Gd2O3 nanoparticles surface‐modified with IPDI were compounded with epoxy. IPDI provided an anchor into the porous Gd2O3 surface and a bridge into the matrix, thus creating strong bonds between matrix and Gd2O3. 1.7 vol.‐% Gd2O3 increased the Young's modulus of epoxy by 16–19%; the surface‐modified Gd2O3 nanoparticles improved the critical strain energy release rate by 64.3% as compared to 26.4% produced by the unmodified nanoparticles. The X‐ray shielding efficiency of neat epoxy was enhanced by 300–360%, independent of the interface modification. Interface debonding consumes energy and leads to crack pinning and matrix shear banding; most fracture energy is consumed by matrix shear banding as shown by the large number of ridges on the fracture surface.
UV‐cured photoluminescent coatings emitting in the visible spectral region are obtained by dispersing Gd2O3:4 mol% Eu3+ nanorods in three different commercially available photocurable epoxy resins. The effect of the concentration of the Gd2O3:4 mol% Eu3+ nanorods on the kinetics of the photocuring reaction is followed using real‐time FT‐IR. Thermal and the mechanical properties of the cured films are also investigated. Moreover, the effect of the matrix and nanorod concentration in the composites on the emission and excitation spectra and the 5D0(C2) decay time of Eu3+ is evaluated. The composite materials present original photoluminescence properties and demonstrate the potential of UV curing as a technique to develop smart photoactive coatings.
Dynamic and transient shear start‐up flow experiments along with TEM, WAXS, and SEM analyses are performed on PP/PET blends and nanocomposites. The TEM results along with a theoretical analysis based on a thermodynamic model reveal that the clay particles are mainly localized in the PET phase. The localization of nanoclay in PET as the matrix phase leads to a refinement of morphology. The localization of clay is also studied by analyzing changes in complex viscosity and storage modulus in oscillation mode as well as the changes in power law index obtained from steady‐state and transient shear start‐up flow experiments. The changes in the rheological behavior of the blends are attributed to formation of clay network‐like structures.
Iron‐oxide nanoparticles were functionalized with epoxy groups and were dispersed into a dicyclo‐aliphatic epoxy resin to obtain organic‐inorganic hybrid coatings via cationic ring‐opening photopolymerization. TEM investigations confirmed that the filler has a size‐distribution range between 5 to 20 nm, without the formation of aggregates. The influence of the presence of Fe2O3 on the rate of polymerization was investigated by real time FT‐IR spectroscopy. Increasing the iron‐oxide nanofiller in the photocurable resin induced an increase in the Tg values. By controlling the phase separation it was possible to obtain transparent iron‐oxide nanostructured coatings, characterized by improved hardness.
The potential for incorporating negative‐CTE zirconium tungstate (ZrW2O8) nanoparticles in an epoxy matrix with the aim of developing epoxy/ZrW2O8 nanocomposites with tailored CTE values for electrical applications is investigated. The ZrW2O8/epoxy nanocomposites are prepared through incorporation of up to 20 vol% unfunctionalized nanoparticles or silane‐functionalized nanoparticles containing either epoxy or amine end groups. Improvements in thermomechanical and dynamic mechanical properties of the epoxy matrix are achived with no detrimental effect on the dielectric strength, which suggests that these nanocomposites could be viable candidates for a wide range of electrical applications.
Sb2O3 nanoparticles were prepared using CMC as the stabilizing agent. The nanocomposite was fabricated with Sb2O3/CMC nanoparticles as the filler in a GPS matrix. Characterization of Sb2O3/CMC nanoparticles revealed that Sb2O3 (about 84 wt.‐%) was encapsulated by CMC (about 16 wt.‐%) with the size of about 30–50 nm. Because there was good interaction between the Sb2O3/CMC filler and the GPS matrix, Sb2O3/CMC nanoparticles could be uniformly dispersed in the GPS matrix at a low filler loading level, resulting in obvious improvement in tensile strength and UV absorbance, and in the resistance of water vapor permeability. However, introduction of the nanoparticles into the matrix, decreased the elongation at break and the thermal stability of the nanocomposites.
Silent partner : In a recent publication, Gunderson and co‐workers described an approach to recruit the abundant U1 snRNP, a splicing subparticle, to the last exon of a pre‐mRNA, in a sequence‐specific manner. This mediates interaction of the U1‐70K protein subunit with poly(A) polymerase, thus blocking polyadenylation and inducing pre‐mRNA degradation. This novel promising strategy expands the repertoire of gene‐silencing concepts.
PLA biodegradable composites reinforced with various silk fibroin powder contents (0, 1, 3, 5 and 7 wt.‐%) were prepared by solution processing technique using CH2Cl2 as solvent. After that the composites and virgin PLA were foamed by using supercritical CO2. The influence of silk contents on PLA/silk fibroin powder composite foams were investigated by using SEM, XRD and DSC. Compared with PLA foam, the composite foams exhibited a reduction in cell size and increase in cell density at high silk content. With an increase in saturation temperature and pressure, the cell size was increasing and both the cell density and foam density were decreased simultaneously.
The first reported use of two‐dimensional mesh thermoplastic fibers in an epoxy matrix for mendable composites is presented, yielding 100% restoration of GIC, failure energy, and peak loads over repeated damage‐healing cycles. SEM imaging and EDS mapping showed different surface structures between CFRPp and CFRPf and confirmed strength recoveries were attained by delivery of EMAA to the fracture plane which enabled the fractured surfaces to rebind after heating to 150 °C for 30 min.
Epoxy/BaTiO3 hybrid materials are prepared as good candidates for organic capacitors. The hybrid system is cured by using camphorquinone and a iodonium salt through a free‐radical promoted cationic polymerization using a long‐wavelength tungsten halogen lamp. The cured films are fully characterized. Morphological characterization shows a well‐dispersed inorganic phase within the organic matrix. Electrical characterization demonstrates a linear increase of the dielectric constant with increasing filler content, while low dielectric loss values are obtained.
The efficiency of melamine cyanurate and a clay filler for improving the flame retardancy and other physical properties of polyamide 6 was examined. Partially intercalated‐exfoliated morphologies were obtained. Nanocomposites suffered from polymer degradation during compounding, while the molecular weight was enhanced in the case of the flame retarded samples. Silicates were shown to restrain crystallization, whereas melamine cyanurate induced heterogeneous nucleation. Both additives positively influenced the tensile modulus of the prepared samples, decreasing their ability to elongate. With respect to the UL94 flammability test, melamine cyanurate was proved to be not sufficiently capable of increasing the tendency of nanocomposites to drip, negatively affecting flammability.
Acrylate‐based nanocomposite coatings prepared from uniformly sized, nanoscaled inorganic, i.e., BaSO4‐ and CaF2‐ as well as organometallic, i.e., Al‐maleate‐derived nanoparticles were prepared applying photochemical curing. Excellent mechanical and thermal stability as well as high optical transparency was achieved as compared to standard SiO2‐based coatings. The performance of CaF2‐based nanocomposites could be further enhanced by addition of nanocorundum. A comprehensive data set on surface and Martens hardness, the penetration depths, glass transition temperatures, and UV–Vis transparency of the final coatings is presented.
New talc/PBAT hybrid materials were prepared through reactive extrusion. First, PBAT was free‐radically grafted with MA to improve the interfacial adhesion between PBAT and talc. Then, the resulting MA‐g‐PBAT was reactively melt‐blended with talc through esterification reactions of MA moieties with the silanol functions from talc. Sn(Oct)2 and DMAP were used as catalysts. Interestingly, the tensile properties for these compatibilized composites were improved due to a better interfacial adhesion between both partners. XPS showed the formation of covalent ester bonds between the silanol functions from talc particles, and the MA moieties grafted onto the polyester backbones.
Crosslinked core/shell PBA/PMMA‐PGMA particles are prepared by emulsion polymerization and dispersed into a UV‐curable cycloaliphatic epoxy resin in the range of 5–15 wt%. The presence of the particles does not significantly affect the UV curing process: a slight decrease of final epoxy group conversion is attributed to an increase in the viscosity when CS‐GMA is added to the photocurable formulation and to an enhanced vitrification effect. The presence of the particles does not modify the Tg of the cured materials, while an enhancement of impact resistance is observed that does not depend on the particle content. FESEM micrographs for epoxy reinforced with core/shell particles indicate a plastic void growth of the epoxy polymer and shear yielding toughening mechanism.
A novel approach using reactive processing is explored that eliminates the labour‐intensive separation of post‐consumer polyolefin waste from the mixed plastics waste stream. The reactive compatibiliser BMI has been used to form a modified blend of PCPW with 40% improved tensile strength relative to the uncompatibilised control. Addition of 60 wt.‐% magnesium hydroxide [Mg(OH)2] during reactive compatibilisation with BMI gave rise to an even more significant enhancement (up to 100%) of the tensile strength. BMI was also able to usefully enhance the properties of a composite based on calcium carbonate and the polyolefin waste.
Novel soy protein/polystyrene nanoblends with core‐shell structures were successfully prepared by introducing nano‐sized PS into soy protein through emulsion polymerization. The nanoblends showed core‐shell structures, with the core being of PS and the shell of sodium dodecane sulfonate and soy protein polypeptides, when investigated by electron microscopy. Nanoblends containing high levels of PS (>30%) exhibited characteristic infrared spectrum bands, X‐ray diffraction peak, and glass transition, since PS microsphere aggregated to form independent PS domains. Mechanical strength and water resistance were effectively improved by introducing PS. An effective structure‐performance relationship was thereby established to describe the nanoblends.
Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na‐MMT clay was pre‐modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading.
The effects of MWNT content and aspect ratio on the properties of epoxy‐based nanocomposites are investigated using nanoindentation and nanoscratch methods. The Halpin‐Tsai model for predicting the elastic modulus and hardness is modified to include the effective aspect ratio factor. The modified model predicts the experimental results more accurately. The frictional behavior is investigated and a new equation is proposed that correlates the ploughing friction with the plasticity index. The dispersion state of MWNTs and the surface features of residual grooves are investigated using scanning electron micrographs and AFM profiles. The mechanisms of improvements in the properties are also discussed.
This paper demonstrates how the electric‐field‐assisted thermal annealing of octadecylamine‐functionalized SWNT/PMMA films induces an increase in the composite transversal conductivity of several orders of magnitude and a decrease in the lateral conductivity. This difference has been rationalized in terms of the nanotube alignment into the polymer matrix along the electric field direction. This result provides an initial understanding of how electric fields can be used to control the bulk physical properties of such nanocomposites.
Novel fluoroalkyl end‐capped oligomer/hydroxyapatite nanocomposites have been easily prepared by the reaction of disodium hydrogenphosphate and calcium chloride in the presence of self‐assembled molecular aggregates formed by fluoroalkyl end‐capped oligomers in aqueous media. The fluorinated hydroxyapatite nanocomposites thus obtained were found to exhibit a good dispersibility in a variety of media, and were applied to the surface modification of glass.
