Comparative effect of metallocene and Ziegler‐Natta polypropylene on the exfoliation of montmorillonite and hectorite clays to obtain nanocomposites

The present study was carried out on the effect of molecular weight and polydispersity of polypropylene (PP) obtained via Ziegler‐Natta or metallocene catalysis on the formation of nanocomposites with montmorillonite and mineral and synthetic hectorite. The formation of the nanocomposites was achieved by the melt‐mix method. X‐ray diffraction, transmission electron microscopy, and analysis of mechanical properties showed that, using PP obtained via metallocene catalysis (polydispersity ～ 2), it is possible to achieve improved formation of nanocomposites compared with PP obtained via Ziegler‐Natta catalysis (polydispersity ～ 4). It was also found that the molecular weight of the PP affects the tendency toward clay exfoliation and consequently the properties of the nanocomposites. Montmorillonite type clay was evaluated at 1%, 3%, and 5% by weight in the nanocomposite. The nanocomposite with 1 wt % clay was found to have better mechanical properties compared with the nanocomposite containing 3 wt % and 5 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 698–706, 2007     

Curing behavior and structure of an epoxy/clay nanocomposite system

The curing behavior of an epoxy/clay nanocomposite system composed of a bifunctional epoxy resin with an aromatic amine curing agent and an organically modified clay was investigated. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the epoxy/clay nanocomposite system. The curing rate of the nanocomposite system increased with increasing clay content. A kinetic equation, considering an autocatalytic reaction mechanism, could describe fairly well the curing behavior of the epoxy/clay nanocomposite system. The reaction kinetic parameters of the kinetic equation were determined by fitting DSC conversion data to the kinetic equation, using a nonlinear numerical method. Dynamic mechanical analysis was used to investigate the thermomechanical properties of the epoxy/clay nanocomposite system. The glass transition temperature of the epoxy/clay nanocomposite system increased slightly with increasing clay content. The structure of the nanocomposite system was characterized by X‐ray diffraction analysis and transmission electron microscope imaging. The formation of intercalated structures was observed dominantly in the epoxy/clay nanocomposites, together with some exfoliated structures. POLYM. ENG. SCI., 46:1318–1325, 2006. © 2006 Society of Plastics Engineers     

Effect of exfoliation and dispersion on the yield behavior of melt‐compounded polyethylene–montmorillonite nanocomposites

The yield behavior of melt‐mixed nanocomposites containing 5 wt % organically modified montmorillonite in matrices of a linear low‐density polyethylene (LLDPE) or a modified polyethylene was studied as a function of the temperature and strain rate. In the melt‐mixed LLDPE nanocomposite, the montmorillonite showed a slight increase in the clay spacing, which suggested that the clay was at best intercalated. Transmission electron microscopy (TEM) images showed that the dispersion in this nanocomposite was poor. The use of the modified polyethylene promoted exfoliation of the clay tactoids in the nanocomposite, as assessed by X‐ray diffraction and TEM. In both nanocomposites, the yield mechanisms were insensitive to the addition of the organoclay, even though modest increases in the modulus were produced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3044–3049, 2006     

Preparation and thermal properties of resole‐type phenol resin–clay nanocomposites

Resole‐type phenol resin–clay nanocomposites have been prepared successfully by melt compounding phenol resin with organophilic clay. In the resulting phenol resin–clay nanocomposite, the silicate layers of the clay were exfoliated and dispersed as monolayers. The nanocomposite exhibited higher long‐term heat resistance when compared with unmodified phenol resin. It was surmised that the silicate layers of the clay acted as barriers to oxygen penetration into the resin, as the degree of heat degradation of the nanocomposite was much lower than that of the straight phenol resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3236–3240, 2006     

Structure and properties of nanocomposites based on poly(butylene succinate) and organically modified montmorillonite

Poly(butylene succinate) and organically modified montmorillonite nanocomposites with there different compositions were prepared via melt blending in a twin‐screw extruder. The structure of the nanocomposites was studied with X‐ray diffraction and transmission electron microscopy, which revealed the formation of intercalated nanocomposites, regardless of the silicate loading. Dynamic mechanical analysis revealed a substantial increase in the storage modulus of the nanocomposites over the entire temperature range investigated. The tensile property measurements showed a relative increase in the stiffness with a simultaneous decrease in the yield strength in comparison with that of neat poly(butylene succinate). The oxygen gas barrier property of neat poly(butylene succinate) improved after nanocomposite preparation with organically modified montmorillonite. The effect of the layered‐silicate loading on the melt‐state linear viscoelastic behavior of the intercalated nanocomposites was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 777–785, 2006     

Polymerization kinetics and thermal properties of dicyanate/clay nanocomposites

The polymerization kinetics and thermal properties of dicyanate/clay nanocomposites were investigated. A type of organically modified clay was used as nanometer‐size fillers for the thermosetting dicyanate resin. Differential scanning calorimetry (DSC) was used to study the curing behavior of the dicyanate/clay nanocomposite systems. The polymerization rate of the nanocomposite systems increased with increasing clay content. An autocatalytic reaction mechanism could adequately describe the polymerization kinetics of the dicyanate/clay nanocomposite systems. The polymerization kinetic parameters were determined by fitting the DSC conversion data to the proposed kinetic equation. The glass‐transition temperature of the dicyanate/clay nanocomposites increased with increasing clay content. The thermal decomposition behavior of the dicyanate/clay nanocomposites was investigated by thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1955–1960, 2004     

Reaction kinetics and characteristics of polyurethane/clay nanocomposites

The reaction behavior and physical properties of polyurethane (PU)/clay nanocomposite systems were investigated. Organically modified clay was used as nanofillers to formulate the nanocomposites. Differential scanning calorimetry was used to study the reaction behavior of the PU/clay nanocomposite systems. The reaction rate of the nanocomposite systems increased with increasing clay content. The reaction kinetic parameters of proposed kinetic equations were determined by numerical methods. The glass transition temperatures of the PU/clay nanocomposite systems increased with increasing clay content. The thermal decomposition behavior of the PU/clay nanocomposites was measured by using thermogravimetric analysis. X‐ray diffractometer and transmission electronic microscope data showed the intercalation of PU resin between the silicate layers of the clay in the PU/clay nanocomposites. A universal testing machine was used to investigate the tensile properties of the PU/clay nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1641–1647, 2005     

Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agent

In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X‐ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphology,thermal, and mechanical properties of flame‐retardant silicone rubber/montmorillonite nanocomposites

Flame‐retardant methyl vinyl silicone rubber (MVMQ)/montmorillonite nanocomposites were prepared by solution intercalation method, using magnesium hydroxide (MH) and red phosphorus (RP) as synergistic flame‐retardant additives, and aero silica (SiO₂) as synergistic reinforcement filler. The morphologies of the flame‐retardant MVMQ/montmorillonite nanocomposites were characterized by environmental scanning electron microscopy (ESEM), and the interlayer spacings were determined by small‐angle X‐ray scattering (SAXS). In addition to mechanical measurements and limited oxygen index (LOI) test, thermal properties were tested by thermogravimetric analysis (TGA). The decomposition temperature of the nanocomposite that contained 1 wt % montmorillonite can be higher (129°C) than that of MVMQ as basal polymer matrix when 5% weight loss was selected as measuring point. This kind of silicone rubber nanocomposite is a promising flame‐retardant polymeric material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3275–3280, 2006     

Nanocomposites from fluoro‐oxygenated polyethylene: A novel route to organoclay exfoliation

We present a novel approach to improving organoclay exfoliation in a nonpolar matrix, polyethylene. High‐density polyethylene (HDPE) particles were modified by exposure to a reactive gas atmosphere containing F₂ and O₂. This treatment was aimed at increasing the polarity of the polymer with the formation of carboxyl, hydroxy, and ketone functionalities on the particle surface. The surface‐treated high‐density polyethylene (ST‐HDPE) particles were then melt‐mixed with an appropriate organoclay to form nanocomposites. Transmission electron microscopy (TEM), wide‐angle X‐ray scattering, stress–strain analysis, and Izod impact measurements were used to evaluate the nanocomposite morphology and physical properties. These data were compared to those of equivalent nanocomposites prepared from unmodified HDPE and high‐density polyethylene grafted with maleic anhydride (HDPE‐g‐MA). The nanocomposites prepared from the ST‐HDPE particles exhibited much better properties and organoclay dispersion than those prepared from unmodified HDPE. The level of reinforcement observed in ST‐HDPE‐based nanocomposites was comparable to, if not better than, that seen in HDPE‐g‐MA‐based nanocomposites. However, a comparison of the TEM micrographs suggested better organoclay exfoliation in HDPE‐g‐MA than the current version of ST‐HDPE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2980–2989, 2006     

Kinetic study on the UV‐induced photopolymerization of epoxy acrylate/TiO2 nanocomposites by FTIR spectroscopy

The kinetics of the photopolymerization of epoxy acrylate/TiO₂ nanocomposites, with 2′2‐dimethoxy‐1,2‐diphenylethan‐1‐one (Irgacure 651) or benzophenone/N‐methyl diethanolamine as photoinitiators, were studied by FTIR spectroscopy. It was found that nanocomposites had a decreasing photopolymerization rates in comparison with pure epoxy acrylate. The photopolymerization rate of the nanocomposite could also be influenced by initiator types, oxygen, film thickness, irradiation intensity, dispersing media of TiO₂ slurry, and so forth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3281–3287, 2006     

Functional copolymer/organo‐MMT nanoarchitectures. II. Dynamic mechanical behavior of poly(MA‐co‐BMA)s‐organo‐MMT clay nanocomposites

Functional copolymer/organo‐silicate [N,N′‐dimethyldodecyl ammonium cation surface modified montmorillonite (MMT)] layered nanocomposites have been synthesized by interlamellar complex‐radical copolymerization of preintercalated maleic anhydride (MA)/ organo‐MMT complex as a ‘nano‐reactor’ with n‐butyl methacrylate (BMA) as an internal plasticization comonomer in the presence of radical initiator. Synthesized copolymers and their nanocomposites were investigated by dynamic mechanic analysis, X‐ray diffraction, SEM, and TEM methods. It was found that nanocomposite dynamic mechanical properties strongly depend on the force of interfacial MA … organo‐MMT complex formation and the amount of flexible n‐butyl ester linkages. An increase in both of these parameters leads to enhanced intercalation and exfoliation in situ processes of copolymer chains and the formation of hybrid nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry     

Synthesis and characteristics of poly(methyl methacrylate)/expanded graphite nanocomposites

In this work, we synthesized poly(methyl methacrylate) (PMMA)/expanded graphite (EG) nanocomposites by a new polymerization method. The volume electrical conductivity of the nanocomposite prepared by this way is very high (when the content of EG is about 8 wt %, the conductivity could reach 60 S/cm). The structure of the nanocomposite was investigated by SEM, TEM, IR, and XRD. And we found temperature and voltage were important parameters of governing the electrical conductivity of PMMA/EG nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1427–1431, 2006     

Rubber‐toughened polypropylene nanocomposite: Effect of polyethylene octene copolymer on mechanical properties and phase morphology

Rubber‐toughened polypropylene (PP)/org‐Montmorillonite (org‐MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twin‐screw extruder at 230°C and injection‐molded. The POE used had 25 wt % 1‐octene content and the weight fraction of POE in the blend was varied in the range of 0–20 wt %. X‐ray diffraction analysis (XRD) revealed that an intercalation org‐MMT silicate layer structure was formed in rubber‐toughened polypropylene nanocomposites (RTPPNC). Izod impact measurements indicated that the addition of POE led to a significant improvement in the impact strength of the RTPPNC, from 6.2 kJ/m² in untoughened PP nanocomposites to 17.8 kJ/m² in RTPPNC containing 20 wt % POE. This shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Young's modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two‐phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3441–3450, 2006     

Novel conducting nanocomposite based on polypyrrole and modified poly(styrene‐alt‐maleic anhydride) via emulsion polymerization: Synthesis,Characterization, Antioxidant,and heavy metal sorbent activity

Novel polypyrrole/modified poly(styrene‐alt‐maleic anhydride) conducting nanocomposites were prepared via emulsion polymerization using sodium dodecyl sulfate as an emulsifier and ammonium persulfate as an oxidant. Modified poly(styrene‐alt‐maleic anhydride) was used as an external dopant for conductivity enhancement of polypyrrole. The conductivity of nanocomposites was measured with a four‐probe method. The maximum electrical conductivity of the nanocomposite was 1.40 S/cm. The data from this research showed that the novel nanocomposite presents good tendency for the removal of heavy metal ions from aqueous solutions. Also the prepared nanocomposites were analyzed for their antioxidant activity using 2,2‐diphenyl‐1‐picrylhydrazyl assay. The results showed that the antioxidant activity of the nanocomposite was 60%. The nanocomposites were characterized by Fourier transform infrared, ultraviolet–visible, X‐ray diffraction, field emission scanning electron microscopy, and differential scanning calorimetry measurements. POLYM. COMPOS., 36:138–144, 2015. © 2014 Society of Plastics Engineers     

Orientation of montmorillonite clay in dicyclopentadiene/organically modified clay dispersions and nanocomposites

Highly delaminated dispersions of the organically modified clay I‐28 (Nanocor, Inc.) in liquid dicyclopentadiene (DCPD) were prepared. In situ ring‐opening metathesis polymerization of I‐28/DCPD nanodispersions generated I‐28/poly(DCPD) nanocomposites. When clay/DCPD dispersions were cured under shear, alignment of clay platelets, tactoids, and small particles was captured. This orientation was confirmed by X‐ray diffraction and transmission electron microscopy. The Herman's orientation parameters were calculated for the oriented nanocomposites. Viscosities of these liquid nanodispersions exhibited thixotropic flow behavior, prior to curing. The time‐dependent viscosity effects became more pronounced with an increase in delamination. Initial viscosities increased with progressive clay platelet generation during delamination and nanodispersion within the liquid monomer. Viscosity can be used to follow clay exfoliation/delamination. Etching the surface of a 2 wt % I‐28 clay/poly(DCPD) nanocomposite with oxygen plasma eroded the matrix, exposing clay tactoids protruding from the surface. These surfaces were examined by SEM and energy dispersive X‐ray spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2743–2751, 2006     

Multiwall‐carbon‐nanotube‐reinforced poly(ethylene terephthalate) nanocomposites by melt compounding

Poly(ethylene terephthalate) (PET) nanocomposites reinforced with multiwall carbon nanotubes (MWCNTs) were prepared through melt compounding in a twin‐screw extruder. The presence of MWCNTs, which acted as good nucleating agents, enhanced the crystallization of PET through heterogeneous nucleation. The incorporation of a small quantity of MWCNTs improved the thermal stability of the PET/MWCNT nanocomposites. The mechanical properties of the PET/MWCNT nanocomposites increased with even a small quantity of MWCNTs. There was a significant dependence of the rheological properties of the PET/MWCNT nanocomposites on the MWCNT content. The MWCNT loading increased the shear‐thinning nature of the polymer‐nanocomposite melt. The storage modulus and loss modulus of the PET/MWCNT nanocomposites increased with increasing frequency, and this increment effect was more pronounced at lower frequencies. At higher MWCNT contents, the dominant nanotube–nanotube interactions led to the formation of interconnected or networklike structures of MWCNTs in the PET/MWCNT nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1450–1457, 2007     

Thermal and surface characterization of polyurethane–urea clay nanocomposite coatings

This paper reports synthesis and characterization of polyurethane–urea (PU‐urea) and the nanocomposites derived from the PU‐urea with silicate clays. Organophilic montmorillonite cotreated by cetyl trimethyl ammonium bromide (CTAB) was synthesized and used to prepare PU‐urea/montmorillonite nanocomposites coatings. PU‐ureas were prepared from polyethylene glycol (PEG), polypropylene glycol (PPG), trimethylol propane (TMP), and 4,4′‐diphenylmethane diisocyanate (MDI) by reacting excess diisocyanate with polyether glycols. The excess isocyanate of the prepolymers was cured with atmospheric moisture. The synthesized moisture cured PU‐urea and nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), and angle resolved X‐ray photoelectron spectroscopy (AR‐XPS). The thermal stability of the PU‐urea nanocomposites was higher relative to the mother PU‐urea films. DSC results showed a slight enhancement in the soft segment glass transition temperature after 3 wt % clay loading. The surface properties showed an enrichment of the soft segment toward the surface. An enhancement in the hard segment composition in the nanocomposite coatings has resulted in enhancing the phase mixing process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2393–2401, 2006     

Microemulsion route to fabrication of silver and platinum‐polymer nanocomposites

Polymethylmethacrylate (PMMA)‐platinum and PMMA‐silver nanocomposites have been produced using polymerization of W/O microemulsions. MMA monomer was used as the oil or continues phase of the microemulsion system and polymerized following formation of Pt and Ag nanoparticles in the fluid medium. The UV‐vis absorption spectra have been used to trace the growth process of the nanoparticles in the microemulsion system. Scanning electron microscopy and transmission electron microscopy (TEM) have been used to determine the morphology and particle size of the Pt and Ag particles in the synthesized nanocomposites. Image analyses of TEM micrographs confirm that the Pt and Ag particles in the synthesized nanocomposites have a narrow size distribution. Meanwhile, Fourier‐transform infrared spectroscopy was used to verify polymer‐nanoparticles interaction in nanocomposite bulk. POLYM. COMPOS., 35:2023–2028, 2014. © 2014 Society of Plastics Engineers