Modified organophilic montmorillonites/LDPE nanocomposites

In this work a commercially available organophilic Montmorillonite (Cloisite 30B) was modified by interaction with different surfactants, namely dodecylsuccinic anhydride (DSA), octadecylamine (ODA), octadecanoic alcohol (ODOH) and octadecanoic acid (ODAc), in order to increase its basal spacing and to achieve a better dispersibility in LDPE. The morphology of the dispersions was investigated through XRD and TEM analyses. Intercalation phenomena were found for all the systems investigated. The thermal properties of the obtained nanocomposites were studied by means of DSC and TGA measurements. No variation of T _m and crystallinity of LDPE was found after the addition of the nanoclays (5 mass/mass%). A significant increase of the air thermal stability of LDPE was achieved in the presence of the modified nanoclays.     

Well-posedness of the transport equation by stochastic perturbation

We consider the linear transport equation with a globally Hölder continuous and bounded vector field, with an integrability condition on the divergence. While uniqueness may fail for the deterministic PDE, we prove that a multiplicative stochastic perturbation of Brownian type is enough to render the equation well-posed. This seems to be the first explicit example of a PDE of fluid dynamics that becomes well-posed under the influence of a (multiplicative) noise. The key tool is a differentiable stochastic flow constructed and analyzed by means of a special transformation of the drift of Itô-Tanaka type.     

Global L p estimates for degenerate Ornstein–Uhlenbeck operators

We consider a class of degenerate Ornstein–Uhlenbeck operators in ${\mathbb{R}^{N}}We consider a class of degenerate Ornstein–Uhlenbeck operators in \mathbbR^N{\mathbb{R}^{N}} , of the kind

A o ?i, j=1p0aij?xixj2 + ?i, j=1Nbijxi?xj\mathcal{A}\equiv\sum_{i, j=1}^{p_{0}}a_{ij}\partial_{x_{i}x_{j}}^{2} + \sum_{i, j=1}^{N}b_{ij}x_{i}\partial_{x_{j}}      15. Preparation and characterization of UV-cured acrylic nanocomposites based on modified organophilic montmorillonites      R. Peila  G. Malucelli  A. Priola 《Journal of Thermal Analysis and Calorimetry》2009,97(3):839-844 UV-cured nanocomposites have been prepared through the photopolymerization of the acrylic resin BEMA (Bisphenol A ethoxylate dimethacrylate) added with organophifilic montmorillonites. Two types of commercially available nanoclays namely Cloisite 30B and Cloisite Na+ were further modified with organic compatibilizers (dodecylsuccinic anhydride, octadecylamine, octadecanoic alcohol and octadecanoic acid) in order to increase their basal spacing and improve the dispersion in the acrylic matrix. The modification with the organic compatibilizers determined an increase of the interlayer distance, as revealed by XRD (X-Ray Diffraction) analysis. The different types of the modified nanoclays were then dispersed in BEMA monomer at 5% m/m concentration and UV-cured in order to prepare the nanocomposites. XRD measurements performed on the nanocomposites showed a slight increase of the interlayer distance indicating the formation of intercalated structures. The photopolymerization reaction was monitored through real-time FT-IR (Fourier Transform Infrared Spectroscopy) in order to check any influence of the nanofillers on the cure kinetics. The nanocomposites were investigated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetric) analyses and compared to the neat UV-cured resin. The presence of the nanofillers did not influence the glass transition temperature (Tg) of the acrylic resin; in addition an increase of the thermal stability in air of the nanocomposites was evidenced through TG analysis.      16. Polymerisationsstudien mit synkatalytischen Systemen auf Basis Al-organischer Verbindungen. 2. Mitt. Die Wechselwirkung der Reaktanten ohne Polymerisationen      A. Priola  S. Cesca  G. Ferraris und M. di Maina 《Colloid and polymer science》1978,256(1):99 Ohne Zusammenfassung      17. EPR spin labelling studies of molecular dynamics in elastomer-silica composites      A. Buttafava  G. M. Ghisoni  A. Faucitano  G. Negroni  A. Priola  F. Peditto  A. Turturro  M. Castellano 《Research on Chemical Intermediates》2002,28(2-3):191-204 Novel methods of nitroxyl spin labelling suitable for molecular dynamics studies within the interface regions of SBR elastomer/silica composites have been developed and used together with the nitroxyl spin probe technique. Fast and slow motional components have been identified within the interface regions and the corresponding rotational diffusion tensors have been measured as a function of the temperature and the SiO2 concentration. The fast rotational frequency is found to be orders of magnitude slower than that measured in the absence of SiO2. This difference is suggested to arise from a closer packing of the macromolecules near the silica surface caused by the van der Waals bonding interactions. Increase of the SiO2 concentration results in a decrease of the molecular mobility. This effect has been imputed to the overlapping of the bonding interaction regions. Spin probe measurements in the SBR-SiO2 matrices using TEMPO, strongly suggest that the hindrance to chain segmental motion induced by the SiO2-SBR interactions propagates beyond the interface regions thus involving the bulk polymer matrix. It is suggested that the information on the segmental chain dynamics obtained through the spin labelling and spin probe measurements can be developed as a method for investigating the polymer/filler interactions within the reinforcing mechanism by the filler.      18. Exponential ergodicity and regularity for equations with Lévy noise      Enrico Priola  Jerzy Zabczyk 《Stochastic Processes and their Applications》2012,122(1):106-133 We prove exponential convergence to the invariant measure, in the total variation norm, for solutions of SDEs driven by α-stable noises in finite and in infinite dimensions. Two approaches are used. The first one is based on Liapunov’s function approach by Harris, and the second on Doeblin’s coupling argument in [8]. Irreducibility and uniform strong Feller property play an essential role in both approaches. We concentrate on two classes of Markov processes: solutions of finite dimensional equations, introduced in [27], with Hölder continuous drift and a general, non-degenerate, symmetric α-stable noise, and infinite dimensional parabolic systems, introduced in [29], with Lipschitz drift and cylindrical α-stable noise. We show that if the nonlinearity is bounded, then the processes are exponential mixing. This improves, in particular, an earlier result established in [28], with a different method.      19. Polymerisationsstudien mit synkatalytischen Systemen auf Basis Al-organischer Verbindungen. 2. Mitt. Die Wechselwirkung der Reaktanten ohne Polymerisationen      A. Priola  S. Cesca  G. Ferraris  M. di Maina 《Colloid and polymer science》1978,256(1):99-99       20.      P. L. Magagnini  S. Cesca  P. Giusti  A. Priola und M. Di Maina 《Colloid and polymer science》1978,256(11):1153 Ohne Zusammenfassung      [首页] « 上一页 [1] 2 [3] [4] [5] [6] 下一页 » 末  页»

Preparation and characterization of UV-cured acrylic nanocomposites based on modified organophilic montmorillonites

UV-cured nanocomposites have been prepared through the photopolymerization of the acrylic resin BEMA (Bisphenol A ethoxylate dimethacrylate) added with organophifilic montmorillonites. Two types of commercially available nanoclays namely Cloisite 30B and Cloisite Na⁺ were further modified with organic compatibilizers (dodecylsuccinic anhydride, octadecylamine, octadecanoic alcohol and octadecanoic acid) in order to increase their basal spacing and improve the dispersion in the acrylic matrix. The modification with the organic compatibilizers determined an increase of the interlayer distance, as revealed by XRD (X-Ray Diffraction) analysis. The different types of the modified nanoclays were then dispersed in BEMA monomer at 5% m/m concentration and UV-cured in order to prepare the nanocomposites. XRD measurements performed on the nanocomposites showed a slight increase of the interlayer distance indicating the formation of intercalated structures. The photopolymerization reaction was monitored through real-time FT-IR (Fourier Transform Infrared Spectroscopy) in order to check any influence of the nanofillers on the cure kinetics. The nanocomposites were investigated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetric) analyses and compared to the neat UV-cured resin. The presence of the nanofillers did not influence the glass transition temperature (T_g) of the acrylic resin; in addition an increase of the thermal stability in air of the nanocomposites was evidenced through TG analysis.     

Polymerisationsstudien mit synkatalytischen Systemen auf Basis Al-organischer Verbindungen. 2. Mitt. Die Wechselwirkung der Reaktanten ohne Polymerisationen

Ohne Zusammenfassung     

EPR spin labelling studies of molecular dynamics in elastomer-silica composites

Novel methods of nitroxyl spin labelling suitable for molecular dynamics studies within the interface regions of SBR elastomer/silica composites have been developed and used together with the nitroxyl spin probe technique. Fast and slow motional components have been identified within the interface regions and the corresponding rotational diffusion tensors have been measured as a function of the temperature and the SiO₂ concentration. The fast rotational frequency is found to be orders of magnitude slower than that measured in the absence of SiO₂. This difference is suggested to arise from a closer packing of the macromolecules near the silica surface caused by the van der Waals bonding interactions. Increase of the SiO₂ concentration results in a decrease of the molecular mobility. This effect has been imputed to the overlapping of the bonding interaction regions. Spin probe measurements in the SBR-SiO₂ matrices using TEMPO, strongly suggest that the hindrance to chain segmental motion induced by the SiO₂-SBR interactions propagates beyond the interface regions thus involving the bulk polymer matrix. It is suggested that the information on the segmental chain dynamics obtained through the spin labelling and spin probe measurements can be developed as a method for investigating the polymer/filler interactions within the reinforcing mechanism by the filler.     

Exponential ergodicity and regularity for equations with Lévy noise

We prove exponential convergence to the invariant measure, in the total variation norm, for solutions of SDEs driven by α-stable noises in finite and in infinite dimensions. Two approaches are used. The first one is based on Liapunov’s function approach by Harris, and the second on Doeblin’s coupling argument in [8]. Irreducibility and uniform strong Feller property play an essential role in both approaches. We concentrate on two classes of Markov processes: solutions of finite dimensional equations, introduced in [27], with Hölder continuous drift and a general, non-degenerate, symmetric α-stable noise, and infinite dimensional parabolic systems, introduced in [29], with Lipschitz drift and cylindrical α-stable noise. We show that if the nonlinearity is bounded, then the processes are exponential mixing. This improves, in particular, an earlier result established in [28], with a different method.