Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterization of poly(glycidyl methacrylate)/Na‐montmorillonite nanocomposites

Poly(glycidyl methacrylate)/Na–montmorillonite nanocomposites were synthesized by free‐radical polymerization of glycidyl methacrylate containing dispersed montmorillonite. By changing the concentration of glycidyl methacrylate several polymer–clay nanocomposites were prepared and the resulting nanocomposites were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results indicated that the properties of the composite were significantly improved. The thermogravimetric analysis results revealed that the degradation temperatures of nanocomposites were higher than that of pure polymer and the thermal degradation rates decreased. Examination of these materials by scanning electron microscopy showed that the clay layers are dispersed homogenously in the polymer matrix and the formation of intercalation nanostructure. Furthermore, adsorptive, moisture regain, and water uptake properties of nanocomposites were also investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1532–1538, 2004     

A comparative study of poly(methyl methacrylate) and polystyrene/clay nanocomposites prepared in supercritical carbon dioxide

Poly(methyl methacrylate) and polystyrene/clay nanocomposites have been prepared via pseudo-dispersion polymerizations in the presence of a poly(dimethylsiloxane) surfactant-modified clay (PDMS-clay) in supercritical carbon dioxide. The effects of the PDMS-clay concentration on polymer conversion, molecular weight, and morphology have been investigated. The insoluble dispersion of PDMS-clay is shown to be an effective stabilizer for both MMA and styrene polymerization in scCO₂. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). While XRD shows featureless patterns for both nanocomposites, the actual distributions of clay are found to be quite different between PMMA and PS nanocomposites, presumably due to the different interaction mechanisms between the polymers and clay. Consequently, the different states of clay in the two nanocomposites play an important role in the mechanical properties of the nanocomposites, and a to a lesser degree in the thermal properties.     

Mechanical properties and rheological behavior of poly(butylene terephthalate)/clay nanocomposites with different organoclays

Poly(butylene terephthalate)–clay nanocomposites with three different organically modified clays were prepared via melt blending in a twin‐screw extruder. Decyl triphenylphosphonium bromide, hexadecyl triphenylphosphonium bromide, and cetyl pyridinium chloride were used to modify the naturally occurring montmorillonite clay. The organically modified clays were characterized with X‐ray diffraction for the d₀₀₁‐spacing and with thermogravimetric analysis to determine the thermal stability. The prepared nanocomposites were injection‐molded and examined for the dispersion quality of the clay, the mechanical properties, and the rheological behavior. The tensile strength of the nanocomposites increased with a 1% addition of clay; however, more clay decreased the tensile strength. Nanocomposites with finely dispersed clay platelets and nanocomposites with poorly dispersed clay platelets showed very different rheological behaviors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

In‐situ synthesis of poly(ethylene terephthalate)/clay nanocomposites using TiO2/SiO2 sol‐intercalated montmorillonite as polycondensation catalyst

A novel organic montmorillonite, which could act as both polycondensation catalyst of poly(ethylene terephthalate) (PET) and filler of PET/clay nanocomposites, was prepared. Original montmorillonite was first treated with different amounts of poly(vinylpyrrolidone) (PVP), and then intercalated by TiO₂/SiO₂ sol to gain polycondensation catalytic activity. The acquired clay possessed excellent thermal stability and would not degrade during the polycondensation step. PET/clay nanocomposites were prepared via in‐situ polymerization using the organo‐clay as polycondensation catalysts. The morphologies of the nanocomposites were characterized by X‐ray diffraction and transmission electron microscope. The results indicated that the amount of PVP and TiO₂/SiO₂ sol strongly affected the dispersion state of the clay, and finally, partially exfoliated PET/clay nanocomposites were obtained. The nanocomposites had better properties than pure PET due to the incorporation of the delaminated clay layers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Poly(methyl methacrylate)/clay nanocomposites by photoinitiated free radical polymerization using intercalated monomer

A series of poly(methyl methacrylate)/montmorillonite (PMMA/MMT) nanocomposite were prepared by successfully dispersing the inorganic nanolayers of MMT clay in an organic PMMA matrix via in situ photoinitiated free radical polymerization. Methyl methacrylate monomer was first intercalated into the interlayer regions of organophilic clay hosts by “click” chemistry followed by a typical photoinitiated free radical polymerization. The intercalated monomer was characterized by FT-IR spectroscopy, elemental analysis and thermogravimetric analysis methods. The intercalation ability of the modified monomer and exfoliated nanocomposite structure were confirmed by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Thermal stability of PMMA/MMT nanocomposites was also studied by both differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

A conducting nanocomposite via intercalative polymerisation of 2-methylaniline with aniline in montmorillonite cation-exchanged

Polymer/montmorillonite nanocomposites were prepared. Intercalation of 2-methylaniline with aniline monomers into montmorillonite modified by cation was followed by subsequent oxidative polymerization of the monomers in the interlayer spacing. The clay was prepared by cation exchange process between sodium cation in (M-Na) and copper cation (M-Cu). We prepared a series of polymer/clay nanocomposite materials that consisted of an emeraldine base of poly(2-MA), poly(2-MA-co-ANI) and PANI by layered copper montmorillonite. All organic monomers used were first intercalated into the interlayer regions of clay hosts followed by a one-step in situ oxidative polymerization. The unique properties of the as-synthesized nanocomposites materials are investigated by electronic conductivity measurements, X-ray diffraction, FTIR spectroscopy, UV-vis spectroscopy, thermogravimetric analysis and SEM, were also studied by cyclic voltammetry which indicates the electroactive effect of nanocomposite gradually increased with aniline in the polymer chain.     

Synthesis and characteristics of polystyrene–clay nanocomposites via in situ intercalative polymerization in a direct current electric field

Polystyrene (PS)/montmorillonite nanocomposites were prepared by the free‐radical polymerization of styrene‐containing dispersed clay in a direct current electric field. The intercalation spacing in the nanocomposites, the dispersion, and the orientation of these composites were investigated. The nanocomposites had higher T_g and better thermal stability when compared with the virgin PS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

An exfoliated clay‐poly(norbornene) nanocomposite prepared by metal‐mediated surface‐initiated polymerization

An exfoliated clay?polymer nanocomposite was prepared by surface‐initiated ring opening metathesis polymerization (SI‐ROMP) of norbornene on a montmorillonite (MMT) clay with a modified surface. Utilizing the hydrothermal‐silylation reaction between a norbornenyl‐bearing chlorosilane agent and silanol groups of the MMT clay, we were able to bind a metal alkylidene catalyst to the surface in order to grow poly(norbornene) chains directly from the surface using ROMP. Our approach produced nanocomposites having poly(norbornene) chains that are covalently attached to the inorganic substrate, as opposed to most conventional polymer‐clay composites that have ionically tethered chains (via the ammonium‐based modifiers of the organoclay) or physically adsorbed polymers. POLYM. ENG. SCI., 55:2349–2354, 2015. © 2015 Society of Plastics Engineers     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of polystyrene/clay nanocomposite by suspension and emulsion polymerization

Organophilic montmorillonite was prepared using ion‐exchange method between sodium ions in clay layers and four kind of quaternary ammonium salt. The montmorillonite has the largest d₀₀₁‐spacing, as determined by X‐ray diffraction in modified by di(hydrogenated tallowalkyl) dimethyl ammonium chloride. Polystyrene montmorillonite nanocomposites were obtained by suspension and emulsion polymerization of styrene in the dispersed organophilic montmorillonite. The d₀₀₁‐spacing of clay was determined by X‐ray diffraction (XRD). The thermal stability of organophilic montmorillonite was investigated by thermogravimetric analysis (TGA). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Thermal and mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites over a wide range of filler loading

BACKGROUND: Poly(methyl methacrylate) (PMMA)–organoclay nanocomposites with octadecylammonium ion‐modified montmorillonite, prepared via melt processing, over a wide range of filler loading (2–16 wt%) were investigated in detail. These hybrids were characterized for their dispersion structure, and thermal and mechanical properties, such as tensile modulus (E), break stress (σ_brk), percent break strain (ε_brk) and ductility (J), using wide‐angle X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile and impact tests. RESULTS: Intercalated nanocomposites were formed even in the presence of 16 wt% clay (high loading) in PMMA matrix. PMMA intercalated into the galleries of the organically modified clay, with a change in d‐spacing in the range 11–16 Å. TGA results showed improved thermal stability of the nanocomposites. The glass transition temperature (T_g) of the nanocomposites, from DSC measurements, was 2–3 °C higher than that of PMMA. The ultimate tensile strength and impact strength decreased with increasing clay fraction. Tensile modulus for the nanocomposites increased by a significant amount (113%) at the highest level of clay fraction (16 wt%) studied. CONCLUSION: We show for the first time the formation of intercalated PMMA nanocomposites with alkylammonium‐modified clays at high clay loadings (>15 wt%). Tensile modulus increases linearly with clay fraction, and the enhancement in modulus is significant. A linear correlation between tensile strength and strain‐at‐break is shown. Thermal properties are not affected appreciably. Organoclay can be dispersed well even at high clay fractions to form nanocomposites with superior bulk properties of practical interest. Copyright © 2007 Society of Chemical Industry     

Synthesis of exfoliated acrylonitrile-butadiene-styrene copolymer (ABS) clay nanocomposites: role of clay as a colloidal stabilizer

Acrylonitrile-butadiene-styrene copolymer (ABS) clay nanocomposites were synthesized using two clays (sodium montmorillonite, laponite). Both colloidal stability and mechanical properties of the nanocomposites were dependant on aspect ratios of clays. Laponite, a low aspect ratio clay, reduced particle sizes of ABS clay nanocomposite latexes, enhanced colloidal stabilities, and increased viscosity of the latexes. The colloidal stability of ABS clay latexes may result from four factors. Firstly, the electrostatic repulsion forces originated from surface charges of clays and anionic surfactant contribute to colloidal stability. Secondly, laponite layers separate sodium montmorillonite layers and polybudadiene latex particles preventing the coagulation. Thirdly, the laponite layers adsorbed on latexes act like steric barriers against coagulation. Fourthly, increased viscosity reduces latex mobility, lowering collision possibility among latex particles. Resultant ABS clay nanocomposites showed exfoliated structures, and their mechanical properties related to the relative weight ratio of sodium montmorillonite to laponite: as portions of sodium montmorillonite increased, dynamic moduli of the nanocomposites increased, because sodium montmorillonite has higher aspect (length/thickness) ratio than laponite.     

Processing of nanocomposite foams in supercritical carbon dioxide. Part I: Effect of surfactant

Polystyrene-clay nanocomposites were prepared by in situ polymerization to achieve the better dispersion of lamellar silicates i.e. montmorillonite and fluorohectorite and were used to process foams with supercritical CO₂. Clay-Polymer interactions were modulated by varying the surface treatment of clays: a physical interface was formed with the compatible surfactant showing aromatic groups (MMT-benz) and a chemical interface was created after reaction of methacrylate group (MMT-MHAB) with the styrene monomer. The dispersion of nanocomposites and the microstructure of resulting foams are very dependent on the quality of the clay/matrix interface. With the compatible clay, exfoliation of aromatic clay in polystyrene matrix is obtained at all scales. On the other hand, with the reactive clay, intercalated primary particles are obtained but the size of foam cells is the smallest and cell density is the highest. Our results suggest that the nucleation occurs primarily on physico-chemical nucleation sites that are the carbonyl group of the tethered copolymers synthesized on reactive clay and that present a strong affinity for CO₂. The relaxation times determined by using solid-state NMR spectroscopy are consistent with the formation of the in situ copolymers.     

Preparation and characterization of polymer/organosilicate nanocomposites based on unmodified LDPE

Low‐density polyethylene (LDPE)/silicate nanocomposites were prepared by the melt compounding and solution blend methods using unmodified LDPE polymer and layered silicates with different aspect ratio. X‐ray diffraction (XRD) analysis performed on composites obtained by dispersing the organosilicates in molten LDPE evidenced an exfoliated or partially exfoliated structure for the low aspect ratio silicate (laponite) in contrast to the high aspect ratio silicate (montmorillonite), which led to the formation of intercalated nanocomposites. With regard to the preparation method, the melt compounding method was more effective in forming exfoliated/highly intercalated LDPE nanocomposites compared with the solution blend method (using CCl₄ as a solvent). A gradual increase in crystallization temperatures (T_c) with increasing laponite content for LDPE‐organolaponite nanocomposites was revealed by differential scanning calorimetry (DSC) measurements. Thermogravimetric analysis and tensile measurements results indicated that thermal stability and elastic modulus increment were more prevalent for nanocomposites prepared using organomontmorillonite as filler. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

悬浮聚合聚甲基丙烯酸甲酯／蒙脱土纳米复合材料的制备及表征

采用悬浮聚合法制备了聚甲基丙烯酸甲酯／蒙脱土（PMMA/MMT）纳米复合材料，利用X射线衍射仪、透射电子显微镜和傅里叶变换红外光谱等手段表征了复合材料的结构，研究了不同改性剂对复合材料结构的影响。通过热重分析考察了复合材料的热性能。结果表明，通过悬浮聚合可以成功制备剥离型纳米复合材料，PMMA基体与MMT可以产生较强的相互作用。MMT的加入可以显著提高复合材料的热稳定性。当MMT含量为10％（质量分数，下同）时，PMMA的最大分解温度提高了15℃。     

In situ polymerization of polyethylene/clay nanocomposites using a novel clay‐supported Ziegler‐Natta catalyst

Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler‐Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl₄ and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nanostructure of composites was investigated by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay in these polyethylene/nanocomposites were exfoliated, intercalated, and uniformly dispersed in the polyethylene matrix even at very high concentration of the clay. Thermogravimetric analysis (TGA) shows good thermal stability of the PECNCs. Differential scanning calorimeter (DSC) results reveal considerable decrease in the crystalline phase of the PECNC samples. Results of permeability analysis show an increase in barrier properties of PECNC films. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Nanocomposite materials based on isosorbide methacrylate/Cloisite 20A

This paper reports experiments on grafting of a new polymerizable monomer onto organophilic montmorillonite. The monomer, 5‐methacryloyloxy‐1,4:36‐D ‐anhydrosorbitol (MAS), was synthesized by reacting methacryloyl chloride and isosorbide in the presence of Et₃N as base. Then, Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogen carbonate to prevent the exchange of quaternary alkylammonium cations with H⁺ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. After the reaction, the product maintained the same basal spacing as the precursor. The radical polymerization of the product with MAS as a vinyl monomer led to chemical grafting of the polymer onto the montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed using infrared spectroscopy. The prepared nanocomposite materials and the grafted nanoparticles were studied using X‐ray diffraction and scanning and transmission electron microscopy. Exfoliated nanocomposite was obtained for 1 wt% clay loadings. The nanocomposites were studied using thermogravimetric and dynamic mechanical analyses. Improved thermal properties were observed for nanocomposites with 1–5 wt% clay content. © 2012 Society of Chemical Industry