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Infrared Linear Dichroism for the Analysis of Molecular Orientation in Polymers and in Polymer Composites. Polymers (Basel) 2022; 14:polym14061257. [PMID: 35335588 PMCID: PMC8954227 DOI: 10.3390/polym14061257] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 03/14/2022] [Accepted: 03/17/2022] [Indexed: 02/07/2023] Open
Abstract
The mechanical properties of polymeric materials are strongly affected by molecular orientation occurring under processing conditions. Infrared dichroism is particularly well suited for characterizing polymer chain orientation at a molecular level. The usefulness of this technique has been demonstrated through various applications in homopolymers, semi-crystalline polymers, copolymers, polymer blends, as well as in polymer composites. Determination of molecular orientation can be carried out in the mid- and near-infrared ranges and very small dichroic effects can be detected with the use of a photoelastic modulator. Chain orientation in polymer composites is seen to increase with the filler content in the case of a strong interface between the two phases, making possible a quantification of the degree of bonding between the host polymeric matrix and the incorporated inclusions.
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2
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Sepiolite-Based Anisotropic Nanoparticles: A New Player in the Rubber Reinforcement Technology for Tire Application. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12052714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Elastomer reinforcement with nanofillers has been a main rubber technology topic since the discovery of rubber vulcanization. Starting from carbon black, many researchers studied the correlations between the reinforcement of rubber and the colloidal properties of the reinforcing filler. The advent of silica allowed the experimentation of a playground of chemistries at the filler-rubber interface. In the increasing complexity of nowadays car manufacturer requests, reinforcing fillers play a pivotal role in determining the set of properties, which make a specific compound suitable for its applications. This effort of continuous improvement of rubber compound properties is pushing the tire industry towards novel solutions, and the silica/CB filler reinforcing technology will likely soon accept at least a third reinforcing filler as a major constituent of rubber compounds. While all major tire manufacturers build continuous knowledge on candidates such as carbon allotropes and 2-D nanoclays, Pirelli is paving the way for Sepiolite-derived nanofillers. Being Sepiolite naturally sourced, safe, and chemically playful, this unique 1-D phyllosilicate bears the promise of changing the game of elastomer nano-reinforcement, with the optional characteristic of giving mechanical anisotropy to the rubber compound. In this review, the historical progress on rubber reinforcement with sepiolite will be summarized, with an example of application in a commercially available Pirelli product, progenitor of the Smart-Net Silica® technology.
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Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study. Polymers (Basel) 2022; 14:polym14040767. [PMID: 35215681 PMCID: PMC8880187 DOI: 10.3390/polym14040767] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/13/2022] [Accepted: 02/14/2022] [Indexed: 11/25/2022] Open
Abstract
The characterization of the structural and dynamic properties of rubber networks is of fundamental importance in rubber science and technology to design materials with optimized mechanical properties. In this work, natural and isoprene rubber networks obtained by curing at three different temperatures (140, 150, and 170 °C) and three different sulfur contents (1, 2, and 3 phr) in the presence of a 3 phr accelerator were studied using a combination of low-field time-domain NMR (TD-NMR) techniques, including 1H multiple-quantum experiments for the measurement of residual dipolar couplings (Dres), the application of the Carr–Purcell–Meiboom–Gill pulse sequence for the measurement of the transverse magnetization decay and the extraction of 1H T2 relaxation times, and the use of field cycling NMR relaxometry for the determination of T1 relaxation times. The microscopic properties determined by TD-NMR experiments were discussed in comparison with the macroscopic properties obtained using equilibrium swelling, moving die rheometer, and calorimetric techniques. The obtained correlations between NMR observables, crosslink density values, maximum torque values, and glass transition temperatures provided insights into the effects of the vulcanization temperature and accelerator/sulfur ratio on the structure of the polymer networks, as well as on the effects of crosslinking on the segmental dynamics of elastomers. Dres and T2 were found to show linear correlations with the crosslink density determined by equilibrium swelling, while T1 depends on the local dynamics of polymer segments related to the glass transition, which is also affected by chemical modifications of the polymer chains occurring during vulcanization.
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Tripaldi L, Callone E, D'Arienzo M, Dirè S, Giannini L, Mascotto S, Meyer A, Scotti R, Tadiello L, Di Credico B. Silica hairy nanoparticles: a promising material for self-assembling processes. SOFT MATTER 2021; 17:9434-9446. [PMID: 34611686 DOI: 10.1039/d1sm01085a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
"Hairy" nanoparticles (HNPs), i.e. inorganic NPs functionalized with polymer chains, are promising building blocks for the synthesis of advanced nanocomposite (NC) materials having several technological applications. Recent evidence shows that HNPs self-organize in a variety of anisotropic structures, resulting in an improvement of the functional properties of the materials, in which are embedded. In this paper, we propose a three-step colloidal synthesis of spherical SiO2-HNPs, with controlled particle morphology and surface chemistry. In detail, the SiO2 core, synthesized by a modified Stöber method, was first functionalized with a short-chain amino-silane, which acts as an anchor, and then covered by maleated polybutadiene (PB), a rubbery polymer having low glass transition temperature, rarely considered until now. An extensive investigation by a multi-technique analysis demonstrates that the synthesis of SiO2-HNPs is simple, scalable, and potentially applicable to different kind of NPs and polymers. Morphological analysis shows the overall distribution of SiO2-HNPs with a certain degree of spatial organization, suggesting that the polymer coating induces a modification of NP-NP interactions. The role of the surface PB brushes in influencing the special arrangement of SiO2-HNPs was observed also in cis-1,4-polybutadiene (cis-PB), since the resulting NC exhibited the particle packing in "string-like" superstructures. This confirms the tendency of SiO2-HNPs to self-assemble and create alternative structures in polymer NCs, which may impart them peculiar functional properties.
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Affiliation(s)
- Laura Tripaldi
- Dept. of Materials Science, INSTM, University of Milano-Bicocca, Via R. Cozzi, 55, 20125 Milano, Italy.
| | - Emanuela Callone
- Klaus Müller Magnetic Resonance Lab., Dept. Industrial Engineering, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Massimiliano D'Arienzo
- Dept. of Materials Science, INSTM, University of Milano-Bicocca, Via R. Cozzi, 55, 20125 Milano, Italy.
| | - Sandra Dirè
- Klaus Müller Magnetic Resonance Lab., Dept. Industrial Engineering, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Luca Giannini
- Pirelli Tyre SpA, Viale Sarca, 222, 20126, Milano, Italy
| | - Simone Mascotto
- Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Andreas Meyer
- Institut für Physikalische Chemie, Universität Hamburg, Grindelallee 177, 20146 Hamburg, Germany
| | - Roberto Scotti
- Dept. of Materials Science, INSTM, University of Milano-Bicocca, Via R. Cozzi, 55, 20125 Milano, Italy.
| | | | - Barbara Di Credico
- Dept. of Materials Science, INSTM, University of Milano-Bicocca, Via R. Cozzi, 55, 20125 Milano, Italy.
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5
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Staropoli M, Rogé V, Moretto E, Didierjean J, Michel M, Duez B, Steiner P, Thielen G, Lenoble D, Thomann JS. Hybrid Silica-Based Fillers in Nanocomposites: Influence of Isotropic/Isotropic and Isotropic/Anisotropic Fillers on Mechanical Properties of Styrene-Butadiene (SBR)-Based Rubber. Polymers (Basel) 2021; 13:2413. [PMID: 34372014 PMCID: PMC8348337 DOI: 10.3390/polym13152413] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 07/14/2021] [Accepted: 07/19/2021] [Indexed: 11/17/2022] Open
Abstract
The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer-silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene (PBD) rubber matrix. Precipitated Highly Dispersed Silica (HDS) nanoparticles (10 nm) have been associated with spherical Stöber silica nanoparticles (250 nm) and anisotropic nano-Sepiolite. By imaging filler at nano scale through Scanning Transmission Electron Microscopy, we have shown that anisotropic fillers align only in presence of a critical amount of HDS. The dynamic mechanical analysis of rubber compounds confirms that this alignment leads to a stiffer nanocomposite when compared to Sepiolite alone. On the contrary, spherical 250 nm nanoparticles inhibit percolation network and reduce the nanocomposite stiffness.
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Affiliation(s)
- Mariapaola Staropoli
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Vincent Rogé
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Enzo Moretto
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Joffrey Didierjean
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Marc Michel
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Benoit Duez
- Goodyear S.A, Avenue Gordon Smith, Colmar-Berg, L-7750 Luxembourg, Luxembourg; (B.D.); (P.S.); (G.T.)
| | - Pascal Steiner
- Goodyear S.A, Avenue Gordon Smith, Colmar-Berg, L-7750 Luxembourg, Luxembourg; (B.D.); (P.S.); (G.T.)
| | - Georges Thielen
- Goodyear S.A, Avenue Gordon Smith, Colmar-Berg, L-7750 Luxembourg, Luxembourg; (B.D.); (P.S.); (G.T.)
| | - Damien Lenoble
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
| | - Jean-Sébastien Thomann
- MRT Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, Belvaux, L-4422 Luxembourg, Luxembourg; (V.R.); (E.M.); (J.D.); (M.M.); (D.L.); (J.-S.T.)
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6
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Nardelli F, Martini F, Carignani E, Rossi E, Borsacchi S, Cettolin M, Susanna A, Arimondi M, Giannini L, Geppi M, Calucci L. Glassy and Polymer Dynamics of Elastomers by 1H-Field-Cycling NMR Relaxometry: Effects of Fillers. J Phys Chem B 2021; 125:4546-4554. [PMID: 33885314 PMCID: PMC8279540 DOI: 10.1021/acs.jpcb.1c00885] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/07/2021] [Indexed: 11/30/2022]
Abstract
1H spin-lattice relaxation rate (R1) dispersions were acquired by field-cycling (FC) NMR relaxometry between 0.01 and 35 MHz over a wide temperature range on polyisoprene rubber (IR), either unfilled or filled with different amounts of carbon black, silica, or a combination of both, and sulfur cured. By exploiting the frequency-temperature superposition principle and constructing master curves for the total FC NMR susceptibility, χ″(ω) = ωR1(ω), the correlation times for glassy dynamics, τs, were determined. Moreover, the contribution of polymer dynamics, χpol″(ω), to χ″(ω) was singled out by subtracting the contribution of glassy dynamics, χglass″(ω), well represented by the Cole-Davidson spectral density. Glassy dynamics resulted moderately modified by the presence of fillers, τs values determined for the filled rubbers being slightly different from those of the unfilled one. Polymer dynamics was affected by the presence of fillers in the Rouse regime. A change in the frequency dependence of χpol″(ω) at low frequencies was observed for all filled rubbers, more pronounced for those reinforced with silica, which suggests that the presence of the filler particles can affect chain conformations, resulting in a different Rouse mode distribution, and/or interchain interactions modulated by translational motions.
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Affiliation(s)
- Francesca Nardelli
- Dipartimento
di Chimica e Chimica Industriale, Università
di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
| | - Francesca Martini
- Dipartimento
di Chimica e Chimica Industriale, Università
di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
- Centro
per l’Integrazione della Strumentazione Scientifica dell’Università
di Pisa (CISUP), Lungarno
Pacinotti 43, 56126 Pisa, Italy
| | - Elisa Carignani
- Dipartimento
di Chimica e Chimica Industriale, Università
di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
| | - Elena Rossi
- Dipartimento
di Chimica e Chimica Industriale, Università
di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
| | - Silvia Borsacchi
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
- Centro
per l’Integrazione della Strumentazione Scientifica dell’Università
di Pisa (CISUP), Lungarno
Pacinotti 43, 56126 Pisa, Italy
| | | | | | | | - Luca Giannini
- Pirelli
Tyre SpA, Viale Sarca 222, 20126 Milano, Italy
| | - Marco Geppi
- Dipartimento
di Chimica e Chimica Industriale, Università
di Pisa, via G. Moruzzi 13, 56124 Pisa, Italy
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
- Centro
per l’Integrazione della Strumentazione Scientifica dell’Università
di Pisa (CISUP), Lungarno
Pacinotti 43, 56126 Pisa, Italy
| | - Lucia Calucci
- Istituto
di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle
Ricerche, via G. Moruzzi
1, 56124 Pisa, Italy
- Centro
per l’Integrazione della Strumentazione Scientifica dell’Università
di Pisa (CISUP), Lungarno
Pacinotti 43, 56126 Pisa, Italy
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7
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Sepiolite-embedded binary nanocomposites of (alkyl)methacrylate-based responsive polymers: Role of silanol groups of fibrillar nanoclay on functional and thermomechanical properties. REACT FUNCT POLYM 2021. [DOI: 10.1016/j.reactfunctpolym.2021.104844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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8
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Morozov IA. Atomic force microscopy nanoindentation kinetics and subsurface visualization of soft inhomogeneous polymer. Microsc Res Tech 2021; 84:1959-1966. [PMID: 33713508 DOI: 10.1002/jemt.23751] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/10/2021] [Accepted: 02/27/2021] [Indexed: 11/11/2022]
Abstract
Modern techniques of nanoindentation by atomic force microscopy (AFM) produce maps of topography and physical-mechanical properties of the material. Analysis of the interaction rate of the AFM tip with the soft surface reveals the surface and subsurface structure and expands standard analysis of the material behavior. Phase-separated polymer (polyurethane, elastic modulus-6 MPa) is studied. Reversible inelastic changes of the surface at different stages of indentation were established in dependence on peculiarities of velocity and position of the AFM-tip in the material: uniform soft nanofilm covering the outer surface gradually passes into fibrillar heterogeneous structure of the polymer. The point of stable mechanical contact is defined, and the elastic moduli of soft and hard blocks of the polymer are estimated using certain intervals of the indentation. The presented methods of surface analysis are useful in the study of a wide class of soft heterogeneous materials.
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Affiliation(s)
- Ilya A Morozov
- Institute of Continuous Media Mechanics UB RAS, Perm, Russia
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9
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García-Beltrán G, Mercado-Zúñiga C, Torres-SanMiguel CR, Trejo-Valdez M, Villalpando I, Torres-Torres C. Dynamic compressibility and third-order optical nonlinearities in carbon/metal-based nanofluids. Phys Chem Chem Phys 2020; 22:4793-4804. [PMID: 32068198 DOI: 10.1039/c9cp06202e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of the superposition of two high-irradiance optical beams on the mechanical properties exhibited by carbon nanotubes decorated with platinum nanoparticles was analyzed. The change in density, compressibility modulus and acoustic velocity in the samples suspended in acetone and ethanol was estimated by measuring the nonlinear refractive index tested by a two-wave mixing experiment. The nanotubes were prepared by a spray pyrolysis processing route and the metal decoration was carried by chemical vapor deposition. High-Resolution Transmission Electron Microscopy studies confirmed the multiwall nature of the carbon nanotubes; while energy-dispersive X-ray spectroscopy reveals the separated presence of platinum nanoparticles incorporated to the hybrid nanostructures. An Nd-YAG laser system emitting at 532 nm wavelength with 4 ns pulse duration was used for conducting the third-order nonlinear optical evaluations by a standard optical Kerr gate technique. Comparative experiments showed that the composition of the liquid solution plays an important role in the manipulation of the density exhibited by the nanofluids. Remarkably, the incorporation of Pt in the tubes originates stronger changes of the mechanical characteristics induced by optical nonlinearities in the nanofluids irradiated by nanosecond pulses. Within this work, it is highlighted that potential applications for developing multivalent logic operations by fuzzy mechano-optic effects exhibited by nanofluids can be contemplated.
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Affiliation(s)
- Geselle García-Beltrán
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Ingeniería Mecánica y Eléctrica Unidad Zacatenco, Instituto Politécnico Nacional, Ciudad de México 07738, Mexico.
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10
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Tagliaro I, Di Credico B, Moncho-Jordá A. Electrostatic depletion effects on the stability of colloidal dispersions of sepiolite and natural rubber latex. J Colloid Interface Sci 2020; 560:606-617. [PMID: 31685278 DOI: 10.1016/j.jcis.2019.10.083] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 11/30/2022]
Abstract
Biocomposites based on sepiolite (Sep) clays and natural rubber latex (NRL) are novel green synthetic materials with significant mechanical performance obtained by an eco-friendly and sustainable mixing procedure, without the use of surfactants. In this work, experiments and theory are combined to investigate the stability of colloidal dispersions formed by a mixture of both negatively charged Sep fibers and non-adsorbing NRL particles. Experiments were performed by adding Sep fibers to NRL dispersions with different Sep/NRL volume fractions to evaluate the effect of Sep dispersion and NRL loading on the flocculation process. In order to theoretically understand the experimental results on colloidal stability, a density functional approach was applied to calculate the depletion interaction between two Sep fibers induced by the presence of naturally charged NRL, and an effective one-component mean-field free energy was developed to predict the phase behavior of the Sep/NRL mixture. The existence of a depletion attraction, enhanced by the electrostatic repulsion between Sep and NRL, is shown to be strong enough to induce the flocculation of the mixture at determined Sep and NRL volume fractions. The theoretical predicted phase diagram is in excellent qualitative and quantitative agreement with the experimental results, indicating that this electrostatically-enhanced depletion effect plays a key role in the colloidal stability of this system. To the best of our knowledge, this study represents the first attempt to tackle how depletion effects can be exploited to produce and control Sep/NR biocomposites.
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Affiliation(s)
- I Tagliaro
- Department of Materials Science, University of Milano-Bicocca, INSTM, Via R. Cozzi, 55, 20125 Milano, Italy
| | - B Di Credico
- Department of Materials Science, University of Milano-Bicocca, INSTM, Via R. Cozzi, 55, 20125 Milano, Italy
| | - A Moncho-Jordá
- Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain; Instituto Carlos I de Física Teórica y Computacional, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva S/N, 18071 Granada, Spain.
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11
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On the Nanoscale Mapping of the Mechanical and Piezoelectric Properties of Poly (L-Lactic Acid) Electrospun Nanofibers. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10020652] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of the post-annealing process on different properties of poly (L-lactic acid) (PLLA) nanofibers has been investigated in view of their use in energy-harvesting devices. Polymeric PLLA nanofibers were prepared by using electrospinning and then were thermally treated above their glass transition. A detailed comparison between as-spun (amorphous) and annealed (semi-crystalline) samples was performed in terms of the crystallinity, morphology and mechanical as well as piezoelectric properties using a multi-technique approach combining DSC, XRD, FTIR, and AFM measurements. A significant increase in the crystallinity of PLLA nanofibers has been observed after the post-annealing process, together with a major improvement of the mechanical and piezoelectric properties.
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