Rashmi Walvekar

Application of CNT nanofluids in a turbulent flow heat exchanger

Nanofluids have received much attention since its discovery owing to its enhanced thermal conductivity and heat transfer characteristics which makes them a promising coolant in heat transfer application. In this study, the enhancement in heat transfer of carbon nanotube (CNT) nanofluids under turbulent flow conditions is investigated experimentally. The CNT concentration was varied from 0.051 to 0.085 wt%, respectively. The nanofluid suspension was stabilised by gum arabic through a process of homogenisation and water bath sonication at 25 °C. The flow rate of cold fluid (water) is varied from 1.7 to 3 L/min, while flow rate of the hot fluid is varied between 2 and 3.5 L/min. Thermal conductivity, density, and viscosity of the nanofluids are also measured as a function of temperature and CNT concentration. The experimental results were validated with theoretical correlations for turbulent flow available in the literature. Results showed an enhancement in heat transfer between 9% and 67% as a function of temperature and CNT concentration.

Effect of nanofillers on the physico-mechanical properties of load bearing bone implants.

Bones are nanocomposites consisting of a collagenous fibre network, embedded with calcium phosphates mainly hydroxyapatite (HA) nanocrystallites. As bones are subjected to continuous loading and unloading process every day, they often tend to become prone to fatigue and breakdown. Therefore, this review addresses the use of nanocomposites particularly polymers reinforced with nanoceramics that can be used as load bearing bone implants. Further, nanocomposite preparation and dispersion modification techniques have been highlighted along with thorough discussion on the influence that various nanofillers have on the physico-mechanical properties of nanocomposites in relation to that of natural bone properties. This review updates the nanocomposites that meet the physico-mechanical properties (strength and elasticity) as well as biocompatibility requirement of a load bearing bone implant and also attempts to highlight the gaps in the reported studies to address the fatigue and creep properties of the nanocomposites.

Sonosynthesis of cellulose nanoparticles (CNP) from kenaf fiber: Effects of processing parameters

This study optimizes the isolation parameters of cellulose nanoparticles (CNP) from kenaf fiber using central composite design (CCD). The extraction of CNP was based on three stages (i.e. 3 factors). The independent variables (factors) were NaOH dosage, amount of NaClO2, and sonication time, while the dependent variables (response) were CNP size quality and degradation temperature. Later, size quality responses were fitted with a quadratic polynomial model and degradation point responses with a 2-factor interaction model (2FI). The quadratic model and 2FI models resulted R2 values of 0.95 and 0.79, respectively. In addition, the morphological, thermal analysis, and Fourier transform infrared (FTIR) spectroscopy indicated a progressive removal of non-cellulosic constituents. Furthermore, transmission electron microscopy (TEM) confirmed reduction in fiber diameter from ~170 μm to ~100 nm. The optimal parameters for extraction of CNP were found to be 0.2 g of NaOH/4 g of fiber at first stage, 5 ml of NaClO2/4 g of fiber at the second stage, and 20 min of sonication period during the third stage. Moreover, obtained cellulose nanoparticles were thermally more stable at higher temperature.

Mechanical and thermal properties of polylactic acid composites reinforced with cellulose nanoparticles extracted from kenaf fibre

Different approaches have been attempted to use biomass as filler for production of biodegradable polymer composites. In this study, cellulose nanoparticles (CNP) extracted from kenaf fibres were used to produce polylactic acid (PLA) based biodegradable nanocomposites. CNP concentration was varied from 1–5 wt. % and blended with PLA using Brabender twin-screw compounder. Effects of CNP loading on the mechanical, thermal and dynamic properties of PLA were investigated. Studies on the morphological properties and influence of CNP loading on the properties of CNP/PLA nanocomposite were also conducted. The results show an adequate compatibility between CNP and PLA matrix. Moreover, addition of 3 wt. % of CNP improved the PLA tensile strength by 25%.

Natural and synthetic biocompatible and biodegradable polymers

Biopolymers, biodegradable polymers, and biocompatible polymers are receiving immense limelight in today’s industry because of their ability to reduce the toxic and nondegradable waste flow. The demands of these polymers are increasing exponentially because their mechanical, physical, and other properties can be feasibly modified. Properties and applications of few most commercially used natural polymers such as collagen, gelatin, gluten, and polysaccharides such as chitin, chitosan, cellulose, and starch have been focused in this chapter. Furthermore, the properties and applications of biocompatible and biodegradable polymers such as polyglycolide, poly(butylene succinate), polyesteramides, polydioxanone, polyanhydride, polylactic acid, polyurethanes, polycarbonate etc. are also listed out. A focus on the biosynthetic pathways of biopolymers, their methods of extraction, and various approaches (chemical, enzymatic, and mechanical) involved in the production of biodegradable and biocompatible polymers is enumerated. Knowing the fundamentals of the aforementioned polymers is very vital to channel these valuable assets to rule tomorrow’s world of green material industry.

Co-PP/EPDM Blend Optimization Using D-Optimal Design for Medical Applications

ABSTRACT This work focuses on the optimization and identification of blend with balanced mechanical properties of Co-PP/EPDM. The blending factors include time, temperature, screw speed, and blend ratio. Tensile strength and elongation at break were studied as the two responses. D-Optimal model was used to fit the regression line, which was validated using analysis of variance and “lack of fit” test. An average error of 10% (for tensile strength) and 3.2% (for elongation at break) was observed between the actual and predicted values. Further, the thermal stability, dynamic mechanical analysis, and phase morphology of the optimized blend were also investigated. GRAPHICAL ABSTRACT

Sonosynthesis of Microcellulose from Kenaf Fiber: Optimization of Process Parameters

ABSTRACT Green composites using cellulose fibers as a reinforcement material provide a sustainable and renewable alternative to petroleum-based polymers. However, controlling the usage of chemicals and processing parameters to extract the cellulose could be sometimes difficult. Therefore, this study aims to optimize the conditions for extracting the microcellulose from kenaf fibers using central composite design (CCD), a statistical tool in design of experiments. Three factors and three levels were chosen for carrying out the analysis. The design was based on sodium hydroxide (NaOH) dosage, Sodium Chlorite (NaClO2) dosage and sonication time as independent variables, while dependent variables were the fiber size and degradation point. Later, size responses were fitted using quadratic polynomial model and degradation responses using 2-factor interaction model (2FI). The R2 values of 0.89 and 0.83 were obtained for the quadratic and the 2FI model, respectively. Further, surface morphology, thermal analysis, Fourier transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD) were also used for design validation. Optimal parameters for microcellulose extraction were found to be 0.15 g of NaOH at first stage, 4.6 mL of NaClO2 at second stage, and 10 min of sonication during third stage.

E-beam sterilizable thermoplastics elastomers for healthcare devices: Mechanical, morphology, and in vivo studies

The effect of electron beam radiation on ethylene–propylene diene terpolymer/polypropylene blends is studied as an attempt to develop radiation sterilizable polypropylene/ethylene–propylene diene terpolymer blends suitable for medical devices. The polypropylene/ethylene–propylene diene terpolymer blends with mixing ratios of 80/20, 50/50, 20/80 were prepared in an internal mixer at 165°C and a rotor speed of 50 rpm/min followed by compression molding. The blends and the individual components were radiated using 3.0 MeV electron beam accelerator at doses ranging from 0 to 100 kGy in air and room temperature. All the samples were tested for tensile strength, elongation at break, hardness, impact strength, and morphological properties. After exposing to 25 and 100 kGy radiation doses, 50% PP blend was selected for in vivo studies. Results revealed that radiation-induced crosslinking is dominating in EPDM dominant blends, while radiation-induced degradation is prevailing in PP dominant blends. The 20% PP blend was found to be most compatible for 20–60 kGy radiation sterilization. The retention in impact strength with enhanced tensile strength of 20% PP blend at 20–60 kGy believed to be associated with increased compatibility between PP and EPDM along with the radiation-induced crosslinking. The scanning electron micrographs of the fracture surfaces of the PP/EPDM blends showed evidences consistent with the above contentation. The in vivo studies provide an instinct that the radiated blends are safe to be used for healthcare devices.

Surface modification techniques of biodegradable and biocompatible polymers

The surface of a polymer is the phase boundary between the bulk polymer and the outer environment. Due to the interaction with the environment, the surface of the polymer is prone to change. This is crucial because change in the surface properties of the polymers can alter the chemical compositions, hydrophilicity, hydrophobicity, roughness, crystallinity, permeability, biocompatibility, conductivity, lubrication/friction, adhesion, and cross-linking density of the polymers. Depending on the surface changes that took place, the polymers can be used for different applications such as medical and food industries, especially the biodegradable and biocompatible polymers (polylactic acid, polyglycolide acid, polylactic-co-glycolic acid, poly( e -caprolactone), polyvinyl alcohol, polybutylene succinate, poly(3-hydroxybutyrate), and polyamide). Hence, up to date, different methods have been developed to modify the surface of polymers. In this chapter, surface modification methods of biodegradable and biocompatible polymers through physicochemical, mechanical, and biological methods will be discussed. Moreover, the mechanism behind the surface modification and further confirmation of the changes using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy will be highlighted.

Reinforced Natural Rubber Nanocomposites: Next Generation Advanced Material

Undoubtedly, the advanced green composites have replaced the use of many conventional mineral based or naturally occurring single materials in wide spread industrial applications including aerospace, automotive, locomotive, chemical and biomedical industries. Specially, the reinforced natural rubber nanocomposites have drawn the attention of the research as well as industrial worlds greatly because of their superior thermal and mechanical properties without major compromise of transperancy/clarity. This chapter presents the preparation of rubber nanocomposites, characterization techniques, and the properties of the developed nanocomposites such as mechanical and thermal characteristics along with the recent applications of these nanocomposites. The rubber nanocomposite (RNC) have found their niche commercially in the tyre and sports industries providing reduced weight and energy dissipation, and enhanced air retention to the applied products.