Effect of dispersion state of organoclay on cellular foam structure and mechanical properties of ethylene vinyl acetate copolymer/ethylene‐1‐butenecopolymer/organoclay nanocomposite foams

In this study, our goal is to obtain lower density of ethylene‐vinyl acetate copolymer (EVA)/ethylene‐1‐butene copolymer (EtBC) foams without sacrificing mechanical properties. For this purpose EVA/EtBC/organoclay (Cloisite 15A, Closite 30B) nanocomposite foams were prepared. To investigate the effect of compatibilizer on the dispersion state of organoclay in cellular foam structure and mechanical properties of the EVA/EtBC/organoclay foams composites were prepared with and without maleic anhydride grafted EtBC (EtBC‐g‐MAH). The dispersion of organoclay in EVA/EtBC/organocaly foams was investigated by X‐ray diffraction and transmission electron microscopy. The EVA/EtBC nanocomposite foamswith the compatibilzer, especially EVA/EtBC/Cloisite 15A/EtBC‐g‐MAH foams displayed more uniform dispersion of organoclay than EVA/EtBC nanocomposite foams without the compatibilzer. As a result, EVA/EtBC/Cloisite 15A/EtBC‐g‐MAH foams have the smallest average cell size and highest 100% tensile modulus followed by EVA/EtBC/Cloisite 30B/EtBC‐g‐MAH foams. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3879–3885, 2007     

Improvement of compression set property of ethylene vinyl acetate copolymer/ethylene‐1‐butene copolymer/organoclay nanocomposite foams

To chemically bond polymer and organoclay, low molecular weight trimethoxysilyl‐modified polybutadiene (Silane) was used in this study. When Silane was added, ethylene‐vinyl acetate copolymer (EVA)/ethylene‐1‐butene copolymer (EtBC)/methyl tallow bis‐2‐hydroxyethyl quaternary ammonium‐modified montmorillonite (OH‐MMT)/Silane foams with and without maleic anhydride grafted EtBC (EtBC‐g‐MAH) display lower compression set than EVA/EtBC foams. According to the compression set result, OH‐MMT is more effective in improvement of compression set than dimethyl dihydrogenated tallow quaternary ammonium‐modified montmorillonite (DM‐MMT) because in addition of OH groups in the organoclay surface, the OH groups of the alkylammonium ion existed in interlayer of OH‐MMT may react with silanol group of Silane. The possible chemical reactions between Silanol groups of Silane and the hydroxyl groups of OH‐MMT and DM‐MMT were proved by ATR‐FTIR experiments. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Effect of organoclay content on the mechanical properties of ethylene‐vinyl acetate copolymer/ multi‐walled carbon nanotube/organoclay foams

The main objective of this study is to obtain ethylene‐vinyl acetate copolymer (EVA)/multi‐walled carbon nanotube (MWCNT)/organoclay foams with improved mechanical properties without increase of their density, compared with EVA/MWCNT foams. MWCNT content was fixed at 5 phr in this study. To achieve the objective, EVA was melt‐mixed with MWCNTs and organoclays in a bench kneader. And the obtained EVA/MWCNT/organoclay mixtures were mixed with chemical blowing agent and cross‐linking agent in a two roll‐mill. After being mixed in a two roll‐mill, the mixtures were put in a mold and the foams were obtained by compression‐molding. The effect of organoclay content on the mechanical properties and surface resistivity of EVA/MWCNT (5 phr)/organoclay foams was investigated. The addition of 1 phr organoclays to the EVA/MWCNT (5 phr) foams resulted in the improvement of tensile strength, 100% tensile modulus, tear strength, and compression set without increase of the density. However, further increase in content of organoclay (3 phr) leaded to a deterioration of mechanical properties. Therefore, determining the optimal content of organoclay was very important in order to achieve the main objective of this study. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Preparation and cell morphology of ethylene‐vinyl acetate copolymer (EVA)/wood‐flour foams with low density

The main objective of this study is to obtain ethylene‐vinyl acetate copolymer (EVA)/wood‐flour foams with low density (< 0.2 g/cm³) using chemical blowing agent. Stearic acid was used as a compatibilizer to improve not only the compatibility between wood‐flour and EVA but also the compatibility between moisture and EVA in this study. The effects of wood‐flour content on the density and mechanical properties of EVA/wood‐flour foams were studied. Also, the effects of content of stearic acid on the cell morphology of EVA/wood‐flour foams were investigated. The shape of EVA/wood‐flour foams with 20% wood‐flour content becomes more uniform with increasing content of stearic acid. The most stabilized shape of the foams is obtained with 5 wt % stearic acid content. The density of EVA/wood‐flour foams with 20% wood‐flour and 5 wt % stearic acid is 0.11 g/cm³. With increasing content of stearic acid, more gas remains in the EVA matrix and consequently, average cell size and density increase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40894.     

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.     

Morphology and tensile properties of crosslinked nanocomposite foams of low‐density polyethylene and poly(ethylene‐co‐vinyl acetate) blends

This paper studies the morphology and tensile properties of nanocomposite foams of blends of low‐density polyethylene (LDPE) and poly(ethylene‐co‐vinyl acetate) (EVA). Preparations of LDPE/EVA nanocomposites were conducted in an internal mixer, and then samples were foamed via a batch foaming method. Morphology of the nanocomposite blends and nanocomposite foams was studied by X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. Morphological observations showed that nanoparticle dispersion in the polymeric matrix was affected by the blend ratio in a way such that EVA‐rich samples had a better dispersion of nanoclay than LDPE‐rich ones. In addition, the tensile properties of the nanocomposite foams were related to different variables such as blend ratio, clay content, and foam density. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

The effect of curing system on the properties of the thermoplastic elastomer foams of ethylene‐vinyl acetate copolymer and styrene‐butadiene and ethylene‐propylene‐diene monomer rubbers

Thermoplastic elastomer (TPE) foams have important application in electrical, toys, and other industries. Several foams were prepared by ethylene‐vinyl acetate copolymer (EVA) lonely, and in combination with styrene‐butadiene and ethylene‐propylene‐diene monomer rubbers (SBR and EPDM). The effects of crosslinking and foaming agents and EVA type on density and mechanical properties of the cured foams with two curing systems, peroxide and sulfur‐peroxide with potential use in automotive applications, were studied. The results showed that proposed compounds formulations were foamed properly. The viscosity of the EVA was a key factor for the density values of the formed foams. The densities of the cured foams with peroxide system with various SBR contents were higher when compared with cured foams with sulfur‐peroxide system. With increasing foaming agent, the densities of the foams were reduced for studied curing systems. The densities of the EVA–EPDM foams were lower than those of the EVA–SBR foams in the same studied conditions. Increasing rubber in foam formulation had adverse effect on tensile properties of the foams. The existence of the talc powder in foam formulation had important role on the shape and type of the formed cells and resulted in foams with mostly closed cells. The results of this study help the automotive article designer to produce suitable TPE foam. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45357.     

Preparation of polyethylene‐octene elastomer/clay nanocomposite and microcellular foam processed in supercritical carbon dioxide

Polyethylene‐octene elastomer (POE)/organoclay nanocomposite was prepared by melt mixing of the POE with an organoclay (Cloisite 20A) in an internal mixer, using poly[ethylene‐co‐(methyl acrylate)‐co‐(glycidyl methacrylate)] copolymer (E‐MG‐GMA) as a compatibilizer. X‐ray diffraction and transmission electron microscopy analysis revealed that an intercalated nanocomposite was formed and the silicate layers of the clay were uniformly dispersed at a nanometre scale in the POE matrix. The nanocomposite exhibited greatly enhanced tensile and dynamic mechanical properties compared with the POE/clay composite without the compatibilizer. The POE/E‐MA‐GMA/clay nanocomposite was used to produce foams by a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite produced a microcellular foam with average cell size as small as 3.4 µm and cell density as high as 2 × 10¹¹ cells cm^?3. Copyright © 2005 Society of Chemical Industry     

Synthesis of silane‐grafted ethylene vinyl acetate copolymer and its application to compatibilize the blend of ethylene‐propylene‐diene copolymer and silicone rubber

Vinyltrimethoxysilane‐grafted ethylene vinyl acetate copolymer (EVA‐g‐VTMS) was synthesized and applied to compatibilize ethylene‐propylene‐diene copolymer (EPDM)/methyl vinyl silicone rubber (MVQ) blends. The silane‐grafting was successfully proved by differential scanning calorimetry, FTIR spectroscopy and XPS spectroscopy. The additive amount of the compatibilizer (EVA‐g‐VTMS) was optimized to be 10 phr (parts per hundred of rubber in weight) based on analysis of scanning electron microscopy, mechanical properties, aging properties, dynamic mechanical properties, rheological properties and thermal properties. Compared with the blend without EVA‐g‐VTMS, results show that the blend with 10 phr of EVA‐g‐VTMS exhibits the finest morphology. Tensile strength, elongation at break, modulus at 100% elongation, tear strength and TE index increase by 82.5%, 16.9%, 60.0%, 40.9%, and 41.9%, respectively. Dynamic mechanical analysis reveals storage modulus increase and glass transition temperatures of EPDM and MVQ move closer to each other. Rheological analysis shows a decrease in complex modulus and complex viscosity, and the processibility of the blend was improved. Furthermore, thermogravimetric analysis shows enhancement of thermal stability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams?

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay‐modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide‐angle X‐ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ethylene vinyl acetate copolymer (EVA)/multiwalled carbon nanotube (MWCNT) nanocomposite foams

In this study, multiwalled carbon nanotube (MWCNT) and ethylene vinyl acetate copolymer (EVA) nanocomposite bulk foams were prepared for static dissipative applications by using melt compounding method, the most compatible with current industrial applications. Closed‐cell structure was verified with Scanning Electron Microscope. All the mechanical properties investigated improved with increasing content of MWCNT except elongation at break. At 5 phr of MWCNT, significant improvement of mechanical properties and compression set were observed. Also, the surface resistivity begins to decrease at 5 phr of MWCNT. Interestingly, the increase of surface resistivity of nanocomposite foams with 8 and 10 phr MWCNT were observed with increasing thickness of removed surface layers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure‐property relationships of LLDPE—highly filled with aluminum hydroxide

The mechanical performance, rheological behavior, and phase morphology of linear low‐density polyethylene (LLDPE) highly loaded with aluminum hydroxide [Al(OH)₃] were investigated. It was found that titanate surface‐active agent and ethylene‐vinyl acetate copolymer (EVA) improve the processing and ductile properties of the composite remarkably but are accompanied by the deterioration of the tensile strength. Addition of vinyl triethoxy silane (VTEO) and dicumyl peroxide (DCP) improves the tensile strength of the composite because of the silane crosslinking structure introduced. A synergistic effect of interface modifying and silane crosslinking method in improving mechanical performance of the composite is presented. Phase morphology of the LLDPE/Al(OH)₃ composites was studied by means of scanning electron microscopy (SEM) technique. SEM micrographs indicate that a core‐shell type with Al(OH)₃ as a core and EVA as a shell is formed in the composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2485–2490, 2002     

Ethylene propylene diene terpolymer/ethylene vinyl acetate/layered silicate ternary nanocomposite by solution method

A new ternary nanocomposite has been developed using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate (16 Me‐MMT) from sodium montmorillonite (Na⁺‐MMT). Wide angle X‐ray diffraction and transmission electron microscopic analysis confirmed the intercalation of the polymer chains in between the organosilicate layers and the nanoscale distribution of 16 Me‐MMT in polymer matrix, respectively. The measurement of mechanical properties for 2–8 wt% of 16 Me‐MMT loadings showed a significant increase in tensile strength, elongation at break, and modulus at different elongations. Such an improvement in mechanical properties has been correlated based on the fracture behavior of nanocomposite by SEM analysis. Thermal stability of EPDM/EVA/layered silicate ternary nanocomposites also showed substantial improvements compared with the neat EPDM/EVA blend, confirming thereby the formation of a high performance nanocomposite. POLYM. ENG. SCI., 46:437–843, 2006. © 2006 Society of Plastics Engineers     

Study on the compatibility of ethylene‐vinyl acetate copolymer/vermiculite in biaxially oriented polypropylene films

A process for preparing expanded vermiculite/ethylene vinyl acetate nanocomposites by ball milling expanded vermiculite (EVMT) in cyclohexane solution of ethylene vinyl acetate copolymer resin (EVA) was presented, and the influence of EVA/EVMT nanocomposites on mechanical, barrier performance of modified biaxially oriented polypropylene (BOPP) films was discussed in this article. By the process, the EVMT is intercalated and exfoliated to obtain a kind of EVMT/EVA nanocomposite, in which EVA serves as both intercalating agent into EVMT and compatibilizer between EVMT and polypropylene (PP); so, when EVMT/EVA was melt blended with PP, platelets of vermiculite can be exfoliated easily and dispersed relatively well in the PP matrix. Compared with original (nonmodified) BOPP, when EVMT loading ranged from 0.1% to 0.5%, both strength and toughness of the modified BOPP films was increased. Moreover, platelets (flakes) of vermiculite dispersed in PP matrix improved barrier properties of modified BOPP films also. The improved barrier properties of BOPP films accorded with Nielsen model. POLYM. COMPOS., 36:78–87, 2015. © 2014 Society of Plastics Engineers     

The role of nanofillers on (natural rubber)/(ethylene vinyl acetate)/clay nanocomposite in blending and foaming

Nanocomposite foams were fabricated from 60/40 wt% ethylene vinyl acetate (EVA)/natural rubber (NR) blends by using azodicarbonamide as a blowing agent. Two different nanofillers (sodium montmorillonite and organoclay) were employed to study their effects on foam properties. The results were also compared with conventional (china clay)‐filled foams. Transmission electron microscopy, X‐ray diffraction, scanning electron microscopy, and three‐dimensional Microfocus X‐ray computed tomography scanning analysis were performed to characterize the EVA/NR blend morphology and foam structures. The results revealed that the nanofiller acted as a blend compatibilizer. Sodium montmorillonite was more effective in compatibilization, generating better phase‐separated EVA/NR blend morphology and improving foam structure. Higher filler loading increased the specific tensile strength of rubber foams. The rubber nanocomposite foam showed superior specific tensile strength to the conventional rubber composite foam. The elastic recovery and compressive strength of the nanocomposite foams decreased with increasing filler content, whereas the opposite trend was observed for the conventional composite foams with china clay. The thermal conductivity measurement indicated that the nanofiller had better beneficial effect on thermal insulation over china clay filler. From the present study, the nanofillers played an important role in obtaining better blend morphology as compatibilizer, rather than the nucleating agent and the nanofiller content of 5 phr (parts by weight per hundred parts of rubber) was recommended for the production of EVA/NR nanocomposite foams. J. VINYL ADDIT. TECHNOL., 21:134–146, 2015. © 2014 Society of Plastics Engineers     

Flour rice husk as filler in block copolymer polypropylene: Effect of different coupling agents

Flour rice husk (FRH) was employed as a filler in block copolymer polypropylene (PPB) in order to prepare polymer‐based reinforced composites. Four coupling agents were selected to modify the surface of the rice husk in the composite materials, including two types of functionalized polymers [PP homopolymer grafted with maleic anhydride (MA‐PP) and an elastomer styrene–ethylene–butadiene–styrene triblock copolymer grafted with MA (MA‐SEBS)] and two bifunctional organometallic coupling agents (silane and titanate with linear low‐density polyethylene as a carrier). The influence of each type of coupling agent on the interfacial bonding strength was studied by dynamic mechanical analysis, scanning electronic microscopy, and rheological tests. The results showed that strong interactions were formed between the coupling agents and the filler surface. The addition of a coupling agent with an elastomeric carrier (MA‐SEBS) increased the loss tangent and reduced the storage modulus of the composite. A similar but less intense effect was observed for the titanate coupling agent. However, an antagonistic performance was obtained when MA‐PP and silane were employed as coupling agents. In addition, when the percentage of MA‐SEBS was increased, the impact properties of FRH/PPB blends were improved and the strength was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1823–1831, 2006     

Effects of clay dispersion on the foam morphology of LDPE/clay nanocomposites

Intercalated and exfoliated low‐density polyethylene (LDPE)/clay nanocomposites were prepared by melt blending with and without a maleated polyethylene (PE‐g‐MAn) as the coupling agent. Their morphology was examined and confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of clay content and dispersion on the cell morphology of nanocomposite foams during extrusion foaming process were also thoroughly investigated, especially with a small amount of clay of 0.05–1.0 wt%. This research shows the optimum clay content for achieving microcellular PE/clay nanocomposite foams blown with supercritical CO₂. It is found that < 0.1 wt% of clay addition can produce the microcellular foam structure with a cell density of > 10⁹ cells/cm³ and a cell size of ～ 5 μm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2129–2134, 2007     

Preparation and investigation of ethylene–vinyl acetate copolymer/silicone rubber/clay nanocomposites

In this article, the combination of silicone rubber (SR) elastomer with synthetic iron montmorillonite (Fe‐MMT) to form a kind of new flame‐retardant system based on an ethylene–vinyl acetate (EVA) copolymer is first reported. Also, the flame retardancy of the EVA/SR/Fe‐MMT hybrid are compared with that of EVA/SR/natural sodium montmorillonite. The structures of the nanocomposites were characterized with X‐ray diffraction and transmission electron microscopy. Cone calorimeter tests and thermogravimetric analysis were used to evaluate the flame‐retardant properties and thermal stability of the composites, respectively. In addition, tensile tests were carried out with a universal testing machine, and the morphology of the fracture surface was observed with environmental scanning electron microscopy. We found that SR/organophilic montmorillonite (Fe‐OMT) was more effective in reducing the primary peak heat release rate of the nanocomposite, and the EVA/SR/Fe‐OMT hybrid had a higher thermal stability in the deacetylated polymer than EVA/SR/sodium organophilic montmorillonite. Moreover, the exfoliated EVA/SR/Fe‐OMT nanocomposite displayed excellent mechanical properties because of a better dispersion of Fe‐OMT in the polymer matrix, and a possible mechanism is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physical properties of ethylene vinyl acetate copolymer (EVA)/natural rubber (NR) blend based foam

In this study an attempt was made to improve the rebound resilience and to decrease the density of ethylene‐vinyl acetate copolymer (EVA) foam. For this purpose, EVA was blended with natural rubber (NR), and EVA/NR blends were foamed at 155°C, 160°C, and 165°C. To investigate the correlation between crosslinking behavior and physical properties of foams, crosslinking behavior of EVA/NR blends was monitored. The physical properties of the foams were then measured as a function of foaming temperatures and blend compositions: 165°C was found to be the optimal temperature for a crosslinking of EVA/NR foam. As a result, the density of EVA/NR blend foamed at 165°C was found to be the lowest. EVA/NR (90/10) blend, foamed at 165°C, showed lower density, better rebound resilience, and greater tear strength than EVA foam. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2212–2216, 2004     

Processing and properties of an ethylene–vinyl acetate blend foam incorporating ethylene–vinyl acetate and polyurethane waste foams

Waste polyurethane foam (w‐PU) and waste ethylene–vinyl acetate foam (w‐EVA) were used as fillers for the production of an ethylene–vinyl acetate (EVA) blend foam. Two different foaming techniques (single‐stage and heat–chill processes) were used for this purpose. The waste foam concentration was varied up to 30 wt % of the original EVA. The physical, mechanical, and morphological properties of the filled foam were studied. The single‐stage process produced blend foams with a lower density and a greater cell size than the foams obtained by the heat–chill process. The density and compression strength of the blend foam increased as the percentage of w‐PU foam increased. However, for the w‐EVA/EVA blend foams, the addition of w‐EVA foam did not significantly affect the density or compression strength compared to the original EVA foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44708.