Bubble pickup

Additional tests to determine wettability of the surfaces include flotation and two-phase separation. In flotation the particles after treatment with the surface modifier are introduced into a stream of bubbles and the amount of solids floated out in a fixed period of tune is taken as a measure of the hydrophobicity of the particles. A modification of the flotation technique is the bubble pickup, in which single bubbles are generated in a controlled manner and contacted with the dispersed particles. The weight of particles thus removed by a fixed number of bubbles is taken as a measure of the hydrophobicity. 

Bubble pickup-. A bubble is formed at the tip of a capillary tube and introduced into a stirred suspension of particles. Hydrophobic particles will adhere to the bubble. Under standardized conditions, the amount of material collected on the bubble(s) can be compared with other suspensions. Microflotation-. Any small-scale flotation cell device can be used to contact a suspension with rising air bubbles onto which hydrophobic particles will become attached. The particle-laden froth that is produced either flows to a collection tube (as in HaUimond or similar type flotation tubes) or can be drawn off into a separate collection vessel (as in small-scale Denver, levitation device or similar type flotation cells). This is also referred to as a levitation technique. 

Four types of fabric substrates were cyanoethylated the control, acid hydrolyzed, 50 and 100 Mrad. Fabric specimens 19 X 89 mm were sprayed with a fine mist of 2% NaOH solution using a hand spray bottle until a 100% pickup by weight was achieved. The specimens were then left to air dry until just damp. Six samples were then placed on a rack inside the sealed reaction vessel, which had inlet and outlet connections to permit the acrylonitrile vapor to flow through and around the reactive fabric. This vessel was connected to two bubble bottles containing water and acrylonitrile with which to saturate nitrogen gas as it entered the reaction vessel. The water was necessary to swell the cellulose so the acrylonitrile could penetrate. It was determined that varying nitrogen flow rates and reaction time had little effect on the percent add-on. 

Another important reinforcement application is in silicone rubber. Historically, fumed silicas have played the major role here, but recently precipitated silicas have been developed that possess the characteristics required for this application (6). Compared to conventional precipitated silicas, a product designed for this end use must have higher purity (to impart acceptable electrical properties, because silicone rubbers are often used as insulating materials) and lower water adsorption (to prevent bubbles from forming during extrusion and to impart resistance against moisture pickup). Good dispersibility is also important. 

Kydex is primarily formed into sheets, to be thermoformed later. The sheets pickup moisture when exposed to humid atmosphere. If sheets contain 0.2% moisture or more, bubbles will result when the material is heated to the thermoforming temperature (205°C). Sheets can be dried in a circulating air oven at 70°C in 16 h (for thickness of 3 mm) or in 24 h (thickness of 6 mm). Drying can be avoided if the sheets are stored in a low humidity environment or thermoformed at 180°C or less. 

In the present paper the circumferential pressure distributions in the statically and dynamically loaded Journal bearing are measured. A pressure pickup mounted in the journal has given more accurate results than pickups of conventional type. And in order to explain the negative pressure or tension which is detected in the present experiment, a hydrodynamic lubrication theory is developed regarding the lubricant as two-phase liquid of oil and small bubbles. 

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