Jiji Abraham

Flexible EMI shielding materials derived by melt blending PVDF and ionic liquid modified MWNTs

Nano composites of PVDF with ionic liquid [EMIM][TF2N] (IL) modified MWNTs were prepared by melt blending to design materials for EMI shielding applications. MWNTs and IL were mixed in two different ratios (1:1 and 1:5) to facilitate better dispersion of MWNTs in PVDF. It was observed that non-covalent interactions between IL and PVDF resulted in a better dispersion of CNTs and was consistent with increasing concentration of IL. Interestingly, IL modified MWNTs induced the formation of γ-phase crystals in PVDF, which was further confirmed by XRD, FTIR and DSC. Melt rheological measurements and DSC analysis revealed the plasticization effect of IL in PVDF composites further manifesting in a decrease in the storage modulus and the glass transition temperature. This phenomenal effect presumably led to better dispersion of IL modified MWNTs in PVDF further resulting in a significant improvement in electrical conductivity and structural properties. More interestingly, the elongational properties in the composites improved with IL modified MWNTs in striking contrast to MWNT filled PVDF composites. The ac conductivity of the composites reached about 10−3 S cm−1 with the addition of 2 wt% IL modified MWNTs (1:1). This further led to a high electro-magnetic interference (EMI) shielding effectiveness of about 20 dB at 2 wt% IL modified MWNTs. Such materials can further be explored for flexible, lightweight EMI shielding materials for a wide range of operating frequency.

Developing highly conducting and mechanically durable styrene butadiene rubber composites with tailored microstructural properties by a green approach using ionic liquid modified MWCNTs

We report the effect of surface modification of multi-walled carbon nanotubes (MWCNTs) by an ionic liquid, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl). An apparent physical (cation–π/π–π) interaction between the ionic liquid and MWCNTs was revealed by Raman and UV-visible spectroscopies. The composite loaded with 10 phr MWCNTs exhibits impressive enhancements in tensile strength (381% increase), hardness (34% increase), and abrasion resistance. High electrical conductivity was also achieved at MWCNT loading levels beyond 3 phr loading, with a low percolation threshold (0.023 vol%) for the composites. The microstructural development of conductive networks and uniform dispersion of MWCNTs in the presence of ionic liquid were analysed by TEM and AFM. The experimentally observed mechanical and electrical properties have been compared with theoretical predictions, and confirm that the dramatic improvement in mechanics and electrical conductivity is the outcome of the extremely fine dispersion, the strong secondary network of MWCNTs and improved interaction at the interface via thermodynamically-induced adsorption and physical interlocking of polymer chains in the nanoscopic MWCNT structure. This study demonstrates a simplified and eco-friendly approach to develop multifunctional advanced materials based on ionic liquid modified MWCNT elastomer composites with a much better balance among mechanical properties, conductivity and filler content.

Static and Dynamic Mechanical Characteristics of Ionic Liquid Modified MWCNT-SBR Composites: Theoretical Perspectives for the Nanoscale Reinforcement Mechanism

Well-dispersed, robust, mechanicaly long-term stable functionalized multiwalled carbon nanotube (f-MWCNT)-styrene butadiene rubber (SBR) nanocomposites were fabricated via a melt mixing route with the assistance of ionic liquid as a dispersing agent. The mechanical properties of f-MWCNT/SBR vulcanizates were compared over a range of loadings, and it was found that the network morphology was highly favorable for mechanical performance with enlarged stiffness. A comparative investigation of composite models found that modified Kelly-Tyson theory gave an excellent fit to tensile strength data of the composites considering the effect of the interphase between polymer and f-MWCNT. Dynamic mechanical analysis highlighted the mechanical reinforcement due to the improved filler-polymer interactions which were the consequence of proper dispersion of the nanotubes in the SBR matrix. Effectiveness of filler, entanglement density, and adhesion factor were evaluated to get an in depth understanding of the reinforcing mechanism of modified MWCNT. The amount of polymer chains immobilized by the filler surface computed from dynamic mechanical analysis further supports a substantial boost up in mechanics. The Cole-Cole plot shows an imperfect semicircular curve representing the heterogeneity of the system and moderately worthy filler polymer bonding. The combined results of structural characterizatrion by Raman spectroscopy, cure characteristics, mechanical properties, and scanning and transmission electron microscopy (SEM, TEM) confirm the role of ionic liquid modified MWCNT as a reinforcing agent in the present system.

Special Purpose Elastomers: Synthesis, Structure-Property Relationship, Compounding, Processing and Applications

Elastomers are notable as very special class of polymers due to their multifunctional applications. The superior mechanical properties, high flexibility, resilience and good viscoelastic behaviour make this class applicable in a wide range of technology and industry. Depending on the various properties and general applications elastomers are classified in to a number of categories. This particular chapter deals with a very important class of special purpose elastomers. The synthesis, structure, different properties, mode of vulcanization, processing and applications of most of the synthetic elastomers are discussed. Apart from providing a basic understanding about the materials, this chapter can facilitate wide information about the technical details and industrial importance of this class of rubbers.

Instrumental Techniques for the Characterization of Nanoparticles

Abstract Advances in nanomaterials have opened a new era in various fields such as industrial, medical, commercial, and consumer products owing to their unique and novel physical and chemical properties. A wide variety of techniques can be used to analyze and characterize nanoparticles depending on the application of interest. Characterization refers to the study of material features such as composition, structure, and various properties such as physical, chemical, electrical, magnetic, etc. This chapter summarizes the techniques that are commonly used to investigate the size, shape, surface properties, composition, purity, and stability of nanomaterials, along with their benefits and drawbacks. Various characterization techniques such as optical (imaging), electron probe, photon probe, ion particle probe, and thermodynamic techniques are discussed briefly in this chapter.

A comprehensive study of surface modified graphene based polymer nanocomposites for multifunctional electronic applications

Graphene is a new emerging nanocarbon material, with exciting unique properties including superb thermal and electrical conductivity, strong mechanical and anti-corrosive property, extremely high surface area etc. It can be considered as new generation reinforcement material for polymer composites due to its cheap production cost comparison with carbon nanotube, ease of functionalization and dramatic improvements in properties at very low filler content, high specific surface area, good compatibility, low mass density, elegant flexibility. This review presents an overview of surface functionalised graphene/polymer nanocomposites discussing different strategies for functionalization of graphene, a series of effective processing routes for producing high quality polymer nanocomposites and recent developments in the electrical properties of functionalised grapheme polymer nanocomposites. Finally, this review provides an overview of potential applications of the graphene based polymer nanocomposites in various areas, such as sensors, electrodes, energy storage, EMI and ESD materials.

Chapter 11 – Liquid Transport Through Polymer Nanocomposites

The present chapter addresses liquid transport through polymer nanocomposites. Transport of liquids through polymeric membranes has an important role in monitoring many factors in many of their applications. Factors affecting transport process include the free volume within the matrix, the nature of the polymer, the cross-link density, the nature of fillers, the penetrant size, temperature, and the degree of reinforcement. Diffusion sorption and permeation processes through polymers have been assessed for different types of polymers. Transport studies are of considerable importance when we come across problems like designing a barrier material or tubes for transporting liquids and gases.

Rheological Characterization of Nanocomposites

Abstract The rheological properties of nanomaterials are important in fundamental areas of research that impact our understanding and ability to use these materials. This chapter presents a summary of a number of important works that have been published on rheological behavior of nanofluids, gels, and bio-based nanoparticles. From the literature review, it has been found that factors including nanoparticle type, its concentration, shape, and temperature have a significant effect on the rheological behavior of any nanomaterial. It has been found that, depending on the base fluid, a nanofluid may be a Newtonian fluid or may behave as a non-Newtonian fluid based on the morphology of the materials and molecular structure of the base fluid material.

Thermoanalytical Techniques of Nanomaterials

Abstract Designing and fabrication of materials with good thermal characteristics is very important for multifunctional applications of nanomaterials. Thermal analysis is a group of techniques that characterize the thermal properties of materials. With these techniques, changes in the temperature of the sample is analyzed. No single thermal analysis tool or technique works best in all situations. Accurate thermal assessments require a combination of different analytical techniques. This chapter presents the basic principles of thermal systems and describes some of the techniques and tools available to complete thermal characterization of nanomaterials.

Conducting Polyurethane Composites

Abstract Conducting polyurethane-based nanocomposites have been identified as one of the promising class of materials which find considerable attractive applications in various fields, such as construction, packaging, automotive, aerospace, military, medical, and electrical and electronics. In this chapter various aspects of conducting polyurethane nanocomposites are addressed, starting with their fabrication and ending with their applications. This chapter discusses various conducting polyurethane nanocomposites reinforced with various conducting fillers, such as carbon black, carbon nanotube, and graphene and also discusses a large variety of applications of composites which include shape memory, actuator sensors, and electromagnetic interference shielding fields.