Aqueous Degreasing

The bonding industry, when presented with the difficulties of reducing solvent emissions to meet the Environmental Protection Act (1990), faced problems in believing that water could solve some of the problem. When clean steel is in contact with water and oxygen, it rapidly oxidises to form ferrous hydroxide, which further oxidises to ferrosoferric oxide hydrate. 

Whether degreasing is by solvent or is aqueous, to ensure that the process is in control, it is necessary to monitor the media and the machine. Trichloroethylene should be tested to ensure there is no build up of acidity and that the oil content of the wash liquor is low. The machine should monitor and reflect the operating temperature during each part of the cycle and a constant watch is necessary to ensure that emission levels are within control. Similar controls are important adjuncts of the aqueous systems. 

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No adhesion was obtained when alkaline washes were used thus neutral aqueous degreasers/cleaners are recommended. 

Aqueous degreasers can be produced using Burco TME and Burco FAE. Equal concentrations of Burco TME and Burco FAE give the optimum performance properties. Additives such as chelates, detergent polymers, and water soluble solvents can enhance the performance of the aqueous degreasers. Typical formulations are given below ... 

Aqueous degreaser formulations containing the Burco TME/Burco FAE combination must be used at dilutions containing at least 2% surfactant to obtain good oil emulsification. Higher levels may be required depending on the soil. 

Wet blasting processes can incorporate a phosphate conversion coating. Such systems are ideally suited to be used in conjunction with aqueous degreasing and wet blasting processes and produce a surface to which rubber can be securely bonded. The resistance to under-bond corrosion is one measure of how well the surface has been prepared. A phosphated metal can show superior performance in this respect over one prepared by poorly controlled dry grit blasting. 

Detergent, emulsifier, wetting agent for formulation of aqueous degreasers and all-purpose industrial and institutional cleaners. 

Aqueous degreasing can be effective, especially when fully automated. However, any aqueous process can leave a surface which requires desorption of water, which adds another process. 

D Yes Solvent attack on PVC and PVDC. Avoid aqueous degreasing of PU No Unless > 50° Shore D PTFE, PVF treat with sodium naphthalene PTFE, PVF prime with a thin coat of Cilbond 30/31, dry and fuse at >200 °C... 

By changing from solvent degreasing to aqueous degreasing systems a 25% reduction in pollution can be achieved. To meet the next target reduction of 67% solvent emission it will be necessary to use only waterborne bonding systems for rubber to substrate bonding. 

Boeing Specifications, BAC 5763 (1995). Emulsion Cleaning and Aqueous Degreasing, Issue E. 

Aqueous degreasing processes use alkaline or acid solutions containing chemicals and various additives. These baths become contaminated with oil and when the bath loses its efficiency, its contents have to be renewed, at a high cost, or the oil must be removed. A well tested method for oil removal is based on using CFCC (carbon fibre-carbon composite) filter membranes, and permanently hydrophilic polymer membranes. 

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