Study on viscoelastic,crystallization, and mechanical properties of HDPE/EVA/Mg(OH)2 composites

In this article, elastomer‐toughened high density polyethylene/magnesium hydroxide (HDPE/MH) composites with various contents of ethylene vinyl acetate copolymer (EVA) are prepared in a twin‐screw extruder and then injection‐molded. The effect of EVA on the viscoelastic, crystallization, morphology, and tensile properties of the HDPE/EVA/MH composites is studied. The rheological behaviors show that the complex viscosity, storage, and loss modulus at low frequencies are largely unaffected with various EVA contents; however, the corresponding values decrease with increasing EVA content at high frequencies. The scanning electronic microscopy studies on the HDPE/EVA/MH composites show that the MH particles mainly disperse in the EVA phase, and the interfacial adhesion has been also enhanced due to the addition of EVA. The crystallization of HDPE diminishes because of the surface energy difference resulting in encapsulation structure. The tensile properties of the HDPE/EVA/MH composites are strong influenced by the incorporation of EVA. POLYM. COMPOS., 38:1221–1226, 2017. © 2015 Society of Plastics Engineers     

Effect of vinyl acetate content on the photovoltaic-encapsulation performance of ethylene vinyl acetate under accelerated ultra-violet aging

The vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 °C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra-red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48268.     

FLAVOR ENCAPSULATION AND RELEASE CHARACTERISTICS OF SPRAY-DRIED POWDER BY THE BLENDED ENCAPSULANT OF CYCLODEXTRIN AND GUM ARABIC

The flavor inclusion powder was prepared by spray drying, using the combined encapsulation method of inclusion by β-cyclodextrin (β-CD) and emulsified by gum arabic (GA). d-Limonene and ethyl n-hexanoate were used as model flavors. The application of high pressure by Microfluidizer to the mixture of flavors and β-CD slurry was an effective means of forming inclusion complex. Flavor retention during spray drying under various compositions of the encapsulants was investigated. The flavor retention using the blended encapsulant was increased by adding GA in the encapsulant. The characteristics of release of encapsulated flavor during storage were evaluated at 50°C and 75% of relative humidity. The release rate of flavor in spray-dried powder depended on kinds of the flavors and composition of the encapsulant. The blending MD and β-CD in the feed liquid decreased the release rate of flavors. The rate of release of flavor was analyzed by Avrami's Equation.     

Effect of rubbers on the flame retardancy of EVA/ultrafine fully vulcanized powdered rubber/nanomagnesium hydroxide ternary composites

Two flame retardant ternary composites of ethylene‐vinyl acetate copolymer (EVA)/ultrafine fully vulcanized powdered rubber (UFPR)/nanomagnesium hydroxide (MH) were studied in this article. It has been found that carboxyl acrylonitrile butadiene UFPR (CNB‐UFPR) and acrylonitrile butadiene UFPR (NB‐UFPR) have different effect on the flame retardancy of related materials when they are used together with nano‐MH. CNB‐UFPR is in favor of lowering the material's heat release rate during its combustion, while NB‐UFPR benefits the material on the resistance to ignition. Observation on the microstructure of the composites by transmission electron micrograph revealed that the aforementioned two ternary composites have quite different morphology. EVA/CNB‐UFPR/nano‐MH composite exhibits partial encapsulation structure, while EVA/NB‐UFPR/nano‐MH composite has full separation structure. POLYM. COMPOS., 28:479–483, 2007. © 2007 Society of Plastics Engineers     

光伏背板粘结涂层与封装胶膜粘结力的研究

光伏背板粘结涂层与封装胶膜乙烯醋酸乙烯酯（ EVA）的粘结力是决定组件封装效果的关键因素。通过考察 EVA胶膜的种类、放置时间,以及涂料配方中氟碳树脂与丙烯酸树脂的质量比、填料的类型和含量、涂层厚度对涂层与 EVA胶膜粘结力的影响,结果发现通用型透明胶膜、抗蜗牛纹的胶膜与涂层的粘结力优于抗电位诱导衰减（ PID）功能的胶膜,胶膜的放置时间越长,与涂层的粘结力越低;涂料中丙烯酸树脂的添加会增大涂层与 EVA的粘结力,消光粉的表面有机处理、填料增多均会降低涂层与 EVA的粘结力;涂层的厚度越厚,与 EVA的粘结力越高。     

Crosslinking and post‐crosslinking of ethylene vinyl acetate in photovoltaic modules

Ethylene vinyl acetate (EVA) is the dominating material for the encapsulation of solar cells. A better understanding of the crosslinking reaction progress during PV module lamination could lead to promising approaches for shortening of PV module lamination times but also for optimization of the EVA formulation. Therefore, the main aim of this study is to investigate the crosslinking behavior of EVA but also for optimization potentials of the EVA formulation. Currently, a degree of crosslinking higher than 70% obtained from Soxhlet extraction, is used as quality control standard in PV industry. Thermomechanical properties of the investigated EVA films demonstrate a sufficient state of crosslinking already after 5 min, which corresponds to a Soxhlet value of around 50%. Nevertheless, the effect of the remaining, still reactive peroxide crosslinker under service relevant conditions cannot be neglected. Therefore, the behavior of mini‐modules manufactured at different lamination times and stored under various aging conditions is investigated. EVA not fully cured during lamination are undergoing postlamination crosslinking. At the same time, remaining active crosslinker causes discoloration at soldering ribbons after accelerated aging. The crosslinking time in the lamination process may be reduced to ≥6 min, compromising between high throughput in production and the need of avoiding degradation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44912.     

An investigation of flavor encapsulation comprising of regenerated cellulose as core and carboxymethyl cellulose as wall

The potential application of flavor encapsulation comprising regenerated porous cellulose particles (RPC) as core and carboxymethyl cellulose (CMC) as wall was investigated using l-menthol as a model flavor. RPC was prepared by sol–gel transition method and characterized by Fourier-transform infrared (FTIR) spectra, scanning electron microscopy (SEM) and micromeritics instruments. The results revealed that the RPC showed the particle size about 300–500 μm as well as the specific surface area about 8.7 m²/g. Based on high adsorptive capability, RPC could encapsulate menthol well and offer high encapsulation yield. The menthol content of RPC-menthol complexes (RPCM) was measured by gas chromatogram (GC) and showed the maximum content of about 12 % menthol with the encapsulation efficiency of 70 %. Besides, RPC provided comparable flavor retention as microcrystalline cellulose during storage under relative humidity of 80 % at 25 °C. CMC was then used to modify RPCM and the construction of RPCM-CMC was confirmed by FTIR and SEM. The studies showed that CMC wall on RPCM surface had no influence on the menthol content and encapsulation efficiency in encapsulation process, but provided a significant increase in menthol retention during storage depending on the content of CMC in RPCM-CMC. Moreover, the stability test at various temperatures showed that both RPCM and RPCM-CMC were stable at room temperature and released flavor at temperatures common in food processing. It was concluded that RPC and CMC modification shows great potential as flavor encapsulant.     

Anti-neoplastic Applications of Heparin Coated Magnetic Nanoparticles Against Human Ovarian Cancer

This study determines the effect of bare and heparin (HP)-based magnetic iron oxide (Fe₃O₄) nanoparticles (MNPs) on the human ovarian cancer cells of CP70 type. Cisplatin (CP) was used as the anticancer drug, entrapped in MNPs. The nanoparticles containing the anticancer drug, CP, were prepared by a solvent evaporation and emulsification cross-linking method. The physicochemical properties of the nanoparticles were characterized by various techniques, and uniform particles of bare and HP coated MNPs, with average particle sizes of 25 and 45 ± 15 nm, having high encapsulation efficiencies, were obtained. Additionally, a sustained release of CP from the MNPs was successful in vitro. Cytotoxicity tests showed that the MNP–HP–CP had higher cell toxicity than the individual HP; and confocal microscopic analysis confirmed excellent cellular uptake efficiency of CP70 cells for MNP–HP–CP. These results indicate that HP based MNPs have potential uses as anticancer drug carriers and have also proved to have enhanced anti-neoplastic effects.     

光伏组件用EVA封装胶膜的老化研究进展

综述了自上世纪80年代以来乙烯一醋酸乙烯酯共聚物（EVA）的老化机理及研究成果,介绍了光伏组件用EVA配方及结构对封装胶膜老化性能和使用寿命的影响。提出了光伏组件封装胶膜老化研究存在的问题。     

FLAVOR ENCAPSULATION AND RELEASE CHARACTERISTICS OF SPRAY-DRIED POWDER BY THE BLENDED ENCAPSULANT OF CYCLODEXTRIN AND GUM ARABIC

The flavor inclusion powder was prepared by spray drying, using the combined encapsulation method of inclusion by β-cyclodextrin (β-CD) and emulsified by gum arabic (GA). d-Limonene and ethyl n-hexanoate were used as model flavors. The application of high pressure by Microfluidizer to the mixture of flavors and β-CD slurry was an effective means of forming inclusion complex. Flavor retention during spray drying under various compositions of the encapsulants was investigated. The flavor retention using the blended encapsulant was increased by adding GA in the encapsulant. The characteristics of release of encapsulated flavor during storage were evaluated at 50°C and 75% of relative humidity. The release rate of flavor in spray-dried powder depended on kinds of the flavors and composition of the encapsulant. The blending MD and β-CD in the feed liquid decreased the release rate of flavors. The rate of release of flavor was analyzed by Avrami's Equation.     

Morphology and interaction of nanocomposite foams formed with organo-palygorskite and ethylene-vinyl acetate copolymers

To obtain excellent mechanical properties of polymer nanocomposite foams without sacrificing the lower density through popular and friendly means. Organically modified palygorskite (OPal) was prepared with γ-aminopropyltriethoxysilane on the surface of rod-shaped Pal particles, and nanocomposite foams based on ethylene-vinyl acetate (EVA) copolymer was prepared by melt-blending EVA with OPal. Fourier transform infrared spectroscopy (FTIR) was used to investigate the interaction between OPal and EVA matrix, and the OPal/EVA nanocomposites were also characterized by X-ray photoelectron spectra (XPS), X-ray diffraction analysis (XRD) and differential scanning calorimetry (DSC). The dispersivity of OPal in the EVA matrix and the morphology of the foams were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the OPal/EVA nanocomposite foams were also characterized by thermogravimetric analysis (TGA). The effect of OPal content in the foam samples on the cellular structure and mechanical properties was investigated. Our studies indicate that the OPal nanofibers could be used as a heterogeneous nucleation agent to reduce the average cell diameter. The uniformity of cell structure of the foams was improved, and the physical properties of OPal/EVA nanocomposite foams were enhanced by the addition of OPal. The density of OPal/EVA nanocomposite foams was decreased to 0.133 g/cm³. Also, the best tear strength, peel strength and compression set values of nanocomposite foams were 4.65, 2.65 N/mm and 25.5 %, which were improved by 36.0, 54.3 and 12.0 %, respectively, compared with those of the initial foam.     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.     

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

Nylon 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     

Fabrication and characterization of cypermethrin nanocapsules in miniemulsion polymerization system

The nanoencapsulation of cypermethrin (CP) was carried out by miniemulsion polymerization, a convenient one‐pot encapsulation technique for nanocapsules. The encapsulation was achieved by polymerization inducing phase separation within minidroplets dispersed in an aqueous phase. For nanocapsules prepared in this way, the type of surfactant and initiator, the level of the crosslinking agent or chain‐transfer agent, and the monomer/CP ratio play a significant role in defining the end morphology of the latex particles. Specifically, for a styrene (St)/CP system, there were optimum levels of ionic surfactant (1.0 wt % sodium dodecyl sulfate), nonionic surfactant [0.5 wt % poly(ethylene glycol) monooctylphenyl ether], oil‐soluble initiator [1.0 wt % azobis(isobutyronitrile)], crosslinking agent (1.0 wt % divinylbenzene), and a St/CP ratio of 1 : 1 for obtaining well‐defined nanocapsules of CP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The Effect of Epoxidized Natural Rubber (ENR-50) or Polyethylene Acrylic Acid (PEA) as Compatibilizer on Properties of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L) Blends

The effect of epoxidized natural rubber (ENR) or polyethylene acrylic acid (PEA) as a compatibilizer on properties of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends was studied. 5 wt.% of compatibilizer was employed in EVA/SMR L blend and the effect of compatibilizer on tensile properties, thermal properties, swelling resistance, and morphological properties were investigated. Blends were prepared by using a laboratory scale of internal mixer at 120°C with 50 rpm of rotor speed. Tensile properties, thermal properties, thermo-oxidative aging resistance, and oil swell resistance were determined according to related ASTM standards. The compatibility of EVA/SMR L blends with 5 wt.% of compatibilizer addition or without compatibilizing agent was compared. The EVA/SMR L blend with compatibilizer shows substantially improvement in tensile properties compared to the EVA/SMR L blend without compatibilizer. Compatibilization had reduced interfacial tension and domain size of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends.     

Characterization of adhesion performance of topcoats and adhesion promoters on TPO substrates

Adhesion of organic coatings to thermoplastic olefin (TPO) substrates in automotive applications has been an issue for makers of automotive parts since TPO was first used in exterior applications, primarily fascia. A widely used technique for assuring paint adhesion to TPO is the use of adhesion promoter primers based on chlorimated polypropylenes (CPO). Much research has been focused on understanding the forces involved at the interfaces of substrate, adhesion promoter, and topcoats resulting in the adhesion or the loss of adhesion in various environmental conditions. This study correlates the adhesion performance of CPO and nonchlorinated adhesion promoters (NCPO) as measured by peel strength with properties observed through microscopy techniques. Adhesion performance of CPOs, NCPOs, and blends are quantified through the use of 90° and 180° peel strength studies. Surface characteristics of adhesion promoters applied over a TPO substrate and cured at various temperatures are examined through the use of atomic force microscopy (AFM).     

Preparation of expandable graphite with silicate assistant intercalation and its effect on flame retardancy of ethylene vinyl acetate composite

A halogen‐free intumescent flame retardant expandable graphite composite (EG), with an initial expansion temperature of 202°C and expansion volume of 517 mL g⁻¹, was successfully prepared via a facile two‐step intercalation method, i.e. using KMnO₄ as oxidant and H₂SO₄, Na₂SiO₃·9H₂O as intercalators. The prepared EG flame retardant was characterized by field emission scanning electron microscope, X‐ray diffraction spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, flame retardancy and thermal property of various ethylene vinyl acetate copolymer (EVA) composites, including EVA/EG and EVA/EG/APP (ammonium polyphosphate) specimens, were studied through limiting oxygen index instrument (LOI), vertical combustion UL‐94 rating, thermal gravimetric and differential thermal analysis. The results indicate that the EVA/EG and EVA/EG/APP composites exhibit a better flame retardancy. Addition of EG at a mass fraction of 30% leads LOI of 70EVA/30EG composite improved to 28.7%. Even more, the synergistic effect between EG and APP improves the LOI of 70EVA/10APP /20EG composite to 30.7%. This synergistic efficiency is attributed to the formation of compact and stable layer‐structure, and the prepared EG can make EVA composite reach the UL‐94 level of V‐0. POLYM. COMPOS., 36:1407–1416, 2015. © 2014 Society of Plastics Engineers     

Phase structure of ternary polypropylene/elastomer/filler composites: effect of elastomer polarity

Phase structure of ternary polypropylene/elastomer/calcium carbonate composites has been investigated using scanning electron microscopy, dynamic mechanical analysis and differential scanning calorimetry. Two kinds of phase structure were observed either a separate dispersion of the phases or encapsulation of the filler by elastomer. The composite phase structure was determined mainly by the chemical character of the components and, to a lesser degree, by the mixing sequences of each component. In this study, the use of non-polar ethylene–octene copolymer (EOR) resulted in a composite having separate dispersion of elastomer and filler particles. When a polar ethylene–vinyl acetate (EVA) elastomer was used, an encapsulation structure was formed. This is attributed to the higher affinity of EVA to calcium carbonate. Analysis of the composite structure formed, using the Geometric Mean approach was found to be useful as a qualitative technique.     

Morphological control of porous ethylene‐vinyl acetate copolymer membrane obtained from a co‐continuous ethylene‐vinyl acetate copolymer/poly(ϵ‐caprolactone) blend

Ethylene‐vinyl acetate copolymer (EVA)/poly(?‐caprolactone) (PCL) blend (50/50 w/w) with co‐continuous morphology was prepared via melt mixing for fabricating microporous EVA membrane materials through selective solvent extraction. Shear flow and quiescent annealing techniques were employed to control co‐continuous phase size in the EVA/PCL blend, and the time‐ and temperature‐dependent relations of phase size were then evaluated theoretically. Using these techniques, microporous EVA membrane materials with various pore sizes ranging from 2 µm to more than 200 µm were obtained. In contrast to the porous EVA membrane prepared by the traditional way of solvent casting/particulate leaching, the as‐obtained microporous membrane shows a higher level of interconnectivity and much narrower pore size distribution with uniform pore structure. © 2013 Society of Chemical Industry     

Effects of the complexed moisture in metal acetylacetonate on the properties of the no‐flow underfill materials

A potential no‐flow (compression filling of encapsulant) underfill encapsulant for simultaneous solder joint reflow and underfill cure has been reported by the authors. The encapsulant is based on a cycloaliphatic epoxy/organic anhydride/Co(II) acetylacetonate system. The key of this no‐flow encapsulant is the use of a latent metal acetylacetonate catalyst that provides the solder reflow prior to the epoxy gellation and fast cure shortly after the solder reflow. However, most of the metal acetylacetonates can easily absorp moisture as their ligand. Therefore, it is of practical importance to understand the effect of the complexed water on the properties of the no‐flow material before and after cure. In this paper, differential scanning calorimetry, thermal gravimetric analysis, thermal mechanical analysis, dynamic mechanical analysis, and Fourier transform infrared spectrometry were used to validate the existence of complexed moisture in the Co(II) acetylacetonate. The effects of the complexed water on the curing profile, glass transition temperature, and storage modulus of the cured no‐flow underfill material were studied. A possible catalytic mechanism of the metal acetylacetonate in the cycloaliphatic epoxy/anhydride system was subsequently discussed and proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 103–111, 1999