Polyaniline–organoclay nanocomposites as curing agent for epoxy: Preparation and characterization

Polyaniline (PANI)–organoclay/Epoxy (EP) nanocomposites were prepared. PANI–organoclay nanocomposites were used as curing agent for EP. Organoclay was prepared by an ion exchange process between sodium cations in MMT and NH₃⁺ groups in polyoxypropylene (D₂₃₀). PANI–organoclay nanocomposite was synthesized by in situ polymerization of aniline in (14 wt%) organoclay. Infrared spectra and differential scanning calorimetry confirm the curing of EP. The absence of d₀₀₁ diffraction band of organoclay in the nanocomposites was observed by X‐ray diffraction. The structure argument was further supported by scanning electron microscopy and transmission electron microscopy. Electrical conductivity of the nanocomposites within the range 2.1 × 10⁻⁷–3.2 × 10⁻⁷ S/cm depending on the concentration of the PANI/D₂₃₀‐MMT. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

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     

Poly(trimethylene terephthalate) nanocomposite fibers comprising different organoclays: Thermomechanical properties and morphology

Poly(trimethylene terephthalate) (PTT) nano composites were synthesized by in situ polymerization at high temperature with two thermally stable organoclays: 1,2‐dimethylhexadecylimidazolium‐montmorillonite (IMD‐MMT) and dodecyltriphenyl phosphonium‐MMT (C₁₂PPh‐MMT). PTT hybrid fibers with various organoclay contents were melt‐spun at various draw ratios (DRs) to produce monofilaments. The thermomechanical properties and morphologies of the PTT hybrid fibers were characterized using differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction, electron microscopy, and mechanical tensile properties analysis. The nanostructure of the hybrid fibers was observed by both scanning and transmission electron microscopy, which showed that the clay layers were well dispersed into the matrix polymer, although some clusters or agglomerated particles were also detected. Unlike the hybrids containing IMD‐MMT, the clay layers of the C₁₂PPh‐MMT hybrid fiber were more dispersed into the matrix polymer. The thermal stability and tensile properties of the hybrid fibers increased with increasing clay content for DR = 1. However, as DR increased from 1 to 9 the ultimate strength and initial modulus of the hybrid fibers with IMD‐MMT increased slightly whereas those of C₁₂PPh‐MMT hybrid fibers decreased slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4535–4545, 2006     

Synthesis and characterization of elastomeric polyurethane and PU/clay nanocomposites based on an aliphatic diisocyanate

This investigation reports preparation of polyurethane and polyurethane/clay nanocomposites based on polyethylene glycol, isophorone diisocyanate (IPDI), an aliphatic diisocyanate and 1,4‐ Butanediol as chain extender by solution polymerization. In this case PU/clay nanocomposites were prepared via ex‐situ method using 1, 3, and 5 wt % of Cloisite 30B. Thermogravimetric analysis showed that the maximum decomposition temperature (T_max) of the PU/clay nanocomposite is much higher than the pristine PU. The tensile properties improved upon increasing the organoclay (Cloisite 30B) content upto 3 wt %, and then decreased to some extent upon further increasing the nanoparticle loading to 5 wt %. Optical properties of the nanocomposites were studied by UV‐vis spectrophotometer. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the morphology of the nanocomposites. It was observed that with the incorporation of 3 wt % nanoclay the crystallinity in PU nanocomposite increases, then diminishes with further loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3328–3334, 2013     

Preparation and characterization of polyimide nanocomposites with different organo‐montmorillonites

Poly(amic acid) nanocomposites were synthesized from a dimethylacetamide (DMAc) solution with two organophilic montmorillonites (organo‐MMTs). It was then heated at various temperatures under vacuum, yielding 15–20 um thick films of polyimide/organo‐MMT hybrid with different clay contents (1–8 wt%). Dodecy‐lamine (C₁₂‐) and hexadecylamine (C₁₆‐) were used as aliphatic alkylamines in organo‐MMT. The ultimate strength monotonically increased with increasing clay content in the polymer matrix. Maximum enhancement in the initial modulus was observed for the blends containing 2 wt% clay with two kinds of organo‐clays, and values did not alter significantly with further increases in clay content. Additions of only 2 wt% C₁₂‐ and C₁₆‐MMT to the polyimide were shown to cause 94%‐95% reduction in oxygen gas permeability. This is caused by the barrier properties of the clay layers dispersed in the composite. In general, C₁₆‐MMT is more effective than C₁₂‐MMT in increasing both the tensile property and the gas barrier in a polyimide matrix. Intercalations of the polymer chains in clay were examined through wide‐angle X‐ray diffraction (XRD) and electron microscopies (SEM and TEM).     

Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization

Two series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (T_cm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (T_m) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the T_cm and T_m peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (T_g) irrespective of clay content, and a noticeable decrease in T_g with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Synthesis and characterization of polyaniline–organoclay nanocomposites

Polyaniline (PANI)–organoclay nanocomposites were prepared. Intercalation of aniline monomer into montmorillonite (MMT) modified by polyoxyalkylene was followed by subsequent oxidative polymerization of the aniline in the interlayer spacing. The organoclay was prepared by cation exchange process between sodium cation in MMT and onium ion in four different types of polyoxyalkylene diamine and triamine with different molecular weight. Infrared spectra confirm the electrostatic interaction between the positively charged onium group (NH₃⁺) and the negatively charged surface of MMT. X‐ray diffraction analysis provides a structural information. The absence of d₀₀₁ diffraction band in the nanocomposites was observed at certain types and contents of organoclay. Scanning electron microscopy and transmission electron microscopy were employed to determine the dispersion of the clay into PANI. The thermal degradation behavior of PANI in the nanocomposites has been investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites are more thermally stable than pristine PANI. This improvement is attributed to the presence of nanolayers with high aspect ratio acting as barriers, thus shielding the diffusion of degraded PANI from the nanocomposites. The electrical conductivity of the nanocomposites was increased 30 times more than that of pure MMT at a certain concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Twin‐screw extrusion of polypropylene‐clay nanocomposites: Influence of masterbatch processing,screw rotation mode,and sequence

This work seeks to optimize the twin‐screw compounding of polymer‐clay nanocomposites (PCNs). Proportional amounts (3:1) of maleic anhydride functionalized polypropylene compatibilizer (PP‐g‐MA) and organically modified montmorillonite clay at clay loadings of 1, 3, and 5 wt% were melt‐blended with a polypropylene (PP) homopolymer using a Leistritz Micro 27 twin‐screw extruder. Three melt‐blending approaches were pursued: (1) a masterbatch of PP‐g‐MA and organoclay were blended in one pass followed by dilution with the PP resin in a second pass; (2) all three components were processed in a single pass; and (3) uncompatibilized PP and organoclay were processed twice. Both corotation and counterrotation operation were utilized to investigate the effect of screw rotation mode and sequence on organoclay exfoliation and dispersion. X‐ray diffraction was employed to characterize basal spacing; however, since rheology is known to be highly sensitive to mesoscale organoclay structure, it is an ideal tool to examine the relationship between the various processing methods and exfoliation and dispersion. A holistic analysis of rheological data demonstrates the efficacy of the masterbatch approach, particularly when compatibilizer and organoclay are blended in counterrotating mode followed by dilution with matrix polymer in corotating mode. POLYM. ENG. SCI., 47:898–911, 2007. © 2007 Society of Plastics Engineers     

Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Novel polyether polyurethane/clay nanocomposites synthesized with organicly modified montmorillonite as chain extenders

A kind of novel polyether polyurethane (PU)/clay nanocomposite was synthesized using poly(tetramethylene glycol), 4,4′‐diphenylmethane diisocyanate (MDI), 1,6‐hexamethylenediamine, and modified Na⁺‐montmorillonite (MMT). Here, organicly modified MMT (O‐MMT) was formed by applying 1,6‐hexamethylenediamine as a swelling agent to treat the Na⁺‐MMT. The X‐ray analysis showed that exfoliation occurred for the higher O‐MMT content (40 wt %) in the polymer matrix. The mechanical analysis indicated that, when the O‐MMT was used as a chain extender to replace a part of the 1,2‐diaminopropane to form PU/clay nanocomposites, the strength and strain at break of the polymer was enhanced when increasing the content of O‐MMT in the matrix. When the O‐MMT content reached about 5%, the tensile strength and elongation at break were over 2 times that of the pure PU. The thermal stability and the glass transition of the O‐MMT/PU nanocomposites also increased with increasing O‐MMT content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 6–13, 2006     

Synthesis and evaluation of high‐performance ethylene–propylene–diene terpolymer/organoclay nanoscale composites

The main objective of this study was to synthesize and characterize the properties of ethylene–propylene–diene terpolymer (EPDM)/clay nanocomposites. Pristine clay, sodium montmorillonite (Na⁺–MMT), was intercalated with hexadecyl ammonium ion to form modified organoclay (16Me–MMT) and the effect of intercalation toward the change in interlayer spacing of the silicate layers was studied by X‐ray diffraction, which showed that the increase in interlayer spacing in Na⁺–MMT by 0.61 nm is attributed to the intercalation of hexadecyl ammonium ion within the clay layers. In the case of EPDM/16Me–MMT nanocomposites, the basal reflection peak was shifted toward a higher angle. However, gallery height remained more or less the same for different EPDM nanocomposites with organoclay content up to 8 wt %. The nanostructure of EPDM/clay composites was characterized by transmission electron microscopy, which established the coexistence of intercalated and exfoliated clay layers with an average layer thickness in the nanometer range within the EPDM matrix. The significant improvement in thermal stability and mechanical properties reflects the high‐performance nanocomposite formation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2429–2436, 2004     

Reactive extrusion of poly(ethylene terephthalate)–(ethylene/methyl acrylate/glycidyl methacrylate)–organoclay nanocomposites

This study was conducted to investigate the effects of component concentrations and addition order of the components on the final properties of ternary nanocomposites composed of poly(ethylene terephthalate), organoclay, and an ethylene–methyl acrylate–glycidyl methacrylate (E‐MA‐GMA) terpolymer acting as an impact modifier for PET. In this context, first, the optimum amount of the impact modifier was determined by melt compounding binary PET‐terpolymer blends in a corotating twin‐screw extruder. The amount of the impact modifier (5 wt%) resulting in the highest Young's modulus and moderate elongation at break was selected owing to its balanced mechanical properties. Thereafter, by using 5 wt% terpolymer content, the effects of organically modified clay concentration and addition order of the components on the properties of ternary nanocomposites were systematically investigated. Mechanical testing revealed that different addition orders of the materials significantly affected the mechanical properties. Among the investigated addition orders, the best sequence of component addition (PI‐C) was the one in which poly(ethylene terephthalate) was first compounded with E‐MA‐GMA. Later, this mixture was compounded with the organoclay in the subsequent run. In X‐ray diffraction analysis, extensive layer separation associated with delamination of the original clay structure occurred in PI‐C and CI‐P (Clay + Impact Modifier followed by PET) sequences with both 1 and 3 wt% clay contents. X‐ray diffraction patterns showed that at these conditions exfoliated structures resulted as indicated by the disappearance of any peaks due to the diffraction within the consecutive clay layers. POLYM. COMPOS., 28:251–258, 2007. © Society of Plastic Engineers     

Polystyrene nanocomposite materials by in situ polymerization into montmorillonite–vinyl monomer interlayers

A different series of new polystyrene–clay nanocomposites have been prepared by grafting polymerization of styrene with vinyl‐montmorillonite (MMT) clay. The synthesis was achieved through two steps. The first step is the modification of clay with the vinyl monomers, such as N,N‐dimethyl‐n‐octadecyl‐4‐vinylbenzyl‐ammonium chloride, n‐octadecyl‐4‐vinylbenzyl‐ammonium chloride, triphenyl‐4‐vinylbenzyl‐phosphonium chloride, and tri‐n‐butyl‐4‐vinylbenzyl‐phosphonium chloride. The second step is the polymerization of styrene with different ratios of vinyl‐MMT clay. The materials produced were characterized by different physical and chemical methods: (1) IR spectra, confirming the intercalation of the vinyl‐cation within the clay interlayers; (2) thermogravimetric analysis (TGA), showing higher thermal stability for PS–nanocomposites than polystyrene (PS) and higher thermal stability of nanocomposites with of phosphonium moieties than nanocomposites with ammonium moieties; (3) swelling measurements in different organic solvents, showing that the swelling degree in hydrophobic solvents increases as the clay ratio decreases; (4) X‐ray diffraction (XRD), illustrating that the nanocomposites were exfoliated at up to a 25 wt % of organoclay content; and (5) scanning electron microscopy (SEM), showing a complete dispersion of PS into clay galleries. Also, transmission electron microscopy (TEM) showed nanosize spherical particles of ～ 150–400 nm appearing in the images. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3739–3750, 2007     

Synthesis,characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

organoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (T_g) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry     

Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams?

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay‐modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide‐angle X‐ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of poly(butylene terephthalate) nanocomposites with various organoclays

Layered‐silicate‐based polymer–clay nanocomposite materials were prepared depending on the surface modification of montmorillonite (MMT). Nanocomposites consisting of poly(butylene terephthalate) (PBT) as a matrix and dispersed inorganic clay modified with cetyl pyridinium chloride (CPC), benzyl dimethyl N‐hexadecyl ammonium chloride, and hexadecyl trimethyl ammonium bromide by direct melt intercalation were studied. The organoclay loading was varied from 1 to 5 wt %. The organoclays were characterized with X‐ray diffraction (XRD) to compute the crystallographic spacing and with thermogravimetric analysis to study the thermal stability. Detailed investigations of the mechanical and thermal properties as well as a dispersion study by XRD of the PBT/clay nanocomposites were conducted. X‐ray scattering showed that the layers of organoclay were intercalated with intercalating agents. According to the results of a differential scanning calorimetry analysis, clay acted as a nucleating agent, affecting the crystallization. The PBT nanocomposites containing clay treated with CPC showed good mechanical properties because of intercalation into the polymer matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New nanocomposite materials based on polymerization of [oligo(oxyethylene) methacrylates] in the presence of montmorillonite clay

Intercalation of poly[oligo(oxyethylene) methacrylates] onto sodium montmorillonite (MMT) clay has been investigated. A polymer–clay hybrid has been synthesized through intercalation of the monomer followed by its solution free‐radical polymerization. Eight polymer–clay hybrids were prepared using different weight ratios of clay, different oligo(oxyethylene) lengths and different proportions of crosslinker. Evidence of the development of nanostructures is obtained from scanning electron microscopy, and wide‐angle X‐ray diffraction studies support these results which show disappearance of the peak characteristic to d₀₀₁ spacing. In this hybrid MMT is dispersed homogeneously in the polymer matrix. © 2003 Society of Chemical Industry     

Polymeric carbon nanocomposites from multiwalled carbon nanotubes functionalized with segmented polyurethane

Multiwalled carbon nanotubes (MWNT) were functionalized with segmented polyurethanes (PU) by the “grafting to” approach. Raman and X‐ray photoelectron spectroscopy (XPS) spectra show that the sidewalls of MWNTs have been functionalized with acid treatment, and the amount of COOH increases with increasing acid treatment time. FTIR and X‐ray diffraction (XRD) spectra confirm that PU is covalently attached to the sidewalls of MWNTs by esterification reaction. Similar to the parent PU, the functionalized carbon nanotube samples are soluble in highly polar solvents, such as dimethyl sulfoxide (DMSO) and N,N‐dimethylformamide (DMF). The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGA). Comparative studies, based on SEM images between the PU‐functionalized and chemically defunctionalized MWNT samples, also reveal the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU‐functionalized MWNTs show enhanced mechanical properties and increased soft segment T_g. Tensile properties indicate that PU‐functionalized MWNTs are effective reinforcing fillers for the polyurethane matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

CO2 sorption and diffusion in polymethyl methacrylate–clay nanocomposites

This study reports the glass transition temperature (T_g), and sorption and diffusion of subcritical CO₂ gas in polymethyl methacrylate (PMMA) nanocomposites containing organically modified smectite clay, Cloisite 20A (C20A). A range of methods for preparing the PMMA‐clay nanocomposites was investigated and a solution coprecipitation method was selected as the most appropriate. Using this method, PMMA nanocomposite containing 2, 4, 6, and 10 wt% nanoclay loadings were prepared. Wide‐angle X‐ray diffraction (XRD) analysis and scanning electron microscopy (SEM) indicated that the 2 wt% nanocomposite materials had a well‐dispersed intercalated clay structure. The T_g for PMMA‐C20A nanocomposites, as measured by differential scanning calorimetry (DSC), was found to be independent of the clay loading. CO₂ solubility studies from 0 to 65°C and pressures up to 5.5 MPa using an in situ gravimetric technique were performed on compression‐molded films. The organoclay was found to have no effect on the solubility of CO₂ in PMMA, and therefore the solubility of CO₂ in the nanocomposite can be determined from the solubility of CO₂ in the matrix polymer alone. Diffusion coefficients were determined using the appropriate transport models for these test conditions and the diffusion coefficients for CO₂ in PMMA‐C20A composites were found to increase with organoclay loading. It is believed that the processing path taken to prepare the nanocomposites may have resulted in the agglomeration of the C20A organoclay, thereby preventing the polymer chains from fully wetting and intercalating a large number of clay particles. These agglomerations are responsible for the formation of large‐scale holes within the glassy nanocomposite, which behave as low resistance pathways for gas transport within the PMMA matrix. POLYM. ENG. SCI., 45:904–914, 2005. © 2005 Society of Plastics Engineers     

Melt compounding of polypropylene‐based clay nanocomposites

Polypropylene (PP)‐based nanocomposites containing 4 wt% maleic anhydride grafted PP (PP‐g‐MA) and 2 wt% Cloisite 20A (C20A) were prepared using various processing devices, viz., twin‐screw extruder (TSE), single‐screw extruder (SSE), and SSE with an extensional flow mixer (EFM). Two processing methods were employed: (I) masterbatch (MB) preparation in a TSE (with 10 wt% C20A and clay/compatibilizer ratio of 1:2), followed by dilution in TSE, SSE, or SSE + EFM, to 2 wt% clay loading; (II) single pass, i.e., directly compounding of dry‐blended PP‐g‐MA/clay in TSE, SSE, or SSE + EFM. It has been indicated that the quality of clay dispersion, both at micro‐ and nanolevel, of the nanocomposites depends very much on the operating conditions during processing, such as mixing intensity and residence time, thus affecting the mechanical performance. Besides that the degradation of the organoclay and the matrix is also very sensitive to these parameters. According to results of X‐ray diffraction, field emission gun scanning electron microscopy, transmission electron microscopy, and mechanical tests, the samples prepared with MB had better overall clay dispersion, which resulted in better mechanical properties. The processing equipment used for diluting MB had a marginal influence on clay dispersion and nanocomposite performance. POLYM. ENG. SCI., 47:1447–1458, 2007. © 2007 Society of Plastics Engineers