No abstract

The development of environment-friendly natural polymer gel-like dispersions in oil media, with functional properties, in terms of formulation design and synthesis protocol, is still a cutting-edge research area for many applications. The aim of this work was to study the manufacture of electrospun ethylcellulose (EC) nanofibrous webs and to examine their usage to thicken vegetable oils as an alternative approach. The role of concentration, molecular weight (M w ), and binary solvent systems on the electrospinnability of EC and subsequently on the rheological properties of EC nanofiber dispersions in castor oil was investigated. It was observed that, for each M w , defect-free nanofibers were produced above a critical concentration, corresponding to about 2.5 the entanglement concentration (C e ). The average fiber diameter increased with both M w and EC concentrations. Dielectric constant and dipole moment of binary solvent systems influenced the morphology of the EC nanofiber web. The morphology of the micro-and nanoarchitectures generated played a key role in the physical stabilization and rheological behavior of electrospun EC dispersions. The storage modulus (G′) of EC dispersions was correlated with both the spinning solution concentration and average fiber diameter. Furthermore, electrospun EC nanofiber dispersions were compared with EC oleogels obtained by traditional thermogelation from thermorheological and tribological points of view. Overall, this work proposes an efficient and innovative approach to produce bio-based oleogel-like dispersions with great potential in different sectors such as pharmaceuticals, food, or lubricants.

This work focuses on the improvement of the electrospinnability of low-sulfonate lignin (LSL)/polyvinylpyrrolidone (PVP) solutions by the addition of surfactants (SDS, CTAB and Tween-20) as well as on the ability of resulting nanofibers to structure castor oil. Solutions with two LSL/PVP weight ratios (70:30 and 90:10) in DMF were prepared by adding variable surfactant concentrations (0–1 wt.%), and physicochemically characterized. Electrical conductivity, surface tension and rheological measurements were performed. Variations of these physicochemical properties were explained on the basis of surfactant-polymer interactions. The addition of surfactants to LSL/PVP solutions improves electrospinnability, producing more compact and uniform fiber mats in 70:30 LSL/PVP systems, generally reducing the average diameter of the nanofibers and the number of beads. In contrast, nanofiber mats were not obtained with 90:10 LSL/PVP solutions, but different nanostructures composed of particle clusters. Dispersions of nanofiber mats obtained by electrospinning from 70:30 LSL/PVP solutions in castor oil were able to generate physically stable strong oleogels. In general, linear viscoelastic functions of oleogels increased with surfactant concentration. In addition, these oleogels exhibited excellent lubrication performance in a tribological contact, with extremely low values of the friction coefficient and wear diameters, which may lead to potential applications as lubricants.

No abstract

This paper describes experiments designed to evaluate the effect of various silane surface treatments on the thin-film adhesion of epoxies filled with spherical silicon oxide. Fracture mechanics-based methods evaluated adhesion of both filled and unfilled epoxies to silicon oxide. SEM was used to examine fracture surfaces and evaluate fracture mechanisms. Two different epoxies were tested, including one with four components and multiple intermediate cure reactions. It was found that the only silanes that augmented adhesion of the epoxies to silicon oxide were those with functional groups identical to those of the epoxies which take part in the final curing reaction. However, when these silanes were used to coat filler, adhesion of filled epoxies to silicon oxide wafers remained the same or was slightly reduced. In all cases, fracture occurred at or near the epoxy-wafer interface, suggesting that deformation within the epoxy layer was limited. Only one set of specimens, in which the silane was improperly prepared, resulted in augmented epoxy-wafer adhesion facilitated by filler-matrix delamination. In other words, filled epoxy-wafer adhesion increases with decreasing efficacy of silane adhesion promoter treatment.