Gelation performance of poly(ethylene imine) crosslinking polymer–layered silicate nanocomposite gel system for potential water‐shutoff use in high‐temperature reservoirs

Polymer gels have been widely used for water shutoff in mature oil fields. In this paper, polyacrylamide (PAM)–montmorillonite (MMT) nanocomposites (NC) were prepared through in situ intercalative polymerization. Fourier transform infrared spectroscopy and X‐ray diffraction were conducted to characterize the prepared PAM/MMT nanocomposites. The gelation performance of poly(ethylene imine) (PEI) crosslinking PAM/MMT nanocomposite gel system (NC/PEI gel system) was systematically investigated by bottle testing and viscosity measurement methods. The results showed that the gelation performance of the NC/PEI gel system was greatly affected by the total dissolved solids, PAM/MMT nanocomposite concentration, and PEI concentration. The NC/PEI gel system exhibited much better thermal stability and gelation performance than the PAM/PEI gel system at the same conditions. The gelation performance after flowing through porous media of the NC/PEI gel system before injection and that of the subsequently injected gel system was different. The gel strength decreased and the gelation time was delayed after the gel system before injection was flowed through porous media. However, the gel strength of the subsequently injected gel system did not decrease, and only the gelation time was delayed after flowing through porous media. This study suggests that the NC/PEI gel system can be used as a potential water‐shutoff agent in high‐temperature reservoirs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44243.     

Performance of fly ash based polymer gels for water reduction in enhanced oil recovery: Gelation kinetics and dynamic rheological studies

The complexity of well and reservoir conditions demands frequent redesigning of water plugging polymer gels during enhanced oil recovery (EOR). In the present study, we developed coal fly ash (CFA) based gels from polyacrylamide (PAM) polymer and polyethyleneimine (PEI) crosslinker for water control in mature oil fields. The CFA acts as an inorganic additive to fine-tune gelation performance and rheological properties of PAM/PEI gel system. Hence, effects of various CFA (0.5 to 2 wt%), PAM (2 to 8.47 wt%) and PEI (0.3 to 1.04 wt%) concentrations on gelation kinetics and dynamic rheology of pure PAM/PEI gel and PAM/PEI-CFA composite gels were studied at a representative reservoir temperature of 90 oC. Experimental results reveal that gelation time of pure PAM/PEI gel increases with increasing CFA addition. Further observation demonstrates that increasing PAM and PEI concentrations decreases the gelation times of PAM/PEI-CFA composite gels. Gelation time was found to be within 3-120 hours. Understanding the property of reaction order enables better prediction of gelation time. Dynamic rheological data show that viscoelastic moduli (G′ and G″) of various PAM/PEI-CFA composite gels improved better as compared to the pure PAM/PEI gel across the strain-sweep and frequency-sweep tests. SEM analysis of selected samples at 72 hours and 720 hours of gelation activity consolidated gelation kinetics and dynamic rheological results. These polymer gels are excellent candidates for sealing water thief zones in oil and gas reservoirs.     

Preparation and characterization of elastomer‐based nanocomposite gels using an unique latex blending technique

Nanocomposite (NC) gels based on natural rubber (NR) and styrene butadiene rubber (SBR) were prepared by using a unique latex blending technique. These NC gels were prepared by first blending the water swollen unmodified montmorillonite clay (Na⁺‐MMT) suspension into the respective latices followed by prevulcanization to generate crosslinked nanogels. Use of water assisted fully delaminated Na⁺‐MMT suspension resulted in predominantly exfoliated morphology in the NC gels, as revealed by X‐ray diffraction study and transmission electron microscopy. Addition of Na⁺‐MMT significantly improved various physical, mechanical and thermal properties of these NC gels. For example, 6 phr of Na⁺‐MMT loaded NR based NC gels registered 54% and 200% increase in tensile strength and Young's modulus, respectively, compared to the unfilled NR gels. SBR based NC gels also showed similar level of improvement in mechanical properties. Mechanical properties of NC gels prepared using this route were also compared with the NC gels prepared by co‐coagulation and conventional curing technique and found to be superior. In the case of dynamic mechanical properties, NC gels showed higher glass transition temperatures along with a concomitant increase in storage moduli, compared to the unfilled gels. These Na⁺‐MMT reinforced NC gels also exhibited markedly improved thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions: comparison of theoretical and experimental results

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/sodium montmorillonite with chromium triacetate as ionic cross-linker. The effect of montmorillonite content on equilibrium swelling in NaCl and CaCl₂ solutions, ultimate storage modulus and effective cross-link density was evaluated. The limiting storage modulus of the nanocomposite (NC) hydrogels dropped by increasing montmorillonite content up to 1,000?ppm, and then it increased by further montmorillonite loading. A mechanism is proposed for the formation of PAMPS/Na⁺-MMT/Cr³⁺ NC hydrogels. According to this mechanism, the drop in limiting storage modulus of the NC gels at low Na⁺-MMT concentration is due to ionic interactions between the negative layers of sodium montmorillonite and Cr³⁺, leading to decreased cross-link density. However, the increase of the limiting storage modulus of the NC gels at high clay concentration results from the strong interactions between the polyacrylamide chains and clay platelets. The equilibrium swelling ratio of the NC networks decreased with increase of montmorillonite content in both aqueous NaCl and CaCl₂ solutions. In addition, the experimental swelling data of these NC hydrogels were described by a modified Flory?CRehner theory. The modified model was sensitive to montmorillonite concentration and it described adequately the swelling data for NC gels in NaCl solutions. Nevertheless, theoretical predictions showed some deviations from experimental results for swelling of NC hydrogels in CaCl₂ solutions.     

Experimental research of hydroquinone (HQ)/hexamethylene tetramine (HMTA) gel for water plugging treatments in high‐temperature and high‐salinity reservoirs

Polymer gel, as a water plugging treatment agent, has been successfully used in enhanced oil recovery (EOR) of mature oil fields. A new thermal‐resistance and salt‐tolerance polymer gel was developed based on HPAM and HQ/HMTA under the condition of high‐temperature (100.8 °C) and high‐salinity (up to 19.8 × 10⁴ mg/L and Ca²⁺&Mg²⁺ 0.8 × 10⁴ mg/L). The influence factors of gelling performance and coreflood performances were studied, the microstructure of the gel was observed with the environmental scanning electron microscopy, and gelation mechanism was proposed to illuminate the detailed gelation process. The gelation time decreases and the gel strength increases with the increase of polymer concentration, crosslinker concentration, or temperature. Although shearing had a negative effect on the viscosity of gelling solution, the gel strength, and the stability of gel have not been affected. The gelling solution has a good ability of injection and could selectively flow into high permeable zone. Additionally, the plugging rate increases and stays above 85% with the increase of the permeability or the gel strength. The microstructure of the gel confirms that the gel formed a three‐dimensional network structure. Based on the microstructure and the reaction process of the gel, a possible gelation mechanism is proposed. This study suggests that the gel system can be used in harsh reservoir conditions and the gelation time and gel strength can be controlled with adjusting the formation rate and the concentration of crosslinking agents. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44359.     

Effects of cyclization and pendant vinyl group reactivity on the swelling behavior of polyacrylamide gels

A series of polyacrylamide (PAAm) gels were prepared by free-radical crosslinking copolymerization of acrylamide and N,N′-methylenebis(acrylamide) (BAAm) in water at various crosslinker (BAAm) and chain transfer agent (isopropyl alcohol, IPA) concentrations. It was shown that only 5% of the crosslinker used in the feed forms effective crosslinks in the final hydrogels. At BAAm contents as high as 3 mole%, the equilibrium swelling ratio of the gels in water is independent of the crosslinker content in the feed. This is due to the prevailing multiple crosslinking reactions during the gel formation process. At a fixed crosslinker content, the onset of gelation is shifted towards higher conversions and reaction times as the amount of IPA increases. Addition of IPA in the monomer mixture also increases the equilibrium swelling ratio of PAAm gels. It was shown that the gel crosslinking density increases on rising IPA concentration in the feed due to the increasing rate of intermolecular crosslinking reactions. Received: 30 May 1997/Accepted: 26 June 1997     

Synthesis and properties of a poly(acrylic acid)/montmorillonite superabsorbent nanocomposite

A novel superabsorbent nanocomposite was synthesized through the intercalation polymerization of partially neutralized acrylic acid and a sodium‐type montmorillonite powder with N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate and sodium sulfite as a type of mixed redox initiator. The effects of such factors as the amounts of the sodium‐type montmorillonite, crosslinker, and initiator and neutralization degree on the water absorbency of the nanocomposite were investigated. The structure and micrographs of the superabsorbent were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The results showed that the acrylic acid monomer was successfully intercalated into the montmorillonite layers and banded together with them. The montmorillonite layers were exfoliated and basically dispersed in the composite on a nanoscale after the polymerization. The water absorbency of the nanocomposite was much higher than that of pure poly(acrylic acid). The optimum absorbency of the nanocomposite in distilled water and saline water (NaCl concentration = 0.9%) was 1201 and 83 g/g, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5725–5730, 2006     

Studies of reinforcement behavior of unique elastomer‐based nanocomposite gels

Unique nanocomposite (NC) gels were prepared by blending water swollen unmodified montmorillonite clay suspension with natural rubber (NR) and styrene‐butadiene rubber (SBR) latices followed by prevulcanization. These were extensively characterized by dynamic light scattering, solvent swelling, tensile, and dynamic mechanical measurements. Reinforcement behavior of NC gels was investigated by adding NC gels into virgin NR and SBR matrices at various loadings. The distribution and morphology of NC gels in the elastomer matrices was studied by X‐ray dot mapping and high‐resolution transmission electron microscopy. Experimental results indicated tremendous improvement of tensile strength (TS) and modulus of the NC gel‐filled matrices along with noticeable changes in dynamic mechanical and rheological properties. Compared with virgin NR, the TS of 16 phr NC gel‐filled NR system increased by 117%. Similar level of enhancement of TS was also registered for the NC gel‐filled SBR systems. NC gel‐filled systems showed higher shear viscosities and lower die‐swell values compared with their virgin counterparts. Contemporary particulate composite and nanofiller reinforcement models were used to understand the reinforcing behavior of these NC gels. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Gelation studies on acrylic acid‐based hydrogels via in situ photo‐crosslinking and rheology

The gelation characteristics of acrylic acid (AA)‐based hydrogels were investigated using real time in situ photocrosslinking and rheological measurements. The gel point and gelation times were established using Winter–Chambon criteria. Frequency independence of tan δ was observed in all cases, such that G′ and G″ scaled as ～ωⁿ. The Flory–Stockmayer theory was used alongside other indices in order to probe the gelation and the post‐gelation characteristics of the critical gels and the fully formed hydrogels. Network relaxation exponents (n) were influenced by the concentrations of AA and methylene bis‐acrylamide. The gel stiffness (S) decreased with an increase in the concentration of the monomer and of the concentration of the crosslinker, while network branching decreased (lower fractal dimensions) at the gel point. The conversion at the gel point was found to be iso‐conversion with respect to the intensity of the UV irradiance used in the photocrosslinking reactions (1–20 mW/cm²). Thus, network clusters and the crosslinking reaction mechanism were the same irrespective of radiation intensity, although the rates of the reactions were affected. Having sufficient amounts of reactive species at the time of cure drive the crosslinking reactions beyond the gel point to greater crosslink density and smaller mesh sizes. The effects of auto‐acceleration and free‐volume were observed and shown to have key effects on the gelation mechanisms and the branching topographies of the network, when the concentration of the known polyacrylamide medium were not controlled. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46691.     

Preparation and investigation of the physical and chemical properties of clay-based polyacrylamide/Cr (III) hydrogels as a water shut-off agent in oil reservoirs

The effects of clay (montmorillonite and kaolinite) in the hydrogels were investigated on various properties such as syneresis and strength of thermal and salinity situations in one of the southern Iranian oil reservoirs. The X-ray diffraction (XRD) patterns exhibited a significant increase in interplanar spacing between the montmorillonite clay layers, varying from the initial value of 12.43 °A to 19.45 °A, which evidences the intercalation formation. It was revealed that even increasing of the interlayer spacing due to kaolinite modification had no effect on the clay compositions. Formation water was used to study the strength of the hydrogel in the presence of ions. The results indicated that 15 wt% increase of kaolinite clay (modified and non-modified) leads to 20% decrease of the hydrogels’ syneresis. The diffusion of polymer chains between the clay layers increased the elastic modulus (G′) of the prepared hydrogels with modified kaolinite and montmorillonite, where the maximum value of G’ was observed in 3 wt% of montmorillonite. Finally, the thermogravimetric analysis (TGA) indicated an increase in the thermal stability of the mentioned hydrogels.     

Polyacrylamide–clay nanocomposite materials prepared by photopolymerization with acrylamide as an intercalating agent

A series of nanocomposite materials consisting of water‐soluble polyacrylamide (PAA) and layered montmorillonite (MMT) clay platelets were prepared by the effective dispersion of the inorganic nanolayers of the MMT clay in the organic PAA matrix via in situ ultraviolet‐radiation polymerization. The acrylamide monomers functioned as both the intercalating agent and the reacting monomers. As a representative procedure for the preparation of the nanocomposites, organic acrylamide monomers were first intercalated into the interlayer regions of acrylamide‐treated organophilic clay hosts, and this was followed by one‐step ultraviolet‐radiation free‐radical polymerization with benzil as a photoinitiator. The as‐prepared polyacrylamide–clay nanocomposite (PCN) materials were subsequently characterized by Fourier transform infrared spectroscopy, wide‐angle powder X‐ray diffraction, and transmission electron microscopy. The effects of the material composition on the thermal stability, optical clarity, and gas‐barrier properties of pristine PAA and PCN materials, in the forms of fine powders and membranes, were also studied by differential scanning calorimetry, thermogravimetric analysis, ultraviolet–visible transmission spectroscopy, and gas permeability analysis. The molecular weights of PAA extracted from PCN materials and pristine PAA were determined by gel permeation chromatography with tetrahydrofuran as an eluant. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3489–3496, 2004     

Passive microrheology for measurement of gelation behavior of a kind of polymer gel P(AM‐AA‐AMPS)

One kind of polymer gel P(AM‐AA‐AMPS) was prepared by radical aqueous copolymerization, using acrylamide (AM), acrylic acid (AA) and 1‐acrylanmido‐2‐methylpropanesulfonic acid (AMPS) as monomers, N,N‐methacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. The microstructure and molecular structure of the polymer gel were characterized by environmental scanning electron microscope (ESEM), infrared spectrometer (IR) and thermal gravity analysis (TGA). Main factors affecting the gelation behavior of P(AM‐AA‐AMPS) were qualitatively and quantitatively studied by multi‐speckle diffusion wave spectroscopy (MS‐DWS) technology, and the elasticity index (EI) and macroscopic viscosity index (MVI) were introduced to evaluate the elasticity and viscosity of the polymer gel. The results show that the synthesized P(AM‐AA‐AMPS) polymer gel has three‐dimensional network structure gel with thermally resistant and salts tolerant groups. The EI and MVI of solution increase abruptly during the gelation time and the two indexes tend to stabilize. Under certain conditions, with the increase of reaction temperature and concentration of monomers and initiator, the gelation time of polymer gel gets shorter and the gel strength increases; with the increase of concentration of crosslinker, the strength of polymer gels increases, while the gelation time remains almost unchanged. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43364.     

Study on strength and gelation time of polyacrylamide/polyethyleneimine composite gels reinforced with coal fly ash for water shut‐off treatment

This study investigates the influence of coal fly ash (CFA) as a reinforcing material on the strength and the gelation of polyacrylamide (PAM)/polyethyleneimine (PEI) composite gels. Pure PAM/PEI gel and PAM/PEI gels containing CFA up to 2 wt % were synthesized via the cross‐linking reaction between PAM and PEI solutions at room temperature (25°C) in distilled water dispersed with CFA. The strength of each composite gel was measured at temperature of 80°C, while the gelation was determined from 80°C to 95°C. Rheological measurements indicated that the strength of PAM/PEI composite gels filled with CFA contents was significantly rigid and stronger than that of pure PAM/PEI gel as a result of the enhanced interfacial interaction of well‐dispersed CFA contents in PAM/PEI gel matrix. The gelation times of PAM/PEI gels containing CFA up to 2 wt % deviated from the gelation time of pure PAM/PEI gel. It was further observed that an increase in temperature resulted in a decrease in gelation time of PAM/PEI gel containing 2 wt % CFA. The scanning electron microscopy revealed the surface micrographs of PAM/PEI gels filled with CFA to be very dense without any noticeable micropores. The micropores were absent as scanning was performed on the dried composite gels. It also establishes the strong interaction between CFA and PAM/PEI gel matrix. Experimental findings showed that PAM/PEI composite gels reinforced with CFA are potential candidates for total water shut‐off treatment in oilfields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41392.     

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     

Studies on preparation and properties of porous biodegradable poly(NIPAAm) hydrogels

A series of biodegradable porous hydrogels, based on thermosensitive N‐isopropylacrylamide (NIPAAm) and biodegradable crosslinker‐polycaprolactone diacrylate (PCLdA) that was synthesized from polycaprolactone diol with acryloyl chloride were prepared by photopolymerization at low temperature. The effect of the crosslinker content and gelation method on the swelling behaviors and physical properties for the poly(NIPAAm) hydrogels was investigated. Results showed that the swelling ratio of the gel in deionized water decreased with an increase of the content of polycaprolactone (PCL) segment in the poly(NIPAAm) hydrogels. The properties of the gels crosslinked with PCLdA were compared with those crosslinked with N, N′‐methylenebisacrylamide (NMBA). The results showed that the critical gel transition temperatures (CGTT) of the gels crosslinked with PCLdA were lower than those of the gels crosslinked with NMBA due to the hydrophobicity of the PCL segment. The results also showed that the gels crosslinked with PCLdA had higher mechanical strength and crosslinking density than those gels crosslinked with NMBA. Comparing the porous gels with nonporous gels, the results showed that the swelling ratio and CGTT of the porous gels were higher than those of the nonporous gels, and the transition temperature curve was smoother for the porous gels. The porous gels also exhibited more rapid thermal response and faster degradation rates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chitosan‐modified nanoclay–poly(AMPS) nanocomposite hydrogels with improved gel strength

BACKGROUND: Making (nano)composite structures is one of the efficient approaches for strengthening hydrogels extended in recent years. The present paper deals with the synthesis and properties of novel nanocomposite hydrogels based on 2‐acrylamido‐2‐methylpropane‐1‐sulfonic acid (AMPS). Initially, a bio‐modified clay, chitosan‐intercalated montmorillonite (chitoMMT), was prepared. Then, this was incorporated into the polymerization of AMPS in the presence of a macro‐crosslinker, i.e. poly(ethylene glycol) dimethacrylate, to yield super‐swelling nanocomposite hydrogels. The swelling capacity as well as some structural, rheological and thermomechanical properties of the hydrogels were studied and compared with those of the clay‐free counterpart. RESULTS: ChitoMMT exhibited no toxicity, which was confirmed using cell‐culture testing. A chitoMMT content of ca 6% was found to be the most favourable content of the bio‐modified clay for achieving a product with improved properties (i.e. the highest gel content, the highest gel strength and optimal thermal stability). Based on a dynamic mechanical thermal analysis study, an increased glass transition temperature (98.2 °C) and improved rubbery modulus (up to 238% higher than that of the clay‐free counterpart) were recorded. Thermogravimetric analysis verified that the thermal stability of nanocomposite samples was higher than that of clay‐free samples. CONCLUSION: Owing to the non‐toxicity of the incorporated chitoMMT, the strengthened hydrogels may be considered as potential candidates for bio‐applications. Copyright © 2009 Society of Chemical Industry     

A facile method for reinforcing poly(N‐isopropylacrylamide)‐hectorite clay nanocomposite hydrogels by heat treatment

A facile method was explored to reinforce the poly(N‐isopropylacrylamide) (PNIPAm)‐hectorite nanocomposite hydrogel (NC gel) by heat treatment at temperature above the volume phase transition temperature (VPTT), which enhanced mechanical strength and reduced swelling capacity with denser microporous structure as compared with the non‐treated NC gel. This reinforcement effect was increased by increasing treating temperature and/or treating time, which still remained even after swelling, indicating an irreversible structure change in the treated NC gels. Heat treatment became more effective when the NC gel contained higher clay content. The quartz crystal microbalance (QCM) data showed that the interaction between PNIPAm chains and clay platelets became stronger at temperatures higher than the VPTT, causing an increase in the crosslinking density of the treated NC gels. A strong hydrogel was obtained by heat treatment of the aqueous mixture of PNIPAm and hectorite clay for the first time. POLYM. COMPOS., 37:1557–1563, 2016. © 2014 Society of Plastics Engineers     

Electron beam synthesis and characterization of poly(vinyl alcohol)/montmorillonite nanocomposites

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT) nanocomposites in the form of films were prepared under the effect of electron beam irradiation. The PVA/MMT nanocomposites gels were characterized by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical measurements. The study showed that the appropriate dose of electron beam irradiation to achieve homogeneous nanocomposites films and highest gel formation was 20 kGy. The introduction of MMT (up to 4 wt %) results in improvement in tensile strength, elongation at break, and thermal stability of the PVA matrix. In addition, the intercalation of PVA with the MMT clay leads to an impressive improved water resistance, indicating that the clay is well dispersed within the polymer matrix. Meanwhile, it was proved that the intercalation has no effect on the metal uptake capability of PVA as determined by a method based on the color measurements. XRD patterns and SEM micrographs suggest the coexistence of exfoliated intercalated MMT layers over the studied MMT contents. The DSC thermograms showed clearly that the intercalation of PVA polymer with these levels of MMT has no influence on the melting transitions; however, the glass transition temperature (T_g) for PVA was completely disappeared, even at low levels of MMT clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1129–1138, 2006     

Preparation and characterization of light‐cured methacrylate/montmorillonite nanocomposites

Polymer/clay nanocomposites were prepared from dimethacrylate monomers, commonly used in dental restorative resins, and an organically modified silicate (montmorillonite). The photopolymerization process was hardly affected by the presence of the silicate filler, and thus 2 mm thick samples containing 3 wt% clay were extensively cured. Transmission electron microscopy revealed that the montmorillonite platelets were either intercalated or exfoliated. Nevertheless, for all formulations, intermediate‐sized aggregates of about 1 µm were present and their fraction increased as the amount of filler increased. The presence of the clay was found to have no major effect on the flexural modulus and compressive yield strength of the nanocomposites. Moreover, the water uptake of nanocomposites containing 3 wt% clay was about 10–15% higher than that of unfilled monomers. Modification of the clay surface with alternative organic cations is certainly necessary in order to achieve an optimal dispersion of the clay in the polymer matrix. Copyright © 2010 Society of Chemical Industry     

Montmorillonite clay/poly(methyl methacrylate) hybrid resin and its barrier property to the plasticizer within poly(vinyl chloride) composite

A poly(methyl methacrylate) (PMMA)‐clay hybrid resin was prepared via bulk polymerization methyl methacrylate monomer in the presence of montmorillonite intercalated with an ammonium salt of dctadecylamine. The products were characterized by infrared spectroscopy, X‐ray diffraction, pyrolysis gas chromatography, and transmission electron microscopy. Results confirm that the resin is intercalated with PMMA molecules. The layer spacing of montmorillonite are enlarged, whereas the silicate layers are homogeneously dispersed individually. When the PMMA‐clay hybrid was blended with plasticized poly(vinyl chloride), the resulting composite exhibited excellent barrier property in preventing the plastizer's migration from the inner matrix to the surface of the product. This is presumably caused by barrier property of the silicate layers dispersed in the composite. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 425–430, 1999