Preparation and morphological evolution of heterophasic PP‐EP/EVA/organoclay nanocomposites: Effect of the nanoclay organic modifier

A study is presented on the morphological effects caused by the nanoclay organic modifier and the nanoclay concentration. This was made under previously determined compatibility conditions of heterophasic polypropylene copolymers (PP‐EP)/poly(ethylene vinyl acetate) (EVA)/organoclay nanocomposites. The nanocomposites were prepared using the fluidity of the EVA phase to disperse the nanoclay platelets. Therefore, no additional compatibilizer was used to achieve the clay dispersion. Two organoclays were used with different characteristics and polarity of the substituent groups. Transmission electron microscopy and X‐ray diffraction results first indicated that two hydrogenated tallow modifiers are more effective than one to enhance nanoclay exfoliation. Thermogravimetric studies indicated a low probability of thermal degradation of the nanoclay modifiers and as a consequence of their effect on the layer–layer exfoliation. Molecular simulations were made with the purpose to study additional factors affecting exfoliation. The introduction of nanoclay, within the compatibility conditions of the PP‐EP/EVA system, was also studied. It was determined that the system preserved its original morphology and that the silicate layers were hosted by the EVA domains. The crystallization characteristics of the PP‐EP/EVA mixtures indicated a gradual evolution of the overall crystalline structures depending on the EVA content. In the case of the ternary nanocomposites PP‐EP/EVA/nanoclay, the β crystalline structure was partially formed, although it decreased with increasing nanoclay content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Natural rubber/poly(ethylene‐co‐vinyl acetate)‐blend‐based nanocomposites

Natural rubber (NR)/poly(ethylene‐co‐vinyl acetate) (EVA) blend–clay nanocomposites were prepared and characterized. The blend nanocomposites were prepared through the melt mixing of NR/EVA in a ratio of 40/60 with various amounts of organoclay with an internal mixer followed by compression molding. X‐ray diffraction patterns revealed that the nanocomposites formed were intercalated. The formation of the intercalated nanocomposites was also indicated by transmission electron microscopy. Scanning electron microscopy, used to study the fractured surface morphology, showed that the distribution of the organoclay in the polymer matrix was homogeneous. The tensile modulus of the nanocomposites increased with an increase in the organoclay content. However, an increase in the organoclay content up to 5 phr did not affect the tensile strength, but the organoclay reduced this property when it was increased further. This study also indicated that a low silicate content dispersed in the blend matrix was capable of increasing the storage modulus of the material. The addition of the organoclay also increased the decomposition temperature of the NR/EVA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 353–362, 2006     

Oxygen permeability and the mechanical and thermal properties of (low‐density polyethylene)/poly (ethylene‐co‐vinyl acetate)/organoclay blown film nanocomposites

Various (low‐density polyethylene)/poly(ethylene‐co‐vinyl acetate) (LDPE/EVA) nanocomposites containing organoclay were prepared by one‐ and two‐step procedures through melt blending. The resultant nanocomposites were then processed via the film blowing method. From the morphological point of view, X‐ray diffraction and optical microscopy studies revealed that although a prevalent intercalated morphology was evident in the absence of EVA, a remarkable increase of organoclay interlayer spacing occurred in the EVA‐containing systems. The advantages of the addition of EVA to the LDPE/organoclay nanocomposites were confirmed in terms of oxygen barrier properties. In other words, the oxygen transmission rates of the LDPE/EVA/organoclay systems were significantly lower than that of the LDPE/organoclay sample. The LDPE/EVA/organoclay films had better mechanical properties than their counterparts lacking the EVA, a result which could be attributed to the improvement of the organoclay reinforcement efficiency in the presence of EVA. Differential scanning calorimetry and thermogravimetric analysis experiments were performed to follow the effects of the EVA and/or organoclay on the thermal properties of LDPE. Finally, the films produced from the two‐step‐procedure compound showed enhanced oxygen barrier properties and mechanical behavior as compared to the properties of the films produced via the one‐step procedure. J. VINYL ADDIT. TECHNOL., 19:132–139, 2013. © 2013 Society of Plastics Engineers     

Transparent copolyester/organoclay nanocomposites prepared by in situ intercalation polymerization: Synthesis,characterization, and properties

In this study, amorphous poly(ethylene terephthalate‐co‐1,3/1,4‐cyclohexylenedimethylene terephthalate) (PETG)/organoclay nanocomposites was synthesized by the in situ intercalation polymerization of terephthalic acid, ethylene glycol, 1,3/1,4‐cyclohexanedimethanol, and organoclay. The organoclay was obtained by modifying sodium montmorillonite (clay) with hexadecyl triphenylphosphonium bromide. The thermal, mechanical, optical, and gas barrier properties of these PETG nanocomposites with various organoclay contents (0–3 wt%) were discussed. The differential scanning calorimetry and X‐ray analyses revealed that all of the nanocomposites were amorphous. X‐ray diffraction and transmission electron micrographs showed that the organoclay was well dispersed in the polymer matrix, although some parts of the agglomerated layers remained on the scale of several hundreds of nanometers. The thermal stability and the mechanical property of the nanocomposites increased with organoclay content. The optical transmittances of nanocomposites that contained 0.5, 1, and 3 wt% of organoclay were 86.8%, 84.4%, and 77.4%, respectively. The oxygen transmission rate of the nanocomposite that contained 3 wt% of organoclay was about 50% of the PETG base polymer. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Preparation and characterization of EVA/clay Nanocomposites with improved barrier performance

Poly (ethylene‐co‐vinyl acetate) (EVA)/clay nanocomposites containing two different organoclays with different clay loadings were prepared. The transport of gases (oxygen and nitrogen) through the composite membranes was investigated and the results were compared. These studies revealed that the incorporation of nanoclays in the polymer increased the efficiency of the membranes toward barrier properties. It was also found that the barrier properties of the membranes decreased with clay loadings. This is mainly due to the aggregation of clay at higher loadings. The morphology of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy and X‐ray scattering. Small angle X‐ray scattering results showed significant intercalation of the polymer chains between the organo‐modified silicate layers in all cases. Better dispersed silicate layer stacking and more homogeneous membranes were obtained for Cloisite® 25A based nanocomposites compared with Cloisite® 20A samples. Microscopic observations (SEM and TEM) were coherent with those results. The dispersion of clay platelets seemed to be maximized for 3 wt % of clay and agglomeration increased with higher clay loading. Wide angle X‐ray scattering results showed no significant modifications in the crystalline structure of the EVA matrix because of the presence of the clays. The effect of free volume on the transport behavior was studied using positron annihilation spectroscopy. The permeability results have been correlated with various permeation models. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of different preparation methods on the properties of poly[ethylene‐co‐(vinyl acetate)]/(Standard Malaysian natural rubber)/organoclay nanocomposites

Poly[ethylene‐co‐(vinyl acetate)] (EVA)/(Standard Malaysian natural rubber) (SMR L)/organoclay nanocomposites were prepared by using melt intercalation and solution blending methods. In both preparation methods, the EVA: (SMR L) ratio was prefixed at 50:50, while the organoclay loading was varied from 0 to 10 phr. The effects of two different processing routes and organoclay loading on the morphology, tensile, properties thermal properties, and flammability of the nanocomposites were studied. X‐ray diffraction results and transmission electron microscopy images proved that solution blending promotes better dispersion of organoclay than melt intercalation. Thus, the nanocomposites prepared by the solution‐blending method exhibited higher values of tensile strength, stress at 100% elongation (M100), and thermal stability. The M100 value and thermal stability improved proportionally with the increase of organoclay content, owing to the demobilizing effect and the barrier properties of the organoclay. The optimum tensile strength value was achieved at a 2‐phr organoclay loading. Further increases in loading decreased the strength of the nanocomposites. Tensile fracture surfaces of the nanocomposites prepared by both methods showed different fracture behavior, as evidenced by scanning electron microscopy images. Flammability decreased when the organoclay loading increased for the nanocomposites prepared by both methods. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Ethylene vinyl acetate/Mg‐Al LDH nanocomposites by solution blending

Partially exfoliated ethylene vinyl acetate (EVA‐40, 40% vinyl acetate content)/layered double hydroxide (LDH) nanocomposites using organically modified layered double hydroxide (DS‐LDH) have been synthesized by solution intercalation method. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) studies of nanocomposites shows the formation of exfoliated LDH nanolayers in EVA‐40 matrix at lower DS‐LDH contents and partially intercalated/exfoliated EVA‐40/MgAl LDH nanocomposites at higher DS‐LDH contents. These EVA‐40/MgAl LDH nanocomposites demonstrate a significant improvement in tensile strength and elongation at break for 3 wt% of DS‐LDH filler loading compare to neat EVA‐40 matrix. Thermogravimetric analysis also shows that the thermal stability of the nanocomposites increases with DS‐LDH content in EVA‐40. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Poly(ethylene‐vinyl co‐vinyl acetate)/clay nanocomposites: Mechanical,morphology, and thermal behavior

Nanocomposites of ethylene‐vinyl acetate copolymer (EVAL) with Dellite organoclay were prepared in a laboratory extruder. The extent of intercalation of the nanocomposites was studied by field emission scanning electron microscopy and X‐ray diffraction. It was established that the organoclay is well dispersed and preferentially embedded in the EVAL phase. Further, the intercalation degree of the organoclay decreased with increasing organoclay content. The mechanical properties of the nanocomposites were studied as a function of clay loading and EVAL type. The nanocomposites exhibited enhanced thermal stability as seen in thermogravimetric studies. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Effect of organoclay structure characteristics on properties of ternary PP‐EP/EVA/nanoclay blend systems

In this study, the effect on the degree of organoclay exfoliation in polypropylene‐ethylene (PP‐EP)/Ethylene vinyl acetate (EVA)/organoclay blend system was studied while varying organoclay structural characteristics. Cloisite 6A, Cloisite 15A, Cloisite 20A, Cloisite 25A, Cloisite 30B, Cloisite 93A, and Cloisite 10A were used because they have different type of modifier. Ternary PP‐EP/EVA/organoclay system was obtained with each type of clay and results were organized to analyze the effect of type of clay chemical modification (C20A, C15A, and C6A), steric effect caused by surfactant structure (C15A and C10A), length of substitute groups on the surfactant (C20 and C25A), and surfactant polarity (C30B and C93A). Samples were characterized by: wide angle X‐ray diffraction, scanning transmission electron microscopy (STEM), dynamic mechanical analysis, and capillary rheometry. Results showed that clay galleries can be saturated with chemical modifier complicating the polymer chain intercalation into the clay galleries. Some clay modifier substituent groups could cause certain steric effect promoting less exfoliated platelets structures. Finally, longer chains in the modifier substituent group can promote a better intercalated–exfoliated structure. Among all the studied organoclays, best results were obtained in the ternary system when using C20A, which modifier has two hydrogenated tallows. In this case, interlayer spacing was increased more noticeable after ternary system was formed. This was corroborated with the obtained increase in viscosity and the intercalated–exfoliated structure observed by STEM. POLYM. COMPOS., 35:2241–2250, 2014. © 2014 Society of Plastics Engineers     

Experimental and computational investigation of EVOH/clay nanocomposites

Ethylene–vinyl alcohol copolymer (EVOH)/organoclay nanocomposites were prepared via a dynamic melt‐intercalation process. The effect of compatibilizers on the melt blending torque, intercalation level, and morphology of EVOH/organoclay systems was investigated. Maleic anhydride grafted ethylene vinyl acetate (EVA‐g‐ MA), or maleic anhydride grafted linear low‐density polyethylene (LLDPE‐g‐MA), were used to compatibilize EVOH with clay, at various concentrations (1, 5, and 10 wt %). Computer‐simulation techniques are used to predict structural properties and interactions of EVOH with compatibilizers in the presence and absence of clay. The simulation results strongly support the experimental findings and their interpretation. X‐ray diffraction shows enhanced intercalation within the galleries when the compatibilizers were added. Interestingly, results were obtained for the EVOH/clay/compatibilizer systems, owing to a high level of interaction developed in these systems. Thermal analysis shows that, upon increasing the compatibilizer content, lower crystallinity levels result, until at a certain compatibilizer content no crystallization is taking place. Significantly higher mixing viscosity levels were obtained for the EVOH/organoclay blends compared with the neat EVOH polymer. The storage modulus was higher compared with the uncompatibilized EVOH/organoclay blend in the presence of EVA‐g‐MA compatibilizer (at all concentrations), and only at low contents of LLDPE‐g‐MA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2060–2066, 2005     

Enhancement of radiation‐resistant effect in ethylene–vinyl acetate copolymers by the formation of ethylene–vinyl acetate copolymers/clay nanocomposites

Ethylene–vinyl acetate (EVA) copolymers/clay nanocomposites, prepared by using nonreactive organophilic clay and reactive organophilic clay, were characterized by X‐ray diffraction and by high‐resolution transmission electron microscopy. The influence of gamma irradiation on the structure and properties of the pure EVA and EVA/clay nanocomposites was systematically investigated. In the presence of gamma radiation, the clay can effectively restrain the increase of the storage modulus of EVA/clay nanocomposites, which was supported by dynamical mechanical analysis. Gamma irradiation had almost no effect on the thermal properties of EVA/clay nanocomposites by using nonreactive organophilic clay, but it obviously improved the thermal stability of EVA/clay nanocomposites by using reactive organophilic clay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2532–2538, 2005     

Synthesis and evaluation of high‐performance ethylene–propylene–diene terpolymer/organoclay nanoscale composites

The main objective of this study was to synthesize and characterize the properties of ethylene–propylene–diene terpolymer (EPDM)/clay nanocomposites. Pristine clay, sodium montmorillonite (Na⁺–MMT), was intercalated with hexadecyl ammonium ion to form modified organoclay (16Me–MMT) and the effect of intercalation toward the change in interlayer spacing of the silicate layers was studied by X‐ray diffraction, which showed that the increase in interlayer spacing in Na⁺–MMT by 0.61 nm is attributed to the intercalation of hexadecyl ammonium ion within the clay layers. In the case of EPDM/16Me–MMT nanocomposites, the basal reflection peak was shifted toward a higher angle. However, gallery height remained more or less the same for different EPDM nanocomposites with organoclay content up to 8 wt %. The nanostructure of EPDM/clay composites was characterized by transmission electron microscopy, which established the coexistence of intercalated and exfoliated clay layers with an average layer thickness in the nanometer range within the EPDM matrix. The significant improvement in thermal stability and mechanical properties reflects the high‐performance nanocomposite formation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2429–2436, 2004     

Nanocomposites of poly(trimethylene terephthalate) with organoclay

Two different kinds of clay were organomodified with cetylpyridinium chloride (CPC) as an intercalation agent. Poly(trimethylene terephthalate) (PTT)/organoclay nanocomposites were prepared by the solution intercalation method. Wide‐angle X‐ray diffraction (WAXD) indicated that the layers of clay were intercalated by CPC and the interlayer spacing was a function of the cationic exchange capacity (CEC) of the clay: the higher the CEC, the larger the interlayer spacing is. The WAXD studies showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. From the results of differential scanning calorimetry analysis it was found that clay behaves as a nucleating agent and enhances the crystallization rate of PTT. The maximum enhancement of the crystallization rate for the nanocomposites was observed in nanocomposites containing about 5 wt % organoclay with a range of 1–15 wt %. The thermal stability of the nanocomposites was enhanced by the addition of 1–10 wt % organoclay as found from thermogravimetric analysis. The thermal stability of the PTT/organoclay nanocomposites was related to the organoclay content and the dispersion in the PTT matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3315–3322, 2003     

Rheological and mechanical characteristics of low density polyethylene/ethylene‐vinyl acetate/organoclay nanocomposites

Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene‐vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LDPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA content, while for LDPE/EVA/OC ternary nanocomposites, such properties showed an increase by increasing the content of EVA. Such behavior was explained by the morphological characteristic of the system in which OC was mainly intercalated/exfoliated in the EVA phase. This morphological characteristic was corroborated by the XRD, TEM and interfacial energies data. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Microstructure and thermal properties of ethylene‐(vinyl acetate) copolymer/rectorite nanocomposites

Ethylene‐(vinyl acetate) copolymer (EVA)/rectorite nanocomposites were prepared by direct melt extrusion of EVA and organo‐rectorite. The microstructures and thermal properties of EVA nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), solid‐state nuclear magnetic spectroscopy, positron annihilation spectroscopy, thermal gravimetric analysis (TGA) and dynamic mechanical analysis techniques. XRD pattern and SEM images show that the intercalated structure is formed and rectorite is finely dispersed in EVA matrix. When organoclay content of the hybrid increases to 7.5 wt%, or pristine rectorite was used instead of organoclay, the crystallization behavior of EVA nanocomposite changes greatly and the ratio of the monoclinic to orthorhombic crystal increases significantly. The relative fractional free volume of the nanocomposite decreases with the increasing organo‐rectorite content, and the values of damping factor (tan δ) for all nanocomposites are lower than that of pure EVA. These facts illuminate that intercalated structure restricts the segment motion and mobilization of polymer chain. TGA results of EVA nanocomposites in air indicate that deacylation of EVA is accelerated because of the catalytic effect and the thermal degradation of the main chain is delayed owing to the barrier effect of silicate layers. Copyright © 2005 Society of Chemical Industry     

Morphological influence on mechanical characterization of ethylene‐vinyl acetate copolymer–clay nanocomposites

Ethylene‐vinyl acetate copolymer (EVA)/montmorillonite (MMT) clay nanocomposites with varying degree of intercalation and exfoliation have been prepared using direct melt blending techniques with various degrees of polarity (9, 18, and 28 wt% vinyl acetate [VA]) and two different types of clay modification. Morphological characterization using wide‐angle X‐ray scattering (WAXS) and transmission electron microscopy (TEM) have indicated/confirmed the presence of intercalation and/or a combination of intercalation and exfoliation existing in the nanocomposites. The effects of these (simple intercalation or mixed intercalation/exfoliation) states and the effect of changing matrix polarity (by changing VA wt% content) on the nanocomposite mechanical behavior were studied. There is sufficient evidence from the mechanical studies that 1) the presence of nanoclay can simultaneously improve modulus and strength of the nanocomposites, and 2) the mechanical properties are a combined function of the clay concentration and the nanocomposite morphology (due to the VA wt% and presence of clay). It is shown here that interrelation between the VA wt% content and the clay exfoliation affects the mechanical properties in a way that has a positive and increasing slope with increasing loading of clay. It is shown that a clear understanding of the nanocomposite mechanical properties can be obtained from its morphological analysis. POLYM. ENG. SCI., 45:889–897, 2005. © 2005 Society of Plastics Engineers     

Effect of layered silicate on EPDM/EVA blend nanocomposite: Dynamic mechanical,thermal, and swelling properties

Polymer blend nanocomposites have been developed by solution method using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate. Morphological investigation made by wide‐angle X‐ray diffraction and transmission electron microscopic analysis indicates intercalated structure of EPDM/EVA nanocomposites with partial disorder. Scanning electron microscopic studies exhibit the phase behavior of EPDM/EVA blend nanocomposites. Dynamic mechanical thermal analysis shows a significant increase in storage modulus in the rubbery plateau. The decrease in damping (tan δ) value and enhanced glass‐transition temperature (T_g) demonstrate the reinforcing effect of layered silicate in the EPDM/EVA blend matrix. The tensile modulus of these nanocomposites also showed a significant improvement with the filler content. The main chain scission of EPDM/EVA blend nanocomposites compared with the neat EPDM/EVA blend showed substantial improvement in thermal stability in nitrogen, whereas a sizeable increase is observed in air. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Morphology and thermal properties of poly(L‐lactic acid)/organoclay nanocomposites

A modified clay was used to prepare poly(L ‐lactic acid)/clay nanocomposite dispersions. X‐ray diffraction and transmission electron microscopy experiments revealed that poly(L ‐lactic acid) was able to intercalate the clay galleries. IR spectra of the poly(L ‐lactic acid)/clay nanocomposites showed the presence of interactions between the exfoliated clay platelets and the poly(L ‐lactic acid). Thermogravimetric analysis and differential scanning calorimetry were performed to study the thermal behavior of the prepared composites. The properties of the poly(L ‐lactic acid)/clay nanocomposites were also examined as functions of the organoclay content. The exfoliated organoclay layers acted as nucleating agents, and as the organoclay content increased, the crystallization temperature increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of poly(ethylene terephthalate) nanocomposites with organoclay

Poly(ethylene terephthalate) (PET)/montmorillonite (MMT) nanocomposites were prepared by solution intercalation method. The clay was organo‐modified with the intercalation agent cetylpyridinium chloride (CPC). Wide‐angle X‐ray diffraction (XRD) showed that the layers of MMT were intercalated by CPC. Four nanocomposites with organoclay contents of 1, 5, 10, and 15 wt % were prepared by solution blending. XRD showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay present. According to the results of differential scanning calorimetry (DSC) analysis, clay behaves as a nucleating agent and enhances the crystallization rate of PET. The maximum enhancement of crystallization rate for the nanocomposites was observed in those containing about 10 wt % organoclay within the studied range of 1–15 wt %. From thermogravimetric analysis (TGA), we found that the thermal stability of the nanocomposites was enhanced by the addition of 1–15 wt % organoclay. These nanocomposites showed high levels of dispersion without agglomeration of particles at low organoclay content (5 wt %). An agglomerated structure did form in the PET matrix at 15 wt % organoclay. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 140–145, 2004     

Nanostructure of EVA/organoclay nanocomposites: Effects of kinds of organoclays and grafting of maleic anhydride onto EVA

Nanostructure of poly(ethylene‐co‐vinyl acetate)/organically modified montmorillonite (MMT; EVA/organoclay) nanocomposites prepared by melt intercalation process was investigated using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Three kinds of organoclays were used to see their influences on the nanostructure of the EVA hybrids. The effects of the polar interactions between the polymer and the silicate layers of organoclays were also investigated by grafting maleic anhydride onto EVA. It was found that the strong polar interactions between the polymer and the silicate layers of organoclays are critical to the formation of polymer‐layered silicate nanocomposites. The results also showed that increasing the mixing temperature was unfavorable to improve the dispersion of organoclays in the EVA matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1901–1909, 2003