Effects of silane grafting on the morphology and thermal stability of poly(ethylene terephthalate)/clay nanocomposites

An alkylammonium intercalated montmorillonite (A‐MMT) was modified by edge grafting with 3‐glycidoxypropyltrimethoxysilane. In comparison with poly(ethylene terephthalate) (PET)/A‐MMT, the resultant grafted clay, S‐A‐MMT, exhibited improved miscibility with PET matrix and revealed better dispersion state in the melting compounded PET/S‐A‐MMT nanocomposites. As a result, the PET/S‐A‐MMT nanocomposite had slower degradation rate owing to the enhanced clay barrier effect. Meanwhile, the nanocomposite exhibited lower degradation onset temperature under nitrogen because of the clay catalysis effect, which can be explained by the decreasing degradation reaction energy calculated from Coats–Redfern method of degradation kinetics. In the other hand, nanocomposite with better clay dispersion state exhibited increasing thermal oxidative stability due to clay barrier effect of hindering oxygen to diffuse in, which accorded with the continuous and compact char surface formed during polymer degradation. The clay catalysis and barrier effect of silicate layers were presented directly in isothermal oxidative TGA experiment. Furthermore, the mechanical and crystallization properties of PET/clay nanocomposites were investigated as well. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

The nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X‐ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d₀₀₁, expansion of clay gallery width W_cg, d‐spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester‐side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40617.     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

Scientific Ethics

A modified melt blending method has been developed for preparing exfoliated nanocomposites of poly(ethylene terephthalate) with sodium‐montmorillonite (Na‐MMT) and poly(m‐xylylene adipamide) with Na‐MMT. In this novel compounding process, a Na‐MMT water solution was blended with the polymer in a twin screw extruder. This mixing process ensured that the silica nanoparticles were exfoliated in the polymer matrix through fixing the nanoparticles within the polymer matrix almost as they were in water. Transmission electron microscopy (TEM) and X‐ray diffraction were used to determine nanoparticle dispersion level. The absence of the X‐ray basal reflections in conjunction with the TEM images revealed the exfoliation of clay platelets. Differential scanning calorimetry illustrated that the nucleating abilities of montmorillonite were related to clay content and dispersion morphology. Oxygen permeation results indicated that the improved morphologies had enhanced the barrier properties of the nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(vinyl alcohol) nanocomposite films: Thermooptical properties,morphology, and gas permeability

Poly(vinyl alcohol) (PVA)/saponite nanocomposites were prepared with various clay concentrations with the solution intercalation method. The intercalations of the polymer chains in the clay were examined with wide‐angle X‐ray diffraction and transmission electron microscopy. The variations of the dispersion, morphology, thermal properties, and gas permeability of the nanocomposites with clay concentrations in the range of 0–10 wt % were examined. Up to a 5 wt % clay loading, the clay particles were highly dispersed in the PVA matrix without any agglomeration of particles. However, some agglomerated structures formed in the polymer matrix above a 7 wt % clay concentration. The thermal stability of the hybrids increased linearly with increases in the clay loading up to 10 wt %. To measure the oxygen permeability and optical properties of the PVA hybrid films, the PVA hybrid solutions were coated onto both biaxially oriented polypropylene and poly(ethylene terephthalate) films, which were used as polymer substrates. The oxygen permeability values monotonically decreased with increases in the clay loading in the range of 0–10 wt %. The optical properties, such as the haze and gloss of the hybrid films when coated onto the matrix films, were nearly constant, that is, independent of the clay loading. These improvements arose because of the largely nanometer‐scale dispersion of the clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 591–596, 2006     

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     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Electromagnetic interference shielding properties of graphene quantum-dots reinforced poly(vinyl alcohol)/polypyrrole blend nanocomposites

Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low-cost material for EMI shielding applications.     

Poly(ethylene terephthalate)/clay nanocomposites with trisilanolphenyl polyhedral oligomeric silsesquioxane as dispersant: simultaneously enhanced reinforcing and stabilizing effects

This paper presents a new approach for the preparation of poly(ethylene terephthalate) (PET)/clay nanocomposites using surfactant‐free clay (sodium montmorillonite, Na‐MMT) with trisilanolphenyl polyhedral oligomeric silsesquioxane (Tsp‐POSS) as dispersant. The dispersion of clay in the PET/Na‐MMT/Tsp‐POSS nanocomposites is enhanced over that in PET/Na‐MMT by using a very small amount of Tsp‐POSS, which acts as functional spacer to keep clay platelets apart and pull monomers in, and, at the same time, acts as a PET chain extender. As a result, thermomechanical properties and thermo‐oxidative stability of PET/Na‐MMT/Tsp‐POSS are improved simultaneously compared with those of PET/organoclay nanocomposites. © 2013 Society of Chemical Industry     

Structure‐property and swelling behavior of electron beam irradiated poly(vinyl alcohol)/acrylamide/sodium montmorillonite clay composites

Composites based on poly(vinyl alcohol) (PVA), acrylamide monomer (AM) and sodium montmorillonite clay (MMT) were prepared, in the form of thin films, by solution casting. The PVA/AM/MMT composites films were then exposed to electron beam irradiation to form crosslinked network structure. The structure‐property behavior of PVA/AM/MMT hybrids was demonstrated by x‐ray diffraction (XRD), scanning electron microscopy, gel content, color intensity, thermogravimetric analysis (TGA) and swelling behavior in aqueous solutions. The results indicated that the introduction of MMT clay ratio up to 5% decreased the gel content of PVA/AM hydrogels. The color measurements indicated that the introduction of MMT clay ratio up to 5% was shown to affect the color intensity of composite films. It was found that both PVA/AM hydrogels and PVA/AM/MMT composites reached the equilibrium swelling state in water after four hours; however PVA/AM/MMT composites displayed higher swelling than PVA/AM hydrogels. However, the swelling of PVA/AM hydrogels or their composites at the equilibrium state increased with increasing temperature up to 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Intercalated clay structures and amorphous behavior of solution cast and melt pressed poly(ethylene oxide)–clay nanocomposites

The polymer nanocomposite (PNC) films consisted of poly(ethylene oxide) (PEO) and sodium cations montmorillonite (MMT) clay were prepared by aqueous solution casting and direct melt press compounding techniques, whereas the films of PEO with trimethyl octadecyl ammonium cations organo‐modified montmorillonite (OMMT) clay were formed by melt pressed technique. The clay concentrations in the nanocomposites used are 1, 2, 3, 5, 10, and 20 wt % of the PEO weight. The X‐ray diffraction patterns of these nanocomposites were measured in the angular range (2θ) of 3.8–30°. The values of basal spacing d₀₀₁ of MMT/OMMT, clay gallery width W_cg, d‐spacings of PEO crystal reflections d₁₂₀ and d₁₁₂, and their corresponding crystallite size L, and the peaks intensity I (counts) were determined for these nanocomposites. Results reveal that the nanocomposites have intercalated clay structures and the amount of intercalation increases with the increase of clay concentration. As compared to melt pressed PEO–MMT nanocomposites, the amount of clay intercalation is higher in aqueous solution cast nanocomposites. At 20 wt % MMT dispersion in PEO matrix, the solution cast PEO–MMT nanocomposite almost changes into amorphous phase. The melt press compounded PEO–OMMT films show more intercalation as compared to the PEO–MMT nanocomposites prepared by same technique. In melt pressed nanocomposites, the PEO crystalline phase significantly reduces when clay concentration exceeds 3 wt %, which is evidenced by the decrease in relative intensity of PEO principal crystalline peaks. The effect of interactions between the functional group (ethylene oxide) of PEO and layered sheets of clay on both the main crystalline peaks of PEO was separately analyzed using their XRD parameters in relation to structural conformations of these nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39898.     

Preparation and characterization of transparent poly(methyl methacrylate)/Na+‐MMT nanocomposite films by solution casting

Films of poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na⁺‐MMT) nanocomposites have been successfully prepared utilizing Na⁺‐MMT by N,N‐dimethylformamide solution casting. The nanocomposite films show high transparency, enhanced thermal resistance, and mechanical properties in comparison with the neat polymer film. The transparency of the films was investigated by UV‐vis spectra. The exfoliated dispersion of Na⁺‐MMT platelets in nanocomposites were investigated by X‐ray diffraction and transmission electron microscopy. The enhanced thermal resistance and mechanical properties of PMMA were studied by thermal gravimetric analysis and dynamic mechanical analysis, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

Rigid PVC/(layered silicate) nanocomposites produced through a novel melt‐blending approach

On the basis of the fusion behavior of poly(vinyl chloride) (PVC), the influence of compounding route on the properties of PVC/(layered silicate) nanocomposites was studied. Four different compounding addition sequences were examined during the melt compounding of PVC with montmorillonite (MMT) clay, including (a) a direct dry mixing of PVC and nanoclay, (b) an addition of nanoclay at compaction, (c) an addition of nanoclay at the onset of fusion, and (d) an addition of nanoclay at equilibrium torque. Both unmodified sodium montmorillonite (Na⁺‐MMT) and organically modified montmorillonite (Org.‐MMT) clays were used, and the effect of the addition sequence of the clay during compounding on its dispersion in the matrix was evaluated by X‐ray diffraction and transmission electron miscroscopy. The surface color change, dynamic mechanical analysis, and flexural and tensile properties of PVC/clay nanocomposites were also studied. The experimental results indicated that both the extent of property improvement and the dispersion of nanoparticles in PVC/(layered silicate) nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing. The addition of nanoclay to PVC must be accomplished at the onset of fusion, when PVC particles are reduced in size, in order to produce nanocomposites with better nanodispersion and enhanced mechanical properties. Overall, rigid PVC nanocomposites with unmodified clay (Na⁺‐MMT) were more thermally stable and exhibited better mechanical properties than their counterparts with organically modified clay (Org.‐MMT). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Flame retardance of montmorillonite/rubber composites

The effect of dispersion of clay in rubber on the mechanical properties and flame retardance of rubber/montmorillonite (MMT) nanocomposites and rubber/MMT microcomposites were investigated in the present article, and the results were compared with the performance of silica reinforced rubber composites. Cone calorimeter test and limiting oxygen index test were employed to evaluate the flame retardance. From the results, it could be seen that the rubber/MMT nanocomposites always possessed the best flame retardance, such as lower peak heat release rate and higher fire performance index value. In addition, the rubber/MMT nanocomposites also showed better mechanical properties than the pure rubber and the other composites, especially in tear strength. With the rubber/silica composites, as expected, the silica could appropriately endow the rubber with flame retardance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nanocomposite polymer films containing carvacrol for antimicrobial active packaging

Nanocomposite films based on low‐density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo‐modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Colorless polyimide nanocomposite films with pristine clay: Thermal behavior,mechanical property,morphology, and optical transparency

Polyimide (PI)/clay hybrids were synthesized using the in situ solution intercalation method via poly(amic acid). The Na ion‐exchanged clays Na⁺‐saponite (SPT), Na⁺‐mica (Mica), and Na⁺‐montmorillonite (MMT) were used for the intercalation of PI polymer chains. Our dispersion results show that pristine SPT is more easily dispersed in a PI matrix than MMT or Mica. PI nanocomposites were prepared with various SPT contents to examine the variations with SPT content in the range 0–1 wt% of the thermomechanical properties, morphology, and optical transparency of the nanocomposites. The PI films have excellent optical transparencies, and are almost colorless. However, the optical transparency of the PI hybrid films decreases slightly with increases in the clay content. We also examined the relationship between the properties and clay content of the PI hybrid films using wide‐angle X‐ray diffraction (XRD) measurements, electronic microscopy (SEM and TEM), and universal tensile machine (UTM). The color intensities of the PI films were evaluated with a spectrophotometer. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Improving the physical properties of PEA/PMMA blends by the uniform dispersion of clay platelets

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA-MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA-MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay.