The dilational rheology and splashing behavior of ionic liquid-type imidazolium Gemini surfactant solutions: Impact of alkyl chain length

Rheological and Mechanical Properties of Silica/Nitrile Butadiene Rubber Vulcanizates with Eco-Friendly Ionic Liquid

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to formulate the nanocomposites. The impact of [EMIM]OAc on silica dispersion in a nitrile rubber (NBR) matrix was investigated by a transmission electron microscope and scanning electron microscopy. The combined use of the ionic liquid and silane in an NBR/silica system facilitates the homogeneous dispersion of the silica volume fraction (φ) from 0.041 to 0.177 and enhances crosslinking density of the matrix up to three-fold in comparison with neat NBR, and also it is beneficial for solving the risks of alcohol emission and ignition during the rubber manufacturing. The introduction of ionic liquid greatly improves the mechanical strength (9.7 MPa) with respect to neat NBR vulcanizate, especially at high temperatures e.g., 100 °C. Furthermore, it impacts on rheological behaviors of the nanocomposites and tends to reduce energy dissipation for the vulcanizates under large amplitude dynamic shear deformation.

A simple and effective strategy to enhance the stability and solid-liquid interfacial interaction of an emulsion by the interfacial dilational rheological properties

The development of an emulsion is an important challenge in many fields, such as agrochemicals, pharmaceutics, paints, cosmetics, inkjet printing, and food science. However, the traditional strategies that refer to the empirical value and complex secondary additives cannot reflect the influence of the structure, content, compound, and adsorption of emulsifiers. Here, we propose a simple and effective strategy to develop the emulsion, wherein the emulsifiers are chosen based on the dilational rheological properties of the interfacial films at the molecular level. The dilational rheological properties of polyoxyethylene (80) castor oil (EL-80), sorbitan monostearate (Span 60), and their emulsions were explored by the oscillating drop method. Based on the dilational rheological properties, the emulsions were prepared by the phase inversion emulsification technique. The results showed that the emulsion was stable and realized effective solid-liquid interfacial interaction, which was attributed to the large dilational modulus (intermolecular interaction) at the oil/water interface and loss modulus (molecular diffusion exchange) at the air/water interface. These factors reduced the Ostwald ripening and coalescence, and finally increased the spreading diameter. Additionally, the prochloraz 25% emulsion in water (EW) and difenoconazole 20% EW were developed to verify the feasibility of the strategy. Therefore, this research advances the understanding of an emulsion by interfacial dilational rheological properties, which can provide a simple and effective strategy to develop a stable emulsion and achieve an effective solid-liquid interfacial interaction of the emulsion.

Environmental behaviour and ecotoxicity of cationic surfactants towards marine organisms

Cationic surfactants are surface-active compounds that can be found in many products, including household and cleaning agents. As a consequence, they tend to be discarded into water streams, ultimately ending up in the aquatic environment. In spite of this environmental issue, studies describing their effects towards marine species are lacking. The aim of this study was therefore to evaluate the short-term exposure effects of two commercial cationic surfactants and three novel gemini surfactants on four marine species, the green microalgae Nannochloropsis gaditana and Tetraselmis chuii, the diatom Phaeodactylum tricornutum, and the crustacean Artemia salina. Furthermore, biodegradation and size distribution of the cationic surfactants in artificial seawater were also studied by UV-vis spectrophotometry and dynamic light scattering, respectively. Ecotoxicity tests revealed that the commercial cationic surfactant N-cetyl-N,N,N-trimethylammonium bromide is toxic to all tested marine species while N-dodecyl-N,N,N-trimethylammonium chloride and 1,4-bis-[N-(1-dodecyl)-N,N-dimethylammoniummethyl]benzene dibromide showed the lowest toxicity among the tested cationic surfactants. Besides the novel insights regarding the effects caused by these five cationic surfactants, this work opens prospects for the replacement of commercially available surfactants by more environmentally friendly alternatives.