Nylons molecular fracture

Natural silk has a high value of 7 x 10 spins/cm. From these data it is clear that very similar amounts of molecular fracture can be obtained in polymers with widely different chemical structures, values approaching 10 spins/g being recorded for CIS PI, CIS PBD, nylon 6 and natural silk under appropriate conditions. Secondly, the lower values obtained for other polymers seem to relate more to their morfdiolo-gy or state rather than their chemical structure e.g. the very low figures for glassy polymers). 

The probability of fracture among a population of molecular chains as a function of tenale strain. Nylon 6. a) Annealed in a slack condition b) unannealed reference specimen (after Ref. 

Zhurkov et al. (1969) studied the nature of the molecular-level fracture processes in Nylon-6 (polycaprolactam) in detail by small-angle X-ray scattering (SAXS) at 300 K in a material having the same level of molecular orientations of 1 = 4.5 for a range of applied stresses of 200 250 MPa. This establishes that rapid fracture at these stress levels involves an increase of a concentration N of nano-voids of a diameter in the range 100-200 mn, increasing at a rate that is exponential in the stress and given by... 

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