Filament break

Upon breakup, the filament breaks into a set of primary or mother drops whose sizes are, to a first approximation, proportional to R. The size of drops produced when the filament breaks can then be obtained from the distribution of R. Each mother drop produced upon breakup carries a distribution of satellites of diminishing size for example, each mother drop of radius r has associated with it one large satellite of radius r, two smaller satellites of radius i 2 four satellites of radius r(3), and so on. For breakup at rest, the distribution of smaller drops is a unique function of the viscosity ratio. 

Using Pyrex ampoules with resistively heated tungsten wire or strip filaments, protactinium metal has been prepared on the milligram scale (9,13,15). An improved technique is to use a quartz van Arkel-De Boer bulb with an inductively heated W sphere which solves the previous problem of filament breaking and considerably improves the deposition rate of Pa metal (109). 

A bulb burns out when the tiny filament wire breaks. When the filament breaks, it breaks the circuit. The electrons no longer... 

Figures 7.18(b) and 7.18(c) show the breakup into droplets of an extended filament of high density polyethylene in a polystyrene matrix. In Fig. 7.18(b) the distance between the extruder die and the quenching bath is short and the fiber freezes before breaking up, whereas in Fig. 7.18(c) the distance was increased, giving the filaments sufficient time for breakup. As the filament extends, its diameter is reduced until shear forces no longer dominate the surface tension cohesive forces and the filaments breaks into droplets, just like a stream of water from a faucet breaks up into droplets.

At the time of reproduction the filament breaks up transversely into short segments, each of which, by fission occurring among its cells, grows into a new filament. 

Microscopic Characteristics Composed of an extensive, fine hyphal network that rarely branches. Rod-like spores form when the filaments break at the cell wall junctions. The filamentous hyphae and spores are minute, measuring only 1 micron in diameter. Within each cell, no well defined nucleus is discernible. Lacking differentiated spore-producing bodies, Actinomyces are Grampositive. 

FILAMENT BREAKS IN LOWER SPINLINE - HIGH STRESS DUE TO AIR DRAG -EXCESSIVE GUIDE FRICTION TU... 

FILAMENT BREAKS IN DRAW ZONE - HIGH STRESS ALONG SPIN LINE aiX)... 

Undesirable adhesion to metal surfaces may cause a problem in injection molding, melt spinning, and thermoforming. In the melt spinning of PAS a variety of adhesion-related problems have been observed. These problems include the build up of polymer on spinneret surfaces resulting from both initial filament extrusion and lick-back from filament breaks. These adhesion-related problems lead to prematme spin pack failure and equipment down-time to replace spent spinneret packs, and can limit the use of PAS in certain melt spinning operations. 

A gradual increase in voltage increases the applied potential past the instability limit, producing instability in the fluid meniscus. In this condition, liquid is extruded in small droplets or long filaments. Each time a filament breaks off, the liquid meniscus relaxes back to its initial shape this cycle is repeated frequently, causing a pulsating mode. As the applied electrical field increases, the frequency of pulsation increases until the electric field reaches a sufficiently high value to form a jet of conical shape at the exit. 

Example 3.1. An elastic textile fiber is manufactured at two sites and their elongation at break—a characteristic parameter indicative of quality— is measured on a tensile measuring instrument (Instron, for example) a 10 cm sample is clamped at both ends and stretched and the distance traversed is recorded until the filament breaks. The two plants performed 10 tests to measure the percent elongation at break. The results of the first plant are 725,655,715, 670,660,710,690,670, 680, and 690. The results of the second plant are 600, 630, 650, 710, 620, 670, 650, 670, 720, and 610. Consider that a difference of 5% elongation is significant ... 

The maximum take-up velocity is very reproducible and depends essentially on every process variable, e.g., polymer composition and molecular weight, spinning dope composition, bath composition, bath temperature, spinneret capillary diameter, and flow rate. A parameter that seems to determine the upper limit in take-up velocity is the free velocity, Vf [244,323]. Recall that the free velocity is the velocity at which the filament leaves the spinneret under zero tension. The free velocity will increase in an approximately linear manner with the volumetric flow rate through the capillary, and at a fixed flow rate it will increase as the capillary diameter is decreased. When the take-up velocity, Fi, is increased while Ff is held constant, the magnitude of the rheological force, F(rheo), will increase until the filament breaks at the spinneret face. 

Fig. 1.19 Experiments showing the shape of the filament between the two main drops (satellite droplet) (a) before the firtst pinch-off and (b) after the last pinch-off, for droplet to surrounding fluid viscosity ratio of 0.4. The initial filament breaks up into rntwe smaller satellite droplets due to the capillary action [94] (Courtesy of Cambridge University Press)...

Fracture Wiredrawing Internal fracture Wire breakage FEA Superconducting wire Acoustic emission Filament breaks... 

If the die half-angle is too large or the reduction/pass is too small, an internal fracture or core and filament breaks are liable to occur, which has been confirmed by simulation and experiment. 

The FEA simulation revealed that high tensile stress is applied to the core of a wire under the conditions under which filament breaks are likely to occur. For this reason, to prevent filament breaks, brittle superconducting filaments should not be placed at the center of a wire. 

Filament breaks of a single-filament wire during drawing can be detected by AE. AE motoring is effective and informative for the detection of internal fractures and filament breaks. 

As for the BSR values of e LCP/polymer blends, i.e., the ratios of the windup speeds to the extrusion speeds corresponding to filament breaking, the values measured at a shear rate of 24 s for the investigated blends are collected in Table 2. It may be observed that the BSR of all the investigated blends decreases upon increasing the LCP content, as it might be expected on the basis of the biphasic nature of the blends. However, the extent of BSR reduction, which depends mainly on the interphase adhesion in the molten state, changes markedly with the chemical structure of the two... 

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