Sono-synthesis of polystyrene/alumina nanocomposites:

Composite material and process for manufacturing the same

Abstract: The invention relates to a method and a material of a three-dimensional molded body of the composite a balkchenartiges each other in communication system encloses cavity. The material is producible that a scaffold is created by serving as a placeholder molded articles are prepared from which the moldings removed and which is filled subsequently by a casting and sprayable form mass, it can be removed by dissolving and melting after its hardening can.

Acoustically-enhanced particle dispersion in polystyrene/alumina nanocomposites

Abstract: Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

Evaluation of the electrochemical behavior of TiO2/Al2O3/PCL composite coatings in Hank’s solution

Abstract: This study focuses in the TiO2/Al2O3 powders synthesized by the sol-gel at low vacuum atmosphere, incorporated to polycaprolactone polymer. The corrosion study of coating was realized by electrochemical techniques. The precursors for synthesis of TiO2/Al2O3 powders were titanium and aluminum isopropoxides. The obtained powders were sintered at 350 °C and 1100 °C, then, they were mixed within polycaprolactone matrix. Results showed the rutile and corundum crystalline phases at 1100 °C. Electrochemical results showed a corrosion resistance improvement by the composite coatings, followed by formation and growing of the porous network. The corrosion behavior was governed by diffusion mechanism through the coating thickness. Scanning Electron Microscopy Characterization complemented the coating evaluation.

Average stress in matrix and average elastic energy of materials with misfitting inclusions

Abstract: Having noted an important role of image stress in work hardening of dispersion hardened materials, (1,3) the present paper discusses a method of calculating the average internal stress in the matrix of a material containing inclusions with transformation strain. It is shown that the average stress in the matrix is uniform throughout the material and independent of the position of the domain where the average treatment is carried out. It is also shown that the actual stress in the matrix is the average stress plus the locally fluctuating stress, the average of which vanishes in the matrix. Average elastic energy is also considered by taking into account the effects of the interaction among the inclusions and of the presence of the free boundary.

Polymer/layered silicate nanocomposites: a review from preparation to processing

Abstract: A review is given of the academic and industrial aspects of the preparation, characterization, materials properties, crystallization behavior, melt rheology, and processing of polymer/layered silicate nanocomposites. These materials are attracting considerable interest in polymer science research. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity and transparency in solution. In their pristine form they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to remove this difficulty is to replace interlayer cations with quarternized ammonium or phosphonium cations, preferably with long alkyl chains. A wide range of polymer matrices is covered in this review, with special emphasis on biodegradable polymers. In general, polymer/layered silicate nanocomposites are of three different types, namely (1) intercalated nanocomposites , for which insertion of polymer chains into a layered silicate structure occurs in a crystallographically regular fashion, with a repeat distance of few nanometers, regardless of polymer to clay ratio, (2) flocculated nanocomposites , for which intercalated and stacked silicate layers flocculated to some extent due to the hydroxylated edge–edge interactions of the silicate layers, and (3) exfoliated nanocomposites , for which the individual silicate layers are separated in the polymer matrix by average distances that depend only on the clay loading. This new family of composite materials frequently exhibits remarkable improvements of material properties when compared with the matrix polymers alone or conventional micro- and macro-composite materials. Improvements can include a high storage modulus, both in solid and melt states, increased tensile and flexural properties, a decrease in gas permeability and flammability, increased heat distortion temperature, an increase in the biodegradability rate of biodegradable polymers, and so forth.

Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials

Abstract: This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young’s modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.

Polymer Layered Silicate Nanocomposites

Abstract: Polymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in-situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine-tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass- or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self-extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.

Synthesis of nylon 6-clay hybrid

Abstract: It was found that montmorillonite cation exchanged for 12-aminolauric acid (12-montmorillonite) was swollen by ∊-caprolactam to form a new intercalated compound. Caprolactam was polymerized in the interlayer of montmorillonite, a layer silicate, yielding a nylon 6-clay hybrid (NCH). The silicate layers of montmorillonite were uniformly dispersed in nylon 6. The carboxyl end groups of 12-aminolauric acid in 12-montmorillonite initiated polymerization of ∊-caprolactam, and as 12-montmorillonite content became larger, the molecular weight of nylon was reduced. From the result of end-group analysis, carboxyl end groups were more than amino end groups. The difference between the carboxyl and the amino end groups was attributed to ammonium cations (-NH3+) of nylon molecules, because the difference agreed with the anion site concentration of the montmorillonite in NCH. It is suggested that the ammonium cations in nylon 6 interact with the anions in montmorillonite.