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Study on structure and morphology of polymer nanocomposites
Get PDFThe reinforcement of polymers using fillers, whether inorganic or organic, is common in modern plastics. Polymer nanocomposites or, with a more inclusive term, polymer nanostructured materials, represent a radical alternative to these traditional filled polymer compositions. In contrast to ordinary polymer systems where reinforcement is on the order of microns, polymer nanocomposites are exemplified by discrete constituents on the order of a few nanometers. In the past decade polymer/clay nanocomposites have emerged as a new class of materials and attracted considerable interest in research and development worldwide after initial reports from the Toyota group on Nylon 6 / clay nanocomposites. Enormous amount of work has been done on preparation and characterization of polymer/organoclay nanocomposites because by this approach it is possible to impart much improved mechanical, thermal, electrical properties with respect to their macro and micro counterparts.
There are now many well-developed techniques that are used to produce conventional polymer blends and composites, and various products have been widely commercialized. There are also numerous papers, patents, books, and handbooks that introduce and discuss the development and application of various polymeric blends and composites. Over the past two decades, however, biodegradable/compatible polymers and polymers from renewable resources (PFRR) have been attracting increasing attention, primarily for two major reasons: environmental concerns, and the realization that our petroleum resources are finite. A third reason for the growing interest in polymers from renewable resources relates to adding value to agricultural products, which is economically important for many countries.
The present thesis is organized and presented in seven chapters. A brief overview of polymer nanocomposites, of the different fillers used for the preparation polymer composites, and of the different matrices used for polymer nanocomposites are discussed in the first chapter. The scope and objectives of the thesis are described in the second chapter. In the third chapter, various characterization techniques used in this work such as wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Infrared spectroscopy (IR), differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), thermogravimetric analysis (TGA), etc. are described. The fourth chapter describes poly(ε-caprolactone) (PCL) based nanocomposites. For this, PCL was reinforced with different kinds of nanofillers such as clay nanoparticles and different types of electrospun nanofibers. The effect of those nanofillers on PCL matrix structure, morphology, tensile mechanical properties and degradation behavior was analyzed. The fifth chapter deals with poly(lactic acid) (PLA) based composites, in which PLA was reinforced with clay nanoparticles, electrospun nanofibers and also natural fibers. We tried to study the morphology, properties, and degradation behavior of these materials, etc.
In the sixth chapter, the efficiency of particles filled electrospun nanofibers as reinforcement for poly(butylene succinate-co-adipate) (PBSA) was studied. Thus, the effect of those fibers on PBSA structure, morphology, and physical mechanical properties was elaborated. It was observed that by using this kind of nanofillers, it is possible to control the structural morphology of pristine polymer matrices and thus their mechanical properties and degradation behavior. Finally, in the seventh chapter, the general conclusions are given.Il rinforzo dei polimeri con cariche, sia organiche che inorganiche, è una comune strategia nella moderna industria delle materie plastiche. I nanocompositi polimerici, o secondo una definizione più ampia i materiali polimerici nanostrutturati, rappresentano una radicale alternativa alle tradizionali formulazioni dei compositi polimerici. Al contrario dei sistemi ordinari, in cui la carica è dell’ordine di grandezza dei micron, i nanocompositi polimerici contengono costituenti discreti di dimensioni nanometriche. A partire dal lavoro del gruppo della Toyota, nello scorso decennio, i nanocompositi polimerici con argilla sono emersi come una nuova classe di materiali che ha attratto l’interesse del mondo della ricerca e sviluppo sia accademico che industriale. Da allora è stata svolta un’enorme mole di lavoro riguardo la preparazione e la caratterizzazione di questo tipo di nanocompositi perché grazie a questo approccio è possibile impartire proprietà meccaniche, termiche ed elettriche molto migliori rispetto ai più comuni micro e macrocompositi.
Oggi esistono molte tecniche sviluppate e mature per produrre compositi e blend polimerici convenzionali e sono stati posti in commercio moltissimi prodotti. Inoltre è disponibile un’ampia letteratura scientifica che introduce e discute gli sviluppi e le applicazioni di questi materiali. Negli ultimi due decenni, tuttavia, è cresciuto l’interesse per polimeri biodegradabili/biocompatibili e per polimeri da fonti rinnovabili, principalmente per due motivi: attenzione all’ambiente e la constatazione che le riserve di petrolio siano finite. Una terza ragione di interesse per i polimeri da fonti rinnovabili consiste nel valore aggiunto che tali materiali possono dare ai prodotti agricoli, un aspetto di grande interesse economico per molti paesi.
Il presente lavoro di tesi è organizzato e presentato in sette capitoli. I nanocompositi polimerici saranno brevemente introdotti, assieme ai diversi additivi ed alle diverse matrici impiegate nei nanocompositi polimerici. Lo scopo e gli obiettivi della tesi sono descritti nel secondo capitolo. Nel terzo capitolo sono descritti i metodi usati per la caratterizzazione dei materiali, come la diffrazione dei raggi X ad alto angolo, la diffusione dei raggi X a basso angolo, la microscopia ottica, la microscopia elettronica a scansione, la microscopia elettronica in trasmissione, la spettroscopia infrarossa, la calorimetria differenziale a scansione, la microscopia ottica in luce polarizzata e la termogravimetria. Il quarto capitolo descrive i nanocompositi basati sul poli(ε-caprolattone) (PCL). Il PCL è stato rinforzato con diversi tipi di nanofiller come nanoparticelle di argilla e diversi tipi di nanofibre da elettrospinning. È stato analizzato l’effetto di questi nanofiller sulla struttura, sulla morfologia, sulle proprietà meccaniche e sul comportamento di degradazione del PCL. Il quinto capitolo presenta i risultati riguardanti i compositi dell’acido polilattico (PLA), nei quali il PLA è stato rinforzato con nanoparticelle di argilla, nanofibre da elettrospinning ed anche con fibre naturali. Anche in questo caso, abbiamo studiato approfonditamente struttura, morfologia e proprietà di questi materiali.
Nel sesto capitolo, è stata studiata l’efficienza di nanofibre da elettrospinning caricate da particelle inorganiche come rinforzo per una matrice di poli(butilen succinato-co-adipato) (PBSA). È stato quindi investigato l’effetto di queste fibre sulla struttura, sulla morfologia e sulle proprietà del PBSA. Si è osservato che usando questo tipo di nanofiller è possibile controllare la morfologia e la struttura delle matrici polimeriche e quindi le loro proprietà meccaniche ed il loro comportamento di degradazione.
Il settimo capitolo, infine, presenterà le conclusioni generali
The effect of clay and of electrospinning on the polymorphism, structure and morphology of poly(vinylidene fluoride)
No full textElectrospun poly(vinylidene fluoride) (PVDF) fibers, containing different amounts of montmorillonite clay were produced, in order to study the effect of clay and of the electrospinning process on the polymorphism, structure and morphology of the PVDF matrix. Clay acted as a processing aid agent, avoiding the formation of beads and improving the quality of the fibers. Clay and the electrospinning process acted synergically on the chain mobility, favoring the formation of β phase of PVDF, the most valuable for its piezoelectric properties, and shaping its semicrystalline morphology. Electrospinning did not significantly aid the dispersion of clay within the matrix. The interplay of formulation and processing in these composites allowed to obtain PVDF-based materials with varying polymorphism, structure and morphology, offering the possibility to ultimately control their functional properties
Nanocomposites improve performance of biodegradable polymers
Get PDFNanocomposites based on polycaprolactone exhibit enhanced tensile properties and controlled biodegradation rates
Conductivity, XRD, and FTIR Studies of New Mg2+-ion-conducting Solid Polymer Electrolytes: [PEG: Mg(CH3COO)2]
No full textSolid polymer electrolytes based on poly (ethylene glycol) (PEG) doped with Mg(CH3COO)2 have been prepared by using the solution-casting method. The X-ray diffraction patterns of PEG with Mg(CH3COO)2 salt indicated a decrease in the degree of crystallinity with increasing concentration of the salt. The complexation of Mg(CH3COO)2 salt with the polymer was confirmed by using Fourier transform infrared spectroscopy (FTIR) studies. The ionic conductivity was measured for the [PEG: Mg(CH3COO)2] system in the frequency range 50 Hz - 1 MHz. The addition of Mg salt was found to improve the ionic conductivity significantly. The 15-wt-% Mg(CH3COO)2-doped system had a maximum conductivity of 1.07 ?10−6 S/cm at 303 K. The conductance spectrum shows two distinct regions: a dc plateau and a dispersive region. The temperature dependence of the ionic conductivity reveals the conduction mechanism to be an Arrhenius-type thermally activated process
Electrospun nanocomposite fibers: fillers for tuning the properties of poly(butylenesuccinate-co-adipate)
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Improvement of tensile properties and tuning of the biodegradation behavior of polycaprolactone by addition of electrospun fibers
No full textA novel approach to simultaneously improve the physical mechanical properties and tune the biodegradation of polycaprolactone (PCL)-based composites is presented. The viability of electrospun fibers as fillers for polymer nanocomposites is shown. Nylon was chosen as the reinforcing material, whereas polyvinylpirrolidone (PVP) was selected to calibrate the biodegradation rate. Nylon fibers were effective reinforcing fillers for the PCL matrix, also in co-presence with PVP fibers. PVP fibers were, on the other hand, critical in shaping the biodegradation behavior, because they were able to create channels by which water can easily penetrate within the bulk of the material. The cooperative effect of nylon and PVP fibers allowed to obtain composites able to degrade more quickly than the matrix or than the samples containing either of the two fibers, while retaining a remarkable dimensional stability even after 20% of the total mass had degraded
Electrospun nylon fibers for the improvement of mechanical properties and for the control of degradation rate of poly(lactide)-based composites
No full textPoly(lactide) (PLA) composites filled with electrospun nylon 6 fibers were prepared. This allowed to simultaneously improve the mechanical properties and tune the degradation of the PLA matrix. The interfacial adhesion between the PLA matrix and the nylon fibers was very good. The major effect of electrospun fibers on the matrix was that of modifying the semicrystalline framework, thickening the polymer lamellae. This allowed increasing the mechanical properties of the material, and on the other hand to modify its degradation rate. The modulus of the composites was increased up to 3-fold with respect to neat PLA. The peculiar morphology of matrix-filler interaction moreover slowed down the degradation rate of the material and improved the dimensional stability of the specimens during the degradation process. This shows the potential of electrospun fibers as a way to tune the durability of PLA-based products, widening the range of application of this promising material
Surface tailored PS/TiO2 composite nanofiber membrane for copper removal from water
Get PDFPolystyrene (PS)/TiO2 composite nanofiber membranes have been fabricated by electrospinning process for Cu2+ ions removal from water. The surface properties of the polystyrene nanofibers were modulated by introducing TiO2 nanoparticles. The contact angle of the PS nanofiber membrane was found to be decreased with increasing concentration of TiO2, depicted enhanced hydrophilicity. These membranes were highly effective in adsorbing Cu2+ ions from water. The adsorption capacity of these membranes was found to be 522 mg/g, which is significantly higher than the results reported by other researchers.This was attributed to enhanced hydrophilicity of the PS/TiO2 composite nanofiber membranes and effective adsorption property of TiO2 nanoparticles
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