Fiber melting, fixed length

Compared to drawing which is a well established and slow process, melt spinning for metals is more recent, much easier and faster. Clearly, melt-spun products do not have the regular round shape and the surface quality of drawn wires. But for many applications, such as fiber reinforcement, this is not the primary concern. A parameter of much greater importance in this field is the mechanical strength. In fact, melt spinning is particularly useful for the production of continuous- or fixed-length filaments of amorphous metals. Many alloys can be spun to fibers, ribbons and foils that have thickness dimensions of only a few tenths of a micrometer and widths from about 100... 

The melting-crystallization cycle of an oriented network that is conducted under equilibrium conditions results in a reversible contractile system when the force is held fixed. Alternatively, large changes in the tension are observed when the length is held constant. These two complementary observations are inherent properties of all types of macromolecular systems. The above analysis has been limited to apure one-component homopolymer of uniform cross-section. However, it can be extended, in a straightforward manner to include inhomogeneous fibers, copolymers, and polymer-diluent mixtures.(4)... 

Two cases must now be distinguished. In one, the total quantity of the nonpoly-meric components is fixed. In the other, the amorphous portion of the fiber is in equilibrium with a supernatant phase containing a large excess of the monomeric species. In the former case the fiber and its contents operate as a closed system. If only a one-component diluent is present, the system is bivariant at constant pressure. As melting progresses, the length of the fiber decreases. The composition of the amorphous phase changes since the polymer concentration increases while that of the diluent is fixed. The differential coefficient of Eq. (8.66) is for constant composition, a condition that can be identified with the constancy A. Hence... 

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