Development of high performance materials based on smart elastomer nanocomposites

 The present thesis explores the fabrication of technologically relevant nanocomposites out of a few elastomers and conducting fillers like carbon nanotubes, graphene and polyaniline. The developed materials have good applications in sensors, shape memory devices and capacitors. Different characterization methods reveal the influence of filler-elastomer interactions on the various properties of the obtained nanocomposites as well

Designing piezoelectric nanogenerator from PVDFHFP nanocomposite fibers containing cellulose nanocrystals and Fedoped ZnO

Self-powering devices harvest energy from the environment and perform based on a maintenance free approach. These materials are of utmost significance as they solve the problems associated with the energy crisis and management, to greater extends. Advances in material science and the design of various polymer nanocomposites developed many self-powering devices that are flexible, sensitive, less power consuming and of low cost. The semi-crystalline polymer, poly vinylidene fluoride (PVDF) and its co-polymers are notable for mechanical energy harvesting because of the typical crystalline phases in their structure. Various nanoparticles are added to such polymers to enhance their dielectric and piezoelectric properties as well. Since the alignment of crystalline phases improve the energy harvesting properties, techniques such as electrical poling are practiced to enhance their applicability. Among various alignment procedures, electrospinning stands as unique since the high voltage applied to the polymer solution generates nanofiber scaffolds in perfect alignments. The present work aims to develop electrospun composite fibers in nano-dimensions for designing self-powering nanogenerators. The co-polymer of PVDF, polyvinylidene fluoride hexa fluoropropylene (PVDF-HFP) was used as the base polymer and the iron-doped zinc oxide (Fe-ZnO) and cellulose nanocrystals (CNC) as the filler reinforcements. Fe-ZnO nanostructures were obtained by hydrothermal synthesis method from the ZnO precursor, while the CNC were synthesized following the acid hydrolysis of cellulose microfibers. The optimized concentration of 20 wt.% was used for obtaining the electrospun fibers of neat PVDF-HFP and various concentrations of nanoparticles were mixed with this base solution. Simple solvent mixing was employed using the acetone/DMF solvent mixture to prepare the composite solutions prior to electrospinning. The electrospinning conditions were also optimized by varying the applied voltage, tip to collector distance and speed of the rotating collector. Nice fibers were obtained at a voltage of 12-13 eV and rotating collector speed of 200 rpm. Composites of CNC with PVDF-HFP, Fe-ZnO with PVDF-HFP and the hybrid material of CNC/Fe-ZnO with PVDF-HFP were prepared and properties were investigated. All the fibers were tested for the morphology, structural, thermal and dielectric properties. The mechanical energy harvesting was performed using an assembled set up containing a frequency generator, shaker and data acquisition system. At 2 wt. % of the nanofillers, the PVDF-HFP/CNC generated about 2 V, the PVDF-HFP/Fe-ZnO generated about 4 V and the hybrid nanocomposite containing both nanoparticles generated about 6 V. The filler synergy plays a major role in regulating the material properties and here the combined effect of the piezoelectric performance of the cellulose nanocrystals and the modified ZnO nanoparticles enhanced the mechanical energy harvesting capability of the final nanocomposite. A nanogenerator is designed based on the developed polymer nanocomposite fibers and the piezoelectric performance on various conditions of stretching, pressing and twisting were also investigated. In all the cases the hybrid composite showed notable performance substantiating its application in designing self-powered nanogenerators. The dielectric properties of the hybrid material showed many fold increase in its dielectric constant, making it useful in electrical energy storage. In short, the designed device by electrospinning technique is highly useful in adding to the energy management and is environmentally safe and of good efficiency.qscienc

Cytocompatibility and Dielectric Properties of Sr2+ Substituted Nano-Hydroxyapatite for Triggered Drug Release

Hydroxyapatite (Ca5(PO4)3OH) is a well-known bioceramics material used in medical applications because of its ability to form direct chemical bonds with living tissues. In this context, we investigate the biocompatibility and dielectric properties of Sr2+-substituted hydroxyapatite nanoparticles were synthesized by sol-gel method. The influence of strontium on the crystal structure, functional group, morphological, electrical properties, and biocompatibility of as-synthesized nano-hydroxyapatite samples was analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM). Dielectrical properties of the bioactive Sr-HA sample were investigated by a dielectric impedance spectroscopy method. The observed results illustrate the incorporation of Sr2+ ions in the apatite lattice could influence the pure HA properties, by reducing the crystallite size and crystallinity quite consistent with the morphology variation. The ac conductivity (σac) increased with an increasing applied frequency confirmed that prepared HA sample exhibited the universal power law nature. Further, the in vitro drug loading and release studies using doxycycline as a model drug demonstrate that the Sr2+ -HA nanoparticles show high drug adsorption capacity and sustained drug release. Thus, the improved bioceramics system could be a promising candidate for future biomedical applications

Curing enhancement and network effects in multi-walled carbon nanotube-filled vulcanized natural rubber: evidence for solvent sensing

Electrically and thermally conductive polymer composites offer great possibilities in various electronic fields because of their low weight and ease of processing. This paper addresses the curing behaviour and network properties of conducting multi-walled carbon nanotube (MWCNT)-reinforced natural rubber (NR) nanocomposites, emphasizing the sensing and diffusion performances. NR/MWCNT composites were prepared following a special master batch technique which allows the appropriate distribution of nanotubes within the elastomer. The sensing responses of the composites towards solvents were observed as variations in electrical resistance. Thermal resistance and glass transition behaviour were examined and correlated with the swelling measurements as evidence for solvent sensing. An optimum level of 3 phr of MWCNTs is understood to lead to the best properties for the NR/MWCNT composites. Finally, the structural morphology and interfacial interactions were found to have correlations with cure reactions, glass transition temperatures and sensing responses of all compositions.This work has been supported by the University Grants Commission-Department of Atomic Energy (UGC-DAE) Consortium for Scientific Research (project no. CRS-K-01/16), Government of India. The authors are also grateful to NPRP grant 6-282-2-119 from the Qatar National Research Fund (QNRF, a member of Qatar Foundation).Scopu

Surface functionalization of chitosan as a coating material for orthopaedic applications:A Comprehensive Review

Metallic implants have dominated the biomedical implant industries for the past century for load-bearing applications, while the polymeric implants have shown great promise for tissue engineering applications. The surface properties of such implants are critical as the interaction of implant surfaces, and the body tissues may lead to unfavourable reactions. Desired implant properties are biocompatibility, corrosion resistance, and antibacterial activity. A polymer coating is an efficient and economical way to produce such surfaces. A lot of research has been carried out on chitosan (CS)-modified metallic and polymer scaffolds in the last decade. Different methods such as electrophoretic deposition, sol-gel methods, dip coating and spin coating, electrospinning, etc. have been utilized to produce CS coatings. However, a systematic review of chitosan coatings on scaffolds focussing on widely employed techniques is lacking. This review surveys literature concerning the current status of orthopaedic applications of CS for the purpose of coatings. In this review, the various preparation methods of coating, and the role of the surface functionalities in determining the efficiency of coatings are discussed. Effect of nanoparticle additions on the polymeric interfaces and in regulating the properties of surface coatings are also investigated in detail

Spectroscopy of Polymer Nanocomposites

Spectroscopy of Polymer Nanocomposites covers all aspects of the spectroscopic characterization of polymer nanocomposites. More than 25 spectroscopy characterization techniques - almost all used in materials science - are treated in the book, with discussion of their potentialities and limitations. By comparing the techniques with each other and presenting the techniques together with their specific application areas, the book provides scientists and engineers the information needed for solving specific problems and choosing the right technique for analyzing the material structure. From this, the dispersion structure of fillers, property relations and filler-polymer interactions can be determined, and, ultimately, the right materials can be chosen for the right applications. Besides the techniques and structure-property relations, aspects covered include: phase segregation of filler particles, filler agglomeration and deagglomeration, filler dispersion, filler-polymer interactions, surfaces and interfaces. The book also examines recent developments, as well as unresolved issues and new challenges, in the characterization of surfaces and interfaces in polymer nanocomposites. This handpicked selection of topics, and the combined expertise of contributors from industry, academia, government and private research organizations across the globe, make this survey an outstanding reference source for anyone involved in the field of polymer nanocomposites in academia or industry. Provides comprehensive coverage of spectroscopy techniques for analyzing polymer nanocomposites. Enables researchers and engineers to choose the right technique and make better materials decisions in research and a range of industries. Presents the fundamentals, information on structure-property relations, and all other aspects relevant for understanding spectroscopic analyses of nanoreinforced polymers and their applications.Scopu

Spectroscopy-introducing the advantages and application areas in polymer nanocomposites

Spectroscopy is an inevitable tool of characterizing polymer nanocomposites. Various spectroscopic techniques unveil the nature of dispersion of nanoparticles within the matrix polymer, the interactions between filler and polymer, functionalization of the polymer or nanofiller, interlayer spacing within the filler platelets, mechanical properties of the nanocomposites, etc. This chapter is the introduction of a book on polymer nanocomposite spectroscopy that addresses the application areas of different spectral methods, their significance, and the challenges existing in this particular field.Scopu

The Separation of Oil/Water Mixtures by Modified Melamine and Polyurethane Foams: A Review

Melamine (MA) and polyurethane (PU) foams, including both commercial sponges for daily use as well as newly synthesized foams are known for their high sorption ability of both polar and unipolar liquids. From this reason, commercial sponges are widely used for cleaning as they absorb a large amount of water, oil as well as their mixtures. These sponges do not preferentially absorb any of those components due to their balanced wettability. On the other hand, chemical and physical modifications of outer surfaces or in the bulk of the foams can significantly change their original wettability. These treatments ensure a suitable wettability of foams needed for an efficient water/oil or oil/water separation. MA and PU foams, dependently on the treatment, can be designed for both types of separations. The particular focus of this review is dealt with the separation of oil contaminants dispersed in water of various composition, however, an opposite case, namely a separation of water content from continuous oily phase is also discussed in some extent. In the former case, water is dominant, continuous phase and oil is dispersed within it at various concentrations, dependently on the source of polluted water. For example, waste waters associated with a crude oil, gas, shale gas extraction and oil refineries consist of oily impurities in the range from tens to thousands ppm [mg/L]. The efficient materials for preferential oil sorption should display significantly high hydrophobicity and oleophilicity and vice versa. This review is dealt with the various modifications of MA and PU foams for separating both oil in water and water in oil mixtures by identifying the chemical composition, porosity, morphology, and crosslinking parameters of the materials. Different functionalization strategies and modifications including the surface grafting with various functional species or by adding various nanomaterials in manipulating the surface properties and wettability are thoroughly reviewed. Despite the laboratory tests proved a multiply reuse of the foams, industrial applications are limited due to fouling problems, longer cleaning protocols and mechanical damages during performance cycles. Various strategies were proposed to resolve those bottlenecks, and they are also reviewed in this study

Influence of BaTiO 3 /white graphene filler synergy on the energy harvesting performance of a piezoelectric polymer nanocomposite

In this work, a novel ternary polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) nanocomposite containing ceramic barium titanate nanoparticles (BaTiO 3 ) and hexagonal boron nitride (h-BN) nanolayers is developed. An efficient filler synergy is achieved through the interaction between BaTiO 3 and the h-BN nanolayers through simple solution mixing. The dielectric properties and the piezoelectric performances of the materials are monitored in order to check the efficiency of the fabricated nanocomposite in mechanical energy harvesting. When compared to the individual nanocomposites (PVDF-HFP/BaTiO 3 and PVDF-HFP/h-BN), the hybrid composite (particularly the one with 3 wt% BaTiO 3 and 1 wt% h-BN) shows the best performance in piezoelectric output voltage (2.4 V) with high dielectric constant (45) and low dielectric loss (7.8). The significance of filler synergy in contributing to the piezoelectric performance of PVDF-HFP is established along with the possibility of its application in self-powering devices.Scopu

Fiber chemistry and technology: their contributions to shaping Society 5.0

Abstract Society 5.0 establishes innovations and innovativeness as the basic platforms for accelerating the development of solution-based strategies for the sustainability problems every society is facing. It features an interactive cycle operating at a society-wide level through which data are collected, analyzed and transformed into applicable technology for the real world. Transforming the current society into a super smart society requires in-depth knowledge of the Internet of Things, robotics and artificial intelligence. Being a member of the 4th industrial revolution is significant; however, it is equally important to alleviate the socioeconomic challenges associated with it and to maintain sustainability. From cellulose to carbon, fibers have utmost importance in technological applications, industrial developments and sustainability. Fibers are identified as useful energy resources, water treatment mediums, supercapacitors in electronic devices and wearable e-textiles. Therefore, knowing the chemistry behind fiber manipulation for advanced applications for Society 5.0 is beneficial. In this paper, we highlight the contributions of fibers to shaping Society 5.0 and their modifications and role in providing a sustainable environment. We highlight the chemical aspects behind tailoring fibers to provide state-of-the-art information on fiber-based products. We also provide background information on fiber technology and the sustainable development goals for a fiber-oriented Society 5.0. Scientists, researchers and specialists in this field should understand the impact of tailoring and influencing society as a whole