Polymer Melt Intercalation Research Articles

Functionalization of layered double hydroxides by intumescent flame retardant: Preparation, characterization, and application in ethylene vinyl acetate copolymer

A phosphorusnitrogen containing compound, N-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)-hexylacetamide-2-propyl acid (PAHPA), is synthesized and characterized. A novel flame retardant, namely layered double hydroxides (LDHs) modified with PAHPA (PAHPA-LDHs), is prepared by ion-exchange of LDHs with PAHPA. The results from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive X-ray analysis with a high-angle annular dark-field scanning transmission electron microscope show that PAHPA intercalated LDHs. The X-ray diffraction and transmission electron microscopy (TEM) results show that PAHPA-LDHs achieve well dispersion in ethylene vinyl acetate copolymer (EVA) matrix and the EVA/PAHPA-LDHs nanocomposites (i.e. EVA filled with 5wt% PAHPA-LDHs) are formed by polymer melt intercalation. Thermal stability and flammability properties are investigated by thermogravimetric analysis and cone calorimeter tests. The results show that the addition of PAHPA-LDHs improves thermal stability and reduces obviously the flammability of EVA resin. Compared with pure EVA resin, the peak heat release rate of the EVA/PAHPA-LDHs nanocomposites is reduced by about 43%. The results of scanning electron microscopy and TEM indicate that a compact and dense intumescent char is formed for the EVA/PAHPA-LDHs nanocomposites after combustion.

Properties of rubber filled with montmorillonite with various surface modifications

Layered silicate/natural rubber composites were prepared by direct polymer melt intercalation. Na‐montmorillonite Kunipia‐F and its organic derivates (organo‐clays) prepared by ion exchange were used as clay fillers. Silica (SiO2) Ultrasil VN3, a filler commonly used in the rubber industry, was used in combination with clay fillers. The effect of clay or organo‐clay loading from 1 up to 10 phr without (0 phr) or with silica (15 phr) showed significant improvement of the tensile properties (stress at break, strain at break and modulus M100). Modification of montmorillonite by three alkylammonium cations with the same length of alkylammonium chain (18 carbons) and different structure resulted in altered reinforcing and plasticizing effects of the filler in composites with rubber matrix. Copyright © 2011 John Wiley & Sons, Ltd.

Preparation and Flame Retardancy Properties of Novel PA12 and PE/Layered Titanoniobates Nanocomposites

AbstractSummary: We report herein a study performed on a layered titanoniobate KTiNbO5 modified by octadecylamine to evaluate the fire retardancy properties of this novel hybrid nanofiller dispersed in PA12 and LLDPE, by polymer melt intercalation. The nanocomposites have been characterized using Electron Microscopy techniques to evaluate the degree of exfoliation and the morphologies. Thermogravimetric analyses and cone calorimeter tests have been carried out to assess the fire retardant performances.

A novel intumescent flame retardant-functionalized montmorillonite: Preparation, characterization, and flammability properties

2,4,8,10-Tetraoxa-3,9-diphosphaspiro[5.5]-undecane-3,9-dioxide-disubstitutio-acetamide-N,N-dimethyl-N-hexadecy-ammonium bromide (PDHAB) containing phosphorus–nitrogen structure was synthesized and characterized. A novel flame retardant, montmorillonite (Mt) modified by PDHAB (PDHAB-Mt), was prepared by ion-exchange of sodium montmorillonite (Na+-Mt) with PDHAB. The results of X-ray diffraction (XRD) indicated that PDHAB had intercalated with Na+-Mt and exfoliated LDPE/EVA/20% PDHAB-Mt nanocomposites had been obtained by polymer melt intercalation which was further supported by TEM. The flammability of LDPE/EVA/PDHAB-Mt nanocomposites was investigated by the cone calorimeter test. The results showed that the addition of flame retardant PDHAB-Mt enhanced the flame retardancy of LDPE/EVA blend significantly. The results of SEM and TEM indicated that PDHAB-Mt can achieve better dispersion in the chars after combustion and the intumescent char is formed for LDPE/EVA/PDHAB-Mt nanocomposites after combustion. It is found that the char structure plays an important role for PDHAB-Mt in LDPE/EVA blend. The flame retardancy of LDPE/EVA blend was also significantly improved by an addition of PDHAB-Mt in LDPE/EVA blend.

Thermodynamic characterization of hybrid polymer blend systems

AbstractA thermodynamic model was used to predict the morphology of hybrid multicomponent polymer blend systems. Two systems were studied, both including two noncompatible polymers, a third compatibilizer polymer and layered, organo‐treated clays. The polar and nonpolar contributions of the surface energies of the components of the systems were calculated using measurements of the contact angles. The morphology of the multicomponent systems and the relative position of the organo‐clays within them, were predicted by calculating the interaction energies between the different components of the system and evaluating these values according to the Vaia and Giannelis thermodynamic model for polymer melt intercalation in organically modified layered silicates. The experimental results show good correlation with the prediction that the organo‐clays will have higher affinity to the compatibilizer polymer component situated at the interface between the two noncompatible blend components. In addition, the presence of the organo‐clays in this interface was found to have a significant additional compatibilizing effect between the two polymer phases. The results presented in this work support the idea that hybrid formation via polymer melt intercalation depends mostly on energetic factors that can be determined from surface energies of polymers and organo‐modified layered silicates, also in the case of multiphase polymer system. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Effect of montmorillonite modification on mechanical properties of vulcanized natural rubber composites

Natural rubber-clay composites were prepared by direct polymer melt intercalation. Ca-montmorillonite Jelsový Potok (JP; Slovakia) and Na-montmorillonite Kunipia-F (KU; Japan) were ion exchanged with octadecyltrimethylammonium (ODTMA) bromide and were used as aluminosilicate fillers. Silica Ultrasil VN3 was used in amount of 15 phr as conventional filler. The effect of clay or organoclay loading from 1 up to 10 phr on the mechanical properties was evaluated from the tensile tests (stress at break, strain at break and modulus M100). Organic modification resulted in an increase of toluene uptake degree for both fillers. While an addition of unmodified KU had no effect on tensile strength and deformation at break, a reinforcing effect was observed for the mixture containing 10 phr of unmodified JP. Both ODTMA modified fillers (KU and JP) exhibited substantial increase in tensile strength and deformation at break; JP proved to be more effective compared to KU also if modified with ODTMA. The highest stress at break and strain at break values for natural rubber composites were obtained with 15 phr of SiO2 and 10 phr of montmorillonite; however, the effect of exchangeable cation was minor.

ポリ(ブチレンサクシネート-<i>co</i>-ラクテート)/アルキルトリメトキシシラン処理有機化モンモリロナイトナノ複合材料の作製と物性

ヘキシルトリメトキシシラン(HTMS)またはオクタデシルトリメトキシシラン(OTMS)によるシランカップリング処理と N-ラウリルジエタノールアミン(LEA)塩酸塩によるイオン交換処理を併用したモンモリロナイト(HTMS-LEA-M または OTMS-LEA-M)とバイオベース生分解性ポリエステルであるポリ(ブチレンサクシネート-co-ラクテート)(PBSL)からなる複合材料をポリマー溶融混練法により作製した．XRD 測定の結果，得られた複合材料のクレイ層間へのポリマーの挿入量は LEA 塩酸塩のみで処理したモンモリロナイト(LEA-M)を用いたものと同等であったが，TEM 観察では明らかにクレイの分散性が向上していた．特に PBSL/OTMS-LEA-M ではクレイが非常に細かく均一に分散していた．クレイのシランカップリング処理と有機アンモニウム化処理を併用することにより，動的粘弾性測定によるゴム状領域での貯蔵弾性率と tan δ ピーク温度の上昇がみられた．引張弾性率においてもシランカップリング処理の効果が認められ，最もクレイの分散性が良かった PBSL/OTMS-LEA-M では無機含量が 5 wt%で PBSL 単体に比べて引張弾性率が約 2 倍，10 wt%で約 3.5 倍まで向上した．

Direct Melt Intercalation of Polylactide Chains into Nano‐Galleries: Interlayer Expansion and Nano‐Composite Structure

AbstractSummary: The polylactide‐based nano‐composites were prepared via melt extrusion method using different types of intercalants and nano‐fillers having different surface charge density. In order to understand the direct polymer melt intercalation into the nano‐galleries, the interdigitated layer structure of the organically modified layered filler (OMLF), where the intercalants are oriented with some inclination to the host layer in the interlayer space, was proposed. After polymer melt intercalation, the smaller initial interlayer opening led to the larger interlayer expansion, suggesting the large amount of the intercalation of the polymer chains. Consequently, the nano‐composite exhibited finer dispersion of the nano‐fillers when compared with the nano‐composites prepared from OMLFs with larger initial interlayer opening.Illustration of a model of interlayer structure of the qC14(OH) in gallery space of HTO.magnified imageIllustration of a model of interlayer structure of the qC14(OH) in gallery space of HTO.

Application of mean-field model of polymer melt intercalation in organo-silicates for nanocomposites

The mean-field, lattice-based model of polymer melt intercalation in organically-modified layered silicates (OLS) originally developed by Vaia and Giannelis was applied for different polymers such as poly(methyl methacrylate) (PMMA), polypropylene (PP), and poly(ethylene oxide) (PEO). The nature of each polymer controls significantly the intercalation of the system. The internal energy change caused by the interaction of polymer, surfactant and clay is the strongest factor in determining the equilibrium structure of the nanocomposite system.

Polymer Melt Intercalation in Clay Modified by Diblock Copolymers

AbstractSummary: The thermodynamic equilibrium in a melt of homopolymer C mixed with clay modified by a diblock copolymer AB is considered in theory. It is assumed that mixing is carried out in two stages. At first, the diblock copolymer penetrates into the interlayers formed by long clay sheets. Then, the clay with adsorbed diblock copolymer chains is added to the homopolymer melt. It is shown that the first process is thermodynamically favorable only if the interlayer width exceeds some threshold value that depends mostly on the difference in the adsorption energy of units A and B. A spontaneous mixing at the second stage is possible only if the enthalpic interactions between homopolymer and copolymer units are not very unfavorable. If so, the formation of an intercalated state is expected for a homopolymer of length comparable to the copolymer length, while for a long homopolymer the anticipated equilibrium state is exfoliation. The spatial distribution of A, B, and C units across the interlayer has been studied for different parameters of the system. The most readily adsorbing units A occupy almost all clay surface. However, the layer of block A is considerably swelled by both B and C units. The mutual distribution of units B and C may vary from almost homogeneous to having rather sharp boundary depending on the value of the Flory‐Huggins parameter χBC. The formation of a pure homopolymer layer at the center of the interlayer indicates about a tendency to exfoliate.Interlayer profiles of the fractions of units A, B, and C, respectively.imageInterlayer profiles of the fractions of units A, B, and C, respectively.

Study on kinetics of polymer melt intercalation by a rheological approach

AbstractThe kinetics of melt intercalation of poly(propylene)/montmorillonite nanocomposites was studied by a rheological approach. The experimental sample was elaborately prepared to investigate the whole intercalating process. The intercalation process was demonstrated by the changes of the viscoelastic response with annealing time. The development of the relative volume fraction of intercalated tactoids was obtained from the rheological characterization. The apparent diffusivities was determined and the activation energy of melt intercalation was found to be about 80 ± 6 kJ/mol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 318–323, 2003

Microstructure changes of a polypropylene/montmorillonite nanocomposite in a single screw extruder

Polymer nanocomposites based on organically modified layered silicates, e.g., organic-montmorillonite (org-MMT), exhibit attractive properties, such as increased mechanical properties, reduced gas and liquid permeability, improved heat, solvent and UV resistance, greater dimensional stability at elevated temperature, improved optical and electrical properties, and enhanced flame retardant properties [1–4]. Three different methods, in situ polymerization, polymer intercalation from solution, and direct polymer melt intercalation, have been used to synthesize layered silicate-based polymer nanocomposites [5]. The third method would greatly expand the commercial opportunities for nanocomposite technology because of its low cost, high productivity and compatibility with current polymer processing techniques [6]. In recent years, some researchers employed the direct melt intercalation technique to prepare the polymer nanocomposites [6–12]. However, these studies used a laboratoryscale twin screw extruder or internal mixer to yield nanocomposites and then investigated the microstructure and properties of only the as-extruded pellets or samples. Recently, the authors [13] used an industrial-scale extrusion blow molding machine to make packaging bottles from polypropylene (PP) or high-density polyethylene (HDPE)/org-MMT nanocomposites prepared by using a twin screw extruder. The changes of the microstructure of nanocomposites occurring after processing using a single screw extruder were investigated preliminarily. In this work, PP/org-MMT nanocomposites were prepared by direct melt intercalation using an industrial-scale co-rotating twin screw extruder. The as-extruded pellets were then extruded into ribbons by using an industrial-scale single screw extruder. The major focus was on the effects of mixing type of the screw on the microstructure changes of polymer nanocomposites. The microstructure of specimens was investigated by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The org-MMT (Fenghong Clay Co.) was supplied as particles with an average size of 25 μm. The polymer matrix was isotactic PP homopolymer (F401,

Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite

The thermal stability of organically modified layered silicate (OLS) plays a key role in the synthesis and processing of polymer-layered silicate (PLS) nanocomposites. The nonoxidative thermal degradation of montmorillonite and alkyl quaternary ammonium-modified montmorillonite were examined using conventional and high-resolution TGA combined with Fourier transform infrared spectroscopy and mass spectrometry (TG−FTIR−MS) and pyrolysis/GC−MS. The onset temperature of decomposition of these OLSs was approximately 155 °C via TGA and 180 °C via TGA−MS, where TGA−MS enables the differentiation of water desorbtion from true organic decomposition. Analysis of products (GC−MS) indicates that the initial degradation of the surfactant in the OLS follows a Hoffmann elimination reaction and that the architecture (trimethyl or dimethyl), chain length, surfactant mixture, exchanged ratio, or preconditioning (washing) does not alter the initial onset temperatures. Catalytic sites on the aluminosilicate layer reduce thermal stability of a fraction of the surfactants by an average of 15−25 °C relative to the parent alkyl quaternary ammonium salt. Finally, the release of organic compounds from the OLS is staged and is associated with retardation of product transfer arising from the morphology of the OLS. These observations have implications to understanding the factors impacting the interfacial strength between polymer and silicate and the subsequent impact on mechanical properties as well as clarifying the role (advantageous or detrimental) of the decomposition products in the fundamental thermodynamic and kinetic aspects of polymer melt intercalation.

Simple "kink" model of melt intercalation in polymer-clay nanocomposites.

We propose a simple semiphenomenological model to describe the dynamics of polymer melt intercalation in the gallery between the adjacent clay sheets in polymer-clay nanocomposites. Within this model, the intercalation process is driven by the motion of localized excitations ("kinks") which open up the tip between the clay sheets. These kinks belong to a novel type of solitonlike excitations that appear due to the interplay between the double-well potential of the clay-clay long-range interaction, bending elasticity of the sheets, and external shear force. We find that the kink solutions can exist only if applied shear is sufficiently strong, in a qualitative agreement with experimental data.

The influence of polymer state on the electrical properties of polymer/layered-silicate nanocomposites

Polymer/layered-silicate nanocomposites (PLSN) are prepared by polymer melt intercalation in layered silicate. The influence of polymer state on the electrical properties is analyzed. The experimental results show that poly(ethylene oxide) (PEO) can intercalate into the silicate interlayer in the molten state, which leads to the addition of the repeated distance of silicate. The polymer structure in the interlayer is similar to that of a PEO melt. Polymethylmethacrylate (PMMA) can dissolve in molten PEO and intercalate into silicate interlayer together with PEO chains. The modification of PMMA in PLSN further enhances the random arrangement of the PEO chains, which are inclined to a random amorphous state. This random amorphous state is beneficial to the ionic transport in the interlayer, which can remarkably enhance the ionic conductivities at room temperature and decrease the apparent conducting activation energies in PLSN.

Layer expansion of layered silicates in solid polymer matrices by compression

Ten years ago, a group of scientists at Toyota demonstrated that expansion and dispersion of layered silicates in nylon-6 could improve the performance envelope of the polymer well beyond the domain of known polymer technologies [1–6]. They adapted a traditional in situ polymerization approach to insert the polymer precursor, e-caprolactam, between the layers of a montmorillonite and then to further expand and disperse the clay layers into the matrix by polymerization. This success has stimulated significant research activities in the development of synthetic methods to produce clay/polymer nanocomposites for various polymer systems [7]. Two methods were immediately developed based on solvent assisted solution synthesis for polyimide [2] and polymer melt intercalation for poly(ethylene oxide) [8]. The solution synthesis is to use a polar solvent to disperse and swell an organoclay and then to add a polymer solution to intercalate the polymer between the clay layers, while the melt synthesis involves heating a polymer with either an organoclay [8] or a hydrophilic clay [9] above the melt or glass transition temperature (Tg) depending on the polymer being crystalline [8, 9] or amorphous [10]. The further development was essentially the application of these three approaches to other polymers including poly(ethylene terephthalate) [11], poly(methyl methacrylate) [12, 13], polystyrene [13–16], polypropylene [17–19], epoxy [20] and polyurethane [21] etc. This paper reports another approach to synthesize clay/polymer nanocomposites based on intercalation in the solid phase. It has been observed that it is possible to expand the interlayer distance of either a hydrophilic layered-silicate or an organophilic clay in a polymer simply by blending and compression of the solid mixture. The results to be shown were obtained from a crystalline polymer, poly(ethylene oxide) (PEO) and an amorphous polymer, polystyrene. Fig. 1 shows the X-ray diffraction (XRD) patterns of the hybrid tablets of a poly(ethylene oxide) with different loadings of a sodium based montmorillonite, G-105. The tablets were produced by blending the powders with the clay and compressing the solid mixture in a mould under 330 MPa pressure at ambient temperature. The sodium montmorillonite, G-105, is a commercial product from the Nanocor. The PEO had Mw 600 000 and was supplied by BDH Chemicals Ltd.

Microwave Assisted Blending-Intercalation of Ion-Conductor Polymers into Layered Silicates

AbstractOrgano-inorganic hybrid nancomposites derived from poly(ethylene oxide) and montmorillonite silicate are prepared by an alternative procedure to classical polymer intercalation either from solutions or by polymer melt-intercalation. XRD, FTIR, DSC, elemental microanalysis and SEM techniques are applied for structural characterization of the resulting materials. The electrical properties of these nanocomposites are studied by means of the electrical impedance spectroscopy (EIS) showing enhanced ionic conductivity compared to similar samples prepared by intercalation from solution.

Polymer Melt Intercalation in Organically-Modified Layered Silicates: Model Predictions and Experiment

The effect of silicate functionalization, anneal temperature, polymer molecular weight, and constituent interactions on polymer melt intercalation of a variety of styrene-derivative polymers in alkylammonium-functionalized silicates is examined. Hybrid formation requires an optimal interlayer structure for the organically-modified layered silicate (OLS), with respect to the number per host area and size of the alkylammonium chains, as well as the presence of polar interactions between the OLS and polymer. From these observations and the qualitative predictions of the mean-field lattice-based model of polymer melt intercalation (preceding paper in this issue), general guidelines may be established for selecting potentially compatible polymer−OLS systems. The interlayer structure of the OLS should be optimized to maximize the configurational freedom of the functionalizing chains upon layer separation while maximizing potential interaction sites with the surface. The most successful polymers for intercalatio...

Lattice Model of Polymer Melt Intercalation in Organically-Modified Layered Silicates

A mean-field, lattice-based model of polymer melt intercalation in organically-modified mica-type silicates (OLS) has been developed. In general, an interplay of entropic and energetic factors determines the outcome of polymer intercalation. Free energy curves and their dependence on energetic and entropic factors suggest three possible equilibrium statesimmiscible, intercalated, and exfoliatedall of which have been experimentally observed. The entropic penalty of polymer confinement may be compensated for by the increased conformational freedom of the surfactant chain as the layers separate. When the total entropy change is small, small changes in the system's internal energy will determine if intercalation is thermodynamically possible. Complete layer separation, though, depends on the establishment of very favorable polymer−OLS interactions to overcome the penalty of polymer confinement. For alkylammonium-modified layered silicates, a favorable energy change is accentuated by maximizing the magnitude a...

Polymer Layered Silicate Nanocomposites

AbstractPolymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in‐situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine‐tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass‐ or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self‐extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.