Craze fibril diameters volume fractions

Craze fibril diameters determined by TEM and SAXS are of the order of 10 nm. Craze fibril volume fractions Vf range from 0.5 to 0.1, depending on the entanglement network of the polymer and the local craze stress. 

The equatorial SAXS curve of extrinsic crazes in PC is shown in Figure 17 for a sample which has been stretched at T = 129 °C to = 1.8, i.e. to 7. < The scattering curve exhibits the well pronounced interfibrillar interference maximum discussed in the previous section. From the position, s, of this maximum the average fibril diameter, D, may be evaluated. If the volume fraction of craze I fibrils is assumed to be vj = 0.5 (see Section 3.2), Equation (49) yields D = 37 nm, which compares well with results obtained under approximately the same drawing conditions by Paredes and Fischer and Brown and Kramer... 

Fig. 19. Volume fraction, Vf , of fibrils within crazes 11 and average fibril diameter, D, as a function of...

Table 2. Mean fibril diameter D and volume fraction of fibrils V, of crazes I and II and of crazes produced in a mixture of polycarbonate with c = 0.01 g/g dimethyl phthalate (PC-DMP),...

This result is consistent with Kramer s results showing that the fibril extension ratio (which is just the inverse of the fibril volume fraction) is equal to the bulk polymer network full extension ratio. As a matter of fact, it is unlikely that the toluene vapor changes the physical and chemical structure of the bulk it just makes the fibril drawing easier . On the other hand, it is generally admitted that the fibril diameter times the craze surface stress is constant. Therefore, the craze surface stress being lower in toluene vapor, the fibrils are probably thicker. 

---