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New polyurethane (PU)-based nanocomposites were synthesized through two-step in situ polymerization by incorporating low loading levels of spherical cellulose nanoparticles (CNs). Structural, mechanical, thermal, and morphological...
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New polyurethane (PU)-based nanocomposites were synthesized through two-step in situ polymerization by incorporating low loading levels of spherical cellulose nanoparticles (CNs). Structural, mechanical, thermal, and morphological characterization of the nanocomposites was done with infrared spectroscopy, X-ray diffraction, tensile test, dynamic mechanical thermal analysis, thermogravimetry, differential scanning calorimetry, and field emission scanning electron microscopy. The results showed with incorporation of CNs there was no significant change in the structure of PU. However, the addition of 1 % CNs into PU increased the modulus nearly 42 % and tensile strength by 112 %. On the contrary, elongation at break decreased with increasing nanoparticles contents, but the nanocomposites maintained an elongation of greater than 800 %, which was still a large elongation. The thermal stability of PU enhanced with increasing the small amounts of nanoparticles. Also, incorporating of the CNs improved the phase separation between the soft and hard domains which led to an upward shift in melting temperatures and enthalpy of crystalline phase melting. These results were very encouraging in terms of using CNs as an inexpensive nanofiller and improving the mechanical and thermal properties of PU without using solvents in nanocomposite preparation.
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Polymer nanocomposites offer design solutions to control and tune optical, conductive, topological, and thermomechanical properties of advanced and multifunctional materials. Because of their ubiquitous nature, methodologies to di...
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Polymer nanocomposites offer design solutions to control and tune optical, conductive, topological, and thermomechanical properties of advanced and multifunctional materials. Because of their ubiquitous nature, methodologies to diagnose failure or structural changes in the nanocomposites are of significant interest. Herein, we report a nanocomposite system loaded with quantum dots and coumarin-modified carbon nanotubes that transduce mechanical force into fluorescence at a strain, for the first time, as low as 7.5%. Our comprehensive studies detail the optical, morphological, and thermomechanical properties of these nanocomposites to establish the fundamental reason behind the activation of fluorescence. Our results indicate that bare carbon nanotubes can irreversibly quench the fluorescence from quantum dots and that the coumarin-modified carbon nanotubes mitigate the quenching through Forster Resonance Energy Transfer. Next, the application of force to the sample changes the quantum dot-carbon nanotube spacing as well as the carbon nanotube morphology to activate fluorescence in the nanocomposite. Overall, this force activation of fluorescence can serve as a general strategy for the development of a new class of mechano-responsive nanocomposites that impart polymeric materials with desirable functionalities including damage sensing and mechanical strength.
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Synthetic polymer nanocomposites display enhanced toughness and energy absorption with regard to unreinforced polymers. The interaction between the polymeric matrix and the reinforcements triggers failure mechanisms such as fiber ...
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Synthetic polymer nanocomposites display enhanced toughness and energy absorption with regard to unreinforced polymers. The interaction between the polymeric matrix and the reinforcements triggers failure mechanisms such as fiber fracture, crack deflection, among others. Biological nanocomposites sometimes exhibit higher toughness than synthetic nanocomposites due to their hierarchical organization. This arrangement triggers failure modes such as mineral bridging and delamination. This review summarizes and classifies systematically the failure mechanisms involved in these nanocomposites. These failures modes are compared for a better understanding and to provide new design criteria for the development of novel bioinspired polymer nanocomposites with enhanced mechanical properties.
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Background: Since the available metals are not able to meet the desired structural, mechanical and electrochemical properties therefore composites and nanocomposites are being used now a days. Composites are an amalgamation of mat...
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Background: Since the available metals are not able to meet the desired structural, mechanical and electrochemical properties therefore composites and nanocomposites are being used now a days. Composites are an amalgamation of materials that are mixed together to develop new compound with special and superior properties as compared to the base material. Nanocomposite is a new approach in which out of two phase, any one phase should consist of single unit sized particle whose dimension lies in between 1 and 1000 nanometres (nm) but usually it lies between 1-100 nm Objective: The present paper provides an overview on the different types of nanocomposites, their manufacturing, mechanical behaviour & industrial applications. Method: Gupta et al. synthesized iron (Fe) - alumina (Al2O3) metal matrix nanocomposites synthesized via powder metallurgy technique. Composition selected for the study was in the range of 5-30wt% of Al2O3 in Fe matrix. Specimens were synthesized by ball milling, compaction and sintering in argon atmosphere in temperature range of 900-1100°C for 1 to 3 hour respectively. Results: It was found that due to reactive sintering between iron and alumina particles an iron aluminate (FeAl2O4) phase forms. Formation of nano iron aluminate phases and related properties also depend on processing parameters. It was also found that the mechanical and electrochemical properties varies with the sintering parameters which in turn depend upon the iron aluminate phase formation. Conclusion: Metal Matrix Nanocomposites are excellent for manufacturing materials having high strength in the case of shear & compression processes and have ability to work at elevated temperature.
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This chapter is an introduction to nanocomposite materials and its classifications with emphasis on orthopedic application. It covers different types of matrix nanocomposites including ceramics, metal, polymer and natural-based na...
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This chapter is an introduction to nanocomposite materials and its classifications with emphasis on orthopedic application. It covers different types of matrix nanocomposites including ceramics, metal, polymer and natural-based nanocomposites with the main features and applications in the orthopedic. In addition, it presents structure, composition, and biomechanical features of bone as a natural nanocomposite. Finally, it deliberately presents developing methods for nanocomposites bone grafting.
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The matrix of carbon fiber/SC-15 epoxy composites was modified with Nanomer((R)) I-28E nanoclay, a surface modified montmorillonite mineral, to determine the effects of particle reinforcement on the response of these materials to ...
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The matrix of carbon fiber/SC-15 epoxy composites was modified with Nanomer((R)) I-28E nanoclay, a surface modified montmorillonite mineral, to determine the effects of particle reinforcement on the response of these materials to flexural and thermomechanical loading. Different weight percentages of nanoclay were dispersed in SC-15 epoxy using sonication route. The nanophased epoxy was then used to manufacture plain weave carbon/epoxy nanocomposites using hand-layup process followed by vacuum bagging. Control samples of woven carbon fiber/epoxy were fabricated for comparison purposes. Effect of post curing on these samples was also investigated. 3-point bend flexure and Dynamic Mechanical Analysis (DMA) studies were carried out on 8- and 3-layered samples respectively. Results of flexural tests indicate significant improvements in flexural strength and modulus for nanoclay reinforced composites as compared to the control samples. DMA studies also showed enhancement in thermomechanical properties especially in storage modulus though no appreciable change was noticed in glass transition temperature, T-g. Scanning electron microscopy (SEM) studies were carried out to comprehend the effect of nanoclay on the microstructure and the failure modes.
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This paper focuses on the study of thermal degradation and evolved gas analysis using thermogravimetric analysis (TGA) coupled to Fourier transform infrared (FTIR) spectroscopy, i.e., TG-IR, to study polyamide 6 (PA6) and PA6-clay...
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This paper focuses on the study of thermal degradation and evolved gas analysis using thermogravimetric analysis (TGA) coupled to Fourier transform infrared (FTIR) spectroscopy, i.e., TG-IR, to study polyamide 6 (PA6) and PA6-clay nanocomposites prepared by melt compounding. The thermal decomposition of PA6 and its clay nanocomposites takes place with the evolution of the cyclic monomer (caprolactam) first, followed by other volatile gases like CO2 and NH3, which are characterized by the presence of oligomeric products with nitrile and vinyl chain ends in the infrared (IR) spectra. The onset temperature for degradation is 12 degreesC higher for PA6 with 2.5 wt.% of clay loading than that for neat PA6, whereas, the onset temperature for degradation remained almost unchanged for samples with higher clay loading (i.e. 5, 7.5 and 10 wt.% clay). The above findings are related to the morphological observations that show an optimal exfoliated structure only for the nanocomposite with 2.5 wt.% clay, and distinct clay agglomeration in those with higher clay loadings. Our study suggests that only exfoliated polymer/clay nanocomposites exhibit improved thermal stability. Agglomerated clay particles do not significantly affect thermal stability of the polymer matrix. The activation energies for degradation, E-a, estimated by Kissinger method, for PA6 and PA6-2.5 wt.% clay nanocomposite were found to be 175 and 199 kJ/mol in N-2, and 228 and 223 kJ/mol in air, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved. [References: 12]
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Poly(epsilon-caprolactone)/clay nanocomposites were prepared by in-situ ring-opening polymerization of epsilon-caprolactone by using dibutyltin dimethoxide as an initiator/catalyst. A nonmodified Na+-montmorillonite and two montmo...
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Poly(epsilon-caprolactone)/clay nanocomposites were prepared by in-situ ring-opening polymerization of epsilon-caprolactone by using dibutyltin dimethoxide as an initiator/catalyst. A nonmodified Na+-montmorillonite and two montmorillonites surface-modified by dimethyl 2-ethylhexyl (hydrogenated tallow alkyl) and methyl bis(2-hydroxyethyl) (hydrogenated tallow alkyl) ammonium cations, respectively, were used. The evolution of molecular weights was followed in relation to silicate surface modification and clay concentration. The alcohol-bearing organo-modified clay was a co-initiator for the polymerization reaction and thus controlled the molecular weight of the PCL chains. Furthermore, the number-average molecular weight of the growing PCL chains linearly increased with the monomer conversion. Nanocomposites were analyzed by small-angle X-ray diffraction, transmission electron microscopy, and thermogravimetry. The clay dispersion depended on the structure of the alkylammonium used to make the clay more hydrophobic. Exfoliated nanocomposites were formed when hydroxyl-containing alkylammonium. was used; otherwise, intercalated structures were reported. Thermogravimetric analyses showed a higher degradation temperature for the exfoliated structures than for the intercalated ones, both of them exceeding the degradation temperature of unfilled poly(E-caprolactone). [References: 27]
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In this study, layered clay/polymer nanocomposites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ...
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In this study, layered clay/polymer nanocomposites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ion exchange reaction. In this way, Na+ interlayer cations of the clay is exchanged with onium cation of the surfactant that turns the hydrophilic clays (MMT) to organophilic (OMMT) characteristics. Thermal analysis results revealed that the glass transition temperature (T-g) and the dynamic mechanical properties including the storage and loss modulus of the neat epoxy resin increases by the incorporation of clay particles. It was also found that flame resistance of the polymer is improved by the addition of the clay particles. (C) 2008 Wiley Periodicals, Inc.
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The use of various copolymers as dispersants/intercalants/exfoliants in polypropylene (PP)-clay nanocomposites based on unmodified montmorillonite clays (NaMMT) has been explored. The primary objective of this research has been to...
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The use of various copolymers as dispersants/intercalants/exfoliants in polypropylene (PP)-clay nanocomposites based on unmodified montmorillonite clays (NaMMT) has been explored. The primary objective of this research has been to find dispersants that allow PP nanocomposites to be formed by direct melt mixing, that are effective with unmodified clays and that comprise only a minor component of the overall composition both with respect to both clay and PP. Two classes of dispersants were investigated: PEO-based nonionic surfactants and amphiphilic copolymers based on a long chain (meth)acrylate (e.g. octadecyl acrylate) and a more polar comonomer (e.g. maleic anhydride, N-vinylpyrrolidone, methyl methacrylate). The state of dispersion achieved and the properties of the derived nanocomposites were found to depend strongly on both on the level of dispersant and its overall composition but interestingly properties are not particularly dependent on the dispersant architecture (i.e. whether statistical, gradient or block copolymer). The nanocomposites possess a tensile modulus up to 40% greater that the precursor PP while elongation at break and impact strength are significantly improved over "clay alone" composites and reference organoclay-based nanocomposites. Also notable are significantly better thermal and thermo-oxiclative stability as compared to both PP and "clay alone" composites. For optimal properties, it is both necessary and desirable that the surfactant should only be a minor constituent (20-50 wt-%) of the composition with respect to clay.
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