Surface structure break elongation

Figure 7a and b show typical three-dimensional surface topographic images of the PHB fibers drawn at a draw ratio of 4.0 and 7. The surfaces of the fibers differ considerably. Depending on the draw ratio, spherulitic or fibril-like surface structures were formed. The textile physical properties of the fibers can be explained by these different structures. The fibers, spun at a draw ratio of 4.0, are brittle without a sufficient elongation at break visible in the stress-strain curve (Fig. 5). The fibers spun at a draw ratio of 7 show a completely different stress-strain behavior with a sufficient elongation at break and a sufficient tenacity, as can be seen from the stress-strain curve (Fig. 5).

Filled rubbers form a complex network of cross-linked chains connected to surface-active particles such as carbon black or amorphous silica (see Carbon Black). Here we will only indicate the structural features of importance in unfilled cross-linked elastomers. Two breakdown mechanisms are conceivable the initiation and growth of a cavity in a moderately strained matrix and the accelerating, cooperative rupture of interconnected, highly loaded network chains. The second mechanism is more important imder conditions, which permit the largest breaking elongation Xbmax to be attained (29). In that case, the quantity >-bmax is expected to be proportional to the inverse square root of the cross-link density Vg in fact, an increase of A,bmax with to is found experimentally for a... 

Other workers have coated nylon by imbibing pyrrole into the film followed by exposure to oxidant.43 Polymerization only occurred in the surface layer (5 pm), resulting in the formation of a heterogeneous structure. Nylon 6,6 (N66) with incorporated PPy had a much higher initial modulus of 2.6 GPa, compared to 1.7 GPa for N66 alone. However, the elongation to break was also markedly reduced, from 350% for N66 to 60% for N66/Ppy. 

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