Tham khảo tài liệu 'friction, lubrication, and wear technology (1997) part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | the elastic film of the fluid thereby allowing it to release the air and drain. Silicones are very effective defoamers. Their major drawback is that if the workpiece is to be coated or painted in a subsequent operation adhesion may be adversely affected. Nonsilicone defoamers include long-chain alcohols certain triglycerides and water-insoluble polyglycols. Antimicrobial agents are materials designed to inhibit the growth of bacteria fungi and yeast in metalworking lubricants. All water-based metalworking lubricants are vulnerable to attack by one or more of these agents even oilbased lubricants containing small amounts of water as a contaminant can be degraded by microbes. Attack of metalworking lubricants by bacteria leads to one or more of the following buildup of acidic materials corrosion of machinery and tools destruction of additives objectionable odors and loss of stability in emulsions. Growth of fungi can lead to slimy material coating the machinery and tools as well as the clogging of pumps and filters. Bacteria fungi and yeast are often monitored on a regular basis through commercially available simple culture techniques and when counts reach a certain level there is cause for alarm. Microbes can generally be controlled at acceptable levels through use of antimicrobial agents known as biocides and fungicides. Standard practice often calls for the addition of two different biocides to the metalworking lubricant at regular intervals in an alternating fashion in order to guard against microbes developing an immunity to one of them resulting in an uncontrolled infestation. Although many types of biocides exist two of the most common are phenolic materials and formaldehyde-release agents. Phenolic materials such as 2 4 5-trichlorophenol destroy bacteria directly. Materials such as 1 3-di hydroxy-methyl -5 5-dimethyl-2 4-dioxoimidazole upon being added to water-based metalworking lubricants release formaldehyde slowly to keep bacteria in check. Materials such
