The value of �� may be obtained by eliminatingSfrom (2):��=Aam[Acr+(acr/aam)Aam].(3)The value of �� can be thus calculated from measurements of absorbance if the ratio of absorption coefficients is known. This parameter is normally estimated calcitriol?hormone using an independent experimental technique. In the literature, the value of 0.58 is found for i-PP [21].The band at 841/cm was chosen for crystalline phase and the band 973/cm for amorphous phase. Because the spectra are the weighted superposition of single absorption peaks, all the absorbencies were obtained by fitting the experimental spectra with a weighted combination of single peaks, adopting Gaussian/Lorentzian peak functions.The results are reported in Figure 4 and show that the overall crystallinity degree, as assessed by IR spectroscopy, only slightly decreases by effect of the cooling rate.

This means that opacity, which is different from sample to sample as shown in Figure 1, is not determined by the overall crystallinity degree alone.Figure 4Overall crystallinity degree as assessed by IR spectroscopy.As mentioned above, FTIR analysis does not allow discriminating between different crystalline phases, and thus the crystallinity degree as measured by FTIR has to be considered as an overall value accounting for all existing crystalline phases. Thus in order to discriminate between different crystalline phases, the samples were analyzed using wide-angle X-ray scattering (WAXS). Plot (a) of Figure 5 shows the WAXS spectra of the samples of virgin material (0 recycling steps) solidified at different cooling rates.

It can be noticed that, on increasing the cooling rate, the spectrum changes from that characteristic of the �� phase to that characteristic of the mesomorphic or smectic phase. This is a result commonly found in the literature [12]. The effect of recycling steps on the samples solidified at the highest applied cooling rates is shown in plot (b) of Figure 5. Despite of the fast cooling rate, the sample subjected to 5 steps presents clear peaks characteristic of the �� phase, indicating a faster crystallization kinetics Brefeldin_A with respect to the virgin material. This is probably due to a reduction of molecular weight (and thus to an increase of molecular mobility) induced by thermomechanical degradation [4]. The sample subjected to 10 steps of recycling presents an intermediate morphology between the virgin and the sample subjected to 5 steps: probably the increase of degradation slows to some extent the crystallization kinetics.