Co(II)-exchanged montmorillonite with ethylenediamine,trimethyl- and tetramethyl-ethylenediamine and their thermal decomposition

The influence of different steric properties of ethylenediamine (EDA), trimethylenediamine (TrMeEDA) and tetraethylenediamine (TeMeEDA) on the type of interactions with Co(II)-exchanged montmorillonite and thermal decomposition of these materials were studied. The results of X-ray diffraction (XRD), thermogravimetry (TG), derivative thermogravimetry (DTG) and spectral analysis shows that the studied ethylenediamines are intercalated into the interlayer space of montmorillonite. Thermal decomposition at 20–500 °C of studied samples with EDA proceeds in three steps (the release of chemosorbed amines, coordinated EDA and dehydroxylation) while the sample with TrMeEDA and TeMeEDA in five steps (also release the protonated forms). The effect of different steric properties of individual diamines is evident.     

Thermal, spectral, and diffraction properties of Co-exchanged montmorillonite with 2-, 3-, and 4-hydroxyphenol

The influence of the 2-, 3-, and 4-OH phenols on the type of interaction with Co-exchanged montmorillonite and thermal properties of these materials were studied. The results of XRD, IR, and thermal (TG, DTG) analysis show that organic species are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20?C700?°C of studied samples with 2- and 3-hydroxyphenol proceeds in three steps (the release of adsorbed H₂O molecules, combustion/desorption of protonated hydroxy phenols and dehydroxylation), while the sample with 4-hydroxyphenol decompose in four steps (the new peak at ~222?°C corresponds to directly coordinated organic species). The effect of different position of the hydroxyl groups on the phenol ring on the thermal decomposition is evident.     

Interactions of 2,5- and 3,5-dimethylphenols with co-exchanged montmorillonite

The influence of different steric and electronic properties of 2,5- and 3,5-dimethylphenols (2,5 and 3,5-DMP) on the type of interactions with Cobalt-exchanged montmorillonite (Co-MMT) was studied. The results of X-ray diffraction (XRD), IR-spectroscopy and thermal (TG, DTG) analysis show that phenol derivatives are intercalated into the interlayer space of montmorillonite. Thermal decomposition in the temperature interval 20–700 °C of Co-MMT with 3,5-DMP proceeds in four steps while Co-MMT with 2,5-DMP decompose only in three steps. These differences are connected with different acid–base interactions of individual phenol derivatives in the interlayer space of montmorillonite, which is in agreement with the results of IR-spectroscopy.     

Thermal properties of different transition metal forms of montmorillonite intercalated with mono-, di-, and triethanolammonium compounds

In the present study, different transition metal forms of montmorillonite have been intercalated with mono-, di-, and triethanolammonium cations via d coordination mechanism to investigate their thermal behavior, structural characteristics, surface properties, and elemental composition using TG, XRD, BET, and CHNS techniques. Thermogravimetric analysis showed two thermal transition steps for transition metal-exchanged montmorillonites, which attributed to desorption of the physically adsorbed water and hydrated water, and dehydroxylation of the structural water; whereas for ammonium-montmorillonite complexes, the TG curves showed three thermal transition steps which attributed to desorption of the adsorbed water and dehydration, decomposition of the ammonium cations in the interlayer space of montmorillonite, and the dehydroxylation of the structural water. The thermal analysis of ammonium-montmorillonites affirmed that the molar mass of amine compounds used affects both desorption temperature (position) and the amount of the adsorbed water (intensity). XRD results revealed that the molar mass of amine used has linear relation with the basal spacings of the corresponding ammonium-montmorillonites, indicating structural changes. BET results showed that the molar mass of amines has an inverse effect on the surface area of the studied samples. CHNS analysis for the studied samples quantitatively confirmed the intercalation of ammonium cations into the interlayer space of montmorillonite.     

Thermal stability and flame retardancy of LDPE/EVA blends filled with synthetic hydromagnesite/aluminium hydroxide/montmorillonite and magnesium hydroxide/aluminium hydroxide/montmorillonite mixtures

The combination of organophillised montmorillonite (MMT), synthetic hydromagnesite and aluminium hydroxide (ATH) as flame retardant system for polyethylene-based materials was studied and compared with a similar system with magnesium hydroxide, ATH and MMT. The thermal stability and the flame retardant properties were evaluated by thermogravimetric analysis (TGA), differential thermal analysis (DTA), limiting oxygen index (LOI) and cone calorimeter tests. The results indicated that the addition of montmorillonite makes it possible to reduce the total filler content to achieve the flame retardant requirements. The thermal stability of filled LDPE/EVA blends increases to a higher extent for the samples containing MMT. In the cone calorimeter tests we observed a reduction of the peak heat release rate for the sample containing montmorillonite in comparison with a sample with higher filler loading without this nanoclay. An increase of the stability of the char formed could be responsible for this favourable behaviour when montmorillonite is added.In addition, mechanical properties significantly improved for the composites containing montmorillonite both for the filler loading reduction and the reinforcement effect of the nanoclay.     

Characterization and thermal properties of Ni-exchanged montmorillonite with benzimidazole

Thermal analysis (TG, DTG), powder diffraction analysis (XRD) and infrared (IR) spectra were used to study of composition and release of benzimidazole from Ni(II)-exchanged montmorillonite under heating. Diffraction analysis indicated that benzimidazole molecules are intercalated into the interlayer space of montmorillonite. IR spectra and the analytical characteristics have shown that different type of interactions of benzimidazole is connected with different reaction conditions (acid or neutral solution). The release of benzimidazole from Ni(II)-montmorillonite under heating from studied samples proceeds in three distinct steps. The first step can be assigned to the release of water molecules while the last (third) one corresponds to the lattice dehydroxylation. The second step can be assigned to release of chemically bonded benzimidazole.     

Bi-hybrid coatings: polyaniline-montmorillonite filler in organic-inorganic polymer matrix

A bi-hybrid composite is represented by an organic-inorganic (O-I) filler dispersed in an O-I matrix. Polyaniline-montmorillonite, as a nanocomposite filler, was synthesised by two independent processes: (1) montmorillonite was surface-modified with a conducting polymer, polyaniline, during the in-situ oxidation of aniline or (2) montmorillonite was pre-treated with aniline, then the aniline was polymerised and the polyaniline subsequently produced penetrated the montmorillonite structure. The organic-inorganic polymer matrix was formed in two independent steps: (1) inorganic building units were formed in situ by the sol-gel process, (2) followed by organic polymeric matrix formation by polyaddition reactions of epoxy groups with amines. Polyaniline-montmorillonite filler was added to the reaction system between these two steps, i.e. when the inorganic structures of the O-I matrix have already been formed but prior to formation of the organic polymeric matrix. Two different O-I matrices were prepared from functionalised organosilicon precursors and oligomeric amines. 3-[(Glycidyloxy)propyl]trimethoxysilane reacted with α,ω-oligo(propylene oxide) diamine and diethoxy[3-(glycidyloxy)propyl]-methylsilane reacted with α,ω-oligo(propylene oxide) triamine. The resulting bi-hybrid coatings, the O-I filler dispersed in the O-I matrix, were characterised by atomic-force and optical microscopies, and also by tensile tests. The filler composition affected both the mechanical and surface properties of the coatings.     

Roles of organic intercalation agent with flame retardant groups in montmorillonite (MMT) in properties of polypropylene composites

Three kinds of organic intercalation agent containing flame retardant groups, melamine (MA), triphenylphonium (TPP) chloride, and tetradecyl trihexyl phosphonium (TTP) bromide were intercalated into montmorillonite (MMT) via cation exchange reactions. These modified MMTs are combined with intumescent systems and compounded with PP. The flame retardant and thermal properties of the PP composites are studied. The organic intercalation agents in the layers of MMT play important roles in the char formation and flame retardant properties of PP composites. MA shows a better performance in limiting oxygen index (LOI) value and TPP helps to increase UL‐94 properties, whereas TTP maintains or deteriorates the flame retardancy of polypropylene/intumescent flame retardant (IFR) composites. The LOI and UL‐94 properties increase firstly and then decrease as the content of MMT increases. The MA acts as a blowing agent and emits an inert gas to provide migration impetus, which results in a better intumescent structured and stronger char to endure heat erosion. Although TPP and TTP emit combustible gas that burn, especially for TTP as it has a more flammable aliphatic chain. The synergistic effect between MA‐MMT and IFR is better than that for TPP‐MMT and TTP‐MMT. Copyright © 2014 John Wiley & Sons, Ltd.     

A thermoanalytical assessment of an organoclay

High resolution thermogravimetric analysis (TG) has attracted much attention in the synthesis of organoclays and its applications. In this study, organoclays were synthesised through ion exchange of a single cationic surfactant for sodium ions, and characterised by methods including X-ray diffraction (XRD) and TG. The changes of surface properties in montmorillonite (MMT) and organoclays intercalated with surfactant were determined using XRD through the changes in the basal spacing. The TG was applied in this study to investigate more information of the configuration and structural changes in the organoclays with thermal decomposition. There are four different decompositions steps in differential thermogravimetric curves. The obtained TG steps are relevant to the arrangement of the surfactant molecules intercalated in MMT and the thermal analysis indicates the thermal stability of surfactant modified clays. This investigation provides new insights into the properties of organoclays and is important in the synthesis and processing of organoclays for environmental applications.     

Exploration of mandelic acid-based polymethacrylates: Synthesis,properties, and stereochemical effects

Mandelic acid (MA) was utilized as a chiral biomass-based precursor to synthesize methacrylic monomers suitable for radical polymerization. A series of polymers were made that incorporated varying feeds of monomer stereopurity and the properties of these materials were investigated. High molar masses (>90 kg/mol) were achieved and the chirality in each polymer closely reflected the stereopurity of the monomer feeds. It was discovered that stereochemical effects had very little influence on the thermal and viscoelastic properties of the polymers produced, however, the steric bulk of the chiral pendants resulted in glassy, amorphous, and thermally stable materials with very low degrees of entanglement. The synthesis, thermal, and viscoelastic properties are discussed.     

Polyamide 66/EPR‐g‐MA blends: mechanical modeling and kinetic analysis of thermal degradation

The present investigation deals with the mechanical, thermal, and morphological properties of binary nylon 66/maleic anhydride grafted ethylene propylene rubber (EPR‐g‐MA) blends at different dispersed phase (EPR‐g‐MA) concentrations. The effects of EPR‐g‐MA concentration and dispersed particle size on the mechanical properties of the blends were studied. Analysis of the tensile data in terms of various theoretical models revealed the variation of stress concentration effect with blend composition and the improvement of interfacial adhesion between dispersed rubber phase and nylon 66 matrix. The thermal degradation of the blends was analyzed by nonisothermal thermogravimetric analysis (TGA). It was found that the activation energy (E_a) and overall reaction order of thermal degradation decreased with increasing EPR‐g‐MA content. The scanning electron microscopic (SEM) analysis showed a significant decrease in dispersed particle size with increasing EPR‐g‐MA content, which was explained on the basis of the level of chemical interaction (in situ compatibilization) between nylon 66 and EPR‐g‐MA. The surface morphology of the nylon 66/EPR‐g‐MA blends was illustrated by the roughness of atomic force microscopy (AFM) images. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of surfactant agent upon the structure of montmorillonite

The modification of sodium montmorillonite (MMT) through the incorporation of amphiphilic octadecylammonium cations in various concentrations (10–200% CEC) into the clay’s interlayer spaces has been studied. High resolution thermogravimetric analysis shows that the thermal decomposition of modified montmorillonite occurs in three steps. The first step of mass loss is related to dehydration of adsorbed water and water hydrating metal cations such as Na⁺. The second step of mass loss is attributed to the decomposition of surfactant. The third step is due to the loss of OH units during the dehydroxylation of the montmorillonite. The conformation of the surfactant cations in the confined space of the silicate galleries is investigated by X-ray diffraction analysis. These analyses are very important for any attempt to incorporate the organomodified MMT particles into different media for various applications such as polymer nanocomposite preparation.     

Interactions of different heterocyclic compounds with monoionic forms of montmorillonite

Interactions of 3-R-and 2-R pyridine (R=CH₃, Cl, NH₂) with Ni(II)-exchanged montmorillonite have been studied. Thermal and X-ray analyses indicate that pyridine derivatives are intercalated into the interlayer spaces of montmorillonite. Infrared spectral data shown that the Lewis and/or Brönsted type of interactions of pyridine derivatives is connected with different steric and inductive effects of the substituents (R) on the pyridine ring. The alkylpyridines increase the electron density on the donor nitrogen atom and support the coordination to the central atom. The halogen substituents have a negative inductive effect (–I), so that those ligands show a lower basicity and weaker σ-bonding properties than pyridine and also the lower possibility of the coordination.     

Block copolymers of styrene and n‐alkyl methacrylates with long alkyl groups. Micellization behavior in selective solvents

The micellization properties of well‐defined block copolymers of styrene and decyl methacrylate (SDMA) were studied in two different solvents, methyl acetate (MAc) selective for the polystyrene (PS) block and dodecane, selective for the poly(decyl methacrylate) (PDMA) block. The results were compared with those obtained, in the same solvents, from block copolymers of styrene and stearyl methacrylate (SSMA). In MAc, SDMA copolymers with a decyl methacrylate (DMA) content of 15% or less formed unimolecular micelles, whereas those with a content of 18.5% or higher formed multimolecular micelles. The degrees of association were lower than the corresponding SSMA samples. In dodecane, SDMA form large, monodisperse, spherical, and thermally stable micelles with degrees of association higher than the corresponding SSMA samples. The different behaviors can be attributed to the steric hindrance effect and the ability of the long alkyl groups of the polymethacrylate, MA blocks to crystallize. When the MA blocks are in the soluble corona of the micelles, the steric hindrance effect prevails, thus leading to higher degrees of association for the less bulky alkyl group. In the case where the MA block is in the insoluble core of the micelles, the higher the tendency for crystallization the higher the degree of association. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4177–4188, 2004     

Thermal properties of Co-, Ni- and Cu-exchanged montmorillonite with 3-hydroxypyridine

Thermal analysis (TG, DTG), powder diffraction analysis (RTG) and infrared absorption spectra (IR spectra) were used to study of release of 3-hydroxypyridine (3-OHpy) from Co-, Ni- and Cu-exchanged montmorillonite (Co-MMT, Ni-MMT, Cu-MMT). It was found that release of 3-OHpy under heating from Co- and Ni-MMT proceeds in three distinct steps while from Cu-MMT in four steps. The first step can be assigned to the release of physically sorbed 3-OHpy while the last one corresponds to the lattice dehydroxylation. The second step (Co-, Ni-MMT) and/or second and third steps (Cu-MMT) can be assigned to release of chemically bonded 3-OHpy. This investigation shows that studied exchanged montmorillonites predominantly exhibit Lewis acid character. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pyrolysis study of a phosphorus-containing aliphatic-aromatic polyester and its nanocomposites with layered silicates

This paper deals with the thermal decomposition behaviour of a new fire retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing aliphatic-aromatic polyester and its nanocomposites with natural layered silicate (montmorillonite) under inert atmosphere studied by TGA-FTIR, Pyrolysis-GC/MS of volatile products and ATR-FTIR of non-volatile decomposition products. The phosphorus-containing polyester undergoes decomposition in two steps between 340 and 516 °C. The first step is associated with the release of carbon dioxide, acetaldehyde, ethene, acid-containing products (mainly benzoic acid) resulting in the formation of polyarylates followed by their decomposition in the second step with the evolution of carbon dioxide. DOPO-containing products, esters (mainly diethenyl terephthalate), carbon monoxide, acids and water are released through both stages. At the end of decomposition polyaromatic structures, diarylketones and organophosphorus esters built into the chemical structure of the char develop in the solid residue. The modification of the polyester with a layered silicate does not change the composition of the pyrolysis products, only their yield, and tended to diminish the charring of the polymer. A thermal decomposition scheme of the P-polyester is proposed and the mass spectra of some DOPO-containing products are discussed.     

Intercalation of Cyclic Amines into α-Titanium Phosphate

The intercalation of some amines (aniline, benzylamine, cyclohexylamine,piperidine, pyridine, pyrazine and piperazine) into -titaniumphosphate, Ti(HPO₄)_2×H₂O,has been investigated by the batch method and/or by exposing the host to thevapour of the amines. The changes in the interlayer distance of the solidduring the intercalation process was followed by X-ray powder diffraction.The new intercalates were characterised by chemical and thermal analysis.Materials with a monolaminar and/or bilaminar arrangement of amine moleculesin the phosphate interlayer region are obtained depending on the nature ofthe amine. Due to steric hindrance, saturated phases are not obtained forall amines studied. The thermal decomposition of the intercalates (nitrogenatmosphere), takes place in three stages: dehydration, removal of amines andcondensation of the hydrogenphosphate to pyrophosphate groups.     

Experimental study on the thermal behaviors of lithium-ion batteries under discharge and overcharge conditions

Iron oxide modified montmorillonite (MMT) as flame retardant was used to polyvinyl chloride (PVC), and the flame retardant and smoke-suppressant properties of the PVC were investigated by the smoke density rating and cone calorimeter tests (CONE), and the thermal degradation behaviors of PVC were studied by thermogravimetric analysis (TG) in air atmosphere. The activation energies for the first stage of thermal degradation were obtained following the equation of Kissinger. The mechanical properties testing resultant data showed that iron oxide modified MMT had little effect on the tensile strength of the sample. The CONE result indicated that iron oxide modified MMT could reduce the heat release rate in flame retardant PVC: a more compact char residue formed on the surface of the sample including iron oxide modified MMT during the combustion process. The TG result showed that the sample with modified iron oxide MMT had higher thermal stability than the pure PVC. Besides, the PVC treated with modified MMT showed high activation energy.     

Amine catalysis in phosphoryl transfer from 2,4-dinitrophenyl phosphate in aprotic and protic solvents

Reactions of tetra-n-butylammonium 2,4-dinitrophenyl hydrogen phosphate, (ArPH)^?(R₄N)⁺, in aprotic and protic solvents, in the absence and in the presence of alcohols or water, ROH, are compared with analogous reactions of the salt in the presence of hindered and unhindered amines, e.g. diisopropylethyl amine and quinuclidine. Similar studies are performed with the acid, ArPH₂, in the presence of variable amounts of amines. The release of phenol and the fate of the phosphorus compounds are followed by ¹H and ³¹P NMR spectrometry. In the absence of free unhindered amine, reactions of the monoanion are relatively slow, sensitive to steric hindrance in the alcohol, and incapable of producing t-butyl phosphate from t-butanol; reactions of the dianion are relatively fast, insensitive to steric hindrance in the alcohol, and produce t-butyl phosphate. In the presence of free unhindered amine, reactions of the monoanion are relatively fast but still sensitive to steric hindrance in the alcohol, and hence do not produce t-butyl phosphate. The intermediate CH(CH₂CH₂)₃⁺NP(O)(OH)O^? is detected in the presence of quinuclidine. Reactions of the dianion in the presence of unhindered amines are analogous to those observed in the presence of hindered amines. The uncatalyzed and the nucleophilic amine-catalyzed reactions of the monoanion are assumed to proceed via oxyphosphorane, P(5), intermediates. The dianion reactions, which are not susceptible to nucleophilic catalysis, are assumed to proceed via the monomeric metaphosphate ion intermediate, PO₃^?. Significant effects related to solvent properties are observed in these reactions.     

高抗冲聚苯乙烯/粘土纳米复合材料的制备、热稳定性及流变性能

用双螺杆挤出共混法制备了高抗冲聚苯乙烯 (HIPS) 有机蒙脱土 (Org MMT)插层纳米复合材料以及HIPS 无机蒙脱土 (MMT)常规复合材料 .分别用TGA和毛细管流变仪研究了它们的热性能与流变性能 ,并比较了两种结构材料的性能差异 .结果表明 ,纳米复合材料比纯HIPS和常规的复合材料具有更好的热稳定性和流动性 ,前者具有更强的剪切变稀行为 .此外 ,当蒙脱土达到纳米级分散时 ,复合材料的表面也变得更加平整光滑 .