Morphology and rheology of polystyrene nanocomposites based upon organoclay

A correlation between morphology development and rheology of polystyrene nanocomposites based upon organophilic layered silicates (organoclay) such as fluoromicas was found as a function of the silicate modification. Organoclay was obtained by means of ion exchange of clay with protonated amine‐terminated polystyrenes with molar mass of M_n = 121 and 5 800 g/mol. Only when applying shear forces during melt compounding of organoclay modified with high molar mass polystyrene (PS), individual silicate platelets of 1 nm diameter and 600 nm length were obtained. Dispersions of such in‐situ formed nanoparticles with aspect ratio of 600 accounted for unique elastic properties observed in the low frequency range of the dynamic modulus, whereas organoclay modified with low molecular PS did not exfoliate and exhibited rheological behavior very similar to that of conventional fillers.     

Chiral poly(amide-imide)/organoclay nanocomposites derived from pyromellitoyl-bis-l-isoleucine and benzimidazole containing diamine: synthesis, nanostructure, and properties

In this study, a series of polymer–clay nanocomposite materials, consisting of organosoluble poly(amide-imide) (PAI) matrix and dispersed nanolayers of inorganic montmorillonite clay, were successfully prepared by solution dispersion technique. At first, the reactive organoclay was prepared by using protonated l-isoleucine amino acid as a swelling agent for silicate layers of Cloisite Na⁺. Then, organosoluble PAI containing isoleucine amino acid was synthesized through step-growth polymerization reaction of N,N′-(pyromellitoyl)-bis-isoleucine diacid and 2-(3,5-diaminophenyl)-benzimidazole under green condition using molten tetrabutylammonium bromide. This polymer was end-capped with amine end groups near the completion of the reaction to interact chemically with acidic group of organoclay. Finally, PAI/organoclay nanocomposite films containing 2%, 5%, 10%, and 15% of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. Dispersion of the modified clay in the PAI matrix resulted in a nanostructured material containing intercalated polymer between the silicate layers. Structures of exfoliation were confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis data indicated that the addition of organoclay into the PAI matrix increased the thermal decomposition temperatures of the obtained nanocomposites compared to the pure PAI.     

Thermal stability and water uptake of high performance epoxy layered silicate nanocomposites

Intercalated and ordered exfoliated layered silicate nanocomposites based on three different epoxy resins of different structures and functionalities were synthesized using an octadecyl ammonium modified smectite clay. Water uptake properties of series of each nanocomposite system with different organoclay concentrations were determined by gravimetric measurements over a period of time. The diffusion coefficients were determined and the effect of the absorbed water on the thermal relaxations investigated. The equilibrium water uptake of all nanocomposites was reduced compared to the neat epoxy system but the rate of water diffusion remained unaffected. Further, the thermal stability of the different nanocomposites was determined using thermogravimetric analysis. The nanocomposites showed slightly reduced thermal stability, as indicated by a slight decrease in onset of degradation, whilst the final char concentration increased for greater organoclay concentrations.     

The effect of organic modifiers with different chain lengths on the dispersion of clay layers in HTPB (hydroxyl terminated polybutadiene)

The series of HTPB (hydroxyl terminated polybutadiene)/organoclay nanocomposite was formed by melt blending with rotationary and revolutionary mixer which generated high shear stress. Organoclays were formed by modifying the pristine clays with organic modifiers which had different hydrophobic chain lengths. As the length of organic modifier increased, the gap size between layers of organoclay became broader. The clays modified with octadecylamine (C18) and dodecyl amine (C12) showed wider gap sizes than that modified with octyl amine (C8). This gap size affected the dispersion state of clays, exfoliation/intercalation in HTPB polymer medium. The mixtures of HTPB with C18 and C12 were transparent without sedimentation and showed almost exfoliated structure. HTPB/C18 mixture showed the higher viscosity and yield strength than HTPB/C12 due to exfoliation. HTPB/C12 showed more elastic behavior than HTPB/C18 mixture because the organoclay C12 had less content of organic modifier.     

New clay-reinforced polyamide nanocomposite based on 4-phenylenediacrylic acid: Synthesis and properties

New type of aromatic polyamide/montmorillonite nanocomposites were produced using solution intercalation technique in N-methyl-2-pyrrolidone. High-molecular-weight amide chains were synthesized from 4,4′-diaminodiphenyl ether and 4-phenylenediacrylic acid in N-methyl-2-pyrrolidone. The resulting nanocomposite films containing 5–20 wt.% of organoclay (Cloisite® 20A) were characterized for FT-IR, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), optical transparency and water absorption measurements. The distribution of organoclay and nanostructure of the composites were investigated by (XRD) and SEM analyses. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. The percentage optical transparency and water absorption of these hybrids was found to be much reduced upon the addition of modified layered silicate indicating decreased permeability.     

Poly(lactic acid)/organoclay nanocomposites: Thermal,rheological properties and foam processing

In this study, polymer nanocomposites based on poly(lactic acid) (PLA) and organically modified layered silicates (organoclay) were prepared by melt mixing in an internal mixer. The exfoliation of organoclay could be attributed to the interaction between the organoclay and PLA molecules and shearing force during mixing. The exfoliated organoclay layers acted as nucleating agents at low content and as the organoclay content increased they became physical hindrance to the chain mobility of PLA. The thermal dynamic mechanical moduli of nanocomposites were also improved by the exfoliation of organoclay; however, the improvement was reduced at high organoclay content. The dynamic rheological studies show that the nanocomposites have higher viscosity and more pronounced elastic properties than pure PLA. Both storage and loss moduli increased with silicate loading at all frequencies and showed nonterminal behavior at low frequencies. The nanocomposites and PLA were then foamed by using the mixture of CO₂ and N₂ as blowing agent in a batch foaming process. Compared with PLA foam, the nanocomposite foams exhibited reduced cell size and increased cell density at very low organoclay content. With the increase of organoclay content, the cell size was decreased and both cell density and foam density were increased. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 689–698, 2005     

Thermo-infrared-spectroscopy analysis of the interaction of naphthylammonium–montmorillonite with sodium nitrite

The deep blue organoclay color pigment (OCCP), naphthylazonaphthylammonium–montmorillonite, was synthesized in an aqueous suspension by treating montmorillonite with naphthylammonium chloride followed after 2 h by NaNO₂. The reddish-brown azo dye naphthylazonaphthylamine (commercial name “Solvent Brown 3”) was synthesized in an aqueous solution in the absence of clay from the same reagents. X-ray diffraction and thermo-infrared (IR) spectroscopy of organoclay prepared by treating montmorillonite with naphthylammonium chloride showed that the organoclay contained two types of tactoids with intercalated naphthylammonium cations and with naphthylammonium–naphthylamine associations. Naphthylammonium clay was obtained after thoroughly washing the latter organoclay. IR spectra of naphthylamine, naphthylammonium chloride, naphthylammonium clay, naphthylammonium–naphthylamine clay (with some naphthylammonium-clay), OCCP, and Solvent Brown 3 in KBr disks were recorded before and after thermal treatments up to 120 °C. IR spectrum of the OCCP was similar to that of Solvent Brown 3. An NH₃ ⁺ group was identified in the spectrum of the OCCP but not in that of Solvent Brown 3. In the latter spectrum, an NH₂ group was identified, suggesting that the amine group of the azo dye in the OCCP was protonated. It appears that the difference in color between OCCP and Solvent Brown 3 resulted from the protonation of the azo molecule in the interlayer space of the clay.     

Effect of Organoclays on Silicate Layer Structures and Thermal Stabilities of in-situ Polymerized Poly(D-lactide)/Clay Nanocomposites

Six kinds of organoclays were prepared through three kinds of polyols (PTMG, PEA and PCL) to investigate the effects of molecular weight and the chemical structure of organifiers. PTMG based organoclays showed higher ion-exchanged fraction than other organoclays and long chain organifier showed better efficiency in ion-exchanged fraction in the case of PTMG based organifiers. From WAXD and TEM analysis, it was confirmed that PTMG based organoclays formed partially exfoliated or fully exfoliated silicate layer structures. PDLA/clay nanocomposites were prepared by in-situ ring-opening polymerization of D-lactide with PTMG based organoclays as macro-initiators in the presence of equimolar Sn(Oct)₂/PPh₃ complex catalysts. The molecular weight of PDLA/clay nanocomposite decreased as increasing the feeding amount of organoclay because organoclay had hydroxyl terminal groups which can initiate the ring-opening polymerization of D-lactide. From TGA analysis, thermal stabilities of PDLA/clay nanocomposites improved with increasing organoclay content. From WAXD and TEM analysis, organoclay which was prepared by high molecular weight of PTMG based organifier was effective on the exfoliation of silicate layers in the in-situ polymerized PDLA/clay nanocomposite.     

Photo‐Oxidation of sPP/Organoclay Nanocomposites

Photo‐oxidation of syndiotactic polypropylene–sPP/organoclay nanocomposites was performed. Nanocomposites were prepared in situ by melt compounding of sPP, compatibilizer (iPP grafted with maleic anhydride–iPP‐g‐MAN) and organoclay filler ME C18 (modified with octadecyl ammonium chains in intergaleries of layered silicate, of which silicate layers (about 1 nm thin) were exfoliated). The influence of ME C18 nanoparticles alone (in content region 1 to 15 wt%) and together with compatibilizer iPP‐g‐MAN on the photostability of the sPP nanocomposite was studied. It was found that the silicate ME C18 nanoparticles alone catalyze the photooxidation and shorten the induction period of photo‐oxidation to one fourth (at the content of 5 wt% of ME C18) in comparison with unfilled sPP) and the presence of compatibilizer supports the photo‐oxidation of sPP nanocomposite. The ME C18 nanoparticles decrease the efficiency of UV stabilizers. The rate of photo‐oxidation of sPP/clay nanocomposite after the induction period is significantly higher than unfilled sPP. The mechanism of photo‐oxidation is discussed.     

XRD,SAXS, and PALS investigations of three different polymers reinforced with tetraoctylammonium exchanged montmorillonite

Three different polymer nanocomposites were prepared using clay modified with tetraoctylammonium (4C8) surfactant. The dispersion of clay silicate layers was studied using X-ray diffraction and small-angle scattering. Free-volume cavity sizes were studied with positron annihilation lifetime spectroscopy. Scattering methods confirmed disruption of all polymer lamellae organization upon organoclay addition and the creation of partially intercalated systems for polyamide and polycaprolactone. The presence of organoclay in the polymers enlarges the lower value of average positronium lifetime τ₃ of polyamide and reduces the higher value of τ₃ for polycaprolactone and polyethylene.     

Effect of surface modification of montmorillonite on the properties of aromatic polyamide/clay nanocomposites

The surface modification of montmorillonite clay was carried out through ion‐ exchange reaction using p‐phenylenediamine as a modifier. This modified clay was employed to prepare aromatic polyamide/organoclay nanocomposite materials. The dispersion behavior of clay was examined in the polyamide matrix. Polyamide chains were synthesized from 4‐aminophenyl sulfone and isophthaloyl chloride (IPC) in dimethylacetamide. These amide chains were suitably end‐capped with carbonyl chloride end groups to interact chemically with modified montmorillonite clay. The resulting nanocomposite films containing 2–20 wt% of organoclay were characterized by TEM, X‐ray diffraction (XRD), thin‐film tensile testing; thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and water absorption measurements. Mechanical testing revealed that modulus and strength improved up to 6 wt% organoclay loading while elongation and toughness of nanocomposites decreased with the addition of clay content in the matrix. Thermal decomposition temperatures of the nanocomposites were in the range 225–450 °C. These nanocomposites expressed increase in the glass‐transition temperature values relative to pure polyamide describing interfacial interactions among the phases. The percent water uptake of these composites reduced upon the addition of modified layered silicate depicting improved barrier properties. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermotropic liquid crystalline polyester nanocomposites via in situ intercalation polycondensation

A thermotropic liquid crystalline polyester (TLCP)/organoclay nanocomposite was synthesized via in situ intercalation polycondensation of diethyl‐2,5‐dihexyloxyterephthalic acid and 4,4′‐biphenol in the presence of organically modified montmorillonite (MMT). The organoclay, C18‐MMT, was prepared by the ion exchange of Na⁺‐MMT with octadecylamine chloride (C18‐Cl^?). TLCP/C18‐MMT nanocomposites were prepared to examine the variations of the thermal properties, morphology, and liquid crystalline phases of the nanocomposites with clay content in the range of 0–7 wt%. It was found that the addition of only a small amount of organoclay was sufficient to improve the thermal behavior of the TLCP hybrids, with maximum enhancement being observed at 1 wt% C18‐MMT. Copyright © 2008 John Wiley & Sons, Ltd.     

Morphology and properties of waterborne polyurethane/clay nanocomposites

Aqueous emulsion of polyurethane ionomers, based on poly(tetramethylene glycol) or poly(butylene adipate) as soft segment, isophorone diisocyanate as diisocyanate, 1,4-butandiol as chain extender, dimethyl propionic acid as potential ionic center, triethylene tetramine as crosslinker, and triethyl amine as neutralizer, were reinforced with organoclay to give nanocomposites. The particle size of emulsion was measured and the morphology of these nanocomposites was observed by transmission electron microscope, where the effectively intercalated or exfoliated organoclay was observed. The reinforcing effects of organoclay in mechanical properties of these nanocomposites were examined by dynamic mechanical and tensile tests, and the Shore A hardness was measured. Enhanced thermal and water resistance and marginal reduction in transparency of these nanocomposites were observed compared with pristine polymer.     

Poly(ester amide)/clay nanocomposites prepared by in situ polymerization of the sodium salt of N‐chloroacetyl‐6‐aminohexanoic acid

Preparation of nanocomposites of organo‐modified montmorillonites and the biodegradable poly(ester amide) derived from glycolic acid and 6‐aminohexanoic acid has been evaluated by the in situ polymerization technique. The reaction was based on the thermal polycondensation of sodium chloroacetylaminohexanoate, which has the formation of the sodium chloride salt as the driving force of the process. Polymerized samples were studied by means of X‐ray diffraction and transmission electron microscopy. The most dispersed structure was obtained by addition of C25A organoclay. Evaluation of thermal stability and crystallization behavior of these samples showed significant differences between the neat polymer and its nanocomposite with C25A. Isothermal and nonisothermal calorimetric analyses of the polymerization reaction revealed that the kinetics was highly influenced by the presence of the silicate particles. Crystallization of the polymer was observed to occur when the process was isothermally conducted at temperatures lower than 145 °C. In this case, dynamic FTIR spectra and WAXD profiles obtained with synchrotron radiation were essential to study the polymerization kinetics. Clay particles seemed to reduce chain mobility and the Arrhenius preexponential factor. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3616–3629, 2009     

Synthesis,rheology, and morphology of nylon‐11/layered silicate nanocomposite

Exfoliated nylon‐11/layered silicate nanocomposites were prepared via in situ polymerization by dispersing organoclay in 11‐aminoundecanoic acid monomer. The original clay was modified by a novel method with 11‐aminoundecanoic acid. In situ Fourier transform infrared spectroscopy results show that stronger hydrogen bonds exist between nylon‐11 and organoclay than that of between nylon‐11 and original clay. The linear dynamic viscoelasticity of organoclay nanocomposites was investigated. Before taking rheological measurements, the exfoliated and intercalating structures and the thermal properties were characterized using X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. The results show that the clay was uniformly distributed in nylon‐11 matrix during in situ polymerization of clay with 4 wt % or less. The presence of clay in nylon‐11 matrix increased the crystallization temperature and the thermal stability of nanocomposites prepared. Rheological properties such as storage modulus, loss modulus, and relative viscosity have close relationship with the dispersion favorably compatible with the organically modified clay. Comparing with neat nylon‐11, the nanocomposites show much higher dynamic modulus and stronger shear thinning behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2161–2172, 2006     

Thermal and colloidal behavior of amine-treated clays: the role of amphiphilic organic cation concentration

The modification of sodium montmorillonite (NaMMT) through the insertion of amphiphilic hexadecylammonium cations into the clay's interlayer spaces has been studied. Alkylammonium concentrations equivalent to 0.15-3.00 times the cation exchange capacity of the clay were used. The conformation of the surfactant cations in the confined space of the silicate galleries was investigated by X-ray diffraction analysis and scanning electron microscopy, while the organoclay's thermal stability was examined by thermogravimetric analysis. The clay's surface properties induced by the ion-exchange process were followed by measurements of the mineral's zeta potential as a function of pH and surfactant concentration, while the coagulation rates of organoclay suspensions in water and in chloroform were examined using dynamic light scattering. All the results are consistent with showing that the overall characteristics and thus the behavior of the modified MMT particles strongly depend on the alkylammonium surfactant concentration used in the modification process. This, however, has very important implications for any attempt to incorporate the organomodified MMT particles into different media for various applications such as polymer nanocomposite preparation.     

TEM, XRD, and thermal stability of adsorbed paranitrophenol on DDOAB organoclay

Water purification is of extreme importance to modern society. Organoclays through adsorption of recalcitrant organics provides one mechanism for the removal of these molecules. The organoclay was synthesised through ion exchange with dimethyldioctadecylammonium bromide labeled as DDOAB of formula (CH3(CH2)17)2NBr(CH3)2. Paranitrophenol (pnp) was adsorbed on the organoclay at a range of concentrations according to the cation exchange capacity (CEC) of the host montmorillonite. The paranitrophenol in solution was analysed by a UV-260 spectrophotometer at 317 nm, with detection limits being 0.05 mg/L. The expansion of the montmorillonite was studied by a combination of X-ray diffraction and transmission electron microscopy. Upon adsorption of the paranitrophenol the basal spacing decreased. The thermal stability of the organoclay was determined by a combination of thermogravimetry and infrared emission spectroscopy. The surfactant molecule DDOAB combusts at 166, 244, and 304 degrees C and upon intercalation into Na-montmorillonite is retained up to 389 degrees C thus showing the organoclay is stable to significantly high temperatures well above the combustion/decomposition temperature of the organoclay.     

Synthesis and characterization of polyurethane‐urea clay nanocomposites using montmorillonite modified by oxyethylene–oxypropylene copolymer

Clay organifier with propylene oxide‐capped polyethylene glycol (PEG) with amine end group (jeffamines ED_600–2003) was synthesized through an ion exchange process between sodium cations in montmorillonite (MMT) and ? NH groups in ED_600–2003. The d‐spacing of organoclay was found to be 1.697–1.734 nm compared to 0.96 nm of pristine MMT. Transmission electron microscopy (TEM) was used to determine the molecular dispersion of the clay within ED₆₀₀. Polyurethane‐urea/montmorillonite (PUU‐MMT) nanocomposites were prepared via in situ polymerization from polyethylene glycol (PEG 400) or 1,4 butane diol (1,4 BD), toluene diisocyanate (TDI), jeffamines ED_600–2003, and 1–12 wt% of organoclay. Intercalation of PUU into modified clays was confirmed by X‐ray diffraction (XRD), scanning electron microscopy, and TEM. The barrier properties were significantly reduced; however, the thermal stability was increased in the nanocomposites as compared to the pristine polymer. Nanocomposites exhibited optical clarity and solvent resistance. The mechanical properties and the glass transition temperature of PUU were improved with the addition of organoclay. The incorporation of silicate layers gave rise to a considerable increase in the storage modulus (stiffness), demonstrating the reinforcing effect of clay on the PUU matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

Nanocomposites by melt intercalation based on polycaprolactone and organoclay

Nanocomposites based on biodegradable polycaprolactone (PCL) and organically modified layered silicates (organoclay) were prepared by melt mixing. Their structures and properties were characterized by wide‐angle X‐ray diffraction, thermal analysis, and rheological measurements. The exfoliation of the organoclay was achieved via a melt mixing process in an internal mixer and showed a dependence on the type of organic modifier, the organoclay contents, and the processing temperature. The addition of the organoclay to PCL increased the crystallization temperature of PCL, but a high content of the organoclay could show an inverse effect. The PCL/organoclay nanocomposites showed a significant enhancement in their mechanical properties and thermal stability due to the exfoliation of the organoclay. The nanocomposites showed a much higher complex viscosity than the neat PCL and significant shear‐thinning behavior in the low frequency range. The shear storage modulus and loss modulus of the nanocomposites also exhibited less frequency dependence than the pure PCL in the low frequency range, and this was caused by the strong interactions between the organoclay layers and PCL molecules and by the good dispersion of exfoliated organoclay platelets in the PCL. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 670–678, 2003     

剥离型硅橡胶/黏土纳米复合材料研究

利用层状硅酸盐制备有机 无机纳米复合材料是当前人们研究的热点[1,2 ] ,这类材料具有较常规聚合物 无机填料复合材料无法比拟的优点 ,可以明显改善高分子材料的物理机械性能、热稳定性、气体阻隔性、阻燃性、导电性、光学性等 .一般来说 ,聚合物 层状硅酸盐 (Ｐｏｌｙｍｅｒｌａｙｅｒｅｄｓｉｌｉｃａｔｅ ,ＰＬＳ)纳米复合材料可分为插层型和剥离型两种类型 .插层型纳米复合材料即聚合物插入到硅酸盐层中 ,硅酸盐在近程仍保持原有的有序晶体结构 ,在远程则是无序的 .对弹性体而言 ,硅酸盐含量在插层型杂化材料中的含量比较高 ,力学性能…