Clay/Conductive Polymer Nanocomposites

This chapter describes the main strategies for designing clay nanocomposites of the most investigated inherently conductive polymers, namely, polypyrrole, polyaniline, and polythiophenes including poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. It is shown that premodification of clays is an essential step to successful intercalation or exfoliation by conductive polymers. Toward this end, surfactants, reactive diazonium, and silanes permit the preparation of adhesive clay sheets for the conductive polymers once polymerization is triggered. Exfoliated nanocomposites usually exhibit superior properties compared to intercalated ones. Through selected applications (e.g., conductive fillers, catalysts, sensors, ultracapacitors), it is clear that research on clay–conductive polymer nanocomposites will continue to grow because these materials combine the best of two worlds: low-cost abundant minerals with remarkable nanostructural properties and nanostructuring abilities on the one hand and ease of synthesis, reactivity, and electrical conductivity of conjugated polymers on the other hand.Scopu

Prestrain relaxation in non-covalently modified ethylene-vinyl acetate | PyChol | multiwall carbon nanotube nanocomposites

Effects of aging on chemical structure and molecular dynamic behaviour of strained thermally active ethylene-vinyl acetate | multiwall carbon nanotube (EVA|MWCNT) composites were investigated by spectroscopy and microscopy techniques. Aged composites showed spatial inhomogeneity due to system relaxation. Inhomogeneity is attributed to segregation of non-covalently linked cholestryl 1-pyrenecarboxylate, acting as MWCNT dispersant and polymer compatibilizer. Analysis of molecular interplay between filler and matrix upon in situ temperature variation showed a lack of synchronicity, which had been observed in fresh composites. Reduced synchronous interplay allowed quantification of degraded π-π interactions, promoting PyChol unlatching as a result of both sonication and strained-derived π-π degradation

Surface modification of low-density polyethylene with poly(2-ethyl-2- oxazoline) using a low-pressure plasma treatment

Low-density polyethylene (LDPE) is a suitable polymer for biomedical applications due to its good physiochemical properties, but its insufficient biocompatibility is often an issue. Therefore, biocompatible substances such as those based on 2-ethyl-2-oxazoline seem to be a good choice to increase the LDPE biocompatibility. In this work, the surface modification of LDPE with poly(2-ethyl-2-oxazoline) with two different end-groups was investigated. This modification led to the improvement of surface and adhesion properties, which were investigated by several analytical methods. The low-temperature plasma treatment of the LDPE surface was sufficient to create binding sites for the permanent attachment of poly(2ethyl-2-oxazoline) chains. This was confirmed by infrared spectroscopy and X-Ray photoelectron spectroscopy. It was found that the polymer containing the acrylic end-group was well attached to the LDPE surface. 2013 Elsevier Ltd. All rights reserved.This work was supported by the Slovak Grant Agency VEGA for projects Nr. 2/0064/10 , Nr. 2/0151/12 , and Nr. 2/0185/10 ). The Center for Materials, Layers and Systems for Applications and Chemical Processes under Extreme Conditions was supported by the Research & Development Operational Program funded by the ERDF. Electron microscopy at IMC was performed with financial support through grant TACR TE01020118 .Scopu

Thermal and electrical characterization of multi-walled carbon nanotubes reinforced polyamide 6 nanocomposites

In this study composites of polyamide 6 and multiwalled carbon nanotubes (MWCNT) were prepared by diluting a masterbatch using melt mixing. Differential scanning calorimetry was employed in order to investigate the influence of nanotubes on the thermal transitions of polyamide 6. Significant changes are reported on crystallization and glass transition by the addition of nanotubes. The results are discussed in terms of polymer-filler interactions. Dielectric relaxation spectroscopy measurements were performed to study both the electrical and dielectric properties of the nanocomposites. Percolation threshold is calculated to be at 1.7 vol.% MWCNT

Photothermal Characterization of Nanocomposites Based on High Density Polyethylene (HDPE) Filled with Expanded Graphite

The effective thermophysical and optical properties of high density polyethylene (HDPE) filled with 50 mu m and 5 mu m particle sizes of expanded graphite (EG50, EG5) are characterized. The methods used were front- and back-detection modulated photothermal radiometry (FD-, BD-PTR) and BD-flash IR thermography. Results were interpreted according to one-dimensional heat diffusion models. The absolute thermal diffusivity was determined at low frequency from FD- and BD-PTR spectra, while the volumetric heat capacity, the thermal effusivity, and the optical absorption coefficient were determined from broad-band FD-PTR spectra. The directly obtained diffusivity values compare well with those calculated from the heat capacity and thermal effusivity, and with BD-flash results. The errors caused by the finite absorption coefficient of diluted samples are also evaluated and corrected for. A particle-size effect with the opposite influence on thermal and optical properties has been observed. Heat transport parameters of HDPE/EG composites are significantly enhanced (factor of 3 to 4 in thermal diffusivity) at low particle charge before reaching saturation above a 0.10 particle volume fraction. These features are explained in the framework of effective medium models by strongly non-spherical EG particles

Preparation and characterization of highly electrically and thermally conductive polymeric nanocomposites

Purpose: The conducting polymers and polymeric composites have attracted considerable attention in recent years because of their potential applications in advanced technologies, for example, in antistatic coatings, electromagnetic shielding. Design/methodology/approach: In this study the conductive fillers were expanded graphite (EG) and untreated graphite (UG), the base material was ethylene-vinyl acetate copolymer (EVA). Nanocomposites containing up to 30 volume % of filler material were prepared by mixing them in a Brabender Plasticorder. Findings: The increase in thermal conductivity was more pronounced for EVA-UG nanocomposites than EVAEG nanocomposites. Practical implications: The recent advancement of nano-scale compounding technique enables the preparation of highly electrically conductive polymeric nanocomposites with very low loading of conductive fillers. Compared with traditional composites, nanocomposites may offer enhanced physical features such as increased stiffness, strength, barrier properties and heat resistance, without loss of impact strength in a very broad range of common synthetic or natural polymers. Originality/value: The introduction of electrically conductive fillers such as graphite, carbon black, metal and metal oxide powders into the polymeric matrix is a promising approach to fabricate electrically conductive polymeric materials. © International OCSCO World Press