Water dispersions special features

The use of antifoams is of special importance for the preparation of water-based paints [202]. Although foam problems also occur in textile and paper industries, there are some special features for paints. First, foam is formed in machines with high and medium shear rates, such as high-speed mills. The presence of a considerable foam volume inhibits the process and considerably reduces the useful load volume of the machine. Besides, foam inhibits the operation of the filling equipment. Problems also occur when paints are applied to a surface, especially using effective sprays, dipping methods and foam-curtain devices. The main reason of foam formation are surfactants used to stabilize aqueous latex dispersions. Thus, nonionic surfactants, instead of anionics, are preferred as they form less foam of low stability. 

As mentioned previously, at the Y-shaped junction droplet formation takes place in a one-step mechanism that is determined by the viscous shear force and the interfacial tension force [11]. Because of this special feature, it was possible to directly measure the effect of interfacial tension on the droplet size using various systems with different static interfacial tensions. Water/ ethanol mixtures were used as continuous phase, and hexadecane and silicon oils as to-be-dispersed phase. The size of the droplets was recorded and a calibration curve constructed, and based on that curve, the dynamic interfacial tension could be estimated in systems that contain surfactants. 

SPECIAL FEATURES OF WATER-DISPERSED POLYURETHANE ELASTOMERS... 

Features Freeze-thaw stable stable In high salt sol ns., pH 3-9 pseudoplastic behavior easily dispersible with special grades Properties Creamy-wh. color sol. In cold water vise. 1400 cps min pH 6-8 6-12% moisture... 

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