The formation and retention of liquid pellets in open capillary tubes

Aspects of the behaviour and release of liquid pellets inside narrow capill aries are discussed. Such systems are models for emulsion formation by extr usion from orifices, and are also of relevance to oily soil detergency from hollow fibres such as cotton. This communication discusses how the system' s contact angle, interfacial tension (static and dynamic) and dimensions ca n influence the uptake, mobility and release of these small drops from thin capillaries. In particular, the important effect of the geometry of the ca pillary end is discussed and new equations predict optimum contact angle fo r droplet extrusion taking the end geometry into account. Some practical im plications are outlined. (C) 1999 Elsevier Science B.V. All rights reserved .