Robustness of surfactant-laden latex films Kwieciński, Wojciech; Klaassen, Dennis; Smit, Chris ...
Progress in organic coatings,
November 2021, 2021-11-00, 20211101, Letnik:
160
Journal Article
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Despite the growing popularity of latex inks in the inkjet printing industry, little is known about the influence of additives present in the ink mixtures on the robustness of the latex films. Here, ...we investigate the influence of a non-ionic surfactant, Dynol 607, on the abrasion robustness of a water-based latex film. For fixation temperature below the minimal film formation temperature (MFFT), we observe an improvement of robustness of the film with increasing surfactant concentration due to the improved film coalescence. However, for temperatures exceeding the MFFT, Dynol clearly has a negative impact on the abrasion robustness. Using AFM in the PeakForce tapping mode we have demonstrated that the surfactant forms ultra-thin surfactant layers at the top of the latex film. Force spectroscopy performed with the colloidal probes showed that these layers can increase the adhesion between the film and abrasive material leading to decreased abrasion robustness. However, other effects such as: macroscopic corrugation of the film or the surfactant layer between latex film and the substrate that may have influence on the mechanical performance of the film, were also identified. Our research showcases that mechanical robustness of latex films is affected by surfactant in various ways, which are poorly understood, even though surfactants are commonly used in latex ink formulations.
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•Abrasion robustness of surfactant-laden latex is investigated using atomic force microscopy (AFM)•Dynol-607 improves the coalescence of latex films with fixation temperatures below the minimal film formation temperature•Above the minimal film formation temperature Dynol has a negative effect on the abrasion robustness of the latex film•Using AFM and optical microscopy we have identified several possible explanations for the reduced robustness
The wetting properties of multicomponent liquids are crucial to numerous industrial applications. The mechanisms that determine the contact angles for such liquids remain poorly understood, with many ...intricacies arising due to complex physical phenomena, for example, due to the presence of surfactants. Here, we consider two-component drops that consist of mixtures of vicinal alkanediols and water. These diols behave surfactant-like in water. However, the contact angles of such mixtures on solid substrates are surprisingly large. We experimentally reveal that the contact angle is determined by two separate mechanisms of completely different nature, namely, Marangoni contraction (hydrodynamic) and autophobing (molecular). The competition between these effects can even inhibit Marangoni contraction, highlighting the importance of molecular structures in physico-chemical hydrodynamics.
Evaporation of surfactant-laden sessile droplets is omnipresent in nature and industrial applications such as inkjet printing. Soluble surfactants start to form micelles in an aqueous solution for ...surfactant concentrations exceeding the critical micelle concentration (CMC). Here, the evaporation of aqueous sodium dodecyl sulfate (SDS) sessile droplets on hydrophobic surfaces was experimentally investigated for SDS concentrations ranging from 0.025 to 1 CMC. In contrast to the constant contact angle of an evaporating sessile water droplet, we observed that, at the same surface, the contact angle of an SDS laden droplet with concentration below 0.5 CMC first decreases, then increases, and finally decreases, resulting in a local contact angle minimum. Surprisingly, the minimum contact angle was found to be substantially lower than the static receding contact angle and decreased with decreasing initial SDS concentration. Furthermore, the bulk SDS concentration at the local contact angle minimum was found to decrease with decrease in the initial SDS concentration. The location of the observed contact angle minimum relative to the normalized evaporation time and its minimum value proved to be independent of both the relative humidity and droplet volume and thus of the total evaporation time. We discuss the observed contact angle dynamics in terms of the formation of a disordered layer of SDS molecules on the substrate at concentrations below 0.5 CMC. The present work underlines the complexity of the evaporation of sessile liquid-surfactant droplets and the influence of surfactant–substrate interactions on the evaporation process.
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Direct growth of flat micrometer-sized bilayer graphene islands in between molybdenum disulfide sheets is achieved by chemical vapor deposition of ethylene at about 800°C. The ...temperature assisted decomposition of ethylene takes place mainly at molybdenum disulfide step edges. The carbon atoms intercalate at this high temperature, and during the deposition process, through defects of the molybdenum disulfide surface such as steps and wrinkles. Post growth atomic force microscopy images reveal that circular flat graphene islands have grown at a high yield. They consist of two graphene layers stacked on top of each other with a total thickness of 0.74nm. Our results demonstrate direct, simple and high yield growth of graphene/molybdenum disulfide heterostructures, which can be of high importance in future nanoelectronic and optoelectronic applications.
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•Surfactant molecules adsorb on a silicon substrate which has a detrimental effect on ink-jet printing.•Solubility parameter is computed using molecular dynamics simulations.•The ...effect of the solvent and the surface properties on surfactant adsorption are investigated.•Surfactant adsorption on solid surfaces can be predicted by the Hansen solubility parameters.
Hypothesis: The Hansen Solubility Parameters (HSP) derived from Molecular Dynamics (MD) simulations can be used as a fast approach to predict surfactants adsorption on a solid surface.
Experiments and simulations: We focused on the specific case of siloxane-based surfactants adsorption on silicon oxide surface (SiO2), encountered in inkjet printing processes. A simplified atomistic model of the SiO2 surface was designed to enable the computation of its solubility parameter using MD, and to subsequently determine the interactions of the SiO2 surface with the siloxane-based surfactant and the various solvents employed. Surfactant adsorption was characterized experimentally using contact angle goniometry, ellipsometry, XPS and AFM.
Findings: Comparison of the numerical results with experiments showed that the HSP theory allows to identify the range of solvents that are likely to prevent surfactant adsorption on the SiO2 surface. The proposed approach indicates that polar solvents, such as acetone and triacetin, which are strongly attracted to the silicon oxide surface might form a shield that prevents siloxane-based surfactants adsorption. This simple approach, can guide the selection of adequate solvents for surfaces and surfactants with specific chemical structures, providing opportunities for controlling interfacial adsorption.
Calcific aortic stenosis (CAS) is associated with advanced age and comorbidities, therefore a non-invasive therapy for it would be beneficial. We previously demonstrated that ultrasound therapy ...improved calcified bioprosthetic valve function in an open chest model. For translational applications, we tested non-invasive ultrasound therapy (NIUT) transthoracically on swine aortic valves and investigated the need for antithrombotic treatment as a follow-up. Primary objective: feasibility and safety of NIUT. Secondary objectives: occurrence, severity and evolution of side effects during therapy and at 1 month follow-up. The device (Valvosoft, Cardiawave) consisted of an electronically steered multi-element transducer and a 2D echocardiographic probe. Three groups of swine received treatment on aortic valves: NIUT (group 1; n = 10); NIUT and 1 month antithrombotic treatment (group 2; n = 5); sham group (group 3; n = 4). Feasibility was successfully reached in all treated swine (n = 15) and no life-threatening arrhythmia were detected. Non-sustained ventricular tachycardia occurred during the procedure in seven swine. Decrease or interruption of NIUT ended arrhythmia. Histopathology revealed no valve or surrounding tissue damage and echocardiography revealed no valvular dysfunction. Only one animal had side effects right ventricle (RV) dilatation, but the RV normalized after therapy cessation with no sequelae at follow-up. No disturbance in biological markers nor valve thrombosis were observed at follow-up. Antithrombotic treatment did not demonstrate any advantage. Survival at 30 d was 100%. We demonstrated, in vivo, the feasibility and safety of transthoracic NIUT on aortic valves in a swine model without serious adverse events. We expect this first-time transthoracic delivery of NIUT to pave the way towards a new non-invasive approach to valve softening in human CAS to restore valve function.
The Todt’s Organisation was a militarised organisation of great importance for the armament potential of the Third Reich. The problems discussed in this text remain on the margins of interest of ...Polish historiography, so the article aims primarily to fill this gap. Due to the wide and multifaceted scope of this issue, the author decided to present the TO in the first phase of its functioning, from its genesis connected with the motorway construction programme to its involvement during the French campaign of 1940. The period encompasses the formative phase and the restructuring of the organisation under the conditions of the war conflict. The TO in the period discussed underwent significant structural changes, becoming not only an efficient construction organisation but also an inseparable element of support for sapper units and efficient Wehrmacht logistics.
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