Number-average crystal thickness

Figure 11.5 SAXS-determined morphology data for compositional fractions of ethylene-octene copolymers number-averaged lamellar thickness (open squares), crystal core thickness (open circles), transition layer thickness (stars). Reprinted with permission from Reference [28]. Copyright 1993 American Chemical Society.

The isotactic polypropylene used was flake grade Profax 6501 containing no additives, with a number average molecular weight of 4.5x10 and a polydis-persity 6.5. Specimens of 0.3 mm thickness were prepared by compression of the powder at 190 0 and 1.75 MPa pressure. The sheets were melted in a Met-tler hot stage in air at 190 0 for 10 minutes and then cooled down to 130 0 0.50c as the apparatus would allow (40 sec) and crystallized for 1 hour at this temperature. After crystallization the samples were quenched in ice-water mixture. 

From here, the steady-state flux of stems over the barrier can be determined—that is, the net rate of transition of a patch with n stems to a patch with n + 1 stems assuming that the total number of patches with n stems in the ensemble remains constant. This flux will depend on the thickness of the crystal. At a particular temperature it is assumed that there is a range of different crystal thicknesses that will grow, and the probability of obtaining a particular thickness is proportional to the steady-state flux for that crystal thickness. This leads to the average thickness of an ensemble of crystals given by... 

Figure 34 Average values of the crystal (circles) and amorphous layer (squares) thickness, (fj and (i,), as a function of dwelling time at 205 C (left) and temperature (right). Filled and empty squares correspond to the paracrystalline model fits with a low (A/=3) and high N=20) number of crystals per stack, respectively. With permission from Ivanov, D. A. ...

Systems copolymer SEO/diethyl phthalate of different concentration have been studied by DSC and low-angle X-ray diffraction as a function of the crystallization temperature. It has been found that for a fixed concentration the characteristic parameters of the LC structure vary stepwise. For instance, for a diethyl phthalate concentration of 10%, the thickness dB of the PEO layer increases suddenly when the crystallization temperature reaches 19°, 29° and 42 °C and each jump of the dB parameter corresponds to a decrease by one of the average number v of folds of PEO chains265. An example of the phase diagram crystallization temperature/solvent concentration is given in Fig. 36 for the copolymer SEO 4 whose molecular parameters are summarized in Table 8. The degree of crystallinity of the PEO chains increases with both the crystallization temperature and solvent concentration265. ... 

In this formula, m is the wei t per unit loigth of crystallizable PEO or PCL chain dcr is the thickness of the crystalliiw layer (d for the LC structure, dpEO for the LCC structure) M is the average number molecular weight of the crystallizable block the factor 2 comes from the fact that the drains are crystallized in two layers Another type of foldiitg has been proposed for EMAEO copolymers, but has not been proven and is in contradiction with the results obtained for copolymers SEO and BEO in solution in a selective solvent of the PEO blocks. 

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