Preparation and characterization of poly(styrene‐co‐butadiene) and polybutadiene rubber/clay nanocomposites

Poly(styrene‐co‐butadiene) rubber (SBR) and polybutadiene rubber (BR)/clay nanocomposites have been prepared. The effects of the incorporation of inorganically and organically modified clays on the vulcanization reactions of SBR and BR were analysed by rheometry and differential scanning calorimetry. A reduction in scorch time (t_s1) and optimum time (t₉₅) was observed for both the rubbers when organoclay was added and this was attributed to the amine groups of the organic modifier. However, t_s1 and t₉₅ were further increased as the clay content was increased. A reduction in torque value was obtained for the organoclay nanocomposites, indicating a lower number of crosslinks formed. The organoclays favoured the vulcanization process although the vulcanizing effect was reduced with increasing clay content. The tensile strength and elongation of SBR were improved significantly with organoclay. The improvement of the tensile properties of BR with organoclay was less noticeable than inorganic‐modified clay. Nevertheless, these mechanical properties were enhanced with addition of clay. The mechanical properties of the nanocomposites were dependent on filler size and dispersion, and also compatibility between fillers and the rubber matrix. Copyright © 2004 Society of Chemical Industry     

Effect of clay modification on the morphology and the mechanical/physical properties of ABS/PMMA blends

The effect of three types of organoclays on the morphology and mechanical properties of lower critical solution temperature‐type poly(acrylonitrile‐butadiene‐styrene)/poly(methyl methacrylate) (ABS/PMMA) blends was investigated. Polymers were melt‐compounded with 2 and 4 wt % of clays using a twin‐screw extruder. X‐ray scattering and transmission electron microscopy revealed that the intercalation of the nanoclay in the hybrid nanocomposite was more affected by the polarity of the organoclay. Although the morphology of the blends varied by PMMA content, scanning electron microscopy showed smaller PMMA domains for the hybrid systems containing clay particles. Although good dispersion of the nanoclay through the ABS matrix and at the blend interface led to enhancement of tensile strength, the increment of the stiffness was more noticeable for nanocomposites including less polar organoclay. Well‐dispersed clay platelets increased the glass transition temperature. In addition, nanoscratching analysis illustrated an improvement in scratch resistance of ABS because of the presence of PMMA and organoclay. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyurethane/clay nanocomposites foams: processing, structure and properties

Polyurethane (PU)/montmorillonite (MMT) nanocomposites were synthesized with organically modified layered silicates (organoclays) by in situ polymerization and foams were prepared by a batch process. Clay dispersion of polyurethane nanocomposites was investigated by X-ray diffraction and transmission electron microscopy. The morphology and properties of PU nanocomposites and foams greatly depend on the functional groups of the organic modifiers, synthesis procedure, and molecular weight of polyols because of the chemical reactions and physical interactions involved. Silicate layers of organoclay can be exfoliated in the PU matrix by adding hydroxyl and organotin functional groups on the clay surface. The presence of clay results in an increase in cell density and a reduction of cell size compared to pure PU foam. In the polyurethane with high molecular weight polyol, a 6 °C increase in T_g, 650% increase in reduced compressive strength, and 780% increase in reduced modulus were observed with the addition of 5% organically treated clays. Opposite effects were observed in PU nanocomposite foams with highly crosslinked structure. The interference of the H-bond in the presence of clay is probably the reason.     

Characterization of latex-based isotactic polypropylene/clay nanocomposites

Polypropylene/clay nanocomposite (PCN) containing 1 wt% organo-modified clay was prepared by latex technology, previously successfully applied for preparation of carbon nanotubes (CNTs)/polymer composites. The level of dispersion of organoclay and the microstructure of the resulting PCNs were characterized by means of X-ray diffraction analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The obtained results have demonstrated that the latex technique represents a promising method for preparation of PP/clay nanocomposites with good dispersion of exfoliated nanoclay particles. The influence of clay nanoparticles on nonisothermal crystallization of PCN was investigated by DSC. The crystallization onset temperature of the matrix rises for about 5 °C when crystallizing from the quiescent melt. Improved thermal stability of PP/nanoclay was observed as evaluated by TGA. The dynamic mechanical analysis reveals an increase in storage modulus of PP matrix in the nanocomposites for 30% over a temperature range, indicating an increase in the stiffness of the material with the addition of organically modified clay.     

有机粘土／SBR纳米复合材料的结构与性能研究

采用十六烷基三甲基溴化铵（CTAB）和十八烷基三甲基溴化铵（STAB）分别对无机粘土进行有机改性,然后制备有机粘上／SBR纳米复合材料,研究不同季铵盐类改性剂对无机粘土的改性效果。结果表明：CTAB改性有机粘土与STAB改性有机粘土的片层间距分别从无机粘土的1．26nm增加到3．77nm和4．39nm;CTAB改性有机粘土的片层结构较稳定,而且在橡胶基体中的分散效果较好;所制备的有机粘土／SBR纳米复合材料的片层结构较多,力学性能较好。     

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     

Effect of the nature of clay on the thermo‐mechanodynamical and electrical properties of epoxy/clay nanocomposites

The effect of nature of clay on the thermo–mechanodynamical and electrical properties of epoxy/clay nanocomposites prepared from bisphenolic epoxy resins and different nanoclays are presented. The thermal–mechanodynamical properties of the nanocomposites were studied by DMTA, showing significant increase in both elastic modulus and glass transition temperature. Short time AC dielectric breakdown strength measurements carried out on the nanocomposites showed an increase in dielectric breakdown strength for the nanocomposites prepared with organically modified clays. The space charges accumulated in the materials as studied by pulsed electroacoustics method showed a significant decrease in the space charge accumulation in the nanocomposites with organoclays as the nanofiller. Similarly the space charge decays almost completely in the nanocomposites prepared with organoclays as nanofiller. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Ternary nanocomposites: Curing,morphology, and mechanical properties of epoxy/thermoplastic/organoclay systems

The influence of two organically modified montmorillonites on the curing, morphology and mechanical properties of epoxy/poly(vinyl acetate)/organoclay ternary nanocomposites was studied. The organoclays and poly(vinyl acetate) (PVAc) provoked contrary effects on the epoxy curing reaction. Ternary nanocomposites developed different morphologies depending on the PVAc content, that were similar to those observed in the epoxy/PVAc binary blends. The organoclays were only located in the epoxy phase independently of the morphology. All nanocomposites showed intercalated structures with similar clay interlayer distances. Both PVAc and organoclays lowered the T_g of the epoxy phase, the presence of clays did not influence the T_g of the PVAc phase. The addition of the organoclays to the epoxy improved stiffness but lowered ductility while the adition of PVAc improved toughness although reduced stiffness of epoxy thermoset. Ternary nanocomposites exhibited optimal properties that combine the favourable effects of the clay and the thermoplastic. POLYM. COMPOS., 37:2184–2195, 2016. © 2015 Society of Plastics Engineers     

Studies on poly(vinylidene fluoride)-clay nanocomposites: Effect of different clay modifiers

Montmorillonite clay based poly(vinylidene fluoride) nanocomposites were prepared by melt-mixing. The clays used included unmodified clay, a commercially available ammonium based clay, and two organically modified clays prepared by cation exchange with hexadecylpyridinium chloride and with octadecyltriphenylphosphonium bromide. PVDF-clay nanocomposites were processed in a mini twin-screw extruder. The structure of nanocomposites, analyzed using WAXD and TEM, indicated different extents of the clay dispersion depending on the modifier. PVDF formed β-phase crystals in the presence of organically modified clay when crystallized from its melt; in contrast, α-crystals were formed in the absence of clay and with unmodified clay. SAXS analysis indicated that the long period and crystalline lamella thickness decreased with the addition of clay. The melting and crystallization temperatures increased around 10 and 13 °C, respectively, with 5 wt% of phosphonium modified clay, which was the highest among the clays used. Further, the clay served as a nucleating agent for PVDF matrix, as observed by hot-stage polarized optical microscopy. The average spherulitic radius, determined from small angle light scattering, decreased with clay content. The elongation at break increased around 200% with the addition of only 5 wt% of ammonium clay. The storage and loss moduli of the nanocomposites were significantly higher than those of PVDF throughout the temperature range. Dielectric measurements showed a maximum increase of about 8 units of dielectric constant at 1 Hz frequency with 5 wt% organoclay.     

Structure,permeability, and rheology of supercritical CO2 dispersed polystyrene-clay nanocomposites

Improvement in clay dispersion and clay-polymer interfacial interactions are keys to producing superior nanocomposites. A supercritical CO₂ (scCO₂) processing method was utilized to pre-disperse commercial organic clays, for further solvent mixing with polystyrene (PS) to form nanocomposites with significant dispersion and interfacial enhancement. The effect of scCO₂ processing on clay pre-dispersion, and clay dispersion and interfacial interaction in nanocomposites were investigated. SEM and WAXD of the clays indicated that after scCO₂ processing the clays lose their long region ordered layer structure appreciably, associated with reduction in particle size. WAXD and TEM of the PS/clay nanocomposites showed that the polymer penetrated into the pre-dispersed clay, leading to a disordered intercalated/exfoliated structure with improved interfacial interaction rather than a disordered intercalated structure as seen with as-received clays. Relationships between those structures, rheological and barrier properties were investigated. The scCO₂-processed nanocomposites showed a plateau in the low-frequency storage modules and increased complex viscosity, each associated with significant clay dispersion in the nanocomposite. With only 1.09% volume fraction of clay, significant reduction (∼49%) of oxygen permeation was achieved.     

Synthesis and rheological properties of polystyrene/layered silicate nanocomposite

Exfoliated polystyrene (PS)/organo-modified montmorillonite (MMT) nanocomposites were synthesized through in situ free radical bulk polymerization by dispersing a modified reactive organophilic MMT layered silicate in styrene monomer. The original MMT was modified by a mixture of two commercial cationic surfactants, [2-(acryloyloxy)ethyl](4-benzoylbenzyl)dimethylammonium bromide (ADAB) and cetyltrimethylammonium bromide (CTAB), with the former containing a polymerizable vinyl group. The exfoliating and intercalating structures were probed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Comparing with pure PS, the nanocomposites show much higher decomposition temperature, higher dynamic modulus, stronger shear thinning behavior and a smaller die swell ratio. The leveling-off of the storage modulus at low frequencies in the oscillatory shear measurements, as well as the observed yield like behavior, implies that the formation of a percolating nanoclay network is the origin of the enhanced viscoelasticity in these composites.     

Preparation and characterization of nanocomposites based on thermoplastic elastomers from rubber–plastic blends

In the present work, thermoplastic elastomer (TPE)–clay nanocomposites (TPN) based on different rubber–plastic blends from ethylene–octene copolymer [Engage]–Polypropylene and brominated poly(isobutylene‐co‐paramethyl styrene)–nylon 6 were prepared by melt blending. Hexadecyltrimethylammonium bromide and octadecyl amine‐modified sodium montmorillonite were used as organoclays. The nanocomposites were prepared by adding the nanoclay separately into the rubber and plastic phases. The TPNs were characterized with the help of transmission electron microscopy (TEM) and X‐ray diffraction. The X‐ray diffraction peaks observed in the range of 3–10° for the modified clays disappeared in the thermoplastic elastomeric nanocomposites. TEM photographs showed exfoliation and intercalation of the clays in the range of 20–30 nm in the particular phase where the clay was added. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus was observed on incorporation of the nanoclays in the rubber phase of TPN. When the nanoclay was added to the plastic phase, the mechanical reinforcement is comparatively poorer due to partial destruction of the crystallinity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1645–1656, 2006     

Vulcanization behavior and mechanical properties of organoclay fluoroelastomer nanocomposites

The vulcanization behavior and mechanical properties of clay/fluoroelastomer nanocomposites produced by melt‐mixing of Dyneon FPO 3741 (a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene) with 10 phr of unmodified montmorillonite (CloisiteNA) or di(hydrogenated tallow‐alkyl) dimethyl ammonium‐modified montmorillonites (Cloisite15A and Cloisite20A) were studied. The properties of clay/FKM nanocomposites were compared with composites prepared using 10 and 30 phr of carbon black. The effects of clay surfactant and surfactant concentration on the vulcanization behavior, mechanical, and dynamical properties of peroxide cured composites were studied. XRD results of cured composites showed a decrease in d‐spacing and indicated deintercalation of the clays after the vulcanization process. It was also found that organoclays retard the FKM peroxide vulcanization process. Significantly, higher maximum torque on vulcanization was obtained with organoclays versus unmodified clay and carbon black. Although the morphologies of organoclay/FKM nanocomposites studied by XRD and TEM suggest similar intercalated/exfoliated structures, the organoclay with the lowest concentration of surfactant (95 meq/100 g clay) resulted in the highest increase in torque, modulus, hardness, and tear strength in the clay/FKM nanocomposites. It was also found that organoclays can increase both the hydrodynamic reinforcement and hysteresis loss of FKM nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Use of acrylic based surfmers for the preparation of exfoliated polystyrene–clay nanocomposites

Two polymerizable cationic surfactants, (11-acryloyloxyundecyl)dimethyl(2-hydroxyethyl)ammonium bromide (hydroxyethyl surfmer) and (11-acryloyloxyundecyl)dimethylethylammonium bromide (ethyl surfmer), were used for the modification of montmorillonite (MMT) clay. The modification of MMT dispersions was carried out by ion exchange of the sodium ions in Na⁺-MMT by surfactants in aqueous media. Modified MMT clays were then dispersed in styrene and subsequently polymerized in bulk by a free-radical polymerization reaction to yield polystyrene–clay nanocomposites. An exfoliated structure was obtained using the ethyl surfmer-modified clay, whereas a mixed exfoliated/intercalated structure was obtained using the hydroxyethyl surfmer-modified clay. Nanocomposite structures were confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability and an increase in glass transition temperature, relative to neat polystyrene. The nanocomposites also exhibited enhanced mechanical properties, which were dependent on the clay loading. Intercalated polystyrene–clay nanocomposites were obtained using the non-polymerizable surfactant-modified clay (cetyltrimethylammonium bromide). Nanocomposites made from mixtures of surfmer-modified and CTAB-modified clays were also prepared, showing intermediate properties. However, when the nanocomposites were prepared in solution only intercalated morphologies were obtained. This was attributed to the competition between the solvent molecules and monomer in penetrating into clay galleries. These nanocomposites also exhibited enhanced thermal stability relative to the virgin polystyrene prepared by the same method. Similar temperatures of degradation (at 50% decomposition) were found for these nanocomposites relative to those prepared by bulk polymerization.     

Influence of organoclay and preparation technique on the morphology of polyamide6/polystyrene/organoclay nanocomposites

To have an improved insight about the compatibilization effect of organoclay on immiscible polymers, two different organoclays and preparation techniques were chosen to prepare polyamide6 (PA6)/polystyrene (PS)/organoclay ternary nanocomposites. The morphology analysis based on the results of X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy demonstrated that the type of organoclay and preparation technique had a significant influence on the dispersion and distribution of organoclay in the polymer. It was concluded that blending PS/organoclay nanocomposite synthesized previously via in situ bulk polymerization, with PA6 can realize the full exfoliation of organoclay in the final ternarynanocomposite, while an intercalated structure was achieved by directly blending the three components. The distribution of organoclay could be controlled by tuning the surface property of clay, and hence the interfacial interaction between clay and the polymer matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of the grafted silane on the dispersion and orientation of clay in polyethylene nanocomposites

The CTAB ammonium intercalated montmorillonite clay, CMT, was modified by an alkylsilane, Dodecyltrimethoxylsilane, to improve the miscibility of organoclays with PE matrix, involving the grafting reaction between the silane and silanol groups on the edge of clay. The silane modified clays (DMT) exhibited improved thermal stability due to the replacement of the physically adsorbed ammonium by the covalently bonded silane. The clays were melt compounded with polyethylene. Compared with the composite of PE/CMT, the clay dispersion state was improved, and a unique orientation of the clay layered was observed in PE/DMT nanocomposites, which was confirmed by XRD and TEM studies. The dispersion state, orientation degree of clay and, as a result, the mechanical and thermal properties of the nanocomposites were enhanced with the increasing amount of the grafted silane, indicating that the edge grafting of silane played a crucial role in controlling the structure and properties of nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Physical properties of polyester-acrylate/clay nanocomposite films with different organoclays

Three different organoclays (VDA-MMT, SDA-MMT, and 20A-MMT) originated from the same pristine clay (Na⁺-MMT) were used to prepare polyester-acrylate/clay nanocomposite films by in-situ ultraviolet (UV)-polymerization. Except for the commercial organoclay (20A-MMT), VDA-MMT and SDA-MMT were synthesized in this study by ion exchange method. The effects of different organoclays on the thermal stability, mechanical, and optical properties of the nanocomposite films were investigated. The physical properties of the nanocomposites were considerably different from each other because of the different characteristics of the organoclays. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

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     

A flammability performance comparison between synthetic and natural clays in polystyrene nanocomposites

Polymer‐clay nanocomposites are a newer class of flame retardant materials of interest due to their balance of mechanical, thermal and flammability properties. Much more work has been done with natural clays than with synthetic clays for nanocomposite flammability applications. There are advantages and disadvantages to both natural and synthetic clay use in a nanocomposite, and some of these, both fundamental and practical, will be discussed in this paper. To compare natural and synthetic clays in regards to polymer flammability, two clays were used. The natural clay was a US mined and refined montmorillonite, while the synthetic clay was a fluorinated synthetic mica. These two clays were used as inorganic clays for control experiments in polystyrene, and then converted into an organoclay by ion exchange with an alkyl ammonium salt. The organoclays were used to synthesize polystyrene nanocomposites by melt compounding. Each of the formulations was analysed by X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Flammability performance was measured by cone calorimeter. The data from the experiments show that the synthetic clay does slightly better at reducing the heat release rate (HRR) than the natural clay. However, all the samples, including the inorganic clay polystyrene microcomposites, showed a decreased time to ignition, with the actual nanocomposites showing the most marked decrease. The reason for this is postulated to be related to the thermal instability of the organoclay (via the quaternary alkyl ammonium). An additional experiment using a more thermally stable organoclay showed a time to ignition identical to that of the base polymer. Finally, it was shown that while polymer‐clay nanocomposites (either synthetic or natural clay based) greatly reduce the HRR of a material, making it more fire safe, they do not provide ignition resistance by themselves, at least, at practical loadings. Specifically, the cone calorimeter HRR curve data appear to support that these nanocomposites continue to burn once ignited, rather than self‐extinguish. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of the Amount and Funtionalization Grade of PPgMA Compatibilization Agent in Polypropylene/clay nanocomposites

Summary Polypropylene-organoclay nanocomposites were prepared by melt processing via twin-screw extrusion of three components: PP, maleic anhydride modified polypropylene oligomers (PPgMA) and clays modified by octadecylammonium for the purpose of evaluating the effect of the amount of the grafted compound of the PP on the mechanical properties. Two ways were used to compatibilize the PP and nanoclay. First, varying the PPgMA percentage on the nanocomposite, and secondly its degree of functionalization. The rheological and mechanical properties were studied in relationship to the microstructure of the nanocomposites varying both parameters. X-ray diffraction was used to detect the formation of nanocomposites and the transmission electron microscopy (TEM) was used to characterise the dispersion of the organoclay.