Silicones in Cosmetics
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
The low surface energy characteristic of silicone polymers renders them excellent water-repellent lubricants (contact angles against water droplets ) and good antifoam agents (3). Polydimethylsiloxane fluids have a pronounced antifoaming action and are the basic components of special defoamers. The latter usually contain a small amount of an activating solid such as fumed silica, generally in the range of . Unmodified silicones readily satisfy the basic criteria for effective defoaming action; i.e. they are insoluble in the foaming media, they have a very low surface tension, and they rapidly spread out over the foaming media, displacing foam-forming agents from the surface. This gives rise to increased capillary and gravitational drainage, excessive localized thinning of the bubble wall, increased Marongonni flow, and ultimately breakage. Figure 2 illustrates the mechanism of foam collapse resulting from silicone fluids in foaming solutions . Incorporation of activating solids such as fumed silica will promote more rapid destruction of foam through a pinholing effect on the bubble lamella. It has been shown that the defoaming action of silicone antifoams is dependent upon the surfactant and electrolyte concentrations in solution and the particular foaming system in question. Adsorption of
Role of Surfactant in Other Organs
Jacques R. Bourbon in Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
In contrast to those more intellectually stimulating pursuits is the vast technology accumulated under the economic motivation of the highly desirable properties which many industrial surfactants can impart to a wide variety of solid surfaces of commercial interest. This involves the direct attachment of the surfactant molecule to the surface by any of a variety of chemical and physical bonds known as adsorption. This process is well defined in the physical sciences,1 in chemical engineering in particular,2 and is quite different to the orientation of molecules which occurs when surfactants simply locate at a liquid-air interface. Before discussing adsorption in more detail, it should be mentioned that the desirable properties which surfactants can impart to solid surfaces are lubricity, protection from wear, inhibition of corrosion, water repellency, modification of permeability, defense against biological invasion, a degree of electrical insulation, release (anti-stick) action, viscosity modification, and several others3 for which an immediate physiological application is not so obvious. This is well-established technology in the physical sciences, although, for some applications, the mechanisms of action have not been reduced to the same degree of molecular detail often presented in interpreting studies at the air-liquid interface.
Biomedical Fourier Transform Infrared Spectroscopy: Applications To Proteins
R. Michael Gendreau in Spectroscopy in the Biomedical Sciences, 1986
Using anticoagulant whole human blood, flowing ATR experiments using crystals which have been coated with films of various polymers have been compared.16 Polymer films which have been studied include Biomer®, silicon rubber (SR), and poly(vinyl chloride) or PVC. These studies showed that in the adsorption process: At 15 sec there are significant differences in the protein adsorption pattern among the three surfaces (Figure 18 — glycoprotein region near 1080 cm-1 and absorption band near 1361 cm-1).After 1 min of flow, the differences between the three surfaces are less pronounced.After 3 hr, differences still exist between the three surfaces, but these are minor compared to the differences observed at 15 sec (Figure 19).
Synthesis and characterization of water stable polymeric metallo organic composite (PMOC) for the removal of arsenic and lead from brackish water
Published in Toxin Reviews, 2022
Khalil Ahmad, Habib-Ur-Rehman Shah, Hafiza Ammara Nasim, Asif Ayub, Muhammad Ashfaq, Abdul Rauf, Syed Shoaib Ahmad Shah, Muhammad Mahboob Ahmad, Haq Nawaz, Ejaz Hussain
Adsorption process is proceeded by various procedures as reported in literature. Some of these are (i) surface area and volume, (ii) electrostatic interactions, (iii) hydrogen bonding, (iv) adsorbents having active sites, (v) chemical and porous nature of the adsorbent, (vi) π–π interaction, and (vii) acid–base interaction. Adsorption process takes place by physically or chemically; chemically based upon functional group and physically be influenced by the surface of adsorbents. Before and after the adsorption process, FTIR spectrum was accomplished to elucidate the adsorption mechanism of Co-MOF/PANI composite. From the FTIR spectrum, it was calculated that the spectra after adsorption indicated peaks at 542, 921.71, and 832.71 cm−1 which are due to the interaction of composite with arsenic and lead, and these peaks are not present in the spectrum before adsorption as shown in Figure S1. From this FTIR spectrum, it was revealed that the hydroxyl group is responsible for adsorption of Pb(II), As(III), As(V), and DMA upon the surface of adsorbent. Moreover, the peaks in FTIR spectrum at 542, 921.71, and 832.71 cm−1 were presented owing to As–O and Pb–O bond, respectively (Li et al.2020). Adsorption mechanism is also represented schematically in Figure 7.
Determination of surface energies of hot-melt extruded sugar–starch pellets
Published in Pharmaceutical Development and Technology, 2018
The specific surface areas of the pellets were determined using a Nova 3000 Series Model N32–7 BET analyzer (Quantachrome GmbH & Co. KG, Odelzhausen, Germany). Nitrogen gas was used as an adsorbate. Specific surface area was calculated according to BET theory. A sample weight of 47 g was degassed for 24 h and subsequently measured under the conditions given as follows:Adsorption: deviation 0.10 mmHg; equilibrium time 180 s; dwell time 360 s.Desorption: deviation 0.10 mmHg; equilibrium time 60 s; dwell time 180 s.Relative pressure: 0.1; 0.15; 0.2; 0.25; 0.3.Temperature: −196 °C.
Dyes adsorption properties of KOH-activated resorcinol-formaldehyde carbon gels -kinetic, isotherm and dynamic studies
Published in Toxin Reviews, 2022
Azrul Nurfaiz Mohd Faizal, Muhammad Abbas Ahmad Zaini
The release of pollutants into the water bodies is a subject of considerable concern. The damaging effect of water contaminants brings bad implications to aquatic ecosystem and human who relies on water resources for routine life. Adsorption is a preferable method that has been widely applied in wastewater treatment. Adsorption is a process where target solute is adhered to solid surface via several mechanisms such as π-π interaction, ion exchange, pore filling, and complex formation (Ming-Twang et al.2015). In addition, adsorption in continuous mode is suitable to handle large volume of wastewater because of simple and easy operation, less space needed for equipment and minimum costs for manufacturing, operating and maintenance. However, commercial adsorbents available today are normally in powder or granular form, so unfit for continuous process. Despite the large specific surface and rich surface chemistry of adsorbent, the column operation may suffer in escalating pressure drop due to hydraulic resistance, hence compromising the column performance and so increasing the operating cost (Masuda et al.2013).
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