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Process aids and additives for latices and thermoplastics
Published in David R. Karsa, Surfactants in Polymers, Coatings, Inks and Adhesives, 2020
Selection of a suitable foam control agent to overcome all these problems may at first seem difficult and it is not surprising that most commercially available defoamers and antifoams contain many components. Although the terms ‘defoamer’ and ‘antifoam’ are often used interchangeably, strictly a ‘defoamer’ (or ‘defoaming agent’) is used to break down foam that is already present, whereas an ‘antifoam’ (or ‘antifoaming agent’) is used to prevent foam formation. The latter is usually the most cost-effective means of chemical control.
Antifoams for Nonaqueous Lubricants
Published in Leslie R. Rudnick, Lubricant Additives, 2017
In order to mitigate these issues, an antifoam is a necessary and critical component of the fluid formulation. The term antifoam refers to a substance that suppresses foam as it forms. The antifoam is added directly to a formulation before use and is designed to disrupt the interfacial forces that stabilize the foam bubbles. In contrast, a defoamer is a material added during the use of the fluid to break any undesired foam buildup and to provide a period of foam suppression before another addition may be necessary. In practice, the terms antifoam and defoamer are often used synonymously, since their compositions are essentially the same or very similar and they perform the same ultimate function. For nonaqueous systems, the term antifoam is generally more precise since, for practical reasons, defoamer additions are almost never done. Although the criteria for choosing an antifoam will vary depending on the specific fluid and requirements, the antifoam must generally exhibit strong initial defoaming, persistence (longevity) of the defoaming, and compatibility (no separation) with the fluid.
Advancements in laundry wastewater treatment for reuse: a review
Published in Journal of Environmental Science and Health, Part A, 2022
Sushil Kumar, Ali Khosravanipour Mostafazadeh, Lalit R. Kumar, R. D. Tyagi, Patrick Drogui, Emmanuel Brien
During biological treatment there is a formation of foam in the aeration basin owing to the presence of surfactants in LWW. The stable foams were generated due to the interaction of gas bubbles with hydrophobic particles and surfactants.[116] The hydrophobic particles come together at the water-air interface and reinforce foam stability.[116] If the presence of surfactant causes excessive forming, antifoam agents (such as Zeta Airspel 300®, dimethyl siloxane (DMS), silicone defoamer, etc.) can be used to minimize foam formation in LWW.[117–119] Some studies also suggest that foaming can be controlled by reducing the sludge retention time (SRT).[120,121]
Low-temperature mechanical properties of polyurethane-modified waterborne epoxy resin for pavement coating
Published in International Journal of Pavement Engineering, 2022
Qian Chen, Chaohui Wang, Sixin Yu, Zhi Song, Hao Fu, Tao An
Epoxy resin has high hardness, brittle quality, poor impact resistance and insufficient durability. It is necessary to add polyurethane to improve flexibility and impact resistance of epoxy resin. After literature investigation and preliminary test analysis (Chen et al. 2022), polyether-based and polyester-based polyurethane prepolymers are selected as modified materials. Among them, polyether-based polyurethane is used to modify E–51 waterborne epoxy resin, and polyester-based polyurethane is used to modify E–44 waterborne epoxy resin. They are supported by Nan Ya Plastics Corp (NPC), and their technical indexes are shown in Table 3. In addition, a catalyst (dibutyltin dilaurate) needs to be added. And a certain amount of defoamer (polydimethylsiloxane) needs to be added to reduce bubbles. They are supported by Xi'an Xinhui Experimental Instrument Co., Ltd.
Production and characterization of yeast extracts produced by Saccharomyces cerevisiae, Saccharomyces boulardii and Kluyveromyces marxianus
Published in Preparative Biochemistry & Biotechnology, 2022
Furkan Demirgül, Ömer Şimşek, Fatih Bozkurt, Enes Dertli, Osman Sağdıç
The yeast cultures counted with hemocytometer (Isolab, Germany) was inoculated into the bioreactor at the rate of 106–107 CFU/mL under aseptic conditions. The fermentation process was carried out for S. boulardii S11 at 37 °C, for other strains at 30 °C and pH 6.0 for 42 h. Medium pH was automatically adjusted using 5 N NaOH and 5 N HCl. The fermentation process was carried out under aerobic conditions (>75 pO2). The agitation process was carried out at 450–550 rpm depending on the oxygen concentration. Silicone oil was used as a defoamer against foaming. During the fermentation, samples were taken from the bioreactor at intervals of 2 h and the amount of sugar was determined by the phenol sulfuric acid method and cell counts with the hemocytometer of the samples. Feeding was carried out according to the amount of sugar after 18 h of batch fermentation. Fed-batch fermentation was continued for 42 h, and after fermentation, the fermentation medium was centrifuged at 4 °C for 9000 rpm/30 min. After centrifugation, the supernatant was decanted and the pellet was washed with saline water (0.85% NaCl) and centrifuged again at 4 °C for 9000 rpm/30 min. Then, the wet weights of the yeast biomasses collected after centrifugation were weighed.