Effect of Ionomeric Compatibilizer on Clay Dispersion in Polyethylene/Clay Nanocomposites

Summary: Linear low‐density polyethylene (LLDPE)/clay nanocomposites are obtained and studied by using a zinc‐neutralized carboxylate ionomer as a compatibilizer. LLDPE‐g‐MA is used as a reference compatibilizer. Two different clays, natural montmorillonite (Closite Na⁺) and a chemically modified clay Closite 20A have been used. Nanocomposites are prepared by melt blending in a twin‐screw extruder using two mixing methods: two‐step mixing and one‐step mixing. The relative influence of each compatibilizer is determined by wide‐angle X‐ray diffraction structural analysis and mechanical properties. The results are analyzed in terms of the effect of the compatibilizing agent and incorporation method in the clay dispersion, and the mechanical properties of the nanocomposites. Experimental results confirm that the film samples with ionomer show a good mechanical performance only slightly below that of the samples with maleic anhydride (MA). The two‐step mixing conditions result in better dispersion and intercalation for the nanofillers than one‐step mixing. The exfoliation of clay platelets leads to an improved thermal stability of the composite. The oxygen permeability of the clay nanocomposites, using ionomer as a compatibilizer, is decreased by the addition of the clay.

TEM image of a PE/4 wt.‐% Closite 20A nanocomposite formed using ionomer.     

Polypropylene/Clay nanocomposites: Effect of compatibilizer on the thermal,crystallization and dynamic mechanical behavior

Polypropylene (PP)/clay nanocomposites are prepared using different grades of PP, compatibilizers, and organically modified clays. The melt intercalation of the PP is carried out in presence of a compatibilizer. The nanocomposites are characterized using various techniques for the structure and properties. X‐ray diffraction results indicate well‐defined structures. Thermogravimetric analysis indicates improved thermal stability of PP/clay nanocomposites. Isothermal crystallization studies carried out using differential scanning calorimeter illustrate enhanced crystallization of PP in all the nanocomposites. Optical microscopic study demonstrates that the nanocomposites can be crystallized at higher temperatures, exhibiting well‐defined birefringent structures. The dynamic mechanical analysis reveals higher storage moduli over a temperature range of ?40⁰C to 120⁰C for nanocomposites, and the extent of increase in the storage modulus is dependent on the type of compatibilizer used.     

Influence of PP‐g‐MA on morphology,mechanical properties and deformation mechanism of copolypropylene/clay nanocomposite

Copolypropylene/organoclay nanocomposites are prepared by melt intercalation method in this research. Two different routes for addition of compatibilizer are examined, i.e. addition in the twin‐screw extruder along with the polymer and the clay powder simultaneously and premixing the compatibilizer with the reinforcement in a batch mixer before addition to the polypropylene (PP) matrix. Morphology, tensile and impact properties and deformation mechanisms of the samples made via two procedures are studied and compared with those of the noncompatibilized system. To study the structure of nanocomposites, x‐ray diffraction and transmission electron microscopy techniques are utilized. The deformation mechanisms of different samples are examined via reflected and transmitted optical microscopy. The results reveal that introduction of compatibilizer and also the procedure in which the compatibilizer is added to the compound, affect structure and mechanical properties of nanocomposite. The elastic modulus of PP‐clay nanocomposite has increased 11.5% with incorporation of compatibilizer. Also, introduction of organoclay without compatibilizer facilitates crazing at the notch tip of PP in 3PB testing. Incorporation of compatibilizer, however, makes difficulties in initiation and growth of crazes at the notch tip. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The structure‐property relationship of novolac cured epoxy resin/clay nanocomposites

Intercalated or exfoliated novolac cured epoxy resin nanocomposites were prepared with two different kinds of layered silicates – montmorillonite (PK‐802) and nontronite (PK‐805). The bifunctional modifiers (PI/BEN or MI/BEN) are used to modify the clays for improvement of the properties of polymer where benzalkonium chloride (BEN) acts as a compatibilizing agent and 2‐phenylimidazole (PI) or 2‐methylimidazole (MI) as the accelerators. Both the compatibilizer and accelerator are simultaneously intercalated into the gallery space of pure clays to form the modified clay. The novolac cured epoxy nanocomposites are prepared with these modified clays by crosslinking polymerization reaction. The properties of novolac cured epoxy/clay nanocomposites were characterized by wide‐angle X‐ray diffraction (WAXD), thermo‐gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM) methods. According to the measurement, these novolac cured epoxy‐clay nanocomposites have been shown the significant improvement in the thermal, mechanical, and barrier properties that may be applied to make printed circuit board. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

New compatibilizer for linear low‐density polyethylene (LLDPE)/clay nanocomposites

Linear low‐density polyethylene (LLDPE) is one of the most widely used polymers in many fields, but it is difficult to prepare LLDPE/clay nanocomposites because of the hydrophobic nature of LLDPE. In this study, the effectiveness of low molecular weight trimethoxysilyl‐modified polybutadiene (Organosilane) as a compatibilizer for LLDPE/clay nanocomposites was studied using X‐ray diffraction (XRD) and correlated with mechanical properties. Organosilane is known to react with dicumyl peroxide (DCP) to form free radicals, which react with LLDPE increasing the polarity of the LLDPE. Based on XRD and mechanical tests, it was concluded that Organosilane is a good compatibilizer for LLDPE and clay. Also when Organosilane was used in preparing LLDPE/clay nanocomposite foams, most mechanical properties were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(4‐methyl‐1‐pentene)/clay nanocomposites: effect of organically modified layered silicates

The preparation and properties of poly(4‐methyl‐1‐pentene) (PMP)/clay nanocomposites are reported. Melt intercalation of PMP is carried out with organoclays of different cation/charge exchange capacities and modifiers to facilitate intercalation of the polymer into the silicate layers. The effect of modifiers on the structure and properties of PMP/clay nanocomposites is explored. XRD patterns confirm the intercalation of polymer in the layered silicates as evidenced by the increase in the inter‐layer spacing which is dependent on the type of modifier used. Dynamic mechanical analysis shows increments in the storage modulus over the temperature range studied for all of the three clays, but the extent depends on the type of clay modifier used. The coefficient of thermal expansion is lower for all of the nanocomposites, as compared to the pristine polymer, indicating improved dimensional stability Copyright © 2003 Society of Chemical Industry     

Melt processing and characterization of polypropylene/pristine montmorillonite nanocomposite: Influence of compatibilizer and hyperbranched polymer

In the present investigation, nanocomposites of polypropylene (PP)‐montmorillonite (MMT) clay were prepared by a single‐step compounding method to study the influence of hyperbranched polyester (HBPE) on rheological and mechanical properties of PP composites in the presence of a compatibilizer. In service of this objective, polyvinylchloride‐grafted‐maleic anhydride (PP‐g‐MA) was used as a compatibilizer for hydrophobic PP and hydrophilic clay. Rheological property in terms of melt viscosity was examined by a Brabender torque rheometer. The composite's morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), whereas the dispersion state of nanoparticles in the PP matrix was studied by X‐ray diffraction (XRD). The thermal behavior of nanocomposites was examined by differential scanning calorimetry (DSC). The analysis of results confirmed that the interactions among both additives significantly influenced the morphology, rheology, and thermomechanical properties of the nanocomposites. J. VINYL ADDIT. TECHNOL., 22:72–79, 2016. © 2014 Society of Plastics Engineers     

Exfoliation targeted toughness enhancement in polypropylene‐blend‐ montmorillonite nanocomposites

BACKGROUND: Both exfoliated and toughened polypropylene‐blend‐montmorillonite (PP/MMT) nanocomposites were prepared by melt extrusion in a twin‐screw extruder. Special attention was paid to the enhancement of clay exfoliation and toughness properties of PP by the introduction of a rubber in the form of compatibilizer toughener: ethylene propylene diene‐based rubber grafted with maleic anhydride (EPDM‐g‐MA). RESULTS: The resultant nanocomposites were characterized using X‐ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis and Izod impact testing methods. It was found that the desired exfoliated nanocomposite structure could be achieved for all compatibilizer to organoclay ratios as well as clay loadings. Moreover, a mechanism involving a decreased size of rubber domains surrounded with nanolayers as well as exfoliation of the nanolayers in the PP matrix was found to be responsible for a dramatic increase in impact resistance of the nanocomposites. CONCLUSION: Improved thermal and dynamic mechanical properties of the resultant nanocomposites promise to open the way for highly toughened super PPs via nanocomposite assemblies even with very low degrees of loading. Copyright © 2008 Society of Chemical Industry     

Polypropylene/clay nanocomposites: Combined effects of clay treatment and compatibilizer polymers on the structure and properties

Combined effects of clay treatment and compatibilizer polymers on the structure and properties of polypropylene/clay nanocomposites were studied. Dynamic mechanical analysis was used to analyze comparatively the dynamic mechanical response of different nanocomposites prepared from polypropylene and montmorillonite‐rich bentonite, and to relate such response with the material microstructure. Two different bentonites were used: a purified Spanish natural bentonite was organophillized by means of 11‐undecyl‐ammonium ion and a commercial bentonite organophillized with dimethyl dehydrogenated tallow ammonium ion. Three different polar copolymers were employed as compatibilizer agents in some of the formulations: maleic anhydride‐grafted polypropylene, maleic anhydride‐grafted poly(styrene‐co‐ethylenebutylene‐co‐styrene), and poly(ethylene terephthalate‐co‐isophthalate) (PET). To ascertain the microstructure characteristics in the nanocomposites, wide angle X‐ray diffraction, transmission electron microscopy, and differential scanning calorimetry techniques were used. The nanocomposites containing both bentonite organophillized with 11‐undecyl‐ammonium ion and PET, and maleated PP as compatibilizer system, were found to have the highest storage modulus and the smallest loss factor values, which was mainly due to the better clay platelets dispersion. The dynamic mechanical response of nanocomposites prepared with bentonite organophillized with dimethyl dehydrogenated tallow ammonium ion and maleated SEBS was strongly affected by the presence of this compatibilizer. The temperature of PP and α, β, and γ relaxations strongly depended on the interactions between the different phases in the nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1213–1223, 2006     

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     

Preparation of polyethylene–clay nanocomposites directly from Na+ montmorillonite by a melt intercalation method

Polyethylene (PE)/clay nanocomposites were prepared directly from Na⁺ montmorillonite by a melt intercalation technique, using hexadecyl trimethyl ammonium bromide (C16) as a reactive compatibilizer. Three other polymer–clay nanocomposites were also prepared by this new technique. Their structures were characterized by X‐ray diffraction and transmission electron microscopy. The mechanism of this new method was studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2583–2585, 2003     

Intumescent flame retardant–montmorillonite synergism in polypropylene‐layered silicate nanocomposites

Polypropylene/clay nanocomposites have been prepared starting from pristine mont morillonite (MMT) and reactive compatibilizer hexadecyltrimethylammonium bromide (C16). The nanocomposite structure is evidenced by the X‐ray diffraction and high resolution electronic microscopy. Intumescent flame retardant has been added to polypropylene/clay hybrids. Their flammability behaviours have been evaluated using cone calorimetry. Synergy was observed between the nanocomposites and intumescent flame retardant. Copyright © 2003 Society of Chemical Industry     

Mechanical properties and structures of dicyanate–clay nanocomposites

Dicyanate–clay nanocomposites comprising a dicyanate resin and a type of organically modified clay were prepared and characterized, and their thermomechanical properties were investigated. The organically modified clay had silicate layers of nanometer size intercalated with an organic modifier, which improved the compatibility between the clay and organic materials, such as dicyanate resins. Dynamic mechanical analysis was performed to investigate the thermomechanical properties of the dicyanate–clay nanocomposites containing various amounts of the clay. The storage modulus of the nanocomposites below their glass‐transition temperatures slightly increased with increasing clay content. The glass‐transition temperature of the dicyanate–clay nanocomposites increased with increasing clay content. The nanostructures of the dicyanate–clay nanocomposites were characterized by transmission electron microscopy and X‐ray diffraction analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2629–2633, 2003     

Thermal,mechanical, and barrier properties of polyethylene/surlyn/organoclay nanocomposites blown films prepared by different mixing methods

(Low‐density polyethylene) (LDPE)/clay nanocomposites were prepared by melt blending in a twin‐screw extruder by using different mixing methods. Zinc‐neutralized carboxylate ionomer was used as a compatibilizer. Blown films of the nanocomposites were then prepared. The effect of mixing method on the clay dispersion and properties of the nanocomposites was evaluated by wide‐angle X‐ray diffraction analysis, mechanical properties, thermal properties, and barrier properties. The structure and properties of nanocomposites containing different amounts of nanoclay prepared by selected mixing techniques were also investigated. It was found that melt compounding of Surlyn/clay masterbatch with pure LDPE and Surlyn (two‐step‐a method) results in better dispersion and intercalation of the nanofillers than melt mixing of LDPE/Surlyn/clay masterbatch with pure LDPE and surlyn (two‐step‐b method) and direct mixing of LDPE with clay. The films containing ionomer have good barrier properties. A wide‐angle X‐ray diffraction pattern indicates that intercalation of polymer chains into the clay galleries decreases by increasing the clay content. Barrier properties and tensile modulus of the films were improved by increasing the clay content. In addition, tensile strength increased in the machine direction, but it decreased in the transverse direction by increasing the clay content. DSC results showed that increasing the clay content does not show significant change in the melting and crystallization temperatures. The results of thermogravimetric analysis showed that the thermal stability of the nanocomposites decreased by increasing the clay content more than 1 wt%. J. VINYL ADDIT. TECHNOL., 21:60–69, 2015. © 2014 Society of Plastics Engineers     

Shear rheology and melt compounding of compatibilized‐polypropylene nanocomposites: Effect of compatibilizer molecular weight

Direct melt compounding was used to prepare nanocomposites of organophilic montmorillonite (o‐mmt) clay dispersed in maleated polypropylenes (PPgMA) as well as nanocomposites of organoclay and polypropylene (PP) modified with various grades of PPgMA compatibilizers. The thermal effect on the rheology and melt compounding was first investigated with a plasticorder. The shear viscosities and the melt flow indices (MFI) of the PPgMA compatibilizers were sensitive to the blending temperature, which had to be varied with the compatibilizer grade to achieve desirable level of torque for extensive exfoliation of organoclay in the plasticorder. However, for low molecular weight oligomer, the clay dispersion was poor because of low shear viscosity and thermal instability. Next, the PPgMA‐modified PP/organoclay nanocomposites were prepared on a corotating twin‐screw extruder. The nanoscale dimensions of the dispersed clay platelets led to significantly increased linear viscoelastic properties, which were qualitatively correlated with the state of exfoliation in the nanocomposites. The relative viscosity (relative to the silicate‐free matrix) curves revealed a systematic trend with the extent of clay exfoliation. Furthermore, the degree of clay dispersion was found to increase with the loading of compatibilizers; however, high loading of compatibilizer compromised the final moduli of the nanocomposites. POLYM. ENG. SCI. 46:289–302, 2006. © 2006 Society of Plastics Engineers     

Preparation and properties of styrene–ethylene–butylene–styrene block copolymer/clay nanocomposites: I. Effect of clay content and compatibilizer types

BACKGROUND: Polymer/clay (silicate) systems exhibit great promise for industrial applications due to their ability to display synergistically advanced properties with relatively small amounts of clay loads. The effects of various compatibilizers on styrene–ethylene–butylene–styrene block copolymer (SEBS)/clay nanocomposites with various amounts of clay using a melt mixing process are investigated. RESULTS: SEBS/clay nanocomposites were prepared via melt mixing. Two types of maleated compatibilizers, styrene–ethylene–butylene–styrene block copolymer grafted maleic anhydride (SEBS‐g‐MA) and polypropylene grafted maleic anhydride (PP‐g‐MA), were incorporated to improve the dispersion of various amounts of commercial organoclay (denoted as 20A). Experimental samples were analyzed using X‐ray diffraction and transmission electron microscopy. Thermal stability was enhanced through the addition of clay with or without compatibilizers. The dynamic mechanical properties and rheological properties indicated enhanced interaction for the compatibilized nanocomposites. In particular, the PP‐g‐MA compatibilized system conferred higher tensile strength or Young's modulus than the SEBS‐g‐MA compatibilized system, although SEBS‐g‐MA seemed to further expand the interlayer spacing of the clay compared with PP‐g‐MA. CONCLUSION: These unusual results suggest that the matrix properties and compatibilizer types are crucial factors in attaining the best mechanical property performance at a specific clay content. Copyright © 2007 Society of Chemical Industry     

Interfacially compatibilized LDPE/POE blends reinforced with nanoclay: investigation of morphology,rheology and dynamic mechanical properties

Morphological, melt rheological and dynamic mechanical properties of low-density polyethylene (LDPE)/ethylene–octene copolymer (POE)/organo-montmorillonite (OMMT) nanocomposites, prepared via melt compounding were studied. The XRD traces indicated different levels of intercalated structures for the nanocomposites. Addition of a compatibilizer (PE-g-MA) improved the intercalation process. TEM results revealed existence of clay layers in both phases but they were mainly localized in the elastomeric POE phase. Addition of 5 wt% OMMT to the LDPE/POE blend led to reduction in the size of the elastomer particles confirmed by AFM. The complex viscosity and storage modulus showed little effect of the presence of the clay when no compatibilizer was added. As the extent of exfoliation increased with addition of compatibilizer, the linear viscoelastic behavior of the composites gradually changed specially at low-frequency regions. The interfacially compatibilized nanocomposites with 5 wt% OMMT had the highest melt viscosity and modulus among all the studied nanocomposites and blends. Also, this particular composition showed the best improvement in dynamic storage modulus. The results indicated that clay dispersion and interfacial adhesion, and consequently different properties of LDPE/POE/clay nanocomposites, are greatly affected by addition of compatibilizer.     

Investigations on clay dispersion in polypropylene/clay nanocomposites using rheological and microscopic analysis

Morphology assessment plays an important role as the ultimate properties of the processed nanocomposites mainly depend upon the morphology. This study focuses on the evaluation of polypropylene/clay nanocomposite structure using rheological and transmission electron microscopic investigation. Melt processing of nanocomposite was carried out on a co‐rotating twin screw extruder. Maleic anhydride grafted polypropylene (PP‐g‐MA) was used as a compatibilizer to facilitate better mixing of clay in polypropylene. The effect of compatibilizer to clay ratio on dispersion was analyzed through rheological data. An increase in complex viscosity and storage modulus with increase in compatibilizer content is observed at lower frequency region. Shifting of crossover frequencies to a lower value also indicate better exfoliation. Improved exfoliated morphology was also corroborated by Cole–Cole and inverse loss tangent plots. Transmission electron microscopy (TEM) micrograph based unique statistical image analysis was carried out using ImageJ software. A compatibilizer to clay content of 2 : 1 was found to be the optimum composition which was further supported by dielectric and mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4464–4473, 2013     

Evaluation of different amine‐functionalized polyethylenes as compatibilizers for polyethylene film nanocomposites

The compatibilization effects provided by different amine‐functionalized polyethylenes (PEs) versus those provided by a maleated polyethylene (PEgMA), for forming PE‐based film nanocomposites, were studied. Amine‐functionalized PEs were prepared by reaction of PEgMA with two primary amines, 2‐aminoethanol (EA) and 1,12‐aminododecane (D12), and a tertiary amine, 2‐[2‐(dimethylamino)ethoxy]ethanol (DMAE), in the melt to form the corresponding PEgEA, PEgD12 and PEgDMAE. Nanocomposites were prepared by melt mixing in a twin‐screw extruder PE and these three functionalized compatibilizers with a modified montmorillonite clay. The purpose of the current work was to determine the effect of the various amine‐functionalized PEs on the degree of exfoliation and optical properties of PE–clay nanocomposites in order to obtain nanocomposite films for greenhouse cover applications. Fourier transform infrared analysis confirmed the formation of the amine‐modified PE compatibilizers. Structural, morphological, mechanical, rheological and optical properties of film samples were used to characterize the nanocomposites. All the amine‐modified PE‐compatibilized nanocomposites had better clay exfoliation compared to uncompatibilized PE composites. Results showed that PEgDMAE formed highly exfoliated morphology and a favorable balance between mechanical (stiffness and ductility), optical and thermal insulating film properties even at higher clay contents. It was determined that nanocomposites with greater exfoliated structure showed better optical and thermal insulating film properties. PEgEA and PEgD12 compatibilizers did not provide a better interaction for exfoliation of the organoclay than the PEgMA material. The PEgDMAE compatibilizer led to a highly exfoliated morphology and a favorable balance between mechanical, optical and thermal insulating film properties even at higher clay contents. The PEgDMAE film nanocomposites could be used ideally for greenhouse cover applications. Copyright © 2010 Society of Chemical Industry     

Rheological properties of poly(acrylonitrile‐co‐methyl acrylate)/clay nanocomposites prepared via emulsion polymerization

Poly(acrylonitrile‐co‐methyl acrylate)/clay nanocomposites were prepared by free radical polymerization in emulsion using 2‐acrylamido‐2‐methyl‐1‐propanesulphonic acid (AMPS) as a compatibilizer. The resultant nanocomposites were of partially exfoliated morphology despite the variations in clay content among the nanocomposites, as confirmed by transmission electron microscopy and small‐angle X‐ray scattering analysis. Rheological studies of these materials were carried out using parallel plate geometry. The storage modulus increased monotonically with increasing clay content throughout the frequency range studied. However, the neat copolymer, poly(acrylonitrile‐co‐methyl acrylate) and its nanocomposites, exhibited long relaxation behavior as the storage modulus (G′) was greater than the loss modulus (G″) throughout the angular frequency range studied. The complex viscosity of the nanocomposites increased with increasing clay content and they exhibited shear‐thinning behavior. Despite the enhanced rheological properties observed, the copolymer and its nanocomposites underwent structural changes during oscillatory measurements due to cyclization reactions. POLYM. COMPOS., 32:59–66, 2011. © 2010 Society of Plastics Engineers