Influence of nanoclays on electrical and morphological properties of thermoplastic polyurethane/multiwalled carbon nanotube/clay nanocomposites

Nanocomposites of thermoplastic polyurethanes (TPUs), multiwalled carbon nanotubes (MWCNTs) and clays were prepared via melt processing using polyether‐ and polyester‐based TPUs, MWCNTs, and organically modified nanoclays (Cloisite C30B and C25A). Coaddition of clays and MWCNTs to TPU nanocomposites increased their electrical conductivities above those without any clay. Nanoclay alone is shown to produce no effect on electrical conductivity. TEM results show that the coaddition of nanoclay affects the nanocomposite morphology by changing the MWCNT distribution. Clay C25A and MWCNTs were observed to form network structures in the nanocomposites, resulting in improved electrical conduction. Interaction between MWCNTs and clays as well as an increase in nanocomposite viscosity caused by the coaddition of clays may influence the morphology change. Most of the nanocomposites containing both MWCNTs and clay exhibited higher dielectric constants, indicating higher electrical conductivities. Tensile properties investigations confirmed the reinforcing effects of the MWCNTs and clays. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of solvent on the properties of thermoplastic polyurethane/clay nanocomposites prepared by solution mixing

Effect of different solvents on the clay dispersion and the final properties of the thermoplastic polyurethanes (TPUs)/clay nanocomposites prepared via solution mixing was studied. The polyether‐ and polyester‐based TPUs were used along with organically modified clays (C30B, C25A, and C15A) and the pristine montmorillonite (PM). Dimethylacetamide (DMAc) and tetrahydrofuran (THF) were used as solvents for solution mixing. Nanocomposites containing C30B prepared from DMAc solution showed the better clay dispersion than the ones from THF solution, while THF gave the better dispersion of clays for nanocomposites containing C15A. Morphologies of the nanocomposites were observed to be determined not only by the state of clay dispersion in different solvents but also by the interaction between the polymer and the specific clay. Affinity between solvents and clays becomes important when there is no specific interaction between the clay and the polymer of interest, or when the interaction between the two is rather weak. The compatibility between clays and polymers becomes dominating if there exists a specific interaction between the two. FTIR analysis was conducted to study the interactions involved in the nanocomposites. Dynamic mechanical properties measurement was also carried out to see the effect of solvents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rectorite/thermoplastic polyurethane nanocomposites: Preparation,characterization, and properties

A newly developed kind of layered clay, rectorite (REC), has been used to yield intercalated or exfoliated thermoplastic polyurethane rubber (TPUR) nanocomposites by melt‐processing intercalation. Because of the swollen layered structure of REC, similar to that of montmorillonite, organic rectorites (OREC) can also be obtained through ion‐exchange reaction with two different quaternary ammonium salts (QAS1, QAS2) and benzidine (QAS3). The microstructure and dispersibility of OREC layers in TPUR matrix were examined by X‐ray diffraction and transmission electron microscopy, which revealed not only that the composites with lower amounts of clay are intercalation or part exfoliation nanocomposites, but also that the mechanical properties of the composites were substantially enhanced. The maximum ultimate tensile strength for TPUR/OREC nanocomposites appeared at 2 wt % OREC loading. With increasing OREC contents, the tear strength of the composites increased significantly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 608–614, 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     

Fracture behavior of thermoplastic polyolefin/clay nanocomposites

A thermoplastic polyolefin (TPO) containing 70 wt % styrene–ethylene–butadiene‐styrene‐g‐maleic anhydride and 30 wt % polypropylene and its nanocomposites reinforced with 0.3–1.5 wt % organoclay were prepared by melt mixing followed by injection molding. The mechanical and fracture behaviors of the TPO/clay nanocomposites were investigated. The essential work of fracture (EWF) approach was used to evaluate the tensile fracture behavior of the nanocomposites toughened with elastomer. Tensile tests showed that the stiffness and tensile strength of TPO was enhanced by the addition of low loading levels of organically modified montmorillonite. EWF measurements revealed that the fracture toughness of the TPO/clay nanocomposites increased with increasing clay content. The organoclay toughened the TPO matrix of the nanocomposites effectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and anticorrosive properties of polyurethane/clay nanocomposites

A montmorillonite clay has been modified with two different quaternary ammonium salts, dilauryldimethylammonium bromide (LD) and 4,4-diaminodiphenylmethane (AP), to form the corresponding organophilic clays, LDM and APM. Two series of PU/clay nanocomposite materials, PU/LDM and PU/APM, were then prepared by the reaction of appropriate amounts of PPG, TDI and 1,4 butandiol, followed by addition of the various amounts of LDM or APM. The X-ray diffraction patterns and transmission electron micrographs of the nanocomposites revealed that the modified clay galleries were exfoliated or intercalated in the polyurethane matrix. In comparison with the corresponding pure PU, the results of the TGA and LOI measurements showed that the thermal stability and the flame retardancy of the PU/clay nanocomposites were significantly enhanced due to the presence of the dispersed nanolayers of the organophilic clay in the PU matrix. Using the Tafel method, the results of the electrochemical measurements, which included the corrosion potential, polarization resistance and corrosion current, showed that all the PU/clay nanocomposites, even with low clay loading, in the form of coating on stainless steel disk (SSD) exhibited better corrosion protection over the pure PU. The SSD coated with the composite containing 2 wt% of APM showed the lowest corrosion rate, which was one order lower than that of the SSD coated with the pure PU.     

Effects of ultrasound on the synthesis and properties of polyurethane foam/clay nanocomposites

Polyurethane foam (PUF)/clay nanocomposites were synthesized with clay modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with the application of ultrasound. Transmission electron micrographs showed that the interlayer distance increased for the polyurethane (PU)/clay nanocomposites where ultrasound was applied. The results of the transmission electron microscopy and X‐ray measurements suggest that the application of ultrasound to the clay modification with PMDI improved the efficiency of the clay modification by the effective breakup of the clay agglomerates and intercalation of the silicate layers. In the mechanical tests of the PUF/clay nanocomposites, the flexural and tensile strengths of the PUF/clay nanocomposites showed the maximum value at 3.0 wt % clay content based on PMDI. These results suggest that the increases in the flexural and tensile strengths were perhaps due to the uniform dispersion of the clay by the application of ultrasound. At the same modified clay content, the fire resistance properties were increased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposites without the application of ultrasound. The cell size and thermal conductivity were decreased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposite without the application of ultrasound. Because of these results, we suggest that the smaller cell size and lower thermal conductivity of the PUF/clay nanocomposites were mainly due to the enhanced dispersion of the clay by the application of ultrasound to the mixture of PMDI and clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3764–3773, 2006     

PP/clay nanocomposites: Effect of clay treatment on morphology and dynamic mechanical properties

The morphology and properties of polypropylene (PP)/clay nanocomposites are described. The melt intercalation of organophilic clay was carried out with a single‐screw extruder. The effects of two kinds of treatments of clay are discussed. Maleic anhydride (MAH)‐grafted PP was used as a compatibilizer. The expansion of the intergallery distance of the clay was governed by the interaction between the clay treatment and the compatibilizer. In one case, the composites exhibited significantly reduced intensities of diffraction peaks, suggesting partial exfoliation of the clay layers, whereas for the second clay sample, expansion of the gallery height was noted. The mechanical properties of the PP/clay composites showed significant enhancement in their mechanical and thermal properties. About a 35% increase in the tensile modulus and about a 10% increase in the tensile strength were observed. The thermal degradation temperature increased from 270 to about 400°C as a result of the incorporation of clay, and the extent depended on the dispersion of clay in the composite. The most interesting outcome of this study was the changes in morphology for PP/clay composites, which are reported here for the first time. An optical microscopic study revealed that the PP/clay composites could be crystallized at higher temperatures than pure PP and that the morphology was remarkably altered because of the presence of layers of clay. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1786–1792, 2001     

Effect of clay on properties of polyimide‐clay nanocomposites

Effect of clay on mechanical, thermal, moisture absorption, and dielectric properties of polyimide‐clay nanocomposites was investigated. Nanocomposites of polyimide (ODA‐BSAA) hybridized with two modified clay (PK‐802 and PK‐805) were synthesized for comparison. The silicate layers in the polymer matrix were intercalated/exfoliated as confirmed by wide‐angle X‐ray diffraction and transmission electron microscopy. Thermal stability, moisture absorption, and storage modulus for these nanocomposites are improved as hybridized clay increases. Reduced dielectric constants due to the hybridization of layered silicates are observed at frequencies of 1 kHz–1 MHz and temperatures of 35–150°C. The tetrahedrally substituted smectite (PK‐805) resulted in higher mechanical strength and dielectric constants than those of octahedrally substituted smectite (PK‐802), which could be attributed to their stronger ionic bonding between clay layer and polymer matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 318–324, 2007     

Effect of the type of clay organo‐modifier on the morphology,thermal/mechanical/impact/barrier properties and biodegradation in soil of polycaprolactone/clay nanocomposites

The effect of addition of unmodified (CNa+) and modified (C30B and C20A) montmorillonites on the performance of polycaprolactone (PCL) based nanocomposites prepared by melt intercalation was studied. The study covers morphological and thermal aspects, mechanical and barrier properties and also biodegradability, which are important for packaging applications. Particular effort was made to find the main characteristics of the clays responsible for the final clay dispersion degree inside the nanocomposite. The most hydrophobic reinforcement (demonstrated by water adsorption tests) also showed the strongest thermal stability (shown by thermogravimetrical analysis) and the larger basal spacing (calculated by X‐ray diffractometry (XRD)), which were the main characteristics that led to the best clay dispersion degree inside the PCL matrix (demonstrated by XRD and Transmission Electron Microscopy (TEM)). The findings demonstrate that a biodegradable polymer/clay nanocomposite with enhanced mechanical, impact, and barrier properties was obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Intercalation and exfoliation behaviour of clay layers in branched polyol and polyurethane/clay nanocomposites

The exfoliation of clay layers was realized in a tri‐hydroxyl branched polyether polyol by direct mixing and the corresponding exfoliated polyurethane/clay nanocomposite was prepared by further in situ curing. The effects of various surface‐modified organoclays and various polyol types on the intercalation and exfoliation behaviour of clay layers were investigated. The interaction between the polyol and clay and the mixing temperature plays an important role in the occurrence of exfoliation and intercalation. The relationship between rheological data of polyol/clay dispersion and the intercalation or exfoliation state of the clay was established. This provides a convenient and efficient way to evaluate the dispersion state of the clay. Based on the experimental results, a possible layer‐by‐layer exfoliation mechanism is proposed. Copyright © 2006 Society of Chemical Industry     

Effect of clay modifiers on the morphology and physical properties of thermoplastic polyurethane/clay nanocomposites

Thermoplastic polyurethanes (TPUs)/clay nanocomposites were prepared via melt processing using the ester type and the ether type TPUs and three differently modified organoclays (denoted as C30B, C25A and C15A) as well as pristine montmorillonite (PM). XRD and TEM results showed that the addition of C30B with hydroxyl group led to the nearly exfoliated structures in both TPUs. In the case of C25A and C15A clays, partially intercalated nanocomposites were obtained in both TPUs, where C25A showed better dispersion than C15A. Natural clay (PM) was not effectively dispersed in both TPUs. The tensile properties of nanocomposites with C30B were better than ones with the other clays. Higher tensile properties were obtained for ester type TPU than ether type TPU nanocomposites with all clays tested. Although the improvement in tensile properties decreased after the second extrusion of the nanocomposites, properties of the nanocomposite after first melt processing were still good enough for practical applications. Morphological changes induced by the addition of clays were analyzed using FTIR, DSC and rheological test results. Some clays were observed to cause demixing of hard and soft segments in the nanocomposites and location of clays in either soft segment or hard segment domains was also studied.     

Relationship between mechanical properties and exfoliation degree of clay in polyurethane nanocomposites

Exfoliated and intercalated polyurethane (PU) nanocomposites were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. Wide‐angle X‐ray diffraction and transmission electron microscopy confirmed an exfoliated structure for clay C30B and an intercalated structure for C20A in polyol and PU. The realization of exfoliated state for clay C30B in polyol during the mixing stage can provide an effective approach for controlling the exfoliation degrees by adjusting the content of intercalated and exfoliated organoclay C20A and C30B before polymerization. The effect of exfoliation degree on the mechanical and viscoelastic properties of PU was investigated. The addition of organoclay improved the tensile strength, modulus and elongation, but the hysteresis loss ratio and relaxation rate increased, and the relaxation time distribution became broad. The effect of organoclay on PU properties varied with the hard segment content. By increasing the exfoliation degree, the tensile strength and modulus increased, whereas the elongation decreased. The exfoliated PU nanocomposite had a lower relaxation rate and hysteresis loss ratio than the intercalated PU. Copyright © 2005 Society of Chemical Industry     

Calculating barrier properties of polymer/clay nanocomposites: Effects of clay layers

We analyzed the effects of clay layers on the barrier properties of polymer/clay nanocomposites containing impermeable and oriented clay layers. Using the relative permeability theory in combination with the detour theory, we obtained new relative permeability expressions that allow us to investigate the relative permeability R_p as a function of lateral separation b, layer thickness w, gallery height H, layer length L, and layer volume fraction Φ_s. It was found that intercalated and/or incomplete exfoliated structures and dispersed tactoids with several layers can effectively enhance the barrier properties of the materials. Furthermore, we developed the chain-segment immobility factor to briefly discuss the chain confinement from clay layers. The results showed that the chain confinement enhanced the barrier properties of the intercalated nanocomposites. Our model is better consistent with the experiments when Φ_s>0.01. The findings provide guidelines for tailoring clay layer length, volume fraction and dispersion for fabricating polymer-clay nanocomposite with the unique barrier properties.     

Rectorite/thermoplastic polyurethane nanocomposites. II. Improvement of thermal and oil‐resistant properties

Organ‐rectorite/thermoplastic polyurethane (OREC/TPUR) nanocomposites were synthesized via melt intercalation. The dynamic mechanical properties by dynamic mechanical analysis (DMA), thermal and oil‐resistant properties were investigated. The results show that the storage modulus (E′), loss modulus (E″), and glass‐transition temperature (T_g) of the nanocomposites have an increase to some extent than those of pure TPUR. The thermal stability of nanocomposites was also studied in detail by thermal gravity analysis (TGA), which was higher than that of pristine TPUR matrix when the content of organic REC is at 2 wt %, and the decomposition temperature at 10% weight loss of OREC/TPUR is greatly increased up to 330°C from 315°C. Oil uptake of the composites is also significantly reduced in comparison with TPUR matrix, which is ascribed to the good barrier effect of nanosheets of OREC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1165–1169, 2005     

Effect of multiple extrusions on the impact properties of polypropylene/clay nanocomposites

Polypropylene (PP)‐based polymer nanocomposites containing organically modified montmorillonite (OMMT) with and without maleic anhydride grafted PP, were compounded by twin‐screw extrusion. The extrusion process was repeated various numbers of times to increase the extruder residence time (T_R) and, through that, the particle dispersion. Rheological measurements fitted to a modified Carreau–Yasuda model defining a melt yield stress were used to indicate changes in the particle dispersion with regard to T_R. This analysis showed a monotonically increased dispersion of clay particles in the PP matrix with increasing extruder T_R. The small‐strain tensile properties were tested at both ambient (20°C) and elevated (90°C) temperatures, and no significant changes were observed in the tensile strength or modulus as a function of T_R. Instrumented Izod impact tests showed that the nanocomposite impact strength (σ_i) increased monotonically with increased T_R by 70% from least dispersed to best dispersed, which was still 20% below the level for neat PP. Both the fracture initiation energy and propagation energy increased with T_R, but the primary effect on σ_i came from the fracture propagation energy, which delivered 80% of the improvement. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

粘土橡胶纳米复合材料研究进展

简要概述了粘土的有机改性机理、橡胶/粘土纳米复合材料的制备方法、结构与表征和橡胶/粘土纳米复合材料的研究进展.     

聚氨酯无机纳米复合材料的研究进展

综述了近年来国内外聚氨酯无机纳米复合材料的种类及其制备方法,介绍了聚氨酯无机纳米复合材料的发展趋势和纳米技术在聚氨酯中应用的重要性。     

Effect of organoclays on the properties of polyurethane/clay nanocomposite coatings

Linear, one‐binding‐site or two‐binding‐site (N⁺) organifiers with two hydroxyl end groups were synthesized, and novel organoclays were prepared through a cation‐exchange reaction between pristine sodium montmorillonite and the synthesized organifiers. After sonication of the as‐prepared organoclay in N,N′‐dimethylformamide for 10 min, the average size of the clay decreased to about 1 μm. The X‐ray diffraction patterns confirmed that the d‐spacing of the silicate layers of the organoclay expanded from 1.1 to about 1.9 nm and the peak intensity decreased with the molecular weight of the organifier increasing. Polyurethane/clay nanocomposites were synthesized by a one‐shot polymerization method. Both intercalated and exfoliated structures of the layered silicates in the polyurethane matrix were observed from transmission electron microscopy micrographs, and the d‐spacing ranged from 4 to 10 nm. The thermal and mechanical properties of the nanocomposite were enhanced by the introduction of the organoclay into the polyurethane matrix. An approximately 40–46°C increase in the onset decomposition temperature, a 200% increase in the tensile strength with a 0.5 wt % clay loading, and a 49% increase in Young's modulus with a 3 wt % clay loading were achieved. The effects of the molecular weight and the number of binding sites of the organifier on the properties of the nanocomposites were also evaluated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Silicate layer dispersion in copolymer/clay nanocomposites

Factors of silicate layer dispersions in polymers have been studied with copolymers. The influence of the copolymerization ratio of copolymers and the alkyl chain lengths of organomodified reagents of organophilic clay has been examined. The dispersion of silicate layers in copolymers is dependent on the copolymerization ratios of the functional groups, that is, the polarity of the polymer matrix. The alkyl chain lengths of organomodified reagents also have an important influence on silicate layer dispersions. From a comprehensive viewpoint, the polarity matching between polymers and organophilic clay is an important factor for silicate layer dispersions in polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1554–1557, 2005