Effects of organoclays on morphology and thermal and rheological properties of polystyrene and poly(methyl methacrylate) blends

Morphology, thermal and rheological properties of polymer‐organoclay composites prepared by melt‐blending of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS/PMMA blends with Cloisite® organoclays were examined by transmission electron microscopy, small‐angle X‐ray scattering, secondary ion mass spectroscopy, differential scanning calorimetry, and rheological techniques. Organoclay particles were finely dispersed and predominantly delaminated in PMMA‐clay composites, whereas organoclays formed micrometer‐sized aggregates in PS‐clay composites. In PS/PMMA blends, the majority of clay particles was concentrated in the PMMA phase and in the interfacial region between PS and PMMA. Although incompatible PS/PMMA blends remained phase‐separated after being melt‐blended with organoclays, the addition of organoclays resulted in a drastic reduction in the average microdomain sizes (from 1–1.5 μm to ca. 300–500 nm), indicating that organoclays partially compatibilized the immiscible PS/PMMA blends. The effect of surfactant (di‐methyl di‐octadecyl‐ammonia chloride), used in the preparation of organoclays, on the PS/PMMA miscibility was also investigated. The free surfactant was more compatible with PMMA than with PS; the surfactant was concentrated in PMMA and in the interfacial region of the blends. The microdomain size reduction resulting from the addition of organoclays was definitely more significant than that caused by adding the same amount of free surfactant without clay. The effect of organoclays on the rheological properties was insignificant in all tested systems, suggesting weak interactions between the clay particles and the polymer matrix. In the PS system, PMMA, and organoclay the extent of clay exfoliation and the resultant properties are controlled by the compatibility between the polymer matrix and the surfactant rather than by interactions between the polymer and the clay surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 44–54, 2003     

Structure–property relationships of polymer blend/clay nanocomposites: Compatibilized and noncompatibilized polystyrene/propylene/clay

Polymer blends represent an important class of materials in engineering applications. The incorporation of clay nanofiller may provide new opportunities for this type of materials to enhance their applications. This article reports on the effects of clay on the structure and properties of compatibilized and noncompatibilized polymer blends and presents a detailed process for quantitative analysis of the elastic moduli of polymer blend/clay nanocomposites, based on immiscible polystyrene/polypropylene (PS/PP) blends with or without maleated PP as the compatibilizer. The results show that in the noncompatibilized PS/PP/clay nanocomposite clay locates solely in the PS phase, whereas in the compatibilized nanocomposite clay disperses in both phases. The addition of clay to both polymer blends reduces the domain size significantly, modifies the crystallinity and improves the stiffness. The Mori–Tanaka and Christensen's models offer a reasonably good prediction of the elastic moduli of both types of nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Impact fracture behavior of nylon-6/ABS blends

Tensile and impact properties of uncompatibilized nylon-6/ABS blends have been studied over the entire range of compositions. The blends were prepared by extrusion and, subsequently, injection molded into tensile specimens and rectangular plaques. The impact fracture performance was characterized using recently proposed models based on fracture mechanics, for various fracture behaviors. The results showed that nylon-6 breaks in a brittle manner. With the addition of ABS, the blend exhibits the same behavior with a slightly lower impact resistance up to about 60 wt %. A sudden jump in the value of impact fracture energy is observed around 70 wt % ABS with a brittle—ductile transition in the mechanism of fracture. The transition in fracture mechanisms is confirmed through observation of the fracture surfaces by scanning electron microscopy (SEM). Tensile tests showed that the elongation at break increases only slightly between 0 and 50% ABS content, but a significant jump occurs around 70% ABS, reaching a 6-fold increase in comparison to that of the pure components. SEM observation of etched samples shows that a cocontinuous morphology occurs around 70 wt % ABS. The peak observed for the elongation at break and the jump in impact performance, as well as the onset of brittle–ductile transition, are attributed to this morphological effect. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2583–2592, 1997     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

Influence of multiwall carbon nanotubes on morphology and electrical conductivity of PP/ABS blends

Polypropylene (PP) and acrylonitrile‐butadiene‐styrene (ABS) blends with multiwall carbon nanotubes (MWNT) were prepared by melt mixing. PP/ABS blends without MWNT revealed coarse co continuous structures on varying the ABS content from 40 to 70 wt %. Bulk electrical conductivity of the blends showed lower percolation threshold (0.4–0.5 wt %) in the 45/55 co continuous blends whereas the percolation threshold was between 2 and 3 wt % in matrix‐particle dispersed morphology of 80/20 blends. Interestingly, droplet size was observed to decrease with addition of MWNT above percolation threshold in 80/20 blends. Further, the bulk electrical conductivity was found to be dependent on the melt flow index of PP. The non‐polar or weakly polar nature of blends constituents resulted in the temperature independent dielectric constant, dielectric loss, and DC electrical conductivity. Rheological analysis revealed the formation of 3D network‐like structure in 80/20 PP/ABS blends at 3 wt % MWNT. An attempt was made to understand the relationship between rheology, morphology, and electrical conductivity of these blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2286–2295, 2008     

Morphological and thermal properties of ABS/montmorillonite nanocomposites using two different ABS polymers and four different montmorillonite clays

ABS/Clay nanocomposites were prepared using two ABS with different Acrylonitrile (AN) contents and four montmorillonite clays; a natural clay (CNa+) and three modified clays, Cloisites 10A, 20A, and 30B. The composites were prepared in a twin‐screw extruder. Results were analyzed considering the effect of clay and ABS type, on the clay dispersion, intercalation and exfoliation, as well as on the storage modulus and thermal stability of the nanocomposites. XRD and TEM confirm that when using an ABS with higher AN content (ABS2), a better dispersion and intercalation–exfoliation can be obtained. Cloisites 20A and 30B, respectively the one with greater initial intergallery spacing, but lower polarity and with smaller inter‐gallery spacing but greater polarity, produce the ABS nanocomposites with the greater intergallery spacing. Both ABS polymers have similar storage modulus and T_g and in both cases, the modulus increases with the 4 wt % clay. This increase is greater with the modified clays and slightly greater with the ABS2. T_g, from tan δ, increases very little with the 4 wt % clay, but again, this is slightly greater with ABS2. TGA and flammability tests show that the dispersed clay enhances the thermal stability and that the ABS with higher AN content produces a greater increase in fire retardancy. Tests also show that the better thermal stability and fire retardancy is obtained with the Cloisites 20A or 30B. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 190–200, 2008     

Thermal and mechanical properties of syndiotactic polystyrene/organoclay nanocomposites with different microstructures

The fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene‐co‐vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1685–1693, 2004     

Effect of the Mixture Composition on Shear and Extensional Rheology of Recycled PET and ABS Nanocomposites

Summary: Recycled PET as well as ABS - organomodified montmorillonite nanocomposites were prepared via melt compounding in a counter-rotating twin screw extruder. The topological changes in polymer matrices as dependency on clay modification have been evaluated from dynamic experiments in the shear flow using low amplitude oscillatory measurements. Flow characteristics of all studied organoclay nanocomposites showed shear-thinning behavior at low frequencies. Filling of PET with some organoclays led to degradation reactions, which were reflected by lower magnitudes of viscosity and storage modulus in the range of higher frequencies as compared to unfilled polymer matrix. On the contrary, no degradation during the processing of different organoclays with recycled ABS has been observed.     

Transition from crazing to shear deformation in ABS/PVC blends

ABS/PVC blends were prepared over a range of compositions by mixing PVC, SAN, and PB‐g‐SAN. All samples were designed to have a constant rubber level of 12 wt % and the ratio of total‐SAN to PVC in the matrix of the blends varied from 70.5/17.5 to 18/80. Transmission electron microscope and scanning electron microscope have been used to study deformation mechanisms in the ABS/PVC blends. Several different types of microscopic deformation mechanisms, depending on the composition of blends, were observed for the ABS/PVC blends. When the blend is a SAN‐rich system, the main deformation mechanisms were crazing of the matrix. When the blend is a PVC‐rich system, crazing could no longer be detected, while shear yielding of the matrix and cavitation of the rubber particles were the main mechanisms of deformation. When the composition of blend is in the intermediate state, both crazing and shear yielding of matrix were observed. This suggests that there is a transition of deformation mechanism in ABS/PVC blends with the change in composition, which is from crazing to shear deformation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 687–695, 2006     

Impact fracture toughness of polyamide‐6/montmorillonite nanocomposites toughened with a maleated styrene/ethylene butylene/styrene elastomer

Polyamide‐6 (PA6)/montmorillonite (MMT) nanocomposites toughened with maleated styrene/ethylene butylene/styrene (SEBS‐g‐MA) were prepared via melt compounding. Before melt intercalation, MMT was treated with an organic surfactant agent. Tensile and impact tests revealed that the PA6/4% MMT nanocomposite fractured in a brittle mode. The effects of SEBS‐g‐MA addition on the static tensile and impact properties of PA6/4% MMT were investigated. The results showed that the SEBS‐g‐MA addition improved the tensile ductility and impact strength of the PA6/4% MMT nanocomposite at the expenses of its tensile strength and stiffness. Accordingly, elastomer toughening represents an attractive route to novel characteristics for brittle clay‐reinforced polymer nanocomposites. The essential work of fracture (EWF) approach under impact drop‐weight conditions was used to evaluate the impact fracture toughness of nanocomposites toughened with an elastomer. Impact EWF measurements indicated that the SEBS‐g‐MA addition increased the fracture toughness of the PA6/4% MMT nanocomposite. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 585–595, 2005     

Effect of process variables on mechanical properties of polyurethane/clay nanocomposites

This paper addresses the effects of operating variables on mechanical properties of polyurethane/clay nanocomposites including tensile strength, abrasion resistance, and hardness. The variables were prepolymer type, clay cation, clay content, and prepolymer–clay mixing time. The experiments were carried out based on the design of experiments using Taguchi methods. The nanocomposites were synthesized via in situ polymerization starting from two different types of prepolymers (polyether‐ and polyester‐types of polyol reacted with toluene diisocyanate), and methylene‐bis‐ortho‐chloroanilline (MOCA) as a chain extender/hardener. Montmorillonite with three types of cation (Na⁺, alkyl ammonium ion, and MOCA) were examined. Among the parameters studied, prepolymer type and clay cation have the most significant effects on mechanical properties. Polyester nanocomposites showed larger improvements in mechanical properties compared to polyether materials due to higher shear forces exerted by polymer matrix on clay aggregates during polymer–clay mixing. The original MMT with Na⁺ cation results in weak improvements in mechanical properties compared to organoclays. It is observed that the stress and elongation at break, and abrasion resistance of the nanocomposite samples can be optimized with 1.5% of clay loading. The morphology and chemical structure of the optimum sample were examined by X‐ray diffraction and FT‐IR spectroscopy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

ABS的MAH/St多单体熔融接枝及其对PA6/ABS共混体系相形态和力学性能的影响

通过多单体熔融接枝的方法制备出了具有较高接枝率的ABS接枝物 (ABS g (MAH co St) ) ,并对其接枝机理进行了初步探讨 .研究表明 ,MAH、St接枝ABS时 ,反应主要发生在ABS中聚丁二烯的双键部位 .同时 ,当MAH与St的用量比约为 1:1时接枝率达到最高 .ABS g (MAH co St)作为尼龙 6 (PA6 ) ABS共混体系相容剂起到了良好的增容效果 .实验证明 ,相容剂使用前后 ,共混物的相区尺寸由几十 μm减小到 1μm以下 ,且分布更加均匀 ;共混物的拉伸强度和冲击强度等力学性能也同时得到均衡改善 .     

异山梨醇型聚碳酸酯与ABS树脂共混体系的结构与性能研究

采用异山梨醇型聚碳酸酯(DB),与掺混型ABS熔融共混制备了具有不同聚丁二烯(PB)含量和丙烯腈(AN)含量的DB/掺混型ABS合金,并在考察掺混型ABS特征对合金结构与性能的影响的基础上,分别使用同种掺混型ABS以及各种商品化ABS树脂,比较了DB/ABS合金和双酚A型聚碳酸酯/ABS合金的性能及其变化规律.结果表明,对DB/掺混型ABS(70/30)合金而言,PB含量变化对于合金拉伸性能的影响明显大于AN含量变化所带来的影响,在PB含量为6.3 wt%条件下,各不同AN含量的合金体系均有最好的性能表现.PB含量和AN含量变化对合金分散相形态的影响与力学拉伸性能变化特征一致.DB/ABS合金体系均具有良好的热稳定性与热力学相容性,受AN含量和PB含量变化的影响较小,合金玻璃化转变温度与DB非常接近.以双酚A型聚碳酸酯为基础的聚碳酸酯(PC)/ABS合金及以异山梨醇型聚碳酸酯为基础的DB/ABS合金,在拉伸性能变化上均表现出完全相同的规律,且无论是采用掺混型ABS还是采用商品化ABS的体系,PC/ABS与DB/ABS合金在拉伸性能所反映出的规律也是基本一致的.     

Synthesis and characterization of polycyanurate/montmorillonite nanocomposites

The advantages of cyanate esters (CEs) versus competitor systems such as epoxies and polyimides, as well as the great reinforcing potential of organoclays properly dispersed into a polymeric matrix, have been examined in a series of polycyanurate (PCN)/montmorillonite (MMT) nanocomposites prepared under appropriate polymerization conditions. The curing schedule applied resulted in gradual propagation of polymerization. Through this procedure, the intragallery curing rate becomes comparable to the extragallery one, allowing intercalation before gelation. Systems with clay loadings from 1 to 3% per weight were synthesized, and their morphology and mechanical properties were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X‐ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile tests. Microscopy investigations revealed better dispersion for the 3 wt % system compared to smaller concentrations, in which aggregation and, in some cases, agglomeration were the conspicuous features. Roughness and area analyses revealed more homogeneous dispersion for this nanocomposite. Topology and 3D‐phase images further suggested considerable reduction of the average particle diameters. WAXS analysis showed that the interlayer spacing of nanocomposites was increased compared to pristine MMT, indicating the formation of intercalated structures. On the other hand, tensile strength and elongation at break values displayed abrupt diminution with MMT addition, while Young's modulus exhibited a slight but systematic increment with MMT content. The decreasing glass transition tendency observed for small clay loadings was reversed in the case of 3 wt %, while secondary transitions were practically unaffected by the presence of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1036–1049, 2008     

Styrenic polymer nanocomposites based on an oligomerically-modified clay with high inorganic content

Clay was modified with an oligomeric surfactant containing styrene and lauryl acrylate units along with a small amount of vinylbenzyl chloride to permit the formation of an ammonium salt so that this can be attached to a clay. The oligomerically-modified clay contains 50% inorganic clay, and styrenic polymer nanocomposites, including those of polystyrene (PS), high-impact polystyrene (HIPS), styrene-acrylonitrile copolymer (SAN) and acrylonitrile-butadiene-styrene (ABS), were prepared by melt blending. The morphologies of the nanocomposites were evaluated by X-ray diffraction and transmission electron microscopy. Mixed intercalated/delaminated nanocomposites were formed for SAN and ABS while largely immiscible nanocomposites were formed for PS and HIPS. The thermal stability and fire properties were evaluated using thermogravimetric analysis and cone calorimetry, respectively. The plasticization from the oligomeric surfactant was suppressed and the tensile strength and Young's modulus were improved, compared to similar oligomerically-modified clays with higher organic content.     

ABS/clay nanocomposites obtained by a solution technique: Influence of clay organic modifiers

Acrylonitrile-butadiene-styrene (ABS) polymer/clay nanocomposites were produced using an intercalation-adsorption technique from polymer in solution: polymer/clay suspensions were subjected to ultrasonic processing to increase the effectiveness of mixing. Several kinds of organically modified layered silicates (OMLS) were used to understand the influence of the surfactant nature on the intercalation-exfoliation mechanism. We show that only imidazolium-treated montmorillonite (DMHDIM-MMT) is stable at the processing temperature of 200 °C, used for hot-pressing, whereas alkyl-ammonium modified clays show significant degradation.The morphology of ABS based polymer nanocomposites prepared in this work was characterized by means of wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Dynamic-mechanical analysis (DMA) was used to determine the storage modulus and damping coefficient as a function of temperature, and to investigate the correlations between mechanical properties and morphology of the nanocomposites. The thermal stability was assessed by means of thermogravimetric analysis (TGA). DMA and TGA show that the nanocomposites based on imidazolium-modified clay out-perform the nanocomposites based on quaternary-ammonium-modified clays in terms of mechanical properties and thermal stability.     

Nanocomposites of poly(ethylene terephthalate‐co‐ethylene naphthalate) with organoclay

Poly(ethylene terephthalate‐co‐ethylene naphthalate) (PETN)/organoclay was synthesized with the solution intercalation method. Hexadecylamine was used as an organophilic alkylamine in organoclay. Our aim was to clarify the intercalation of PETN chains to hexadecylamine–montmorillonite (C₁₆–MMT) and to improve both the thermal stability and tensile property. We found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PETN/C₁₆–MMT hybrid films. Maximum enhancement in both the ultimate tensile strength and initial modulus for the hybrids was observed in blends containing 4 wt % C₁₆–MMT. Below a 4 wt % clay loading, the clay particles could be highly dispersed in the polymer matrix without a large agglomeration of particles. However, an agglomerated structure did form in the polymer matrix at a 6 wt % clay content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2581–2588, 2001     

PC/ABS及PC/ABS/PE-g-MAH共混体系相容性的研究

研究了聚碳酸酯与ＡＢＳ（ＰＣ／ＡＢＳ）及ＰＣ／ＡＢＳ与马来酸酐接枝聚乙烯共聚物（ＰＣ／ＡＢＳ／ＰＥ－ｇ－ＭＡＨ）共混体系的力学性能和应力开裂性能。用ＤＳＣ和ＳＥＭ研究了共混体系的相容性。结果表明：ＡＢＳ的加入能提高ＰＣ的冲击强度,ＡＢＳ的含量及品种影响ＰＣ／ＡＢＳ合金的力学性能,ＡＢＳ能提高ＰＣ的耐溶剂应力开裂性能。ＰＣ／ＡＢＳ／ＰＥ－ｇ－ＭＡＨ共混体系的力学性能和相容性优于ＰＣ／ＡＢＳ共混体系,     

Compatibilization efficiency of styrene–butadiene multiblock copolymers in PS/PP blends

The compatibilizing effect of di‐, tri‐, penta‐, and heptablock (two types) copolymers with styrene and butadiene blocks was studied in polystyrene/polypropylene (PS/PP) 4/1 blends. The structure of PS/PP blends with the addition of 5 or 10 wt % of a block copolymer (BC) was determined on several scale levels by means of transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS). The results of the structure analysis were correlated with measured stress‐transfer properties: elongation at break, impact, and tensile strength. Despite the fact that the molar mass of the PS blocks in all the BCs used was about 10,000, that is, below the critical value M^* (～18,000) necessary for the formation of entanglements of PS chains, all the BCs used were found to be good compatibilizers. According to TEM, a certain amount of a BC is localized at the interface in all the analyzed samples, and this results in a finer dispersion of the PP particles in the PS matrix, the effect being more pronounced with S‐B‐S triblock and S‐B‐S‐B‐S pentablock copolymers. The addition of these two BCs to the PS/PP blend also has the most pronounced effect on the improvement of mechanical properties of these blends. Hence, these two BCs can be assumed to be better compatibilizers for the PS/PP (4/1) blend than the S‐B diblock as well as both S‐B‐S‐B‐S‐B‐S and B‐S‐B‐S‐B‐S‐B heptablock copolymers. In both types of PS/PP/BC blends (5 or 10 wt % BC), the BC added was distributed between both the PS/PP interface and the PS phase, and, according to SAXS, it maintained a more or less ordered supermolecular structure of neat BCs. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 931–942, 2001     

Nanocomposites of polyurethane with various organoclays: Thermomechanical properties,morphology, and gas permeability*

The properties of polyurethane (PU) nanocomposites with three different organoclays were compared in terms of their thermal stabilities, mechanical properties, morphologies, and gas permeabilities. Hexadecylamine–montmorillonite, dodecyltrimethyl ammonium–montmorillonite, and Cloisite 25A were used as organoclays for making PU hybrid films. The properties were examined as a function of the organoclay content in a matrix polymer. Transmission electron microscopy photographs showed that most clay layers were dispersed homogeneously into the matrix polymer on the nanoscale, although some particles of clay were agglomerated. Moreover, the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PU hybrid films, whereas gas permeability was reduced. Even polymers with low organoclay contents (3–4 wt %) showed much higher strength and modulus values than pure PU. Gas permeability was reduced linearly with an increasing amount of organoclay in the PU matrix. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 670–677, 2002; DOI 10.1002/polb.10124