Poly(ε-caprolactone)-based nanocomposites: Influence of compatibilization on properties of poly(ε-caprolactone)–silica nanocomposites

In the present paper, results about preparation and characterization of poly(ε-caprolactone) (PCL) based nanocomposites filled with silica nanoparticles are reported. In order to promote polymer/inorganic nanofiller compatibility and to increase the interfacial adhesion between the two components, silica nanoparticles surface has been functionalised by grafting a M_w = 10,000 Da PCL onto it. Successively, PCL based nanocomposites have been prepared by extrusion process. The relationships among size, amount of the nanofiller, organic coating and the final properties have been investigated. The morphological analysis has revealed that the silica functionalization can provide a useful method of preparation of the nanocomposites with the achievement of a fine, a good dispersion and a strong adhesion level. Thermal characterization has shown an improved thermal stability due to the presence of the silica nanoparticles, especially in the case of modified nanofillers. Finally mechanical tests revealed an increase of the Young’s modulus in the PCL based nanocomposites.     

Synergy in hybrid polymer/nanocarbon composites. A review

The aim of this review article is to report the most recent developments in the understanding of and beliefs about the properties of polymer hybrid composites that are reinforced with various combinations of nanometer-sized carbon and mineral fillers. The discussions are primarily focused on an analysis and comparison of the electrical, thermal, and mechanical properties. It is shown that the introduction of a mixed (hybrid) system of filler nanoparticles into polymer matrices enhances the macro- and microproperties of the composites as a result of the synergistic interactions between the fillers and the simultaneous creation of a unique filler network in the polymer. The synergy of various types of carbon nanofillers and combinations of nanocarbon materials with inorganic fillers manifests itself as modifications of most of the properties of hybrid polymer composites relative to the properties of a polymer system containing a single filler. The reinforcing effect is related to the structure and particle geometry of the hybrid fillers, the interactions between the fillers, the concentrations and the processing methods.The existence of synergy between different types of carbon nanofillers, as well as with mineral fillers, shows great potential and could significantly increase applications of carbon-based nanomaterials.     

Porous poly<Emphasis Type="SmallCaps">(l</Emphasis>-lactic acid) nanocomposite scaffolds with functionalized TiO<Subscript>2</Subscript> nanoparticles: properties,cytocompatibility and drug release capability

Cytocompatibility is one of the most important aspects in evaluating biomaterials for tissue engineering applications. In this study, biodegradable polymer scaffolds based on nanocomposites of poly(l-lactic acid) and TiO₂ nanoparticles functionalized with oleic acid (5 and 10 wt%) were prepared by thermally induced phase separation method. The aim of this research was to evaluate the properties of nanocomposite scaffolds and to investigate the influence of functionalized nanofiller on their bioactivity, biodegradability and cytocompatibility. The nanocomposite scaffolds showed bioactivity in supersaturated fluids and reduced biodegradation in simulated body fluid when compared to pure PLA scaffold. Cell viability and proliferation potential in contact with nanocomposite scaffolds were tested via MTT assay, while the scaffolds cytotoxic potential was evaluated using lactate dehydrogenase method. It was found that incorporation of functionalized TiO₂ nanofiller with content of 5 wt% in the corresponding PLA matrix has a significant positive effect on the cell viability and proliferation, while at higher nanofiller content (10 wt%), insignificant cell proliferation and increased cytotoxicity were confirmed. Furthermore, PLA/TiO₂–OA nanocomposite scaffolds were proved as promising materials for drug delivery.     

Influence of mesoporous silica and hydroxyapatite nanoparticles on the mechanical and morphological properties of polypropylene

This paper presents the effect of different types of additives on the morphology and mechanical performance of polypropylene (PP). Three different types of nanoparticles, containing mesoporous silica (MCM-41), Hydroxyapatite (HA) and the composite of MCM-41 and HA (MH) were used. Nanocomposites containing PP, 3 wt.% of maleic anhydride grafted polypropylene (PP-g-MA) and 3 wt.% of different nanoparticles were prepared using the melt-compounding technique in a twin-screw extruder. The bulk mechanical response of the nanocomposites such as tensile, flexural and Izod impact properties were studied. The results of mechanical tests show that at the same nanomaterial content, all the nanofillers cause better tensile, flexural and impact strength than neat PP. The MH nanoparticle improves the mechanical properties of PP, better than the other nanoparticles because this nanofiller contains good properties of both MCM-41 and HA nanoparticles in itself. In order to investigate the effect of foam agent on the mechanical properties of neat PP and nanocomposites based on PP, inorganic azodicarboxamide was added to the aforementioned mixtures as chemical blowing agent and the foamed specimens were resulted using the melt-compounding technique. The results reveal that addition of foam agent to mixtures, leads to increase the flexural characteristics of samples, but the tensile properties and impact strength decrease. Scanning electron microscopy (SEM) was used to assess the fracture surface morphology and the dispersion of the nanoparticles. X ray diffractometry (XRD) was used to examine the intercalation effect on the nanocomposites. The observations show that the nanomaterials were well dispersed in the polymer matrix and the enhancement of the interface between the matrix and fillers was obtained by the incorporation of MH, MCM-41 and HA nanoparticles into PP matrix.     

Nanoindentation in polymer nanocomposites

This article reviews recent literature on polymer nanocomposites using advanced indentation techniques to evaluate the surface mechanical properties down to the nanoscale level. Special emphasis is placed on nanocomposites incorporating carbon-based (nanotubes, graphene, nanodiamond) or inorganic (nanoclays, spherical nanoparticles) nanofillers. The current literature on instrumented indentation provides apparently conflicting information on the synergistic effect of polymer nanocomposites on mechanical properties. An effort has been done to gather information from different sources to offer a clear picture of the state-of-the-art in the field. Nanoindentation is a most valuable tool for the evaluation of the modulus, hardness and creep enhancements upon incorporation of the filler. It is shown that thermoset, glassy and semicrystalline matrices can exhibit distinct reinforcing mechanisms. The improvement of mechanical properties is found to mainly depend on the nature of the filler and the dispersion and interaction with the matrix. Other factors such as shape, dimensions and degree of orientation of the nanofiller, as well as matrix morphology are discussed. A comparison between nanoindentation results and macroscopic properties is offered. Finally, indentation size effects are also critically examined. Challenges and future perspectives in the application of depth-sensing instrumentation to characterize mechanical properties of polymer nanocomposite materials are suggested.     

Design of Multifunctional Fluorescent Hybrid Materials Based on SiO2 Materials and Core–Shell Fe3O4@SiO2 Nanoparticles for Metal Ion Sensing

Hybrid fluorescent materials constructed from organic chelating fluorescent probes and inorganic solid supports by covalent interactions are a special type of hybrid sensing platform that has gained much interest in the context of metal ion sensing applications owing to their excellent advantages, recyclability, and solubility/dispersibility in particular, as compared with single organic fluorescent molecules. In recent decades, SiO₂ materials and core–shell Fe₃O₄@SiO₂ nanoparticles have become important inorganic solid materials and have been used as inorganic solid supports to hybridize with organic fluorescent receptors, resulting in multifunctional fluorescent hybrid systems for potential applications in sensing and related research fields. Therefore, recent progress in various fluorescent‐group‐functionalized SiO₂ materials is reviewed, with a focus on mesoporous silica nanoparticles and core–shell Fe₃O₄@SiO₂ nanoparticles, as interesting fluorescent organic–inorganic hybrid materials for sensing applications toward essential and toxic metal ions. Selective examples of other types of silica/silicon materials, such as periodic mesoporous organosilicas, solid SiO₂ nanoparticles, fibrous silica spheres, silica nanowires, silica nanotubes, and silica hollow microspheres, are also mentioned. Finally, relevant perspectives of metal‐ion‐sensing‐oriented silica‐fluorescent probe hybrid materials are provided.     

Recent advances and perspectives on starch nanocomposites for packaging applications

Starch nanocomposites are popular and abundant materials in packaging sectors. The aim of this work is to review some of the most popular starch nanocomposite systems that have been used nowadays. Due to a wide range of applicable reinforcements, nanocomposite systems are investigated based on nanofiller type such as nanoclays, polysaccharides and carbonaceous nanofillers. Furthermore, the structures of starch and material preparation methods for their nanocomposites are also mentioned in this review. It is clearly presented that mechanical, thermal and barrier properties of plasticised starch can be improved with well-dispersed nanofillers in starch nanocomposites.     

Development and properties of advanced composites based on cork and nanometric silicon carbide-filled phenolic resin

This paper presents the obtaining of advanced materials based on cork powder as reinforcement and phenolic resin (PR) with silicon carbide (nSiC) nanofiller as matrix with potential applications in aerospace industry. Three formulations were obtained: one control sample PR/cork with no nanofiller, two nanofilled samples with 1 and 2 wt% nSiC loadings into the resin. The materials were tested by flexural and compressive mechanical tests to determine their strength and stiffness, to determine their friction coefficient by tribological tests, to determine their thermal decomposition behaviour by TG-DSC analysis and to evaluate their thermal behaviour by thermal shock tests when subjected to extreme temperature directly from room temperature. The material structure was analysed by SEM visualizing the fracture cross-section after mechanical testing. The test results illustrate that silicon carbide nanoparticles improve flexural and compressive strength, but also stiffness and friction coefficient, delay thermal decomposition onset and improve thermal shock resistance. All these sustain the PR/nSiC/cork materials as potential advanced materials candidates for thermal protection applications.     

Furan-Based Bionanocomposites Reinforced with a Hybrid System of Carbon Nanofillers

Bionanocomposites based on poly(trimethylene 2,5-furandicarboxylate)-block-poly(tetramethylene oxide) (PTF-b-F-PTMO) with various contents of carbon nanofibers, graphene nanoplatelets and a hybrid system of these nanoparticles are synthesized via in situ polymerization. The dispersion of nanoparticles in the nanocomposites is determined using a scanning electron microscope and optical microscopy images. The thermal properties are studied employing differential scanning calorimetry, dynamic mechanical thermal analysis, and thermogravimetric analysis. The melt viscosity of the synthesized materials is determined using rheological measurements. Mechanical properties, along with the thermal and electrical conductivity, are also analyzed. The synthesized polymer nanocomposites are processed using injection molding and they display mechanical properties of elastomers during mechanical testing, which indicates that the obtained materials are, in fact, thermoplastic elastomers (TPE). Compared to a neat matrix (PTF-b-F-PTMO 50/50), the incorporation of nanoparticles causes an increase in the value of the degree of crystallinity and the value of the tensile modulus values (E) of the nanocomposites. Such reinforced bionanocomposites are especially interesting from an applicative point of view. They can be used as components of fuel systems, bumpers, or cupholders.     

Anorganische Fasern. Herstellung,Eigenschaften und Verwendung

Inorganic Fibres – Fabrication, Properties and Application Glass- and carbon fibres are preferred reinforcement materials for composites with polymer matrix. Basing on an analysis of their properties it is shown that other inorganic fibres can combine the advantages of both, and avoid their disadvantages. Boron-, siliconcarbide- and alumina-fibres are discussed in detail. The boron fibre has a YOUNG's modulus up to 45 MN/m² and a strength of 3000–4000 MN/m² as well as high compressive and shear strength. Therefore the boron fibres are superior to the carbon fibres as high modulus reinforcement material. The disadvantages of the boron fibres are their complicated fabrication process (chemical vapour deposition on a tungsten monofilament), and their only availability in form of monofilaments with diameters of at least 60 μm. The boron fibre recristallizes at 6000 °C and reacts also with the tungsten substrat. Thus, its application at elevated temperatures is limited. The SiC-fibre shows the same mechanical properties as the boron fibre but it can be fabricated by chemical vapour deposition also on a carbon monofilament. The advantages are the chemical compatibility with carbon substrat and the resistance against oxidation. The disadvantage is the higher density compared with that of boron (3,5 against 2,6 · 10³ kg/m³) Carbon yarns (with 10 000 monofilaments of 10 μm diameter) with SiC coatings of 0,5 μm can be seen as an alternative to the relatively thick SiC-monofilaments with 60 μm diameter. The advantage of such coated carbon yarn is a better applicability in fibre reinforced composite materials. There exists a further alternative preparation process for SiC-yarn, namely the spinning of polycarbosilanes with subsequent formation of SiC by pyrolysis treatment. Al₂O₃-fibres are chemically inert against most oxidic and metallic matrix materials, and promises to be candidate reinforcement materials for aluminium. They can be prepared by melt-spinning process as well as by a hydrolysis-process starting from aluminium organic compounds with subsequent heat treatment for thermal decomposition. The properties of all these fibre materials are compared with those of glass-, polyamid- and carbon-fibres as well as with metal wires.     

Potential and challenges of metal-matrix-composites reinforced with carbon nanofibers and carbon nanotubes

With a continuous improvement of the production techniques for carbon nanofibers and carbon nanotubes along with an improvement of the available qualities of the materials, these reinforcements have been introduced into polymers, ceramics and metals. While in the field of polymers first success stories have been published on carbon nanofiller reinforcements, up to now metals containing these types of nanofillers are still a topic of intensive research. Basically a similar situation were found in those days, when micron sized carbon fibers came on the market. Today many applications of carbon fiber reinforced composites are existing, while metals reinforced with conventional carbon fibers are still only found in niche applications.     

Ordered nanoporous polymer-carbon composites

Nanostructured organic materials, particularly those constructed with uniform nanopores, have been sought for a long time in materials science. There have been many successful reports on the synthesis of nanostructured organic materials using the so-called, 'supramolecular liquid crystal templating' route. Ordered nanoporous polymeric materials can also be synthesized through a polymerization route using colloidal or mesoporous silica templates. The organic pore structures constructed by these approaches, however, are lower in mechanical strength and resistance to chemical treatments than nanoporous inorganic, silica and carbon materials. Moreover, the synthesis of the organic materials is yet of limited success in the variation of pore sizes and structures, whereas a rich variety of hexagonal and cubic structures is available with tunable pore diameters in the case of the inorganic materials. Here we describe a synthesis strategy towards ordered nanoporous organic polymers, using mesoporous carbon as the retaining framework. The polymer-carbon composite nanoporous materials exhibit the same chemical properties of the organic polymers, whereas the stability of the pores against mechanical compression, thermal and chemical treatments is greatly enhanced. The synthesis strategy can be extended to various compositions of hydrophilic and hydrophobic organic polymers, with various pore diameters, connectivity and shapes. The resultant materials exhibiting surface properties of the polymers, as well as the electric conductivity of the carbon framework, could provide new possibilities for advanced applications. Furthermore, the synthesis strategy can be extended to other inorganic supports such as mesoporous silicas.     

A simulation study on the effect of spring-shaped fillers on the viscoelasticity of rubber nanocomposite

Background/PurposeRubber nanocomposites have been widely used in many engineering fields due to their unique properties such as high elasticity and viscoelasticity. Much attention has been paid to the viscoelasticity of rubbers because it directly relates to the performance of the rubber products.MethodsBased on the micromechanical theory, the finite element method is used to analyze the effect of elastic modulus and volume content of spring-shape nanofillers on the dynamic viscosity of composites.ResultsThe simulation results show that there is an optimal elastic modulus of spring-shape nanofillers to make the loss factor a minimum. There is a threshold value of spring-shape nanofiller content for the dissipation energy density of composite.ConclusionThe elastic modulus of spring-shape nanofillers has a large effect on the loss factor of composites. The selection of elastic modulus of spring-shape nanofillers is critical for applications of composites. The efficiency of spring-shape nanofillers in reducing the dynamic viscosity of composites is so high that volume content of spring-shape nanofillers as low as 0.1% can greatly reduce the loss factor of composites with bonding interface.     

Synthesis of nanostructured materials using supercritical CO<Subscript>2</Subscript>: Part I. Physical transformations

Nanostructured materials have been attracting increased attention for a wide variety of applications due to their superior properties compared to their bulk counterparts. Current methods to synthesize nanostructured materials have various drawbacks such as difficulties in control of the nanostructure and morphology, excessive use of solvents, abundant energy consumption, and costly purification steps. Supercritical fluids especially supercritical carbon dioxide (scCO₂) is an attractive medium for the synthesis of nanostructured materials due to its favorable properties such as being abundant, inexpensive, non-flammable, non-toxic, and environmentally benign. Furthermore, the thermophysical properties of scCO₂ can be adjusted by changing the processing temperature and pressure. The synthesis of nanostructured materials in scCO₂ can be classified as physical and chemical transformations. In this article, Part I of our review series, synthesis of nanostructured materials using physical transformations is described where scCO₂ functions as a solvent, an anti-solvent or as a solute. The nanostructured materials, which can be synthesized by these techniques include nanoparticles, nanowires, nanofibers, foams, aerogels, and polymer nanocomposites. scCO₂ based processes can also be utilized in the intensification of the conventional processes by elimination of some of the costly purification or separation steps. The fundamental aspects of the processes, which would be beneficial for further development of the technologies, are also reviewed.     

Functional composite materials based on chemically converted graphene

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG-based functional composite materials are also discussed.     

Review on polymer/graphite nanoplatelet nanocomposites

Graphite nanoplatelets (GNPs) are a type of graphitic nanofillers composed of stacked 2D graphene sheets, having outstanding electrical, thermal, and mechanical properties. Furthermore, owing to the abundance of naturally existing graphite as the source material for GNPs, it is considered an ideal reinforcing component to modify the properties of polymers. The 2D confinement of GNPs to the polymer matrix and the high surface area make the GNP a distinctive nanofiller, showing superiorities in modification of most properties, compared with other carbon nanofillers. This review will summarize the development of polymer/GNP nanocomposites in recent years, including the fabrication of GNPs and its nanocomposites, processing issues, viscoelastic properties, mechanical properties, electrical and dielectric properties, thermal conductivity and thermal stability. The discussion of reinforcing effect will be based on dispersion, particle geometry, concentrations, as well as the 2D structures and exfoliation of GNPs. The synergy of GNPs with other types of carbon nanofillers used as hybrid reinforcing systems shows great potential and could significantly broaden the application of GNPs. The relevant research will also be included in this review.     

Thermal and optical properties of poly(methyl methacrylate)/calcium carbonate nanocomposite

The study deals with thermal and optical properties of poly(methyl methacrylate) (PMMA) containing 2wt% calcium carbonate (CaCO₃) nanofiller. It was found that the thermal conductivity increases with increasing temperatures, due to thermal activation of the phonons in the PMMA/CaCO₃ nanocomposite. This enhancement in the thermal conduction is mainly attributed to the heat transferred by lattice vibrations as major contributors and electrons as minor contributors during thermal conduction. The optical properties were investigated as a function of wavelength and photon energy of UV radiation. The optical results obtained were analysed in terms of absorption formula for noncrystalline materials. It was found that the measured optical energy gap for the pure PMMA is greater than the PMMA/CaCO₃ nanocomposite. The width of the energy tails of the localised states was calculated. Adding CaCO₃ nanofiller into PMMA matrix may cause the localised states of different colour centres to overlap and extend in the mobility gap. This overlap may give an evidence for decreasing energy gap when adding CaCO₃ nanofiller in the polymer matrix.     

Nanoalumina obtained by pyrosol method

Ceramic materials are interesting due to their properties such as chemical and thermal stability, corrosion resistance, biocompatibility, piezoelectricity, high dielectricity. Also, nano-sized materials may have properties different from the micro scale materials. Pyrosol method is an alternative method to obtain nanoscale particles. In this study alumina particles were prepared by pyrosol method using AlCl₃ (0.1 M and 0.05 M) as precursor solutions. The particles were obtained by maintaining the temperature of 400 °C in the pyrolysis furnace. Then, the powders were heat treated at 1000 °C for 2 hours. The X-ray diffraction analyses indicated that the obtained nanoparticles were identified as a mixture of a and g crystalline alumina. Scanning electron microscopy images showed that the prepared Al₂O₃ nanoparticles obtained from the concentration of 0.05 M had smaller dimensions than those obtained from the concentration of 0.1 M. Images of transmission electron microscopy showed spherical particles with the median diameter approximately of 150 nm, using as precursor AlCl₃ solution (0.05 M).     

Easy‐to‐clean Schichten – spezielle Anwendungen

Easy to clean surfaces – special applications Easy to clean surfaces can be made by wet‐chemical coating with subsequent heat‐treatment. Organically modified metal oxide films form the base reinforced by nano composite structures. The hydro‐ and oleophobic effect is obtained by perfluorinated organic molecule chains in the nano composite sol‐gel coatings. Application specific materials can be synthesized by the proper choice of suitable starting compounds and process parameters. The resulting coatings consist of a three‐dimensional cross‐linked inorganic part (such as a silica network) combined with an organic part. The organic material acts either as a surface modifier (example: alkyl, phenyl) or as crosslinker (example: acrylic, epoxy). The properties of such coating systems can be adjusted to obtain a wide range of glass‐ceramic or polymer‐like properties. The incorporation of nanoparticles into these materials significantly enhances the abrasion and the scratch resistance. Such coatings mainly on metal parts are used in diagnostics, analytical chemistry and medical technology.     

Synthesis and characterization of amorphous hollow carbon spheres

Nanostructured carbon materials have attracted enormous attention in last two decades due to their unique chemical, electrical, and mechanical properties. In this work, amorphous hollow carbon spheres (AHCSs) with diameters in the range of 100–750 nm, which are dispersed among bent graphitized carbon nanotubes, are synthesized by using radio frequency plasma enhanced chemical vapor deposition in mixed CH₄/H₂ gases. The carbon spheres were characterized with scanning electron microscope, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and transmission electron microscopy. It is found that MgO and Co/Ni nanoparticles as well as hydrogen play crucial roles in the formation of AHCSs. Moreover, a possible growth mechanism of AHCSs was proposed. The results of this study provide new insights into the fundamental understanding of nonstructural carbon materials toward applications in nanodevices.