, and thermal conductivity and a decrease of the elasticity. Finally, biodegradability tests showed how increases the biodegradation with the amount of starch in the foam, which reaches 60% at 100 days for the foam with 70% of starch. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Flame Retardancy and Mechanical Properties of Ethylene-vinyl Acetate Rubber with Expandable Graphite/Ammonium Polyphosphate/Dipentaerythritol System

Ethylene-vinyl acetate thermoset rubber (EVM) with high vinyl acetate content has been widely used in wires and cables for many years. However, the problem of melting drip and efficient flame retardance has not been effectively solved. The combination of expandable graphite (EG), ammonium polyphosphate (APP), and dipentaerythritol (DPER) as a flame retardant system for EVM rubber has been proven to be effective in preventing melting drip and improving flame retardance in this study. This is shown by limiting oxygen index (LOI) and vertical flammability (UL-94) tests. The thermal behavior of EVM treated with this instumescent-flame retardant (IFR) system was investigated by thermogravimetric analysis (TGA) experiments. The results indicated that the char residue of treated samples could reach up to 27.1% at 600°C, which is much higher than that of the untreated EVM. Scanning electron microscopy (SEM) micrographs of residue of treated and untreated EVM showed that the IFR system could promote formation of residual char which imparts the antidripping property to EVM. However, the mechanical properties, such as tensile strength (TS) and elongation at break (EB), decreased gradually with the increase of EG content. Compared to the EVM/APP/DPER system without EG, the TS decreased from 6.55 MPa to 6.13 MPa, while the EB decreased slightly from 570% to 558% when the EG content was 15 wt%.

Preparation of microencapsulated ammonium polyphosphate with montmorillonite‐melamine formaldehyde resin and its flame retardancy in EVM

AbstractMicroencapsulated ammonium polyphosphate (MMT‐MF‐APP) with a montmorillonite‐melamine formaldehyde resin coating layer was successfully prepared by in situ polymerization. The product was characterized by Fourier‐transform infrared, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Water absorption analysis showed that the microencapsulation of APP with the MMT‐MF resin leads to a decrease in the particle's water solubility. The microcapsules also exhibited better mechanical properties and higher flame retardancy in the ethylene–vinyl acetate copolymer with high vinyl acetate content (EVM) rubber compared with the common ammonium polyphosphate. Moreover, thermogravimetric analysis results showed that the EVM composites with MMT‐MF‐APP and dipentaerythritol (DPER) as flame retardants possess higher thermal stability than those with common APP and DPER as flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.

UV aging behaviour of ethylene-vinyl acetate copolymers (EVA) with different vinyl acetate contents

The mild UV aging of ethylene-vinyl acetate copolymer (EVA) with two vinyl acetate (VAc) contents (14, 18 wt%) was performed in a xenon arc source chamber. The degradation mechanism was analyzed via attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), gel content and high temperature gel permeation chromatography (HTGPC). Photo-chemically induced deterioration was first initiated from vulnerable VAc units. Ketone formation preceded lactone generation, especially in EVA with high VAc content. Un-stable structures induced further degradation in the main chain. Competition between radiation induced cross-linking and chain scission in EVA was observed, and the later was confirmed to be dominant. Higher VAc content resulted in remarkable drop in molecular weight and growth in polydispersity. Apparent re-arrangement in crystallisation and consequent decrease in thermal stability are discussed through differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA), which accorded well with the chain scission tendency. Interaction between photo-chemical degradation and physical annealing accounted for the first increasing then decreasing tendency in the mechanical properties of both EVAs.

Toughening effects of ethylene–vinyl acetate copolymers with different vinyl acetate content and viscosity on nylon 1010 blends

AbstractNylon 1010 blends with ethylene–vinyl acetate copolymer (EVA) and maleated ethylene–vinyl acetate (EVA‐g‐MAH) were prepared through melt blending. The vinyl acetate (VA) content and viscosity of EVA significantly affected the notched impact strength of nylon/EVA/EVA‐g‐MAH (80/15/5) blends. The nylon/EVA/EVA‐g‐MAH blends with high notched impact strength (over 60 kJ/m2) were obtained when the VA content in EVA ranged from 28 to 60 wt%. The effect of VA content on the notched impact strength of blends was related to the glass transition temperature for EVA with high VA content and crystallinity for EVA with low VA content. For nylon blends with EVA with the same VA content, low viscosity of EVA led to high notched impact strength. Fracture morphology of nylon/EVA/EVA‐g‐MAH (80/15/5) blends showed that blends with ductile fracture behavior usually had large matrix plastic deformation, which was the main energy dissipation mechanism. A relationship between the notched impact strength and the morphology of nylon/EVA/EVA‐g‐MAH (80/15/5) blends was well correlated by the interparticle distance model. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Influence of Matrix Polarity on the Properties of Ethylene Vinyl Acetate–Carbon Nanofiller Nanocomposites

A series of ethylene vinyl acetate (EVA) nanocomposites using four kinds of EVA with 40, 50, 60, and 70 wt% vinyl acetate (VA) contents and three different carbon-based nanofillers—expanded graphite (EG), multi-walled carbon nanotube (MWCNT), and carbon nanofiber (CNF) have been prepared via solution blending. The influence of the matrix polarity and the nature of nanofillers on the morphology and properties of EVA nanocomposites have been investigated. It is observed that the sample with lowest vinyl acetate content exhibits highest mechanical properties. However, the enhancement in mechanical properties with the incorporation of various nanofillers is the highest for EVA with high VA content. This trend has been followed in both dynamic mechanical properties and thermal conductivity of the nanocomposites. EVA copolymer undergoes a transition from partial to complete amorphousness between 40 and 50 wt% VA content, and this changes the dispersion of the nanofillers. The high VA-containing polymers show more affinity toward fillers due to the large free volume available and allow easy dispersion of nanofillers in the amorphous rubbery phase, as confirmed from the morphological studies. The thermal stability of the nanocomposites is also influenced by the type of nanofiller.

Effects of compatibilizer on the layered silicate/ethylene vinyl acetate nanocomposite

Dispersion behavior of monmorillonite (MMT) is investigated in ethylene vinyl acetate (EVA)/MMT nanocomposite with various vinyl acetate content. Maleic anhydride (MAH) grafted polyethylenes with various MAH contents are used as a compatibilizer to enhance the dispersion of MMT. DMA and XRD studies indicate that an intercalated/exfoliated structure is obtained and vinyl acetate content and the concentration of PEMA play a critical role in EVA/MMT nanocomposite. Higher vinyl acetate content and concentration of grafted maleic anhydride result in better dispersion of MMT. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1057–1061, 2004

Effects of different kinds of clay and different vinyl acetate content on the morphology and properties of EVA/clay nanocomposites

A series of EVA/clay nanocomposites and microcomposites have been prepared via melt-blending. Using four kinds of EVA with different vinyl acetate (VA) contents: 28, 40, 50 and 80 wt%, and four kinds of clay: three are organophilic clay (OMMT) and one unfunctionalized clay (Na-MMT), the effects of different VA content of EVA and the kinds of the clay on the morphology and properties of EVA/clay nanocomposites were systematically investigated. In previous studies, there are only two distinct nanostructures to distinguish polymer/clay nanocomposites: the intercalated and the exfoliated. But in this paper, we proposed a new nanostructure—‘the wedged’ to describe the dispersion degree of clay in nanocomposites, it means the sheets of clay were partly wedged by the chains of polymer. The wedged, the intercalated and the partially exfoliated structures of EVA/clay nanocomposites were characterized by X-ray diffraction (XRD) and by high-resolution transmission electron microscopy (HRTEM). The enhanced storage modulus of EVA/clay nanocomposites was characterized by dynamic mechanical thermal analysis (DMTA). The enhanced degree in the storage modulus of the OMMT on EVA/clay nanocomposites with the partially exfoliated and intercalated structure is much higher than that with wedged structure, and that with the higher VA content is higher than that with the lower. The thermal stabilities of EVA/clay nanocomposites were also studied by thermal gravimetric analysis (TGA).

Cocontinuous morphologies in polystyrene/ethylene–vinyl acetate blends: The influence of the processing temperature

AbstractThe influence of the compression‐molding temperature on the range of cocontinuity in polystyrene (PS)/ethylene–vinyl acetate (EVA) copolymer blends was studied. The blends presented a broad range of cocontinuity when compression‐molded at 160°C, and they became narrower when compression‐molded at higher temperatures. A coarsening effect was observed in PS/EVA (60:40 vol %) blends upon compression molding at higher temperature with an increase in the phase size of the cocontinuous structure. Concerning PS/EVA (40:60 vol %) blends, an increase in the mixing and molding temperatures resulted in a change from a cocontinuous morphology to a droplet–matrix morphology. This effect was observed by selective extraction experiments and scanning electron microscopy. The changes in the morphology with the molding conditions affected the storage modulus. An increase in the storage modulus in blends compression‐molded at 160°C was observed as a result of dual‐phase continuity. An EVA copolymer with a higher vinyl acetate content (28 wt %) and a higher melt‐flow index resulted in blends with a broader range of cocontinuity. This effect was more pronounced in blends with lower amounts of PS, that is, when EVA formed the matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 386–398, 2003

High-resolution solid-state NMR and SEM study of the interaction behavior of poly(ethylene-co-vinyl acetate)/poly(vinyl acetate) blends

Binary blends formed by two types of ethylene-co-vinyl acetate (EVA), which have different vinyl acetate contents, and poly(vinyl acetate) (PVAc) were prepared in a Haake Rheocord 9000 plastograph. A series of samples were obtained varying the PVAc amount up to 50%. The studies were carried out employing solid-state nuclear magnetic resonance spectroscopy (NMR) and scanning electronic microscopy (SEM). The xenon-129 (129Xe) and carbon-13 (13C) NMR response together with the microscopy results showed that the systems are heterogeneous. Therefore, EVA with a higher vinyl acetate content presented some interaction between the polymer blend components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 116–124, 2002