PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.     

Exfoliated high-impact polystyrene/MMT nanocomposites prepared using anchored cationic radical initiator-MMT hybrid

High-impact polystyrene (HIPS)/montmorillonite (MMT) nanocomposites were prepared via in-situ polymerization of styrene in the presence of polybutadiene, using intercalated cationic radical initiator-MMT hybrid. Incomplete exfoliation of the silicate layers in the HIPS nanocomposites was observed when a bulk polymerization was employed. On the other hand, the silicate layers were efficiently exfoliated in the PS matrix during a solution polymerization, due to the low extra-gallery viscosity, which can facilitate the diffusion of styrene monomers into the clay layers. The resulting exfoliated HIPS/MMT nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, particle size analysis, gel permeation chromatography, and dynamic mechanical analysis. The nanocomposites exhibited significant improvement in thermal and mechanical properties. For example, about 50% improvement in Young’s modulus was achieved with 5 wt% of clay, compared to the unmodified polymer counterpart.     

Structure and thermal stability of PMMA/MMT nanocomposites as denture base material

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by in situ suspension polymerization. MMT was previously organically modified by three different intercalating agents: methacrylatoethyl trimethyl ammonium chloride (DMC), dodecylamine (12CNH), and hexadecyl allyl ammonium chloride (HADC). The structures of the nanocomposites were investigated by X-ray diffraction and transmission electron microscopy, while the interaction between PMMA and MMT was characterized by Fourier transform infrared spectroscopy. The molecular mass of the extracted PMMA was measured by gel permeation chromatography. The thermal stability of PMMA/MMT nanocomposites was evaluated by thermogravimetric and differential scanning calorimetry. The results indicated that PMMA/MMT nanocomposites were successfully prepared and the interaction between PMMA and MMT of PMMA/MMT–HADC nanocomposites was the strongest. The thermal stability of the nanocomposites was improved and found to be optimal for PMMA/MMT–HADC with T ₁₀ increasing to 304 °C, 52 °C higher than that of neat PMMA.     

Polystyrene/MMT nanocomposites prepared by soap-free emulsion polymerization with high solids content

Polystyrene/montmorillonite (PSt/MMT) nanocomposite latexes have been synthesized by soap-free emulsion polymerization using MMT clay platelets as stabilizer. Small amounts of methacrylic acid were used as auxiliary monomer to promote clay adhesion to the surface of the particles. Overall solids content of the composite latexes in complete absence of coagulation of up to 30.7?wt% are reported under batch conditions. The 3?wt% MMT clay platelets were sufficient to maintain the colloidal stability and increasing MMT clay content resulted in the increase of particle diameter due to the improved viscosity of reaction medium. Transmission electron microscopy results demonstrate the existence of MMT platelets on the particle surface. X-ray diffraction spectroscopy (XRD) results show that an exfoliated structure of PSt/MMT nanocomposites was obtained in this study with the absence of d₀₀₁ diffraction peak of MMT in the XRD region.     

Kinetic study of the thermal degradation of PS/MMT nanocomposites preparedwith imidazolium surfactants

Styrene and montmorillonite organically modified with imidazolium surfactants (MMT) at various alkyl chain lengths (C₁₂, C₁₆ and C₁₈) were used to prepare the corresponding PS/MMT/C₁₂, PS/MMT/C₁₆ and PS/MMT/C₁₈ nanocomposites by in situ polymerization. XRD and TEM analyses evidenced the formation of both intercalated and exfoliated structures. The glass transition temperatures (T _g) of nanocomposites, as well as that of neat PS, were obtained by DSC measurements. The thermal degradations were carried out in the scanning mode, in both inert and oxidative environments, and the initial temperatures of decomposition (T _i) and the apparent activation energies of degradation (E _a) were determined. Due to an oxidative degradation mechanism, the T _i and E _a values in air atmosphere were lower than those under nitrogen. The results indicated that nanocomposites are more thermally stable than polystyrene, and suggested an increasing degree of exfoliation as a function of alkyl chain length of surfactant, associated with enhancing thermal stability.     

Manufacturing homogenous PVC/graphene nanocomposites using a novel dispersion agent

The goal of the study was to prepare a graphene (GN) dispersion in a poly (vinyl chloride) (PVC) solution with enhanced stability of the nanofiller thanks to the application of curcuma extract (CE). The stable dispersion was used to obtain PVC/GN nanocomposites with more homogeneous graphene by the solvent evaporation method. The CE effectiveness was compared with two commercially available dispersants in the form of oleic acid (OA) and polysorbate 80 (P80).The chemical composition of the CE was examined by Fourier-transform infrared spectroscopy. The dispersion stability was tested by the multiple light scattering method (Turbiscan Lab) and evaluated visually over a period of 40 days. The homogeneity of the filler's dispersion in the PVC matrix was evaluated by scanning electron microscopy and Raman spectroscopy.The application of the dispersing agents led to improved stability of the graphene dispersion in PVC solution. CE was the agent that most effectively improved the homogeneity of graphene dispersion, both in dispersions in a PVC solution and in PVC/GN nanocomposite films.     

RAFT-mediated polystyrene-clay nanocomposites prepared by making use of initiator-bound MMT clay

The initiator 2,2′-azobis(2-(1-(2-hydroxyethyl)-2-imidazolin-2-yl)propane)dihydrochloride monohydrate (VA060) was used to surface-modify sodium montmorillonite clay (Na-MMT). The obtained organically modified clay was then used as a macro-initiator in the preparation of polystyrene-clay nanocomposites by in situ free radical polymerization of styrene in bulk. The polymerization was carried out in the presence of various reversible addition-fragmentation chain transfer (RAFT) agents: 1,4-phenylenebis(methylene)dibenzenecarbodithioate (PCDBDCP), didodecyl-1,4-phenylenebis(methylene)bistrithiocarbonate (DCTBTCD) and 11-(((benzylthio)-carbonothioyl)thio)undecanoic acid (BCTUA). All of the nanocomposites prepared were found to have intercalated morphologies. In the absence of RAFT agents, typical uncontrolled free radical polymerization occurred, giving polystyrenes with high molar masses and high polydispersity indices. In contrast, when the polymerization was conducted in the presence of any of the RAFT agents, the polymerization was found to occur in a controlled manner, as the polystyrene-clay nanocomposites obtained contained polymer chains of narrow polydispersities. The influences of clay loading and molar mass on thermal stability of the polystyrene-clay nanocomposites were investigated. Increases in the clay loading or the molar masses resulted in improvement of the thermal stability of the nanocomposites.     

Study of the quiescent and shear‐induced crystallization kinetics of intercalated PTT/MMT nanocomposites

An intercalated nanocomposite made of montmorillonite nanoclay, MMT, and poly(trimethylene terephthalate), PTT, was produced by twin screw extrusion and characterized by wide angle X‐ray diffraction, WAXD, and transmission electron microscopy, TEM. The quiescent isothermal and non‐isothermal and the flow‐induced crystallization of the nanocomposite were studied by differential scanning calorimetry, DSC, polarized light optical microscopy, PLOM, and rheometry. The quiescent results showed that the nanoclay acted as an efficient nucleating agent for the PTT, which result in an anticipation of the transition temperature between regimes II and III of crystallization. The fold interfacial free energy, σ_e, of the PTT in the nanocomposite during regime III was lower than in the pure state; that is, the pure PTT developed spherulites, whereas in the nanocomposite it produced a paracrystalline morphology. Under shear rate, the total times for crystallization in the nanocomposite were higher than in the pure PTT. In flow‐induced crystallization, a fibrillar nucleus must be formed as a result of chain orientation. In the nanocomposite, chain orientation only occurred after the percolated structure was broken. Therefore, the formation of a fibrillar nucleus in the nanocomposite took more time, which increased the total crystallization time. Inc. J Polym Sci Part B: Polym Phys 48: 113–127, 2010     

Influence of Fe‐MMT on crosslinking and thermal degradation in silicone rubber/clay nanocomposites

In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd.     

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

In this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na⁺‐MMT nanocomposites are decreased with increasing the amount of Na⁺‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na⁺‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005     

Effects of chemical modifications and MMT nanoclay addition on transport phenomena of naturally woven coconut sheath/polyester nanocomposites

Studies on the behavior of molecular transport properties such as thermal conductivity, gas permeability, volume and surface resistivity have been carried out for the naturally woven coconut sheath (CS) fiber reinforced composites with the addition of nanoclay and chemical treatment of fiber. The compression molding technique was used to fabricate the coconut sheath/clay reinforced hybrid composites. The morphological studies such as X-ray diffractogram (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been carried out for polyester nanocomposites and coconut sheath fiber. The decreased gas permeability, thermal conductivity and volume and surface resistivity have been observed with increasing the weight percentage of nanoclay in polyester matrix. In chemical modifications, the alkali and silane treated coconut sheath reinforced composites have shown great influence on the transport properties due to the increasing hydrophilic nature by the topographical changes at the fiber surface. Dielectric strength has also been reported in this paper for all types of composites. Infra-red (IR) spectra have also been taken to study the physical and chemical structural changes of treated coconut sheath.     

Preparation and properties of organo‐modifier free PET/MMT nanocomposites via monomer intercalation and in situ polymerization

In order to prevent the properties, especially transparency, color and health security, of PET/clay nanocomposites from being deteriorated due to the thermal degradation of clay organo‐modifer, we had directly modified sodium montmorillonite (Na⁺‐MMT) with PET's monomer, bis (hydroxyethyl) terephthalate (BHET) which had a degradation temperature higher than 400°C, and successfully prepared the hybrids via in situ polymerization. Nanodispersion of clay and the intercalated morphology were determined, and compared with PET/Na⁺‐MMT hybirds in which Na⁺‐MMT was directly added without any treatment. Improved mechanical properties and T_g were observed for the prepared PET/ BHET‐modified clay composites. More importantly, the film produced from the composites had the same transparency as that of pure PET even when 2 wt% of clay was added. Non‐isothermal and isothermal crystallization experiments showed a very good neculation capability of the nano‐dispersed clay, particularly at higher crystallization temperatures. Copyright © 2009 John Wiley & Sons, Ltd.     

Microstructure and dynamic mechanical analysis of extruded layered silicate PVC nanocomposites

The nanostructure and dynamic mechanical properties of polyvinyl chloride (PVC) and the bentonite nanocomposites have been investigated. Nanocomposites with 5 wt% concentration of bentonite were prepared by melt extrusion followed by two‐roll‐milled processing. Atomic force microscopy (AFM) and wide‐angle X‐ray scattering (WAXS) were utilized to study the micro and nanostructure of the two‐roll‐milled sheets. The nanocomposites were compounded with two types of coupling agents: KZTPP® and Tamol 2001®. Optical microscopy showed that the materials remained optically transparent, i.e. they did not show evidence of nanoclay agglomeration. The WAXS patterns of PVC‐bentonite‐KZTPP nanocomposite were anisotropic, suggesting flow‐induced preferred orientation of the nanoplates. Moreover, the 001 reflection of the bentonite was shifted toward smaller angles, suggesting that the nanoplates were intercalated by the macromolecules. On the other hand, the WAXS patterns of PVC‐bentonite‐Tamol 2001 nanocomposite remained isotropic and did not show evidence of bentonite, suggesting exfoliation of the nanoplates. The nanocomposites showed an increase in glass transition temperature T_g, with the sequence T_g,PVC < T_g,KZTPP < T_{g,Tamol 2001}. Moreover, dynamic mechanical analysis (DMA) showed an increase in mechanical moduli and activation energy (and a decrease in the intensity of the mechanical damping Tan δ) following the same sequence. Interestingly, the improvement in mechanical moduli became more pronounced above the glass transition temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of Modified MMT on Mechanical Properties of EVA/MMT Nanocomposites and Their Foams

In this study, nanocomposites of poly(ethylene-co-vinyl acetate) with two kinds of organically modified montmorillonite (OMMT) were prepared by melt intercalation. Their structures and mechanical properties were characterized by X-ray diffraction (XRD) and tensile test respectively. Especially, foaming of these nanocomposites mixed with chemical blowing agent was carried out through compression molding. Influences of OMMT on foaming ratio and mechanical properties were investigated by density test, tensile test and tear test. Results revealed that both kinds of OMMT with proper content increased tensile strength and Young's modulus of nanocomposites without a compromise of elongation at break. For foaming, OMMTs apparently improved foaming ratio and in particular, one of them can improve tear strength, tensile strength, Young's modulus and elongation although the density was decreased.     

Functional copolymer/organo‐MMT nanoarchitectures. III. Dynamic mechanical behavior of poly(IA‐co‐BMA)‐organo‐MMT clay nanocomposites

Functional copolymer/organo‐silicate [N,N′‐dimethyldodecyl ammonium cation surface modified montmorillonite (MMT)] layered nanocomposites have been synthesized by interlamellar complex‐radical copolymerization of pre‐intercalated itaconic acid (IA)/organo‐MMT complex as a “nanoreactor” with n‐butyl methacrylate (BMA) as an internal plasticization comonomer in the presence of radical initiator. Comparative analysis of physical structure, dynamic mechanical analysis parameters, and surface morphology of the obtained copolymers and their nanocomposites indicated that the interlayer H‐bonding and flexible n‐butyl ester linkages take place an important role in interlamellar copolymerization and intercalation/exfoliation of copolymer chains. It was found that nanocomposites' dynamic mechanical properties strongly depended on the force of interfacial H‐bonding and amount of BMA units. An increase in both of these parameters leads to enhanced intercalation and exfoliation in situ processes of copolymer chains and the formation of hybrid nanocomposites. Copyright © 2009 John Wiley & Sons, Ltd.     

Cure behavior of epoxy resin/MMT/DETA nanocomposite

The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict the gel time t _g and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation time t _gand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t_1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60°C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent activation energy of the cure reaction after gelation point. There is no special curing process required for the formation of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of processing technique on morphology and mechanical properties of PVC nanocomposites

This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were prepared on a two-roll mill or in a microcompounder, both were either processed once or via a masterbatch containing 20 phr MMT. The MMT was treated with non-ionic surfactants and analysed by thermo gravimetric analysis and X-ray diffraction prior to being added. The final composites were analysed and tested using X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), tensile test, and Charpy impact test. The dispersion was found to be best in the roll milled samples prepared via the masterbatch and the elongation at break and impact strength was also better for the roll milled samples. E-modulus and tensile strength, on the other hand, were significantly better for the microcompounded samples despite the larger particle size. This can be explained by a higher degree of orientation in these samples. Finally, it must be stated that the change in properties are not satisfactory. Although we see an increase in E-modulus, the decreased impact properties are not acceptable. The main reason for this is the lack of compatibility between the clay particles as observed by high resolution SEM.     

Preparation of PAA/AM/MMT Hybrid by Intercalation Polymerization

Over the last few years, Montmorillonite (MMT) was widely used as a special inorganic material for preparing Polymer/MMT nanocompsites. MMT is a clay imineral consisting of stacked silicate sheets whose thickness is about 10A. Through intercalation a large number of polymer-clay nanocomposites have been prepared such as Nylon-clay hybrid [1], PS-clay hybrid [2], Poly (methyl methacrylate) (PMMA)-clay hybrid [3], etc. In this article, the synthesis and properties of Poly (acrylic acid/acrylamide)/MMT hybrid (PAAAM/MMT) were studied. X-ray diffraction and Transmission electron microscopy were used to characterize the hybrid material. DSC has been used to study its property. Results showed that the intercalating reagents have entered the space of MMT's layers and enlarged them. At the same time, the MMT dispersed homogeneously in acrylic acid and acrylamide monomers that allow MMT to disperse in PAAAM matrix in the monolayer form.     

Development of PVC/Silica Hybrids Using PVC Plastisols

A novel method for producing a plasticised PVC with increased porosity has been developed, by the use of an organic-inorganic hybrid. Silica was produced in situ from tetraethoxysilane via a hydrolytic sol-gel processing route. Tetrahydrofuran was used as co-solvent, and γ-glycidyloxypropyl-trimethoxysilane as coupling agent. The films produced were transparent, with moderate mechanical properties. A film containing 20% silica showed a 45% increase in water vapour permeability.     

乳液聚合法制备剥离型PS/MMT纳米复合材料

以阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)和烯丙基十八烷基二甲基氯化铵(ATAC)为插层处理剂改性蒙脱土(MMT),原位乳液聚合分别制备了PS/C18MMT和PS/AC18MMT两种纳米复合材料.XRD和TEM分析表明,MMT均被剥离成单个或几个片层无规的分散在PS基体中,TGA分析表明,MMT的加入提高了材料的耐热性能,当PS基体与有机化处理的MMT片层发生一定的化学连接后,PS/AC18MMT纳米复合材料表现出更好的耐热性能.动态力学分析表明,MMT的加入提高了PS的玻璃态储能模量,降低了材料的动态损耗;PS/AC18MMT纳米复合材料的玻璃化温度较PS有所提高,而PS/C18MMT的玻璃化温度与PS相比略有降低.