Theoretical and experimental investigation of ultrasonic wave propagation in suspensions of particles: effects of concentration and polymer modification

Ultrasound has been used as a Non-Destructive Testing method for colloids for characterising or monitoring purposes. The principle of ultrasound characterisation is based on measurements of ultrasound propagation in the tested sample, followed by interpretation of the experimental data using scattering models. One of the commonly used models is the single scattering model of Epstein and Carhart and Allegra and Hawley, which is often combined with the multiple scattering approach developed by Lloyd and Berry to account for the particle interactions in the acoustic field. These models have proved successful in application to dilute colloidal systems, but they are known to break down in highly concentrated systems due to non-acoustic field interactions. There are also situations where the particles to be characterised have unusual structures, such as hybrid particles with polymer modification on their surface. These particles have growing interest due to the potential application of their smart surface . The core-shell model by Anson and Chivers, has been shown to have some success in predicting the ultrasonic behaviour of such particles. However, the original core-shell model is a complicated model, which can be ill-conditioned under certain conditions and therefore limiting the application of this model. In order to address the issues above, the primary aim of this research was to develop and validate models for ultrasonic propagation in concentrated nano-suspensions and suspensions of particles modified with polymers. The limits of applicability of the classic ECAH/LB model for highly concentrated suspensions in the nano-scale was explored experimentally. The new model developed by Forrester and Pinfield was studied as a solution to interpret shear interactions between particles in concentrated suspensions. An analytical approximation was derived for the core-shell model and validated. The analytical solution was compared both analytically and numerically with Anson and Chivers full matrix model and the ECAH model. The possibility of applying the ultrasonic technique to core-shell nano-particles was investigated, and the core-shell model was validated experimentally with polymer-modified particle suspensions

Modelling viscous boundary layer dissipation effects in liquid surrounding individual solid nano and micro-particles in an ultrasonic field

Upon application of ultrasonic waves to a suspension of solid particles in liquid, multiple scattering occurs at the particle/liquid interfaces leading to attenuation. It was recently shown through experimental verification that multiple scattering theory must include shear wave influences at the boundary between the liquid and solid particles in a nanofluid when the concentration of the scatterers is even as low as a few percent by volume. Herein, we consider silica spheres of 50−450 nm diameter in the long-wavelength regime to elucidate the form of the shear decay fields at the liquid/solid interface for individual particles. This is important because the overlap of these fields ultimately leads to the conversion of a compressional wave to shear waves and back into the compressional wave, the effect originating due to the density contrast between the particle and the liquid. Therefore, we examine in detail the velocity, vorticity and viscous dissipation in the shear wave field and around the silica spheres using finite element modelling, giving clarity to the viscous boundary effects. We also compare the numerical modelling to semi-analytical results

Synthesis of Tung-Oil-Based Triglycidyl Ester Plasticizer and Its Effects on Poly(vinyl chloride) Soft Films

A tung-oil-derived renewable plasticizer, tung-maleic triglycidyl esters (TMTE), was prepared and incorporated into poly­(vinyl chloride) (PVC) for the first time. The chemical structure was studied by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), and ¹³C NMR. The plasticizing effects of TMTE replacement of dioctyl phthalate (DOP) in soft PVC films were researched. Thermal stability, thermal degradation performance, dynamic mechanical property, and mechanical properties of pure PVC and PVC films were investigated with thermogravimetric analysis (TGA), TGA-FTIR, TGA-mass spectrometry, dynamic mechanical analysis, and mechanical test. The results showed that PVC films plasticized with the TMTE exhibited increased thermal stability, plasticizing effect, compatibility, and flexibility. When 30 phr (parts per hundred parts of resin) DOP was substituted with TMTE in PVC blends, glass transition temperature (<i>T</i>_g) dropped from 41.46 to 40.18 °C, the initial decomposition temperature (<i>T</i>_i), 10% and 50% mass loss temperatures (<i>T</i>₁₀ and <i>T</i>₅₀), had maximum increases of 8.0, 20.0, and 27.5 °C, respectively. The interaction between TMTE and PVC molecule was also discussed. Furthermore, the extraction, exudation, and volatility resistance of plasticizers were carried out and analyzed by solubility parameters, the results of which revealed the migration stabilities of PVC films were promoted with the increasing amount of TMTE

Parallel Carbon Nanotube Stripes in Polymer Thin Film with Remarkable Conductive Anisotropy

In our previous study (Mao et al. J. Phys. Chem. Lett. 2013, 4, 43−47), we proposed a novel method, that is, the shear-flow-induced hierarchical self-assembly of two-dimensional fillers (octadecylamine-functionalized graphene) into the well-ordered parallel stripes in a polymer matrix, to fabricate the anisotropic conductive materials. In this study, we extend this method to one-dimensional multiwalled carbon nanotubes (MWCNTs). Under the induction of shear flow, the dispersed poly­(styrene ethylene/butadiene-styrene) (SEBS) phase and MWCNTs can spontaneously assemble into well-ordered parallel stripes in the polypropylene (PP) thin film. The electrical measurements indicate that the electrical resistivity in the direction parallel to the stripes is almost 6 orders of magnitude lower than that in the perpendicular direction, which is by far the most striking conductive anisotropy for the plastic anisotropic conductive materials. In addition, it is found that the size of the MWCNT stripe as well as the electrical property of the resulting anisotropic conductive thin film can be well-controlled by the gap of the shear cell

Tailored Parallel Graphene Stripes in Plastic Film with Conductive Anisotropy by Shear-Induced Self-Assembly

We present a simple but efficient route to prepare a highly anisotropic conductive plastic thin film from the polypropylene/(styrene-ethylene/butadiene-styrene) triblock copolymer/graphene blend via shear-induced self-assembly. Under the shear-flow induction, GE nanosheets dispersed in the polymer matrix can spontaneously assemble into ordered parallel stripes, which endow the materials significantly conductive anisotropy. The electrical resistivity in the direction parallel to the graphene stripes is almost four orders of magnitude lower than that which is perpendicular to the stripes. This study provides a new method for the precise control of the organization of functional nano-objects in polymer matrix, which can be widely extended to the fabrication of other multifunctional anisotropic materials of interest in various fields

Parallel Carbon Nanotube Stripes in Polymer Thin Film with Remarkable Conductive Anisotropy

In our previous study (Mao et al. J. Phys. Chem. Lett. 2013, 4, 43−47), we proposed a novel method, that is, the shear-flow-induced hierarchical self-assembly of two-dimensional fillers (octadecylamine-functionalized graphene) into the well-ordered parallel stripes in a polymer matrix, to fabricate the anisotropic conductive materials. In this study, we extend this method to one-dimensional multiwalled carbon nanotubes (MWCNTs). Under the induction of shear flow, the dispersed poly­(styrene ethylene/butadiene-styrene) (SEBS) phase and MWCNTs can spontaneously assemble into well-ordered parallel stripes in the polypropylene (PP) thin film. The electrical measurements indicate that the electrical resistivity in the direction parallel to the stripes is almost 6 orders of magnitude lower than that in the perpendicular direction, which is by far the most striking conductive anisotropy for the plastic anisotropic conductive materials. In addition, it is found that the size of the MWCNT stripe as well as the electrical property of the resulting anisotropic conductive thin film can be well-controlled by the gap of the shear cell