Organophilic Montmorillonite Research Articles

Mechanical properties of PLA/PBS foamed composites reinforced by organophilic montmorillonite

ABSTRACTPorous materials have specific properties, such as high surface area, high permeability, lightweight, and low thermal conductivity. In foaming process of thermoplastics, high melt viscosity is indispensable. Neither poly(lactic acid) (PLA) nor poly(butylene succinate) (PBS) has sufficient melt viscosity. In this manuscript, Organophilic montmorillonite (OMMT) was employed to improve the foaming performance PLA/PBS blends. Mechanical tests were undertaken to compare the performance change of PLA/PBS foams before and after reinforcement of OMMT. The compression feature of PLA/PBS foams was discussed. X‐ray diffraction (XRD) and scanning electron microscopes were performed to investigate the interaction between OMMT and PLA/PBS foams and the influence of OMMT on cell structure. The results indicated that OMMT can improve the effect of foaming markedly. With 3 wt % OMMT, The compressive strength, flexural strength, and impact strength raised up to 9.2 MPa, 14.0 MPa, and 31.2 kJ/m2, respectively, and the average size of cells changed from 475.6 to 261.4 µm. FT‐IR, TGA, and XRD analysis suggested that CTAC has inserted into the Na‐MMT platelets and OMMT platelets are more likely to be intercalated or completely separated in PLA/PBS matrix. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40773.

Influence of screw speed on the mechanical and rheological properties of poly(ethylene-co -vinyl acetate)-organomodified montmorillonite nanocomposites

Poly(ethylene-co-vinyl acetate) (EVA) and organophilic montmorillonite clay nanocomposites were manufactured in a co-rotating twin-screw extruder using screw speeds ranging between 200 and 800 rpm. The morphology and thermal-mechanical and rheological properties were studied to establish processing–morphology–property relationships. Particularly for samples produced under higher screw speed ranges, X-ray diffraction and transmission electron microscopy revealed a tendency of increased exfoliated clay. Although the mechanical properties improved by the presence of clay, they were not altered by the screw speed. The rheological behavior in the solid and melt states were evaluated and showed that the storage modulus of neat EVA subjected to higher screw speed undergoes more pronounced decrease in the storage modulus than the nanocomposites, suggesting that the clay minimizes the effect of the screw speed. This minimization effect could be explained in the light of the assessment of relaxation times that showed stronger physical interactions with the nanocomposites in the molten state. POLYM. COMPOS., 36:854–860, 2015. © 2014 Society of Plastics Engineers

Flame-retardant and Anti-dripping Properties of Intumescent Flame-retardant Polylactide with Different Synergists

The flame-retardant and anti-dripping properties of biodegradable polylactide (PLA) materials during the combustion process were improved using intumescent flame-retardant (IFR) and different synergists. Organophilic montmorillonite (OMT), zinc borate (ZB), fumed silica (FS), tetraethoxysilane (TEOS) and polytetrafluoroethylene (PTFE) were chosen as the anti-dripping synergists for IFR in flame-retardant PLA. The flammability properties and thermal stability of PLA composites were investigated with UL-94, limiting oxygen index (LOI), thermogravimetric analysis (TGA), melt flow index (MFI), etc. It is found that OMT and ZB are the best anti-dripping synergists for IFR PLA. The anti-dripping mechanisms of all the additives are discussed.

Effect of nanofillers on low energy impact performance of sandwich structures with nanoreinforced polyurethane foam cores

Sandwich panels were fabricated with nanoclay-filled polyurethane foams and glass fiber-reinforced polyamide and polypropylenes face sheets. Nanoclay-filled foam cores, with organophilic montmorillonite loadings of 0–10 wt%, were synthesized through polyaddition of the polyol premix with 4,4'-diphenylmethane diisocyanate, and bound to the injected molded face sheets. Produced sandwich structures were then subjected to low energy impact (15 J) tests under localized point and surface loads, in an instrumented impact test setup. Additionally, quasi-static compressive behavior of the sandwiches panels was studied. The results showed that the addition of nanoclay in the polyurethane foam core improved both energy absorption and maximal deflection during impact. The improvement in energy absorption was between 66% and 92% for polypropylenes face sheet sandwiches and 23% and 34% for the polyamide face sheet sandwiches during point load. Furthermore, an increase in the compression modulus of 20–37% was recorded for the sandwiches with polyamide face sheets.

Radiation synthesis and characterization of styrene/acrylic acid/organophilic montmorillonite hybrid nanocomposite for sorption of dyes from aqueous solutions

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange reaction of Na+‐MMT and vinyl benzyl triethyl ammonium chloride (VBTAC) as a reactive organic modifier in an aqueous solution. A series of styrene (St)/acrylic acid (AA)/OMMT nanocomposite hydrogel containing different wt% of OMMT was synthesized through in situ polymerization using γ‐ray. The samples were characterized using Fourier transform infrared (FTIR), X‐ray powder diffraction (XRD), and transmission electron microscope (TEM), whereas thermal stability was examined by thermogravimetric analysis (TGA). The adsorption capacity and rate for both Acid Green B (anionic) and Maxilon C.I. Basic (cationic) dye including adsorption kinetics and isotherm were investigated at 30°C. TEM measurements showed spherical nanosized particles of average diameter 30–40 nm and XRD suggested the formation of exfoliated nanocomposite. TGA measurements showed that the addition of OMMT did not enhance the thermal stability where the onset temperature of the degradation for all samples was around 125°C. The effect of some important parameters on dye adsorption such as solution pH, initial dye concentration, and contact time was investigated. The equilibrium data obtained in batch experiments were correlated to Langmuir and Freundlich isotherm equations. Results showed that the adsorption of Acid Green B fitted well to the Langmuir model while the adsorption pattern of Maxilon C.I. Basic followed the Freundlich isotherm, which suggests heterogeneity of the adsorption sites on the nanocomposite. POLYM. COMPOS., 35:2353–2364, 2014. © 2014 Society of Plastics Engineers

Theoretical and Experimental Studies on Preparation of OMMT-Based Composite Phase Change Materials Used in Asphalt Pavement

With the global warming, phase change materials are being expected to be applied in asphalt pavement to help lower its surface temperature. In this study, a kind of composite phase change material was prepared and its technique parameters were optimized through theoretical analysis and experimental study. A solid-liquid phase change material, with melt point of 43°C and phase transition heat of 161.6J/g, was used as core. The organophilic montmorillonite (OMMT) was used as a carrier and can prevent leakage of the melted phase change materials. The results showed that the ratio of OMMT to lauric acid was 2.6:1, and the melting temperature and time were 74°Cand 1.5hours, respectively. The composite phase change material prepared in this study had the phase transition latent heat of 36.168J/g and the transition temperature of 40.094°C. And the experimental results are in good agreement with theoretical analysis.

Pararosaniline and crystal violet tagged montmorillonite for latent fingerprint investigation

Use of cationic pigment-intercalated bentonite (montmorillonite, Mt) as the latent print development powder was investigated. The cationic dyes, crystal violet (CV) and pararosaniline (PS), were substituted with sodium ions present in the interlayers of Mt by ion exchange mechanism. Organophilic montmorillonites (OMts) were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), elemental analysis and Fourier transform infrared spectroscopy (FTIR). TGA results determined the average amount of dye molecules in OMts as 52mmol/100g for both PS and CV. Modified bentonite powders were applied to develop fresh and aged (1, 7 and 15days) fingermarks deposited on non-porous surfaces such as glass, metal and porcelain using a fiberglass brush. Sharp and clear prints with complete ridge details were developed on glass and metal surfaces even for the 15-day-old fingermarks. Surprisingly, CV- and PS-intercalated fingerprint powders successfully worked for the development of the seven-month-old fingerprints on the glass surface. In contrast, physically mixed bentonite and dye mixtures were not very successful in the development of even fresh fingerprints on the glass surface. CV-tagged bentonite also exhibited strong fluorescence at around 500nm when excited at 450nm.

The effect of polyethylene graft maleic anhydride compatibilizer on the physical, mechanical, and thermal properties of extruded noncross-linked low-density polyethylene nanocomposite foams

An investigation was carried out on the noncross-linked low-density polyethylene (LDPE) nanocomposite foams with polyethylene graft maleic anhydride (PE-g-MA) compatibilizer. Nanocomposite foams with similar densities were produced by extrusion method, and the effect of organophilic montmorillonite (OMMT) nanoclay (closite20A) content on cell microstructure, mechanical properties, thermal conductivity, and flame retardancy of samples were studied. X-ray diffraction (XRD) was used to investigate the nanoclay dispersion in LDPE matrix. In XRD patterns of LDPE nanocomposite foams, closite20A characteristic peak was not observed as an evidence of nanoclay intercalation–exfoliation in the polymer matrix. For increasing the compatibility of PE and nanoclay, PE-g-MA compatibilizer was used. Due to the presence of compatibilizer in the nanocomposite foams and decreasing the cell nucleation energy around the nanoclay, the average cell size was reduced, but the cell density and microstructure uniformity increased. Furthermore, the compatibilized nanocomposites showed lower thermal conductivity and burning rate than that of the nanocomposites without PE-g-MA compatibilizer and neat LDPE foams, which can be attributed to the cell size reduction as well as distribution of cells of narrow size in nanocomposite foams.

Bismuth complex catalysts for the in situ preparation of polycaprolactone/silicate bionanocomposites

Solvent-free, bismuth-catalysed in situ polymerization of caprolactone in the presence of layered silicates enables the formulation of a series of polycaprolactone/silicate bionanocomposites. Three organophilic montmorillonites obtained by cationic exchange reaction with tetrabutylammonium iodide, benzyltriethylammonium chloride and vinylbenzyltriphenylphosphonium chloride salts, respectively, were used as reinforcing reagents for these materials. The effects of clay and bismuth catalyst type (bismuth(III) acetate and triphenylbismuth) are discussed on the basis of composite morphologies and molecular weights of resulting polymers. © 2013 Society of Chemical Industry

Synthesis of clay-CNTs nanocomposite

Nanocomposite of clay-carbon nanotubes (CNTs) is prepared by using carboxyl-modified multiwalled carbon nanotubes and amino-functionalized organophilic montmorillonite (clay). The nanocomposite is characterized by scanning electron microscopy to evaluate the morphology. The findings show uniform dispersion of CNTs.

Surface modification of natural Na-montmorillonite in alkane solvents using a quaternary ammonium surfactant

The surface properties of a natural sodium montmorillonite (Na-MMT) was dramatically altered by a cationic surfactant dioctadecyldimethylammonium chloride (DODMAC) through an intercalation and ion exchange reaction in alkane solvents. Optical micrographs show that in situ organo-modification with surfactant DODMAC significantly improves the dispersibility of Na-MMT in alkane solvents. Changes in the structure and surface properties of the organophilic montmorillonite (OMMT) formed in octane, a volatile alkane, were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA/DTG) and Fourier transform infrared spectroscopy (FTIR). It is shown that organo-modification of Na-MMT surfaces based on ion exchange reaction in alkane solvents results in dispersion of the hydrophilic Na-MMT in the organic medium. And most importantly, viscosity curves of the clay suspensions suggest a potential method to control the rheological behavior of dispersions in alkane solvents instead of using organophilic montmorillonites. Furthermore, dispersion approaches and mechanism presented here will be useful for choosing compatibilizer and optimizing processing conditions especially in developing pristine-clay polymer nanocomposites.

Organoclay-Filled Vinyl Ester Monomer Toughened Epoxy-Intercrosslinked Matrix Materials

A vinyl ester monomer (VEM), namely cyclohexyl-1,1′-bis[4-(γ-2-methylphenoxy)-α-hydroxypropylacrylate], was synthesized from 1, 1-bis (3-methyl-4-glycidyloxyphenyl) cyclohexane, and acrylic acid via nucleophilic addition. The structure of VEM was confirmed by FTIR, 1H, 13C NMR, and electron impact-mass spectroscopy. Diglycidyl ethers of bisphenol-A (DGEBA) epoxy resin were toughened with varying percentages of 5, 10, and 15% (by wt) VEM using 4, 4′-diaminodiphenylmethane (DDM). VEM-modified epoxy systems were further modified with organophilic montmorillonite (OMMT) clay. OMMT clay-filled hybrid VEM-epoxy resin systems, developed in the form of casting, were characterized for their mechanical, thermomechanical, dielectric, and morphological properties.

Preparation of Polypyrrole Nanocomposites with Organophilic and Hydrophilic Montmorillonite and Investigation of Their Corrosion Protection on Iron

ABSTRACTThe nanocomposite of polypyrrole with organonophilic montmorillonite and hydrophilic montmorillonite clays was prepared by in situ polymerization of pyrrole monomer in the presence of montmorillonite nanoclays. FTIR spectroscopy studies and X‐ray diffraction pattern were used to confirm the formation of a polypyrrole/montmorillonite nanocomposite. The scanning electron microscopy image of the nanocomposite showed the homogeneous and continuous structure of the nanocomposite. Also cyclic voltammetry studies revealed that the synthesized nanocomposites were electroactive. The anticorrosive properties of nanocomposite coatings on iron coupons were evaluated and compared with pure polypyrrole coating. According to the results in corrosive environments, the polypyrrole/organonophilic montmorillonite nanocomposite has enhanced corrosion protection effect in comparison to pure polypyrrole and polypyrrole/hydrophilic montmorillonite coating. It was concluded that the better corrosion protection effect was due to the better dispersion of organophilic montmorillonite nanoclays in the polymer matrix, which results in a decrease in the corrosion current and corrosion rate. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21337; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21337

Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite.The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR).The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9nm, 2.6nm and 3.4nm respectively.The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

Preparation and Research of Coupling Agent Modified Organophilic Montmorillonite

A novel method is proposed to modify montmorillonite with coupling agents and Hexadecyl triphenyl phosphonium bromide surfactants made by our group (named P-surfactant in the following). The structure of organophilic montmorillonite (OMMT) was investigated by FT-IR, XRD and TG. The FT-IR shows the coupling agents were inserted between the layers of MMT and reacted with –OH of MMT. The results of X-ray diffraction shows that the coupling agents were all intercalated into the layers of MMT. The interlayer spacing of montmorillonite increases to 4.00 nm, the effect of modification is well. The results of TG showed the thermal stability was better.

Influence of the layered silicate type on the structure, morphology and properties of cellulose acetate nanocomposites

This paper deals with the effect of different montmorillonite source clays, including pristine and organophilic montmorillonites, on the structure, morphology and properties of cellulose acetate (CA)/clay nanocomposites. In this study, the nanocomposites were prepared by melt extrusion in the presence of the environmentally friendly triethyl citrate plasticizer. The structure and morphology of the materials were analysed by X-ray diffraction and scattering (SAXS), X-ray microtomography and energy filtered transmission electron microscopy (EFTEM). SAXS and EFTEM results indicated that the nanocomposite morphologies were made up of tactoids together with exfoliated clay platelets in different proportions depending on the clay type. It can be concluded that well distributed clay tactoids and platelets can be achieved in CA nanocomposites prepared by melt extrusion and consequently property improvements can be found by using pristine or organophilic clays. In this case, the addition of a plasticizer, able to intercalate in the clay gallery, seems to be sufficient to promote the clay delamination mechanism under shearing inside the cellulose acetate matrix.

Polymer–clay nanocomposites via chemical grafting of polyacrylonitrile onto cloisite 20A

The synthesis and characterization of polyacrylonitrile (PAN) nanocomposites through grafting the polymer onto organophilic montmorillonite have been reported. Cloisite 20A reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction liberates HCl, it was performed in the presence of sodium hydrogen carbonate to prevent the exchange of quaternary alkylammonium cations with H + ions. Only the silanol groups on the edge of the clay reacted with vinyltrichlorosilane. The radical polymerization of the product with acrylonitrile (AN) as a vinyl monomer leads to chemical grafting of polyacrylonitrile onto montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and grafted nanoparticles were studied by XRD and TEM. Exfoliated nanocomposites were obtained for 0·5–7 wt% clay content. The nanocomposites were studied by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMTA).

Thermogravimetric Analysis of OMMT Filled HDPE/EPDM Treated EB Irradiation

In the current study, high density polyethylene (HDPE)/ ethylene propylene diene monomer (EPDM) blend and organophilic montmorillonite (OMMT) filled HDPE/EPDM was develop aiming at enhancing the thermal properties. Maleic anhydride polyethylene (MAPE) agent and electron beam (EB) irradiation technique were applied as HDPE/EPDM blend and OMMT filled HDPE/EPDM treatments. HDPE/EPDM blend and OMMT filled HDPE/EPDM were first prepared via melt intercalation technique at 4 vol% OMMT loading. For EB irradiation technique, the absorbed dose was set at 100 kGy. The effectiveness of these surface modification treatments were compared with control one (no surface modification) and analyzed based on the thermal test as well as transmission electron microscope (TEM). It was found that the thermal properties of both HDPE/EPDM blend and OMMT filled HDPE/EPDM were significantly enhanced by EB irradiation technique as compared to the control and MAPE systems. Transmission electron microscope (TEM) illustrated the mixed intercalated and partial exfoliated structures of OMMT filled HDPE/EPDM with EB irradiation technique.

Preparation and Characterization of Vinyl Ester Monomer–Toughened Epoxy-Clay Hybrid Nanocomposites: Thermal and Morphological Properties

An intercross-linked network of vinyl ester monomer (VEM)-toughened epoxy-clay hybrid nanocomposites was developed and characterized using analytical methods. Cyclohexyl-1,1′-bis[4-(γ-2-methylphenoxy)-α-hydroxypropylacrylate]-based VEM was synthesized from 1,1-bis(3-methyl-4-glycidyloxyphenyl) cyclohexane and acrylic acid. The VEM was subsequently blended with diglycidyl ether of bisphenol-A (DGEBA) resin cast and cured with 4,4′-diaminodiphenylmethane (DDM). VEM-toughened epoxy matrices were reinforced with organophilic montmorillonite (OMMT) clay yielding hybrid epoxy nanocomposites. Data obtained from thermal characterization indicate that the introduction of VEM into epoxy resin improves thermal properties. The morphological behavior of the nanocomposite was analyzed by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM).

Polymer-clay nanocomposites: chemical grafting of polystyrene onto Cloisite 20A

An account of the experiments on preparing polystyrene (PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported. Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Because the reaction may liberate HCl, it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H+ ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface. The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction. Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy. The prepared nanocomposite materials and the grafted nano-particles were studied by XRD. Exfoliated nanocomposites may be obtained for 0.5 wt%–1 wt% clay content. The nanocomposites were studied by thermogravimertic analysis (TGA) dynamic thermal analysis (DTA) and dynamic mechanical analysis (DMTA).