Modulating the surface and mechanical properties of textile by oil-in-water emulsion design.

The synergistic effect of oil viscosity and oil droplet size on the deposition profile of oil on cotton fabric was studied using polydimethylsiloxane (PDMS) as a model oil-in-water emulsion system. Under the same preparation conditions, low viscosity PDMS produced emulsions containing small droplets, which resulted in a uniform surface deposition profile, whilst high viscosity PDMS resulted in a localised deposition profile. Interfacial phenomena such as wicking and penetration of PDMS into cotton fabrics were found to be viscosity-dependent, which agrees with the surface deposition data. Both mechanical characterisation (friction, compression, stiffness) and consumer evaluation confirm that the fabrics treated by the emulsion containing low viscosity PDMS were preferred, suggesting that a homogeneous surface deposition and an excellent penetration profile of PDMS are critical for maximising tactile sensorial benefits, which could be accomplished by optimising the emulsion formulation to contain oil of low viscosity and small PDMS droplets.

Characterization of Open-Cell Sponges via Magnetic Resonance and X-ray Tomography.

The applications of polymeric sponges are varied, ranging from cleaning and filtration to medical applications. The specific properties of polymeric foams, such as pore size and connectivity, are dependent on their constituent materials and production methods. Nuclear magnetic resonance imaging (MRI) and X-ray micro-computed tomography (µCT) offer complementary information about the structure and properties of porous media. In this study, we employed MRI, in combination with µCT, to characterize the structure of polymeric open-cell foam, and to determine how it changes upon compression, µCT was used to identify the morphology of the pores within sponge plugs, extracted from polyurethane open-cell sponges. MRI T2 relaxation maps and bulk T2 relaxation times measurements were performed for 7° dH water contained within the same polyurethane foams used for µCT. Magnetic resonance and µCT measurements were conducted on both uncompressed and 60% compressed sponge plugs. Compression was achieved using a graduated sample holder with plunger. A relationship between the average T2 relaxation time and maximum opening was observed, where smaller maximum openings were found to have a shorter T2 relaxation times. It was also found that upon compression, the average maximum opening of pores decreased. Average pore size ranges of 375-632 ± 1 µm, for uncompressed plugs, and 301-473 ± 1 µm, for compressed plugs, were observed. By determining maximum opening values and T2 relaxation times, it was observed that the pore structure varies between sponges within the same production batch, as well as even with a single sponge.

Fabrication of optimized skin biomimics for improved interfacial retention of cosmetic emulsions.

Retention of hydrophobic active agents on human skin following the use of skin-care formulations is an important indication of the performance of the deposited product. We have developed a novel system which replicates the interaction between human skin and a cosmetic emulsion to systematically establish and characterize the key parameters driving the retention process at the interface. This included a comprehensive study of the skin's biology and physical properties which influenced the process, the fabrication of advanced, improved skin biomimics, the formulation of a cosmetic model-system emulsion, comprising a hydrophobic active agent i.e. petrolatum, commonly used in cosmetic products, the development of a dedicated and highly consistent deposition rig with a corresponding cleaning set-up and the systematic characterization of retention processes on the developed mimics. This study further explores the interplay of petrolatum with skin biomimics and studies the mechanisms that give rise to improved interfacial retention. Petrolatum has been found to create an occlusive layer on the skin mimic, displaying high coverage from emulsion formulations. The large particle size emulsions yielded improved retention on the developed skin biomimics due to the microstructure of the emulsion and the counter effect of the surfactant.

Adsorption kinetics of laponite and ludox silica nanoparticles onto a deposited poly(diallyldimethylammonium chloride) layer measured by a quartz crystal microbalance and optical reflectometry.

A quartz crystal microbalance with dissipation (QCM-D) and an optical reflectometer (OR) have been used to investigate the adsorption behavior of Laponite and Ludox silica nanoparticles at the solid-liquid interface. The adsorption of both Laponite and Ludox silica onto poly(diallyldimethylammonium chloride) (PDADMAC)-coated surfaces over the first few seconds were studied by OR. Both types of nanoparticles adsorbed rapidly and obtained a stable adsorbed amount after only a few minutes. The rate of adsorption for both nanoparticle types was concentration dependent. The maximum adsorption rate of Ludox nanoparticles was found to be approximately five times faster than that for Laponite nanoparticles. The QCM data for the Laponite remained stable after the initial adsorption period at each concentration tested. The observed plateau values for the frequency shifts increased with increasing Laponite particle concentration. The QCM data for the Ludox nanoparticles had a more complex long-time behavior. In particular, the dissipation data at 3 ppm and 10 ppm Ludox increased slowly with time, never obtaining a stable value within the duration of the experiment. We postulate here that this is caused by slow structural rearrangements of the particles and the PDADMAC within the surface adsorbed layer. Furthermore, the QCM dissipation values were significantly smaller for Laponite when compared with those for Ludox for all nanoparticle concentrations, suggesting that the Laponite adsorbed layer is more compact and more rigidly bound than the Ludox adsorbed layer.

A QCM study on the adsorption of colloidal laponite at the solid/liquid interface.

The adsorption of colloidal laponite at the solid/liquid interface on various substrates and over a range of laponite concentrations (10-1000 ppm) has been investigated. Although a wide range of surfaces were studied, only on a positively charged poly(diallyldimethylammonium chloride) (PDADMAC) surface was any adsorption of the laponite observed. This shows that when fully wetted, laponite adsorption depends primarily on the surface charge rather than the degree of hydrophobicity of the surface. The adsorption of spherical Ludox silica nanoparticles on PDADMAC surfaces was also examined for comparison with the disklike laponite. The QCM data for both laponite and Ludox show strong adsorption on PDADMAC surfaces; however, larger frequency shifts were seen for Ludox than laponite at all concentrations tested. Within the concentration range examined in this work, the dissipation data from the QCM suggested a simple monolayer formation for Ludox but a monolayer to multilayer transition for laponite as the concentration increases.