Utpal Basuli

A comprehensive assessment on degradation of multi-walled carbon nanotube-reinforced EMA nanocomposites

Thermal degradation kinetics of MWNT-reinforced EMA-based nanocomposites having different methyl acrylate (MA) contents (by % mass) ranging from 9 to 30% have been monitored. Kissinger and Flynn–Wall–Ozawa methods for evaluating non-isothermal degradation of polymers have been examined. Overall, the thermal stabilities of the nanocomposites are the function of amount of MWNTs loading and their state of dispersion that depends on the MA content of respective EMAs. Composite samples exhibit higher activation energy (Ea) than the neat EMAs but the Eas of the composites diminish with increased MA contents of the matrices. TG-Mass spectrometry has been used to identify the volatile products resulting from thermal degradation of composites, and a promising mechanism has been proposed over different range of temperatures of degradation. It is proposed that the side-group scission of methoxycarbonyl group initiates thermal decomposition following combination of chain end and random chain scission reactions, ensuing pseudo second-order kinetics.

Thermomechanical and rheological behaviour of polymer nanocomposites based on ethylene–methyl acrylate (EMA) and multiwalled carbon nanotube (MWNT)

Abstract Ethylene–methyl acrylate copolymer and multiwalled carbon nanotubes (MWNTs) were melt processed in order to determine the structure–property relationship of the resulting nanocomposites. The effect of MWNT loading on the thermomechanical and rheological properties of the nanocomposites is systematically investigated. Morphological characteristics these reinforced were investigated using field emission scanning electron microscopy and high resolution transmission electron microscopy. X-ray diffraction and differential scanning calorimetry studies showed that the MWNTs affect the crystallisation process. Dynamic mechanical analysis revealed that the storage modulus of the composites was significantly increased particularly at high temperatures. Thermogravimetric analysis showed that the MWNTs stabilise the ethylene–methyl acrylate matrix. The influence of concentration of filler was also realised by a frequency sweep experiment. Storage modulus (in dynamic shear) value increases especially at higher frequency levels due to increased polymer–filler interactions. Both the unfilled and filled composites exhibit rheological behaviour of non-Newtonian fluids. The dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of such systems.

Effect of Plasma, Gamma and Chemically Surface Modified MWNTs on the Rheological and Electrical Properties of Ethylene Methyl Acrylate (EMA) Nanocomposites

Surface modifications of the MWNTs have been carried out by treating the as received MWNTs with plasma (N2 and O2), piranha (H2SO4/H2O2) and γ-ray irradiation under well specified conditions. Surface modifications introduce polar functional groups onto MWNTs surfaces. A variety of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to characterize the functional group introduced onto MWNTs after the modification. A series of poly(ethylene-comethyl acrylate) (EMA) based nanocomposites containing modified MWNTs has been prepared. Mechanical, morphological, thermal, rheological and electrical properties of these nanocomposites have been investigated. Morphological analyses revealed that MWNTs are more uniformly dispersed in EMA especially for plasma modified MWNTs. Rheological and electrical properties of the nanocomposites are also studied. The nanocomposites register a slightly higher viscosity than that of neat EMA depending on the type of treatment. Storage modulus (in dynamic shear) increases especially at higher frequency levels due to increased polymer-filler interactions. The EMA/MWNT nanocomposites were tested to evaluate their electromagnetic interference (EMI) shielding effectiveness. The enhancements of mechanical properties along with the improvements in electrical and electromagnetic properties by the addition of modified MWNTs have been observed. The MWNTs treated by O2 plasma provides EMA nanocomposites with a higher conductivity than those produced by N2 plasma or by chemical oxidation or by γ-ray irradiation. Overall, the improvements of technical properties of the matrix have been found to be highest with the plasma modified MWNTs in comparison with other modified MWNTs.

Preparation, Properties, and Processibility of Nanocomposites Based on Poly(ethylene-Co-Methyl Acrylate) and Multiwalled Carbon Nanotubes

In this chapter, the preparation, characterization, processibility, and properties of nanocomposites based on multiwall carbon nanotubes (MWNTs) and different commercial grades of poly(ethylene-co-methyl acrylate) (EMA) having a variable methyl acrylate (MA) content are covered. The results showed that melt blending after solution mixing offers a simple and effective means to fabricate EMA/MWNT nanocomposites. The mechanical electrical properties and thermal degradation characteristics of the nanocomposites improve with increase in wt% of MWNT loading. The states of dispersions of the unmodified MWNTs are found to be inferior with increasing MA content in the EMA matrix. Better dispersions of MWNTs in EMA matrix lead to increased crystallite size and increased temperature of crystallization. The capillary rheological parameters can be correlated with the developed morphology under steady shear conditions. The effects of MWNTs and MA content in EMA on thermal stability and degradation kinetics are also presented. The kinetic parameters of degradation can be correlated with the degree of conversion. A promising mechanism is proposed over a different range of temperatures of degradation. The significant improvements in the mechanical and electrical properties of the polymeric matrix are observed by the addition of commercially available functionalized (hydroxyl and carboxyl) MWNTs. However, the states of dispersion of the functionalized MWNTs are found to be inferior in EMA matrix having lower MA contents. The morphology and properties of EMA-/modified MWNT-based nanocomposites are also investigated by using the plasma exposed, γ-ray irradiated, and chemically modified MWNTs. The improvement of technical properties of the matrix has been found to be higher with the plasma-modified MWNTs among all. It is also found that the electrical conductivity and EMI shielding effectiveness depend heavily on the type of functional groups present on the surface of MWNTs and also on MA content in EMA. These EMA/MWNT nanocomposites have potential applications especially, as a semiconductive layer in nuclear power plant cables, as an EMI shielding materials or as reinforced functional materials.