Nanocomposite fibers of poly(ethylene terephthalate) with montmorillonite and mica: thermomechanical properties and morphology

The thermal stabilities, mechanical properties, and morphologies of nanocomposites of poly(ethylene terephthalate) (PET) with two different organoclays are compared. Dodecyltriphenylphosphonium‐montmorillonite (C₁₂PPh‐MMT) and dodecyltriphenylphosphonium‐mica (C₁₂PPh‐Mica) were used as reinforcing fillers in the fabrication of PET hybrid fibers. The variations of their properties with organoclay content in the polymer matrix and draw ratio (DR) are discussed. Transmission electron microscopy micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nanoscale, although some clay particles are agglomerated. It was also found that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the PET hybrid fibers. Even polymers with low organoclay contents (1–5 wt%) were found to exhibit much higher strength and modulus values than pure PET. In the case of C₁₂PPh‐MMT/PET, the values of the tensile mechanical properties of the hybrid fibers were found to decrease linearly with increases in DR from 1 to 16. However, the tensile mechanical properties of the C₁₂PPh‐Mica hybrid fibers were found to be independent of DR. Copyright © 2006 Society of Chemical Industry     

Synthesis and characterization of poly(butylene terephthalate) nanocomposite fibers: Thermo‐mechanical properties and morphology

Nanocomposites of poly(butylene terephthalate) (PBT) with the organoclay C₁₂PPh‐MMT were prepared using in situ intercalation polymerization. Hybrids with various organoclay contents were processed for fiber spinning to examine their thermal behavior, tensile mechanical properties, and morphologies for various draw ratios (DRs). The thermal properties (T_g, T_m, and T_Dⁱ) of the hybrid fibers were found to be better than those of pure PBT fibers and were unchanged by variation of the organoclay loading up to 2 wt %. However, these thermal properties remained unchanged for DRs ranging from 1 to 18. Most clay layers were dispersed homogeneously in the matrix polymer, although some clusters were also detected. The tensile properties of the hybrid fibers increased gradually with increasing C₁₂PPh‐MMT content at DR = 1. However, the ultimate strengths and initial moduli of the hybrid fibers decreased markedly with increasing DR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1247–1254, 2006     

Poly(ethylene terephthalate) nanocomposite fibers by in situ polymerization: The thermomechanical properties and morphology

A series of nanocomposites of poly(ethylene terephthalate) (PET) with the organoclay dodecyltriphenylphosphonium‐mica (C₁₂PPh‐mica) were synthesized with the in situ polymerization method. PET hybrid fibers with various organoclay concentrations were melt‐spun at various draw ratios (DRs) to produce monofilaments. The thermomechanical properties and morphologies of the PET hybrid fibers were characterized with differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction, electron microscopy, and universal tensile analysis. The organoclay was intercalated in the polymer matrix at all magnification levels, and some of the agglomerated organoclay layers were greater than 50 nm thick. The thermal stabilities and initial tensile moduli of the hybrid fibers increased with an increasing clay content for DR = 1. For DR = 1, the ultimate tensile strengths of the PET hybrid fibers increased with the addition of clay up to a critical clay loading and then decreased above that critical concentration. However, the tensile mechanical properties of the hybrid fibers did not improve with increasing DR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2009–2016, 2005     

Poly(trimethylene terephthalate) nanocomposite fibers by in situ intercalation polymerization: thermo-mechanical properties and morphology (I)

A series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (C₁₂PPh-MMT), were prepared by in situ intercalation polymerization of dimethyl terephthalate (DMT) and 1,3-propanediol (PDO). The PTT nanocomposites were melt-spun at different organoclay contents and different draw ratios (DRs) to produce monofilaments. The nanocomposites were characterized by X-ray diffraction, electron microscopy, universal tensile testing, differential scanning calorimetry and thermogravimetric analysis. Some of the clay particles appeared well dispersed within the PTT matrix, while others were found to agglomerate with a size greater than 10 nm. The addition of a small amount of C₁₂PPh-MMT was sufficient to improve the thermo-mechanical properties of the PTT hybrid fibers. Both the thermal stability and the tensile strength increased with increasing clay content at DR=1. As the DR was increased from 1 to 9, the ultimate tensile strength of the hybrid fibers decreased, while the initial modulus remained constant.     

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).     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Comparison of Thermomechanical Properties and Morphologies of Polyester Nanocomposite Fibers: PBT,PET, and PTT

Nanocomposites of three different polyesters with dodecyltriphenyl-phosphonium-montmorillonite (C₁₂PPh-MMT) organoclay are compared with respect to their thermal properties, mechanical properties, and morphologies. Poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and poly(trimethylene terephthalate) (PTT) were used as matrix polymers in the fabrication of polyester nanocomposite fibers. The variations in their properties with respect to both the organoclay content in the polymer matrix and the draw ratio (DR) are discussed. Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nanoscale, although some clay particles are agglomerated. The results additionally show that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the polyester nanocomposite fibers.     

Poly(ethylene terephthalate) nanocomposites by in situ interlayer polymerization: the thermo-mechanical properties and morphology of the hybrid fibers

Nanocomposites of poly(ethylene terephthalate) (PET) with C₁₂PPh-MMT as an organoclay were synthesized by using the in situ interlayer polymerization approach. The PET nanocomposites were melt-spun at different organoclay contents and different draw ratios to produce monofilaments. The thermo-mechanical properties and the morphologies of the PET nanocomposites were examined by using a differential scanning calorimeter, a thermogravimetric analyzer, a wide angle X-ray diffactometer, scanning and transmission electron microscopes, and a universal tensile machine. Some of the clay particles were well dispersed in the PET matrix, and some of them were agglomerated at a size level of greater than approximately 10 nm. The thermal stability and the tensile mechanical properties of the PET hybrid fibers increased with increasing clay content at a DR=1. However, the values of the ultimate tensile strength and the initial modulus of the hybrid fibers decreased markedly with increasing DR from 1 to 16.     

Colorless polyimide nanocomposite films: Thermomechanical properties,morphology, and optical transparency

Polyimide (PI)/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium‐mica (C₁₂PPh‐Mica) as the organoclay. The variations with organoclay content of the thermomechanical properties, morphology, and optical transparency of the hybrids were examined for concentrations from 0 to 1.0 wt %. For low clay contents (≤ 0.5 wt %), the clay particles are better dispersed in the matrix polymer, without the formation of large agglomerates of particles, than they are for high clay contents. However, agglomerated structures form and become denser in the PI matrix for clay contents ≥ 0.75 wt %. This is in agreement with the observed trends in the thermomechanical properties and the optical transparency, which worsen drastically when the clay content of the C₁₂PPh‐Mica/PI hybrids reaches 0.75 wt %. However, when the amount of organoclay in the hybrid is 0.75 wt %, the initial modulus of the hybrid film is at its maximum value. The PI hybrid films were found to exhibit excellent optical transparencies and to be almost colorless. It was found, however, that the transparency decreases slightly with increases in the organoclay content because of agglomeration of the clay particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of polyethylene/montmorillonite nanocomposites formed via ethylene copolymerization

BACKGROUND: In situ formation of polyethylene/clay nanocomposites is one of the prevalent preparation methods that include also solution blending and melt blending with regard to process simplification, economy in cost, environment protection and marked improvement in the mechanical properties of the polymeric matrix. In the work reported here, the preparation of linear low‐density polyethylene (LLDPE) and fabrication of polymer/clay nanocomposites were combined into a facile route by immobilizing pre‐catalysts for ethylene oligomerization on montmorillonite (MMT). RESULTS: [(2‐ArN?C(Me))₂C₅H₃N]FeCl₂ (Ar = 2,4‐Me₂(C₆H₃)) was supported on MMT treated using three different methods. The MMT‐supported iron complex together with metallocene compound rac‐Et(Ind)₂ZrCl₂ catalyzed ethylene to LLDPE/MMT nanocomposites upon activation with methylaluminoxane. The oligomer that was formed between layers of MMT promoted further exfoliation of MMT layers. The LLDPE/MMT nanocomposites were highly stable upon heating. Detailed scanning electron microscopy analysis revealed that the marked improvement in impact strength of the LLDPE/MMT nanocomposites originated from the dispersed MMT layers which underwent cavitation upon impact and caused plastic deformation to absorb most of the impact energy. In general, the mechanical properties of the LLDPE/MMT nanocomposites were improved as a result of the uniform dispersion of MMT layers in the LLDPE matrix. CONCLUSION: The use of the MMT‐supported iron‐based diimine complex together with metallocene led to ethylene copolymerization between layers of MMT to form LLDPE/MMT nanocomposites. The introduction of exfoliated MMT layers greatly improved the thermal stability and mechanical properties of LLDPE. Copyright © 2009 Society of Chemical Industry     

Electron beam synthesis and characterization of poly(vinyl alcohol)/montmorillonite nanocomposites

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT) nanocomposites in the form of films were prepared under the effect of electron beam irradiation. The PVA/MMT nanocomposites gels were characterized by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical measurements. The study showed that the appropriate dose of electron beam irradiation to achieve homogeneous nanocomposites films and highest gel formation was 20 kGy. The introduction of MMT (up to 4 wt %) results in improvement in tensile strength, elongation at break, and thermal stability of the PVA matrix. In addition, the intercalation of PVA with the MMT clay leads to an impressive improved water resistance, indicating that the clay is well dispersed within the polymer matrix. Meanwhile, it was proved that the intercalation has no effect on the metal uptake capability of PVA as determined by a method based on the color measurements. XRD patterns and SEM micrographs suggest the coexistence of exfoliated intercalated MMT layers over the studied MMT contents. The DSC thermograms showed clearly that the intercalation of PVA polymer with these levels of MMT has no influence on the melting transitions; however, the glass transition temperature (T_g) for PVA was completely disappeared, even at low levels of MMT clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1129–1138, 2006     

Polyimide nanocomposite with a hexadecylamine clay: Synthesis and characterization

A poly(amic acid) was prepared by the reaction of 3,3′‐dihydroxybenzidine and pyromellitic dianhydride in N,N‐dimethylacetamide. Hexadecylamine was used as an organophilic alkylamine in organoclay. Cast films were obtained from blend solutions of the precursor polymer and the organoclay. The cast film was heat treated at different temperatures to create polyimide (PI) hybrid films. We set out to clarify the intercalation of PI chains to hexadecylamine–montmorillonite (C₁₆–MMT) and to improve thermal and tensile properties and the gas barrier. It was found that the addition of only a small amount of organoclay was enough to improve both the thermal and the mechanical properties of PIs. Maximum enhancement in the ultimate tensile strength for PI hybrids was observed for the blends containing 4% C₁₆–MMT. The initial modulus monotonically increased with further increases in C₁₆–MMT content. Water vapor permeability was decreased with increasing clay loading from 1 to 8 wt %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2294–2301, 2002     

A one‐pot method to prepare transparent poly(methyl methacrylate)/montmorillonite nanocomposites using imidazolium‐based ionic liquids

Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by a new one‐pot technique, where the hydrophilic Na‐MMT layers were decorated with hydrophobic 1‐dodecyl‐3‐methylimidazolium hexafluorophosphate (C₁₂mimPF₆) ionic liquid in situ during melt blending with PMMA and intercalation of polymer chains took place subsequently. The in situ modification and intercalation of Na‐MMT were confirmed using X‐ray diffraction and transmission electron microscopy. The combination of the compatible C₁₂mimPF₆ with PMMA and the good dispersion of MMT layers at the nanoscale rendered the resultant PMMA/MMT nanocomposites with improved optical transparency, thermal stability and mechanical properties. Copyright © 2012 Society of Chemical Industry     

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     

Preparation and characterization of carboxymethyl konjac glucomannan/sodium montmorillonite hybrid films

Carboxymethyl konjac glucomannan (CKGM)/ sodium montmorillonite (MMT) hybrid films of various compositions were prepared by casting from a polymer/silicate water suspension. The structure and properties of the hybrid films were investigated by wide angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), attenuated total reflection infrared spectroscopy (ATR‐IR), differential scanning calorimetry (DSC), and tensile tests. The results from WXRD and TEM indicated that an intercalated CKGM/MMT nanocomposite film was obtained by polymer solution intercalation. WXRD and DSC showed that the high‐T_m crystal phase was induced by the presence of lower MMT loading, but the T_m of the hybrid films became weak with the increase of MMT content due to the polymer confinement. The hybrid films showed higher thermal stability and mechanical properties than that of the neat polysaccharide due to the strong interaction between hydroxyl and carbonyl group of CKGM and the silicate layer of MMT. Furthermore, the degree of swelling of the hybrid films was investigated in acidic buffer solutions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2954–2961, 2007     

Preparation and characterization of polyurethane–organoclay nanocomposites

Nanocomposite polyurethane (PU)–organoclay materials have been synthesized via in‐situ polymerization. The organoclay is first prepared by intercalation of tyramine into montmorillonite (MMT)‐clay through ion exchange process. The syntheses of polyurethane–organoclay hybrid films containing different ratios of clay were carried out by swelling the organoclay into diol and diamine followed by addition of diisocyanate and then cured. The nanocomposites with dispersed and exfoliated structure of MMT were obtained as evidenced by X‐ray diffraction and scanning electron microscope. X‐ray diffraction showed that there is no peak corresponding to d₀₀₁ spacing in organoclay with the ratios up to 20 wt%. SEM images confirmed the dispersion of nanometer silicate layers in the polyurethane matrix. Also, it was found that the presence of organoclay leads to improvement in the mechanical properties. The tensile strength was increased with increasing the organoclay contents to 20 wt% by 221% in comparision to the PU with 0% organoclay. POLYM. COMPOS. 28:108–115, 2007. © 2007 Society of Plastics Engineers     

Effect of nanofillers on the properties of flexible protective polymer coatings

Nanofillers with different size, shape, chemical structure, aspect ratio, and purity, including pristine montmorillonite (MMT‐Na) and hydrotalcite (HT) lamellar clays, and nonpurified single‐walled carbon nanotubes (SWNT) and fullerenes (FUL) were dispersed in a waterborne flexible acrylic coating. SEM and WAXD analysis of drawn‐down composite films containing 5 and 10 wt% fillers confirmed the random orientation of the MMT‐Na and HT platelets having intercalated or partially exfoliated structures. SEM analysis of composites containing SWNTs revealed the presence of clusters rather than single fibers and irregularly shaped carbonaceous impurities. Low aspect ratio, but well‐dispersed particles were observed in the FUL composites. Only the SWNT filler improved the thermal stability of the unfilled polymer; the presence of SWNT and MMT‐Na had a negligible effect on the glass transition temperature (T_g) of the coating. The presence of all nanofillers increased the tensile secant modulus of the polymer and decreased somewhat tensile strength and elongation at break to different degrees depending on type of filler and concentration. Some nanofillers significantly reduced the water vapor transmission rate of the unfilled matrix. Experimental data are discussed in terms of parameters known to affect mechanical and barrier properties including volume fraction, orientation, aspect ratio, dispersion, interfacial adhesion, and filler hydrophilicity. The results of this work indicate that it is possible to improve certain properties of acrylic protective coatings through the addition of low cost, unmodified nanoclays or by using nonpurified carbon allotropes, without a significant compromise of the strength and ductility of the polymeric matrix. POLYM COMPOS., 27:368–380, 2006. © 2006 Society of Plastics Engineers     

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     

Influence of clay and predispersion method on the structure and properties of polystyrene (PS)‐clay nanocomposites

To prepare the polystyrene (PS)‐clay nanocomposites via an in situ emulsion polymerization, a clay predispersion method, i.e. dispersing the organic clay in the emulsifier solution by the assistance of ultrasonic, was proposed in this study. The conventional method, predispersing the organic clay into the monomer, was also presented for the comparison. The morphology analysis based on the X‐ray Deflection (XRD) and Transmission Electronic Microscopy (TEM) results suggested that the more uniform clay dispersion in the final nanocomposites could be achieved through the new method. The inorganic clay (Na‐MMT) and two organic clays (C₁₈‐MMT and VC₁₈‐MMT) synthesized by exchanging inorganic cations with the trimethyloctadecyl ammonium chloride (OTAC) and the vinylbenzyldimethyloctadecyl ammoniun chloride (VOAC) were chosen to investigate the influence of the clay surface modification on the properties of nanocomposites. The Dynamic Mechanical Analysis (DMA) results showed the storage modulus G′s of the nanocomposites had different enhancements over that of the pure PS, especially when the temperature approached the glass transition temperature (T_g). The T_gs of the nanocomposites, however, varied with the microstructure and the interactions between the polymer and the clay layers. The Na‐MMT and VC₁₈‐MMT increased the T_g, while the T_gs of PS/C₁₈‐MMT nanocomposites were slightly lower than that of the pure PS. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Polyester nanocomposite fibers: comparison of their properties with poly(ethylene terephthalate) and poly(trimethylene terephthalate) (II)

Summary Two polyester nanocomposites were synthesized, one with poly(ethylene terephthalate) (PET) and the other with poly(trimethylene terephthalate) (PTT), by using organoclay. The in-situ interlayer polymerization method was used to disperse the organoclay in polyesters at different organoclay contents and at different draw ratios to produce monofilaments. The thermal stability and tensile mechanical properties increased with increasing organoclay content at a DR=1 . However, the values of the tensile mechanical properties of the hybrid fibers decreased with increasing DR. The reinforcing effects of the organoclay of the PET hybrid fibers were higher than those of the PTT hybrid fibers.