Influence of surfactants on interaction forces between polyethylene surfaces in a hydrocarbon solvent

Book ChapterThe polyolefins, mainly polyethylene and polypropylene particles, are used as an active filler material in polymer-polymer blends and are being used for the modification of asphalts to provide for high-load, low-maintenance road construction. The stability of prepared blends depends on the interaction forces between polyolefin filler and the matrix and/or between two polyolefin filler surfaces in the polymeric matrix. Various additives, especially surfactants, can be used to modify these interactions and improve the stability of polymer blends. In current research, direct force measurements between polyethylene (PE) surfaces in n-tetradecane, a nonaqueous solvent imitating the polymer matrix, were performed in the presence oflauric acid and dodecylamine using the AFM colloidal probe technique. Additionally, the zeta potential of polyethylene particles in the presence of surfactants in n-tetradecane was measured. The interaction forces between the polyethylene surfaces can be described as a combination of electrical double layer repulsion and steric repulsion between polymer chains extending into the n-tetradecane solvent. The addition of surfactant to the n-tetradecane was found to increase the repulsive force between the PE surfaces. The strongest repulsion was observed for dodecylamine. Additionally, the temperature effect on the interactions in n-tetradecane was studied. It was found that steric repulsion between the PE surfaces increases with an increase in temperature

Atomic force microscopy investigation of interaction forces between polyethylene and asphaltene surfaces

Book ChapterMany petroleum-derived asphalts used for road construction exhibit poor rheological properties. These properties of asphalt can be improved by addition of various polymer fillers to the asphalt blend. Recycled polyolefines, especially polyethylene and polypropylene have been used as the asphalt modifying fillers. Unfortunately the polyolefine-asphalt mixtures are not stable and have a tendency to separate because of the chemical incompatibility of the components. In our research, surfactants were used to improve polymer-asphalt compatibility. Interaction forces between a polyethylene particle and a polyethylene surface and between a polyethylene particle and an asphaltene-surface were measured in surfactant solutions in n-tetradecane and pyridine using the atomic force microscopy colloidal probe technique. Dodecylamine, lauric acid and lauric alcohol (C12E4) were used as surfactants. The most pronounced change the interactions was observed for polyethylene-polyethylene surfaces in the solution of lauric acid. At the same conditions polyethylene-asphaltene interactions were decreased. The most increase was the increase in the repulsion range (to 26 nm) between the spherical PE probe and flat polyethylene surface for 10~3 M n-tetradecane solution of ethoxylated lauryl alcohol (C12E4). In the case of lauric acid the interaction range extended to 24 nm and for dodecylamine to 21 nm. The interaction between the polyethylene sphere and flat asphaltene surface extended to 16 nmfor dodecylamine, to 18 nmfor lauryl alcohol ethoxylated (C12E4) and to 14 nmfor lauric acid

2014, 373−386 Physicochemical Problems of Mineral Processing

Abstract: Ionic liquids are widely used in supported ionic liquid membranes technology, especially in gas separation and purification processes. This work characterizes the ability of ionic liquids to wet commercially available porous supports used for such purposes. Characterization of supports and membrane phases was carried out in order to determine factors influencing wetting process. Experimental method based on capillary rise is widely used for porous media characterization (i.e. pore radius, contact angle). Measurements of penetration distance or liquid mass are two main experimental methods, in which the Washburn equation is a basic instrument to analyze the obtained results. However, polymeric porous supports do not meet Washburn assumptions and the method is loaded with human errors, so the sessile drop method was used. The rate of wetting influences swelling effects and therefore changes in permeation path during gas separation processes are observed. Influence of ionic liquids structure on wetting and swelling of porous supports was investigated. The families of 1-alkyl-3-methylimidazolium (C n mim), ammonium (N nnnn ), 1-alkyl-1-methylpyrrolidinium (C n Pyrr) and 1-alkylpyridinium (C n Py) compounds with variable alkyl chain lengths in cation structures and changeable anions were taken into account in wetting and swelling experiments

Wetting of supports by ionic liquids used in gas separation processes

Abstract. Ionic liquids were found to be selective solvents for separation of gases. They are widely used in supported ionic liquid membranes (SILMs) technology, especially in gas separation and purification processes. This work has characterized commercially available porous membranes employed in such purposes. Characterization of supports and membrane phases was carried out in order to determine factors influencing membrane stability. Scanning electron microscopy (SEM) was used to determine morphology of membrane surface

Influence of Urea and Dimethyl Sulfoxide on K-Peptide Fibrillation

Protein fibrillation leads to formation of amyloids—linear aggregates that are hallmarks of many serious diseases, including Alzheimer’s and Parkinson’s diseases. In this work, we investigate the fibrillation of a short peptide (K-peptide) from the amyloidogenic core of hen egg white lysozyme in the presence of dimethyl sulfoxide or urea. During the studies, a variety of spectroscopic methods were used: fluorescence spectroscopy and the Thioflavin T assay, circular dichroism, Fourier-transform infrared spectroscopy, optical density measurements, dynamic light scattering and intrinsic fluorescence. Additionally, the presence of amyloids was confirmed by atomic force microscopy. The obtained results show that the K-peptide is highly prone to form fibrillar aggregates. The measurements also confirm the weak impact of dimethyl sulfoxide on peptide fibrillation and distinct influence of urea. We believe that the K-peptide has higher amyloidogenic propensity than the whole protein, i.e., hen egg white lysozyme, most likely due to the lack of the first step of amyloidogenesis—partial unfolding of the native structure. Urea influences the second step of K-peptide amyloidogenesis, i.e., folding into amyloids