Impact‐modified polypropylene/vermiculite nanocomposites

Impact‐modified polypropylene (PP)/vermiculite (VMT) nanocomposites toughened with maleated styrene–ethylene butylene–styrene (SEBS‐g‐MA) were compounded in a twin‐screw extruder and injection‐molded. VMT was treated with maleic anhydride, which acted both as a compatibilizer for the polymeric matrices and as a swelling agent for VMT in the nanocomposites. The effects of the impact modifier on the morphology and the impact, static, and dynamic mechanical properties of the PP/VMT nanocomposites were investigated. Transmission electron microscopy revealed that an exfoliated VMT silicate layer structure was formed in ternary (PP–SEBS‐g‐MA)/VMT nanocomposites. Tensile tests showed that the styrene–ethylene butylene–styrene additions improved the tensile ductility of the (PP–SEBS‐g‐MA)/VMT ternary nanocomposites at the expense of their tensile stiffness and strength. Moreover, Izod impact measurements indicated that the SEBS‐g‐MA addition led to a significant improvement in the impact strength of the nanocomposites. The SEBS‐g‐MA elastomer was found to be very effective at converting brittle PP/VMT organoclay composites into tough nanocomposites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2332–2341, 2003     

Structure and properties of polyamide‐6/vermiculite nanocomposites prepared by direct melt compounding

Polyamide‐6 (PA6)/vermiculite nanocomposites were fabricated through the direct melt compounding of maleic anhydride‐modified vermiculite (MAV) with PA6 in a twin‐screw extruder followed by injection molding. The structure and morphology of the nanocomposites were determined by X‐ray diffraction and scanning and transmission electron microscopy techniques. The results revealed the formation of intercalated and exfoliated vermiculite platelets in the PA6 matrix. Tensile measurement showed that the tensile modulus and strength of the nanocomposites tended to increase with increasing vermiculite content. The thermal properties of the nanocomposites were determined by dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetry measurements. The storage modulus of the PA6–MAV nanocomposites increased to almost twice that of the neat PA6. The thermal stability of the nanocomposites increased dramatically, and this was associated with the addition of vermiculite. The effect of the addition of maleic anhydride on the formation of the PA6–vermiculite nanocomposites was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2860–2870, 2002     

Effect of a post‐annealing process on microstructure and mechanical properties of high‐density polyethylene/silica nanocomposites

High‐density polyethylene (HDPE) and nanosilica nanocomposites were prepared for SiO₂ content up to 15 wt%. Microstructural characterization evidenced a homogenous distribution of silica aggregates with a mean size increasing with the filler content finally resulting in a rheological percolation between 7.5 and 10 wt%. Nanoparticles did not induce any significant impact on the matrix crystallinity but led to a real improvement on elastic properties accompanied with a large embrittlement above the percolation threshold. The effect of annealing near HDPE melting temperature was studied. Differential scanning calorimetry, X‐ray diffraction, and small‐angle X‐ray scattering analyses showed a significant change in the HDPE microstructure after annealing at 125°C. A large increase in the crystallinity (from 68 to 76%) and a clear improvement of Young's modulus (by 55%) were observed prior to polymer degradation. A valuable impact of silica particles on thermal stability was also obvious regarding the evolution of elastic properties for extended exposure times (850–1,200 h). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 535–546     

Synthesis and characterization of polyethylene/clay–silica nanocomposites: A montmorillonite/silica‐hybrid‐supported catalyst and in situ polymerization

A novel approach to the preparation of polyethylene (PE) nanocomposites, with montmorillonite/silica hybrid (MT‐Si) supported catalyst, was developed. MT‐Si was prepared by depositing silica nanoparticles between galleries of the MT. A common zirconocene catalyst [bis(cyclopentadienyl)zirconium dichloride/methylaluminoxane] was fixed on the MT‐Si surface by a simple method. After ethylene polymerization, two classes of nanofillers (clay layers and silica nanoparticles) were dispersed concurrently in the PE matrix and PE/clay–silica nanocomposites were obtained. Exfoliation of the clay layers and dispersion of the silica nanoparticles were examined with transmission electron microscopy. Physical properties of the nanocomposites were characterized by tensile tests, dynamic mechanical analysis, and DSC. The nanocomposites with a low nanofiller loading (<10 wt %) exhibited good mechanical properties. The nanocomposite powder produced with the supported catalyst had a granular morphology and a high bulk density, typical of a heterogeneous catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 941–949, 2004     

Influence of gamma irradiation on high density polyethylene/ethylene‐vinyl acetate/clay nanocomposites

The study of high density polyethylene (HDPE)/ethylene‐vinyl acetate (EVA)/and organically‐modified montmorillonite (OMT) nanocomposites prepared by melt intercalation followed by exposure to gamma‐rays have been carried out. The morphology and properties of the nanocomposites were studied using X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cone calorimetry. The purpose of the study focuses on the influence of gamma irradiation on the morphology, thermal stability and flammability properties of the nanocomposites. XRD studies and TEM images verified that the ordered intercalated nanomorphology of the nanocomposites was not disturbed by gamma irradiation. TGA data showed that the nano‐dispersion of clay throughout the polymer inhibited the irradiation degradation of HDPE/EVA blend, which led to the nanocomposites exhibiting superior irradiation‐resistant properties than that of the pure blend. Cone calorimetry results indicated that the improvement in heat release rate (HRR) for irradiated HDPE/EVA blend was suppressed efficiently when clay was present. Increasing clay loading from 2 to 10% was beneficial by improving the flammability properties of the nanocomposites, but promoted a rapid increase in the sub‐peak HRR at high irradiation dose level. Copyright © 2004 John Wiley & Sons, Ltd.     

Biodegradable poly(p‐dioxanone) reinforced and toughened by organo‐modified vermiculite

Poly(p‐dioxanone) (PPDO)/vermiculite (VMT) nanocomposites with exfoliated structure were prepared successfully by in situ intercalative polymerization of p‐dioxanone (PDO) in the presence of organo‐modified vermiculite (OVMT) with the aid of ultrasonic action. The nano‐structure of the nanocomposites was established using X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations. The investigation of crystallization behavior by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) proved that exfoliated OVMT platelets acted as a template for spherulite growth. The thermal stability of nanocomposites was enhanced than that of pure PPDO. Dynamic mechanical analysis (DMA) indicated nanoscale OVMT platelets restricted the motion of PPDO segments, which benefitted the increase of storage and loss modulus. The tensile properties showed that nanocomposites were reinforced and toughened significantly by the addition of nanoscale OVMT platelets. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and enhanced properties of poly(propylene)/ silica‐grafted‐hyperbranched polyester nanocomposites

A series of poly(propylene) silica‐grafted‐hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn? H20), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface of SiO₂ particles (30 nm) through 3‐glycidoxy‐propyltrimethoxysilane (GPTS) was prepared. The effect of silica‐grafted‐modified Boltorn? H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn? H20 was successfully grafted onto the SiO₂ surface confirmed by FT‐IR and X‐ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica‐grafted‐modified Boltorn? H20 (3–5 wt% SiO₂) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica‐grafted‐modified Boltorn? H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica‐grafted‐modified Boltorn? H20 particles were added compared with PP/SiO₂ or PP/SiO₂‐GPTS composites. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of extrusion and photo-oxidation on polyethylene/clay nanocomposites

Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) and the clays on the behaviour of the nanocomposites during processing and under accelerated weathering conditions were investigated. X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), rheometry and attenuated reflectance spectroscopy (ATR-FTIR) showed that the nanocomposite structure obtained is dependent on the type of clay used, the presence or absence of a compatibiliser and the environment the samples are exposed to. The results revealed that during processing PE/clay nanocomposites are formed in the presence of the compatibiliser PEgMA giving a hybrid exfoliated and intercalated structures, while microcomposites were obtained in the absence of PEgMA; the unmodified NaMMT-containing samples showed encapsulated clay structures with limited extent of dispersion in the polymer matrix. The effect of processing on the thermal stability of the OMMT-containing polymer samples was determined by measuring the additional amount of vinyl-type unsaturation formed due to a Hoffman elimination reaction that takes place in the alkyl ammonium surfactant of the modified clay at elevated temperatures. The results indicate that OMMT is responsible for the higher levels of unsaturation found in OMMT-PE samples when compared to both the polymer control and the NaMMT-PE samples and confirms the instability of the alkyl ammonium surfactant during melt processing and its deleterious effects on the durability aspects of nanocomposite products. The photostability of the PE/clay nanocomposites under accelerated weathering conditions was monitored by following changes in their infrared signatures and mechanical properties. The rate of photo-oxidation of the compatibilised PE/PEgMA/OMMT nanocomposites was much higher than that of the PE/OMMT (in absence of PEgMA) counterparts, the polymer controls and the PE–NaMMT sample. Several factors have been observed that can explain the difference in the photo-oxidative stability of the PE/clay nanocomposites including the adverse role played by the thermal decomposition products of the alkyl ammonium surfactant, the photo-instability of PEgMA, unfavourable interactions between PEgMA and products formed in the polymer as a consequence of the degradation of the surfactant on the clay, as well as a contribution from a much higher extent of exfoliated structures, determined by TEM, formed with increasing UV-exposure times.     

Cold‐drawn induced microstructure in PVC‐bentonite nanocomposites

The mechanical properties and cold drawn‐induced micro and nanostructure of polyvinyl chloride (PVC)‐bentonite nanocomposites have been investigated. Molded sheets with 5 wt% concentration of bentonite and two processing additives were melt extruded and two‐roll‐milled processed. The flame retardant additive promoted polymer intercalation whereas a pigment dispersant promoted clay exfoliation, the polymer matrix showed isotropic orientation. The intercalated nanocomposite exhibited nanoplates oriented with their planes parallel to the molded sheet surface and the Young's modulus and yield stress were significantly enhanced relative to neat PVC. The strain at fracture (～144%) was slightly reduced relative to the matrix (～167%). Cold drawing induced molecular chain orientation along the tensile axis and preserved the orientation of the intercalated nanoclays. The fracture mechanism, as investigated via scanning electron microscopy (SEM) revealed plastic fracture mechanism (similar to neat PVC). On the other hand, the exfoliated nanocomposite did not show any improvement in mechanical properties but rather a significant decay of strain at fracture (～44%). The fractured region, as examined by SEM, exhibited microvoid morphology. Analysis of the fractured region showed PVC macromolecules oriented along the tensile axis but no preferred orientation of the nanoclays. The limited strain at fracture found for this material appears to be associated with the initially randomly oriented nanoclays being unable to orient under the tensile deformation. The nanoclays would act as stress concentrators leading to rapid material's failure due to loss of adhesion with the polymer matrix. The results suggest that exfoliated nanoclays could play a detrimental role when the nanocomposite is subjected to large deformations at temperatures well within the glassy regime. Copyright © 2009 John Wiley & Sons, Ltd.     

A molecular‐level computational study of the diffusion and solubility of water and oxygen in carbonaceous polyethylene nanocomposites

Monte Carlo and molecular dynamics simulations were performed to investigate the effect on the solubility, diffusion, and permeability of water and oxygen when adding graphene or single‐walled carbon nanotubes (SWCNTs) to polyethylene (PE). When compared with pure PE, addition of graphene lowered the solubility of water, whereas at lower temperatures, the oxygen solubility increased because of the oxygen–graphene interaction. Addition of SWCNTs lowered the solubility of both water and oxygen when compared with pure PE. A detailed analysis showed that an ordered structure of PE is induced near the additive surface, which leads to a decrease in the diffusion coefficient of both penetrants in this region. The addition of graphene does not change the permeation coefficient of oxygen (in the direction parallel to the filler) and, in fact, may even increase this coefficient when compared with pure PE. In contrast, the water permeability is decreased when graphene is added to PE. The addition of SWCNTs decreases the permeability of both penetrants. Graphene can consequently be added to selectively increase the solubility and permeation of oxygen over water, at least at lower temperatures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 589–602     

Crystallization regime characteristics of exfoliated polyethylene/vermiculite nanocomposites

Polyethylene (PE)–vermiculite (VMT) nanocomposites containing 0.5, 2, 4, 6, and 8 wt % clay loadings were fabricated via direct melt compounding in a twin‐screw extruder. Crystallization kinetics was investigated by means of polarized optical microscopy and differential scanning calorimetry. Moreover, the kinetics of the spherulitic growth of PE–VMT nanocomposites was evaluated with the Lauritzen–Hoffman (LH) secondary nucleation theory. The results showed that the PE–VMT nanocomposite exhibits crystallization regime characteristics. The nucleation constants for regimes I and II were determined from the slope of the LH plots. The fold surface energies (σ_e) of the PE–VMT nanocomposites were estimated from these slopes. The σ_e values were found to decrease with an increasing VMT content, up to 2%, in regime I. Further increasing the VMT content resulted in a slight increase of the σ_e values. In regime II, the σ_e values of the nanocomposites were generally lower than that of pure PE. These results demonstrated that the exfoliated silicate layers acted as effective nucleation sites for the secondary nucleus of the nanocomposites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 253–263, 2005     

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

Polyethylene (PE) composites with titanium oxide (TiO₂) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO₂ nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO₂). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO₂ and Mod‐TiO₂ nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO₂ nanocomposites containing 8 wt % of TiO₂ exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO₂ nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Solidlike transition of melt‐intercalated biodegradable polymer/clay nanocomposites

Synthetic biodegradable aliphatic polyester (BAP) intercalated into organoclay was prepared by melt compounding, and its solidlike characteristics were investigated via several rheological test modes: steady shear rotation, oscillation, and creep testing. Structural investigations with X‐ray diffraction and transmission electron spectroscopy were also performed for a better understanding of the characteristic rheological behaviors. The creep, recovery, and stress modulus exhibited a solidlike transition of BAP/clay nanocomposites that depended on the clay content. An increase in the zero shear rate viscosity and a shifting of the crossover point (storage modulus vs loss modulus) to a lower frequency were also observed with increasing clay contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2052–2061, 2003     

Influence of MWCNT morphology on dispersion and thermal properties of polyethylene nanocomposites

In this study a series of multi-walled carbon nanotube (MWCNT)/Polyethylene (PE) composites with different kinds and several concentrations of carbon nanotubes (CNTs) were investigated. The morphology and degree of dispersion of the fillers in the polymer matrix at different length scales was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both individual and agglomerated MWCNTs were evident but a good dispersion was observed for some of them. TGA measurements were performed on nanocomposites in order to understand if CNTs affect the stabilization mechanism during thermal and oxidative degradation. The analysis demonstrates that MWCNTs presence slightly delays thermal volatilisation (15-20 °C) without modification of thermal degradation mechanism. In contrast, thermal oxidative degradation in air is delayed up to about 100 °C dependently from MWCNTs concentration, in the range used here (0.1-2.0 wt%), and degree of dispersion. The stabilization is due to the formation of a thin protective layer of entangled MWCNTs kept together by carbon char generated on the surface of the nanocomposites as shown by SEM images taken on degradation residues.     

Review of melt‐processed nanocomposites based on EVOH/organoclay

EVOH nanocomposites containing organically treated clays are unique systems in which the clay is strongly attracted to EVOH, thus affecting the morphology and the resultant thermal and mechanical properties. A strong effect of the processing conditions on morphology, thermal, and mechanical properties was observed. In highly interacting systems, under dynamic mixing conditions, in addition to a fracturing process of the clay particles, an onion‐like delamination process is suggested. EVA‐g‐MA and LLDPE‐g‐MA, having polar groups, were studied as compatibilizers to further induce clay intercalation and exfoliation. The compatibilizers affected both the thermal and mechanical properties of the composites at different levels. Thermal analysis showed that with increasing compatibilizer content lower crystallinity levels result, until at a certain content no crystallization has taken place. A Ny‐6 (nylon‐6)/EVOH blend is an interesting host matrix for incorporation of low organoclay contents. The Ny‐6/EVOH blend is a unique system that tends to hydrogen bond and also to in situ chemically react during melt mixing. The addition of clay seems to interrupt the chemical reaction between the two host polymers at certain compositions, leading to lower melt blending torque levels when clay is present. A competition between Ny‐6 and EVOH regarding the intercalation process takes place. However, Ny‐6 seems to lead to exfoliated structures, whereas EVOH forms intercalated structures, as revealed from combined XRD and TEM experiments, owing to thermodynamic considerations and preferential localization of the clay in Ny‐6. Of special interest is the increased storage modulus seen by the presence of only 1 wt % clay, which was achieved by extrusion under high shear forces, leading to a completely exfoliated structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1931–1943, 2005     

Characterization of polysuccinate and hydroxyapatite‐based nanocomposites containing poly(ester‐anhydride) microspheres

Repair and regeneration of bone defects with particular shape may be enhanced by in situ forming biomaterials which can be used in minimal invasive surgery. This study is aimed to prepare novel in situ forming biodegradable nanocomposites based on poly(3‐allyloxy‐1,2‐propylene) succinate (PSAGE) and nanosized hydroxyapatite (HA). These nanocomposite materials contain poly(ester‐anhydride) (PEA) microspheres embedded in a polyester matrix prepared by crosslinking PSAGE with oligo(1,2‐propylene maleate) and methacrylic monomers. Methyl methacrylate and one of hydrophilic oligo(ethylene glycol) methacrylates with different functionality and various length of oligooxyethylene chains were used as polymerizable diluents. Incorporation of microspheres which degrade faster than crosslinked polyester matrices enables formation of porous structure in situ. The obtained materials are liquid before curing and harden in several minutes with moderate exothermic effect. The effect of the composition of nanocomposite materials on selected properties, such as water sorption, mechanical strength, porosity and hydrolytic degradation process, was investigated. Rheological behavior and injectability of liquid formulations were studied. Analysis by energy dispersive spectroscopy confirmed the presence of characteristic features of HA in the nanocomposite materials. The morphology of the cured nanocomposites subjected to hydrolytic degradation was evaluated by scanning electron microscopy. The MTS cytotoxicity assay was carried out for extracts from crosslinked materials using hFOB1.19 cells. It was found that the extracts exhibit a dose‐dependent cytotoxic response. Copyright © 2014 John Wiley & Sons, Ltd.     

魔芋葡甘聚糖／SiO2纳米复合物的制备与表征

用纳米SiO2为原料,以魔芋葡甘聚糖(KGM)为基体,采用共混法制得KGM/SiO2纳米复合物。通过傅立叶红外光谱(FTIR)、热重分析(TG)、透射电镜(TEM)等手段对该体系进行了表征。结果表明:由于纳米SiO2粒子的引入,KGM分子FTIR的某些特征峰的波数发生明显变化;纳米SiO2在复合物中的分散性较好;复合材料的热稳定性高于KGM薄膜;此外,复合材料的力学性能有所提高。     

Incorporation of carbon nanotubes into polyethylene by high energy ball milling: Morphology and physical properties

High energy ball milling (HEBM) was utilized, as an innovative process, to incorporate carbon nanotubes (CNTs) into a polyethylene (PE) matrix avoiding: high temperatures, solvents, ultrasonication, chemical modification of carbon nanotubes. Composites with 1, 2, 3, 5, and 10 wt % of carbon nanotubes were prepared. Films were obtained melting the powders in a hot press. Morphology and physical properties (thermal, mechanical, electrical properties) were evaluated. The used processing conditions allowed to obtain a satisfactory level of dispersion of CNTs into the PE matrix with a consequent improvement of the physical properties of the samples. The thermal degradation was significantly delayed already with 1–2% wt of CNTs. The mechanical properties resulted greatly improved for low filler content (up to 3% wt). The electrical measurements showed a percolation threshold in the range 1–3 wt % of CNTs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 597–606, 2007     

Water‐assisted melt compounding of nylon‐6/pristine montmorillonite nanocomposites

An exploratory pioneering study on the fabrication of nylon‐6/montmorillonite (MMT) nanocomposites with the aid of water as an intercalating/exfoliating agent via melt compounding in a twin‐screw extruder was conducted. Commercial nylon‐6 pellets and pristine MMT powder were directly fed into the hopper of the extruder. Water was then injected into the extruder downstream. After interactions with the nylon‐6 melt/pristine MMT system, water was removed from the extruder further downstream via a venting gate. As such, no third‐component residual was left within the extrudates. Transmission electron microscopy micrographs showed that pristine MMT was uniformly dispersed in the nylon‐6 matrix. The contact time between water and the nylon‐6/pristine MMT system inside the extruder was so short that nylon‐6 was subjected to very little hydrolysis, if any. The resultant nanocomposites showed higher stiffness, superior tensile strength, and improved thermal stability in comparison with their counterparts obtained without water assistance and the nylon‐6/organic MMT nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1100–1112, 2005     

Poly(1‐butene)/clay nanocomposites: Preparation and properties

The preparation and properties of poly(1‐butene) (PB)/clay nanocomposites are described for the first time. Nanocomposites were prepared with the melt‐intercalation technique, using organically modified clay. The X‐ray diffraction patterns portrayed well‐defined diffraction peaks at higher d‐spacing than pristine clay, confirming the intercalation of polymer in silicate layers. Because PB exhibits time‐dependent polymorphism, the effect of clay on the phase transformation of PB was examined with thermal analysis. The phase transformation from a metastable tetragonal form to a stable hexagonal form was enhanced because of incorporation of layered silicates in the polymer matrix. The nanocomposites exhibited about a 40–140% increase in storage modulus depending on the clay content and significantly lower coefficient of thermal expansion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1014–1021, 2003