Preparation of poly(ethylene terephthalate)/organoclay nanocomposites using a polyester ionomer as a compatibilizer

In this work, poly(ethylene terephthalate)/organically modified montmorillonite (PET/o‐MMT) nanocomposites were prepared via direct melt compounding in a twin‐screw extruder. The main objective was to study the effects of using a polyester ionomer (PETi) as a compatibilizer to promote the intercalation and/or exfoliation of the o‐MMT in the PET. The o‐MMT content was 0, 1, 3, or 5 wt % and the PETi/o‐MMT mass ratio was 0/1, 1/1, or 3/1. The PETi was efficient to promote the intercalation/exfoliation of the o‐MMT in the PET matrix, as revealed by wide angle X‐ray scattering and transmission electron microscopy. Rheological characterization showed that the PET/o‐MMT nanocomposites exhibited a higher complex viscosity at low frequencies than PET, which is characteristic of materials presenting yield strength. Moreover, the higher the content and/or the degree of intercalation/exfoliation of the o‐MMT, the more the nanocomposite behaved like a solid because of a percolated structure formed by the o‐MMT layers, and the more the storage and loss modulus, G′ and G″, became independent of the frequency at low frequencies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3084–3091, 2007     

Effects of melt‐processing conditions on the quality of poly(ethylene terephthalate) montmorillonite clay nanocomposites

Organically modified montmorillonite was synthesized with a novel 1,2‐dimethyl‐3‐N‐alkyl imidazolium salt or a typical quaternary ammonium salt as a control. Poly(ethylene terephthalate) montmorillonite clay nanocomposites were compounded via melt‐blending in a corotating mini twin‐screw extruder operating at 285 °C. The nanocomposites were characterized with thermal analysis, X‐ray diffraction, and transmission electron microscopy to determine the extent of intercalation and/or exfoliation present in the system. Nanocomposites produced with N,N‐dimethyl‐N,N‐dioctadecylammonium treated montmorillonite (DMDODA‐MMT), which has a decomposition temperature of 250 °C, were black, brittle, and tarlike resulting from DMDODA degradation under the processing conditions. Nanocomposites compounded with 1,2‐dimethyl‐3‐N‐hexadecyl imidazolium treated MMT, which has a decomposition temperature of 350 °C, showed high levels of dispersion and delamination. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2661–2666, 2002     

Functional copolymer/organo‐MMT nanoarchitectures. III. Dynamic mechanical behavior of poly(IA‐co‐BMA)‐organo‐MMT clay nanocomposites

Functional copolymer/organo‐silicate [N,N′‐dimethyldodecyl ammonium cation surface modified montmorillonite (MMT)] layered nanocomposites have been synthesized by interlamellar complex‐radical copolymerization of pre‐intercalated itaconic acid (IA)/organo‐MMT complex as a “nanoreactor” with n‐butyl methacrylate (BMA) as an internal plasticization comonomer in the presence of radical initiator. Comparative analysis of physical structure, dynamic mechanical analysis parameters, and surface morphology of the obtained copolymers and their nanocomposites indicated that the interlayer H‐bonding and flexible n‐butyl ester linkages take place an important role in interlamellar copolymerization and intercalation/exfoliation of copolymer chains. It was found that nanocomposites' dynamic mechanical properties strongly depended on the force of interfacial H‐bonding and amount of BMA units. An increase in both of these parameters leads to enhanced intercalation and exfoliation in situ processes of copolymer chains and the formation of hybrid nanocomposites. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and Characterization of Poly(butyleneterephthalate)/Organoclay Nanocomposites

PBT/organic montmorillonite (MMT) nanocomposites were prepared via melt intercalation and their nanostructure was characterized by means of X‐ray diffraction and transmission electron microscopy. Nanocomposite formation requires sufficiently hydrophobic organically modified layered silicates, as well as the presence of polar interactions between silicate and polymer. Three different alkylammonium surfactants were used to modify MMT. In addition, epoxy resin was added as a third component, and the effects on the intercalation and exfoliation behavior of the PBT nanocomposites were investigated.     

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     

Interdigitated crystalline MMT‐MCA: Preparation and characterization

A novel nanomaterial, montmorillonite–melamine cyanurate (MMT‐MCA), was successfully synthesized, in which the number of MCA layers in between 2 MMT layers can be controlled at 1 or a very large value (over 100 nm thick). Its interdigitated crystalline structure was thoroughly characterized. The MMT‐MCA shows outstanding dispersion ability in different polymers to easily prepare MMT nanocomposites by melt blending due to the π‐π stacking exfoliation between MCA layers. The paper opens the way to the synthesis of novel interdigitated nanomaterials.     

Insertion of Polypyrrole Chains into Montmorillonite Galleries by a Solvent‐Free Mechanochemical Route

Summary: Non‐ionic pyrrole was directly intercalated into unmodified montmorillonite (MMT) and organically modified MMT galleries by adsorption, and subsequently polymerized within the interlamellar spaces by a mechanochemical route under solvent‐free conditions. XRD analysis revealed the successful intercalation of pyrrole into unmodified MMT and organically modified MMT clay galleries by mechanochemical grinding. After in situ polymerization, the XRD and FT‐IR analyses confirmed the insertion of polypyrrole chains between both MMT galleries.

X‐ray powder diffraction patterns of (A) pyrrole‐intercalated MMT and (B) pyrrole‐intercalated C18‐MMT.     

Simple Preparation of Sulfate Anion‐Doped Polyaniline‐Clay Nanocomposites by an Environmentally Friendly Mechanochemical Synthesis Route

Summary: Conducting polyaniline (PANI) and montmorillonite (MMT) nanocomposites were prepared from aniline sulfate and MMT by a mechanochemical synthesis route. X‐Ray diffraction analysis confirmed that, by controlling the aniline sulfate content, mechanochemical synthesis led to two types of different formations. After polymerization, the mechanochemical route synthesized much more PANI between the clay layers compared to a solution method. The electrical conductivities of the synthesized PANI‐MMT nanocomposites in pressed pellets ranged in the order of between 10⁻⁴ and 10⁻³ S · cm⁻¹.

X‐ray powder diffraction patterns of the intercalation products prepared by grinding montmorillonite with various amounts of Ani‐SO₄ in a mortar.     

Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (T_g's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher T_g's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004     

Polypropylene/polystyrene/clay blends prepared by an innovative eccentric rotor extruder based on continuous elongational flow: Analysis of morphology,rheology property,and crystallization behavior

The polypropylene (PP)/polystyrene (PS)/montmorillonite (MMT) blends were prepared by an innovative eccentric rotor extruder based on continuous elongational flow. Addition of MMT nanoparticles was found to reduce the PS droplet size and improve the compatibility of PP/PS. The MMT nanoparticles had clear intercalation and/or exfoliation structures and were located mostly at the interface of PP/PS. It was found that the intercalation and exfoliation of MMT was finished under the synergy of interfacial interaction and tensile deformation so that we called the mechanism as “MMT exfoliation mechanism induced by synergy of interface and tensile deformation”. The rheological analysis showed that incorporation of MMT led to an increase in complex viscosity to an optimum level (5 wt%), after which any further increase in MMT concentration decreased the complex viscosity. Moreover, the degree of crystallinity of blends was controlled by the heterogeneous nucleation effect of MMT and the inhibition effect of PS.     

An acrylic acid modified polypropylene as a compatibilizing agent for the intercalation/exfoliation of an organically modified montmorillonite in polypropylene

This work dealt with the effect of using an acrylic acid modified polypropylene (PP‐g‐AA) as a compatibilizing agent for the intercalation/exfoliation of an organically modified montmorillonite (o‐MMT) in a polypropylene matrix (PP). Two PP‐g‐AA containing the same AA content (6 wt %) and having different molar masses were used. The o‐MMT content was 0, 1, or 5 wt % of total mass and the PP‐g‐AA/o‐MMT mass ratio was 0/1, 1/1, 2/1, or 5/1. Results of wide angle X‐ray scattering (WAXS) and transmission electronic microscopy (TEM) showed that without the PP‐g‐AA, the o‐MMT was dispersed in the PP/o‐MMT in a micrometer scale, similar to a conventional microcomposite. With the PP‐g‐AA, the o‐MMT was much better dispersed and its interlayers were intercalated and partly exfoliated by the polymer chains. Compared with the neat PP, some PP/PP‐g‐AA/o‐MMT systems exhibited higher G′ values and a yield stress at low frequencies, indicating that the PP‐g‐AA promoted the intercalation/exfoliation of the o‐MMT. The compatibilizing efficiency of those two PP‐g‐AA was very similar. Generally speaking, the higher the PP‐g‐AA/o‐MMT mass ratio, the better the state of dispersion and the degree of intercalation/exfoliation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1811–1819, 2008     

Revisit to the formation mechanism of exfoliated montmorillonite/PMMA nanocomposite latex through soap‐free emulsion polymerization

Soap‐free emulsion polymerization of methyl methacrylate (MMA) in the aqueous suspension of montmorillonite (MMT) was able to fabricate the exfoliated MMT/PMMA nanocomposite latex. Because neither MMA nor substantial quantity of potassium persulfide (KPS) initiator could be individually absorbed into the interlayer region of MMT, the polymerizing ionic radicals in water phase were considered as a major component to diffuse into the gallery of MMT. They have been observed to organize into disk‐like micelles in the interlayer regions to exfoliate MMT. The diffusion of the polymerizing ionic radicals was further supported by using sodium dodecyl sulfate (SDS) surfactant as a model compound to diffuse into the gallery of MMT. The exfoliation of MMT was almost completed before micellization stage was over. After exfoliation, the disk‐like micelles became a polymerization loci for monomers. Because the disk‐like micelles in numbers were substantially over the commonly formed spherical micelles in the typical soap‐free emulsion polymerization, the conversion rate of MMA to MMT/PMMA nanocomposite latex was faster. Based on the above experimental observation, a justified exfoliation mechanism of MMT was proposed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 459–466, 2009     

Immobilization of poly(fluorene) within clay nanocomposite: an easy way to control keto defect

Blue light emitting cationic polyfluorene polymer(PF)/montmorillonite (MMT) nanocomposites were prepared by solution intercalation and exfoliation method to evaluate the effect of MMT on the nanocomposite structures, properties and morphologies. The properties of PF-MMT composites, containing 1-50 mass% MMT, were characterized unambiguously with the help of multiple analytical techniques, with focus on the keto defect and photostability of PF in the nanocomposites. XRD and HRTEM studies reveal both exfoliation of MMT galleries at lower content of MMT in composites and intercalation of PF chains into the MMT galleries at higher MMT content. The nanocomposites show higher thermal stability than pristine PF as anchorage of nanoclay in PF matrix occur through the electrostatic interaction between nanoclay and polymer. The decrease in Si-O-Si stretching frequency during exfoliation is much higher than in intercalation, as Si-O-Si experience lesser hindrance to vibrate in exfoliated MMT galleries. The gradual redshift of π-π(*) transition peak of PF with increasing MMT content in composites confirms the uncoiling of PF in clay galleries. The photoluminescence characteristics reveal interruption of interchain interaction in this intercalated and exfoliated organic/inorganic hybrid system, which reduces the low-energy emission that results from keto defect. Due to very high aspect ratio of MMT, it can act as an efficient exciton blocking layer and a barrier to oxygen diffusion, which may lead to a device with high color purity and enhanced photostability. Again current-voltage characteristics of nanocomposite films confirm the retention of LED properties after nanocomposite formation.     

Synthesis of Novolac/Layered Silicate Nanocomposites by Reaction Exfoliation Using Acid‐Modified Montmorillonite

Novolac/layered silicate nanocomposites were synthesized by condensation polymerization of phenol and formaldehyde catalyzed by H‐montmorillonite (H‐MMT). Exfoliation of the clay was investigated by X‐ray diffraction and transmission electron microscopy (TEM). It turned out that the intra‐gallery condensation of phenol and formaldehyde played a predominant role in the exfoliation of MMT. Exfoliated clay plates with interlayer spacings of 10–30 nm were dispersed in the matrix uniformly as shown by the TEM micrograph.     

尼龙1212/蒙脱土体系在剪切流场中蒙脱土片层剥离机理的研究

在聚合物熔体插层蒙脱土(MMT)过程中,流场的作用使得蒙脱土晶粒表面的片层在超过临界值时发生弯曲,与内核之间形成一楔状,并进一步发生断裂,形成剥离结构.结果表明,合适的流场强度是得到适当大小的片状粒子的关键.     

Fluorene‐based polyester nanocomposites via in situ interlayer polymerization

Fluorene‐based polyester nanocomposites were prepared by in situ polymerization of equivalent weights of 9,9′‐dihexylfluorene‐2,7‐dicarboxylic acid and 4,4′‐dihydroxy‐1,4‐diphenoxybutane (DPB‐OH) in the presence of octadecyl‐montmorillonite (C₁₈‐MMT) as an organoclay. We investigated the intercalation of the organoclay among the polymer chains, with the aim of improving the thermal properties of the polyester. It was found that the addition of only a small amount of organoclay was enough to improve the polyester's thermal properties. The maximum enhancement of the thermal properties of the fluorene‐based polyester nanocomposites was observed with the dispersion of 5 wt% organoclay. Copyright © 2008 John Wiley & Sons, Ltd.     

聚乙烯醇/氟基蒙脱土纳米复合材料的合成及性能研究

采用水热方法,在493 K条件下反应72小时,合成了氟基蒙脱土(F-MMT),在这种F-MMT中,硅酸盐结构中的一些OH-被F-取代。采用溶液插层方法,制备了聚乙烯醇/F-MMT纳米复合材料(PVA/F-MMT)。采用X 射线衍射、扫描电镜和透射电镜对F-MMT 和 PVA/F-MMT纳米复合材料进行了表征;结果表明,片状结构的F-MMT均匀分散于PVA中,形成了层离结构的纳米复合材料。热重分析、力学性能和紫外可见光谱的测试结果表明,在没有牺牲光学性能情况下,PVA/F-MMT纳米复合材料的热稳定性和力学性能都得到了提高。力学和热学性能的提高归功于F-MMT均匀而好的分散于聚合物基体中,以及PVA中的 OH- 和F-MMT 中F-之间强的氢键作用。     

Dispersibility of clay and crystallization kinetics for in situ polymerized PET/pristine and modified montmorillonite nanocomposites

Nanocomposite materials composed of poly (ethylene terephthalate) (PET) and montmorillonite (MMT) clays were prepared by in situ polymerization. Samples consisted of PET blended with various quantities of either pristine (Na⁺‐MMT) or organically modified MMT (A10‐MMT). The morphology and thermal and mechanical properties were evaluated for each sample. TEM micrographs, acquired at a 20 nm resolution, provide direct evidence of exfoliation of the clay particles into the PET matrix and show the effect of the alkyl‐modifier on clay dispersibility. The dispersion of PET/A10‐MMT was greater than that observed for the PET/Na⁺‐MMT nanocomposites. The greatest degree of exfoliation occurred for PET/A10‐MMT 0.5 wt %. However, PET/Na⁺‐MMT exhibited higher crystallization temperatures and rates suggesting that Na⁺‐MMT is a more efficient nucleating agent. Both mechanically and thermally, PET/A10‐MMT nanocomposites exhibited superior properties over pure PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1022–1035, 2008     

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     

4,4'-二氨基二苯醚二苯酮固化环氧树脂/粘土纳米复合材料的研究

采用离子交换法, 用十六烷基三甲基溴化铵处理钙基蒙脱土(MMT), 使蒙脱土的层间距由1.49 nm扩大到2.21 nm, 制备了环氧树脂/ BADK/MMT纳米复合材料, 并用XRD等手段研究了有机蒙脱土在环氧树脂中的插层及剥离行为. 研究结果表明, 蒙脱土含量及环氧树脂与有机土的混合温度和时间均对固化后复合材料的剥离产生影响, 只有在特定条件下才能得到剥离型纳米复合材料.