Mechanical properties of layered silicate/starch polycaprolactone blend nanocomposites

The mechanical behavior of layered silicate/starch polycaprolactone blend nanocomposites was evaluated. Three different clays (Cloisite Na⁺, Cloisite 30B and Cloisite 10A) were used as reinforcement. Nanocomposites were prepared by melt intercalation followed by compression molding. These nanocomposites were characterized using X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis and tensile testing. X‐ray diffraction results showed that most of the clays were intercalated within the polymeric chains. In all cases, mechanical properties were improved with clay incorporation and the improvement was better as the clay content was increased. The best properties were achieved with Cloisite 10A due to their greatest compatibility with the matrix. A mechanical model, which takes into account the effective parameters of the clay, was used in order to estimate the dispersion of clay within the polymer. The highest dispersion was obtained for Cloisite 10A, which is in accordance with the experimental mechanical properties. Although dynamical‐mechanical properties improved with clay incorporation, the glass transition temperature was not affected. Copyright © 2006 Society of Chemical Industry     

Effect of some compatibilizing agents on clay dispersion of polypropylene‐clay nanocomposites

Polypropylene (PP)‐clay nanocomposites were obtained and studied by using three different coupling agents, glycidyl methacrylate (GMA), acrylic acid (AA), and maleic anhydride (MA). Three different clays, natural montmorillonite (Cloisite Na+) and chemically modified clays Cloisite 20A and Cloisite 30B, have also been used. Nanocomposites were prepared by melt‐blending in a twin‐screw extruder using two mixing methods: two‐step mixing and one‐step mixing. The relative influence of each factor was observed from structural analysis by WAXD, POM, TEM, and mechanical properties. The results were analyzed in terms of the effect of each compatibilizing agent and incorporation method in the clay dispersion and mechanical properties of the nanocomposite. Experimental results showed that clay dispersion and interfacial adhesion are greatly affected by the kind of matrix modification. The polarity and reactivity of polar groups give as a result better interfacial adhesion and subsequent mechanical performance. PP‐g‐GMA and PP‐g‐MA were better compatibilizing agents than PP‐g‐AA. Better dispersion and exfoliation for the nanoclays were obtained when using two‐step mixing than one‐step mixing conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4748–4756, 2006     

Synthesis and characterization of epoxy based nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of the content and type of different clays on the structure and mechanical properties of the nanocomposites. Diglycidyl ether of bisphenol‐A (epoxy) was reinforced by 0.5–11 wt % natural (Cloisite Na⁺) and organically modified (Cloisite 30B) types of montmorillonite. SEM results showed that as the clay content increased, larger agglomerates of clay were present. Nanocomposites with Cloisite 30B exhibited better dispersion and a lower degree of agglomeration than nanocomposites with Cloisite Na⁺. X‐ray results indicated that in nanocomposites with 3 wt % Cloisite 30B, d‐spacing expanded from 18.4 Å (the initial value of the pure clay) to 38.2 Å. The glass transition temperature increased from 73°C, in the unfilled epoxy resin, to 83.5°C in the nanocomposite with 9 wt % Cloisite 30B. The tensile strength exhibited a maximum at 1 wt % modified clay loading. Addition of 0.5 wt % organically modified clay improved the impact strength of the epoxy resin by 137%; in contrast, addition of 0.5 wt % unmodified clay improved the impact strength by 72%. Tensile modulus increased with increasing clay loading in both types of nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1081–1086, 2005     

Gel time and polymerization kinetics of unsaturated polyester resin/clay montmorillonite nanocomposites

This article presents the variation of viscosity, gel point, and curing kinetic process of nanocomposites based on unsaturated polyester resin (UPR) and natural nano‐clay CloisiteNa^+® and organomodified Cloisite15A^® montmorillonites (MMT). Different amounts (1–10 wt%) of nanoclays were added homogeneously before the cross‐linking reaction of the thermoset polymer. The complex viscosity before curing was especially dependent on the CloisiteNa^+® content more than Cloisite15A^®. The G' and G'' slope also as the complex viscosity criterion were used to determine the nanocomposites gel time variation. Isothermal differential scanning calorimetry measurements were performed to calculate the reaction order and the rate constant using different empirical equations. These results demonstrated a catalytic effect of the clays on the UPR cure, with diffusion controlled phenomena predominating at high conversions. The X‐ray diffraction patterns were useful for identifying the nanocomposites formation, and gave information about the clays dispersion, which served to support the rheological and polymerization kinetic results. Finally, natural MMT CloisiteNa^+®decreased gel time and was more compatible with UPR than the organomodified Cloisite15A^®. POLYM. COMPOS., 36:1931–1940, 2015. © 2014 Society of Plastics Engineers     

The effect of clay type and of clay–masterbatch product in the preparation of polypropylene/clay nanocomposites

Clay containing polypropylene (PP) nanocomposites were prepared by direct melt mixing in a twin screw extruder using different types of organo‐modified montmorillonite (Cloisite 15 and Cloisite 20) and two masterbatch products, one based on pre‐exfoliated clays (Nanofil SE 3000) and another one based on clay–polyolefin resin (Nanomax‐PP). Maleic anhydride‐grafted polypropylene (PP‐g‐MA) was used as a coupling agent to improve the dispersability of organo‐modified clays. The effect of clay type and clay–masterbatch product on the clay exfoliation and nanocomposite properties was investigated. The effect of PP‐g‐MA concentration was also considered. Composite morphologies were characterized by X‐ray diffraction (XRD), field emission gun scanning electron microscopy (FEG‐SEM), and transmission electron microscopy (TEM). The degree of dispersion of organo‐modified clay increased with the PP‐g‐MA content. The thermal and mechanical properties were not affected by organo‐modified clay type, although the masterbatch products did have a significant influence on thermal and mechanical properties of nanocomposites. Intercalation/exfoliation was not achieved in the Nanofil SE 3000 composite. This masterbatch product has intercalants, whose initial decomposition temperature is lower than the processing temperature (T ～ 180°C), indicating that their stability decreased during the process. The Nanomax‐PP composite showed higher thermal and flexural properties than pure PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of polysulfone–clay composite membranes

Porous membranes and dense films were prepared from polysulfone solutions in N‐methyl‐2‐pyrrolidone (NMP) containing different types and amounts of clay. Commercial clays supplied by Southern Clay, either unmodified (Cloisite Na) or organically modified (Cloisite 30B and Cloisite 93A), were used. The clay behavior in the organic solvent was dependent on the presence and type of the organic compatibilizer: Cloisite containing Na ions did not swell in NMP, whereas those with the organic compatibilizer swelled, though to a different degree. Electron microscopy observations were made to examine the clay dispersion in the membrane structure. At variance with Cloisite Na and Cloisite 93A formed microaggregates, Cloisite 30B yielded nanostructures composed of both single sheets and well‐ordered multilayer silicate clusters, which were characterized by an interlayer distance higher than that of the neat clay. The increase in the distance between the layers of Cloisite 30B was related to the formation of intercalated nanocomposites, whereas the presence of single sheets well distributed in the polymer matrix supported the occurrence of delaminated nanocomposites. The intercalation of the polymer into clay layers was confirmed with wide‐angle X‐ray diffractometry. The addition of Cloisite 30B to the casting solution influenced the phase‐separation process in the coagulation bath. Therefore, by the variation of the layered‐silicate concentration in the casting solution, membranes with different morphological structures and ultrafiltration properties were obtained. Cloisite 30B was also found to improve the wettability and mechanical properties of dense films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3637–3644, 2007     

Properties of Waterborne Polyurethane/Clay Nanocomposite Adhesives

A series of waterborne polyurethane (WBPU)/clay nanocomposite dispersions using two different organically modified clays, namely Cloisite 15A and Cloisite 30B, were prepared. It was found that the properties of WBPU/clay nanocomposites were highly dependent on both the clay content and the clay surface characteristic (hydrophilic/hydrophobic). A WBPU/clay nanocomposite dispersion with a higher clay content showed a less negative zeta potential. A lower zeta potential for dispersion with Cloisite 30B compared to Cloisite 15A was observed indicating a higher stability of the dispersion. The tensile strength, Young's modulus and adhesive strength of WBPU/clay nanocomposite containing Cloisite 30B were also higher than those of nanocomposite containing Cloisite 15A. The optimum clay contents, with respect to these properties, for nanocomposites with Cloisite 15A and Cloisite 30B were found to be 2 wt% and 3 wt%, respectively.     

Preparation and mechanical properties of PP/PP-g-MA/Org-MMT nanocomposites with different MA content

Summary Polypropylene-clay nanocomposites were prepared by melt intercalation in a twin screw extruder using two mixing methods: two-step mixing and one-step mixing. The effect of using two different kinds of PP-g-MA (polypropylene-grafted maleic anhydride), with graft efficiencies of 0.1 and 1.0 wt% of MA and with different molecular weight, on clay dispersion and mechanical properties of nanocomposites was investigated. Three different clays, natural montmorillonite (Cloisite Na+) and chemically modified clays Cloisite 20A and Cloisite 30B were used. The relative influence of each factor was observed from structural analysis by WAXD, TEM, and mechanical properties. X-ray diffractometry (XRD) was used to investigate the intercalation effect in the nanocomposites. The results indicted that the intercalation effect and mechanical properties, specially modulus, tensile strength and impact strength, were enhanced by increasing the content of MA, using maleated PP with higher graft efficiency, and using the two step mixing conditions. Better dispersion and exfoliation were obtained when using clay 20A than 30B and natural Na+ montmorillonite. The results showed that clay dispersion and interfacial adhesion are greatly affected by the kind of maleated PP. The increase in content of polar groups gives as a result better interfacial adhesion and subsequent mechanical performance.     

Supercritical CO2 dispersion of nano-clays and clay/polymer nanocomposites

Dispersed polymer/clay nanocomposites are of great interest because they can significantly improve the properties of existing polymeric materials. However, achieving a high level of clay dispersion has been a key challenge in the production of polymer/clay nanocomposites. In this paper, we explore a novel supercritical carbon dioxide (scCO₂) processing method that utilizes scCO₂ to disperse nano-clays. The structure and properties of the clays and the resultant nanocomposites are characterized using a combination of wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and rheology. Significant dispersion was achieved with dry Cloisite 93A clay, whereas relatively poor dispersion was achieved with dry Cloisite Na⁺ (natural clay). The extent of clay dispersion appears to be dependent on the ‘CO₂-philicity’, which in turn appears to depend on the surface modifications and inter-gallery spacing. The presence of an acidic hydrogen on the surfactant in Cloisite 93A appears to play a strong role in its ‘CO₂-philicity’. The ability to delaminate dry clays is significant because it will likely increase the ability to produce dispersed clay/polymer nanocomposites via melt processing. In addition to delaminating dry clays, we demonstrate that CO₂-phobic Cloisite Na⁺ (natural clay) can be partially dispersed with scCO₂, using a CO₂-philic polymer, polydimethylsiloxane (PDMS). The dispersed clay/PDMS nanocomposite shows an order of magnitude increase in the dynamic storage modulus at low frequencies, accompanied by the emergence of a ‘solid-like’ plateau, characteristic of dispersed nanocomposites with enhanced clay/polymer interactions.     

Method for the characterization of electrophoretic properties of clay slips

The present study presents experiments performed in an aqueous dispersion of clays and clay minerals using three different instruments, which were prepared to measure electric conductance, relative viscosity, and electrophoretic mobility of slip in flow. Smectite–kaolinite and Cloisite Na⁺ were used, in addition to an aqueous solution of sodium silicate in deionized water. Laboratory tests of zeta potential and viscosity were also carried out. The starting point was the natural behavior of the electric current when sodium silicate was added to the aqueous dispersion of clay or clay minerals. The results were analyzed and correlated considering the electrophoretic phenomenon. The method proved to be effective for understanding electrophoretic properties acting on the dispersion slips.     

Effect of the silane modification of clay on the tensile properties of nylon 6/clay nanocomposites

A commercially available organomodified clay, Cloisite 25A, was modified with 3‐aminopropyltriethoxysilane, 3‐(glycidoxypropyl)trimethoxysilane, and 3‐isocyanate propyltriethoxysilane to enhance its interaction with the nylon 6 matrix. Composites made of nylon 6 and clays modified with the different silane compounds were prepared by melt mixing with a twin‐screw extruder. The dispersion and degree of exfoliation of the organomodified clays were evaluated from X‐ray diffraction patterns and transmission electron microscopy images of the corresponding composites. The tensile properties of the composites were measured, and their enhancement was attributed to the work of adhesion and interfacial tension of the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Properties of epoxy nanoclay system based on diaminodiphenyl sulfone and diglycidyl ether of bisphenol F: influence of post cure and structure of amine and epoxy

Materials were prepared with Cloisite 30B, diglycidyl ether of bisphenol F and diaminodiphenyl sulfone (DDS) to investigate the relationship between exfoliation and property enhancement. A higher level of exfoliation was found with 4,4′‐DDS than in the material cured with 3,3′‐DDS. The material with 4,4′‐DDS that exhibited a higher degree of exfoliation also resulted in larger improvements in physical properties with nanoclay. Increasing the ratio of trifunctional to difunctional epoxy led to a significant decrease in the level of clay dispersion. Increasing the ratio of trifunctional epoxy in the nanocomposite also caused a decrease in T_g with the addition of nanoclay. However, an increase in T_g with increasing clay loadings was detected in samples with a higher degree of exfoliation, with only difunctional epoxy. Similar behaviour was found for samples with and without a post cure. Excessive post cure led to a decrease in thermal stability in Cloisite 30B‐containing samples. Copyright © 2007 Society of Chemical Industry     

Chitosan/clay nanocomposite film preparation and characterization

Nanocomposites of chitosan and nanoclays (MMT‐Na⁺ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT‐Na⁺ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT‐Na⁺. Micro‐scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation‐at‐break decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1684–1691, 2006     

Electrical conductivity behavior of epoxy matrix nanocomposites with simultaneous dispersion of carbon nanotubes and clays

In this work, nanocomposites with simultaneous dispersion of multiwalled carbon nanotubes (MWCNT) and montmorillonite clays in an epoxy matrix were prepared by in situ polymerization. A high energy sonication was employed as the dispersion method, without the aid of solvents in the process. The simultaneous dispersion of clays with carbon nanotubes (CNT) in different polymeric matrices has shown a synergic potential of increasing mechanical properties and electrical conductivity. Two different montmorillonite clays were used: a natural (MMT‐Na⁺) and an organoclay (MMT‐30B). The nanocomposites had their electrical conductivity (σ) and dielectric constant (ε_r) measured by impedance spectroscopy. The sharp increase in electrical conductivity was found between 0.10 and 0.25 wt% of the MWCNTs. Transmission electron microscopy (TEM) of the samples showed a lower tendency of MWCNT segregation on the MMT‐30B clay surface, which is connected to intercalation/exfoliation in the matrix, that generates less free volume available for MWCNTs in the epoxy matrix. Data from electrical measurement showed that simultaneously adding organoclay reduces the electrical conduction in the nanocomposite. Moreover, conductivity and permittivity dispersion in low frequency suggest agglomeration of nanotubes surrounding the natural clay (MMT‐Na⁺) particles, which is confirmed by TEM. POLYM. COMPOS., 37:1603–1611, 2016. © 2014 Society of Plastics Engineers     

Curing kinetics and mechanical properties of epoxy nanocomposites based on different organoclays

The effect of different organoclays and mixing methods on the cure kinetics and properties of epoxy nanocomposites based on Epon828 and Epicure3046 was studied. The two kinds of organoclay used in this study, both based on natural montmorillonite but differing in intercalant chemistry, were I.30E (Nanomer I.30E—treated with a long‐chain primary amine intercalant) and C.30B (Cloisite 30B—treated with a quaternary ammonium intercalant, less reactive with epoxy than the primary amine). The two mixing processes used to prepare the nanocomposites were (i) a room‐temperature process, in which the clay and epoxy are mixed at room temperature, and (ii) a high‐temperature process, in which the clay and epoxy are mixed at 120°C for 1 h by means of mechanical mixing. The nanocomposites were cured at room temperature and at high temperature. The quality of dispersion and intercalation/exfoliation were analyzed by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The heat evolution of the epoxy resin formulation and its nanocomposite systems was measured using differential scanning calorimetry at different heating rates of 2.5, 5, 10, 15, and 20°C min^?1. The cure kinetics of these systems was modeled by means of different approaches. Kissinger and isoconversional models were used to calculate the kinetics parameters while the Avrami model was utilized to compare the cure behavior of the epoxy systems. The cure kinetics and mechanical properties were found to be influenced by the presence of nanoclay, by the type of intercalant, and by the mixing method. POLYM. ENG. SCI., 47:649–661, 2007. © 2007 Society of Plastics Engineers.     

Quantitative analysis of cloisite 93A infused into linear low‐density polyethylene and maleated linear low‐density polyethylene in a supercritical carbon dioxide medium

Linear low‐density polyethylene (LLDPE) is a widely used polymer that can benefit from the enhanced barrier, thermal, and mechanical properties offered by nanoclay fillers. However, optimal property enhancement requires complete exfoliation and uniform dispersion, both of which are difficult to achieve with nanoclay fillers. Supercritical carbon dioxide (scCO₂) processing is an inexpensive and environmentally benign method for exfoliating and dispersing clays into polymers. In a scCO₂ medium under controlled environments, the organically modified clay Cloisite 93A was infused into LLDPE and maleated linear low‐density polyethylene (LLDPE‐g‐MA). Upon microscopic inspection, it was evident that clay infusion was achieved near the surface of the polymer pellet, but no clay found its way into the interior of the pellet. In this article, we describe an analytical method for determining the amount of nanoclay infused into a polymer matrix via Fourier transform infrared analysis. Using this method, we determined the weight percentage of Cloisite 93A infused into LLDPE and LLDPE‐g‐MA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of water‐assisted extrusion and solid‐state polymerization on the microstructure of PET/Clay nanocomposites

An melt‐mixing process has been used to prepare Poly(ethylene terephthalate) (PET)/clay nanocomposites with high degree of clay delamination. In this method, steam was fed into a twin‐screw extruder (TSE) to reduce the PET molecular weight and to facilitate their diffusion into the gallery spacing of organoclays. Subsequently, the molecular weight (M_W) reduction of the PET matrix due to hydrolysis by water was compensated by solid‐state polymerization (SSP). The effect of the thermodynamic compatibility of PET and organoclays on the exfoliated microstructure of the nanocomposites was also examined by using three different nanoclays. The dispersion of Cloisite 30B (C30B) in PET was found to be better than that of Nanomer I.28E (I28E) and Cloisite Na⁺. The effect of feeding rate and consequently residence time on the properties of PET nanocomposites was also investigated. The results reveal more delamination of organoclay platelets in PET‐C30B nanocomposites processed at low feeding rate compared to those processed at high feeding rate. Enhanced mechanical and barrier properties were observed in PET nanocomposites after SSP compared to the nanocomposites prepared by conventional melt‐mixing. POLYM. ENG. SCI., 54:1723–1736, 2014. © 2013 Society of Plastics Engineers     

Phase separation behavior and morphologies of PMMA/poly(styrene‐co‐acrylonitrile)/clay nanocomposites prepared by solution mixing

Nanocomposites of blends of PMMA and poly(styrene‐co‐acrylonitrile) (SAN) with natural (PM) or organically modified montmorillonite clays (Cloisite 30B, 25A, and 15A) were prepared by solution mixing and the effect of clay on the phase separation behavior along with morphologies of nanocomposites was investigated. Nanocomposites containing clay C30B prepared from methyl ethyl ketone showed the noticeable decrease in the cloud points. None of the other nanocomposites showed the increase in the cloud point. Location of clay particles in the phase separated matrix is observed to be different depending on the type of clays and solvents. The lowest cloud point of nanocomposites containing C30B may arise from the good dispersion of C30B where Clay C30B may act as the nucleating agent inducing phase separation. Dynamic mechanical and thermal analyses support above observations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical,thermal, and barrier properties of nanocomposites based on poly(butylene succinate)/thermoplastic starch blends containing different types of clay

Nanocomposites based on blends of poly(butylene succinate) (PBS) and thermoplastic cassava starch (TPS) were prepared using a two‐roll mill and compression molding, respectively. Two different types of clay, namely sodium montmorillonite (CloisiteNa) and the organo‐modified MMT (Cloisite30B) were used. The morphological and mechanical properties of the nanocomposite materials were determined by using XRD technique and a tensile test, respectively. Thermal properties of the composite were also examined by dynamic mechanical thermal analysis and thermal gravimetric techniques. Barrier properties of the nanocomposites were determined using oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) tests. From the results, it was found that by adding 5 pph of the clay, the tensile modulus and the thermal properties of the blend containing high TPS (75 wt %) changed significantly. The effects were also dependent on the type of clay used. The use of Cloisite30B led to a nanocomposite with a higher tensile modulus value, whereas the use of CloisiteNa slightly enhanced the thermal stability of the material. OTR and WVTR values of the blend composites containing high PBS ratio (75 wt %) also decreased when compared to those of the neat PBS/TPS blend. XRD patterns of the nanocomposites suggested some intercalation and exfoliation of the clays in the polymer matrix. The above effects are discussed in the light of different interaction between clays and the polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1114‐1123, 2013     

Morphology and Thermal Stability of Novolac Phenolic Resin/Clay Nanocomposites Prepared via Solution High‐Shear Mixing

Phenolic resin/clay composites were prepared by high‐shear mixing of clay suspended in CH₃OH solutions of Novolac resin and curing agent. Pure clay Cloisite Na⁺ and pillared clays Cloisite 10A, 30B, and Na⁺Cloisite that was pillared by 3‐hexadecyl‐1‐methylimidazolium bromide were studied. After CH₃OH evaporation, Novolac was cured at low temperatures. XRD showed that clay gallery d‐spacings decreased upon solvent evaporation and partial curing. Slight d‐spacing increases were sometimes observed from a partially cured stage to a further cured composite. Na⁺Cloisite gave the highest nanodispersion, Cloisites 10A and 30B the lowest. TGA revealed that Na⁺ clay or organoclay incorporation in partially cured and cured composites did not improve the thermal stability of Novolac.