Page 318 - Fiber Fracture

300 Y. Termonia

M = 250,000. The dependence of fiber strength on blend composition is studied in
Fig. 13 (Termonia et al., 1986). Intuitively, one could have expected that the addition
of only a small amount of the high molecular weight component would lead to a
tremendous increase in fiber strength (upper curve). Alternatively, one could argue that
a minute amount of short chains in a high M fiber would have a deleterious effect on
mechanical properties (lower curve). Actual model results (circles) indicate that neither
of these two scenarios applies and the tensile strength for the blend follows the weight
average summation of the two-component properties.

Effect of Chain-End Segregation

It is well known that chain ends easily segregate during crystallization of polymers
and more generally in all polymeric systems under conditions of relatively great

Ill// II

II
lllll I Ill1

Fig. 14. Segregated structure for a fiber having diameter d = 40 lattice units (compare with Fig. Ib).