Depth Profile of the Damage

As somewhat of a side note on the exposure of these materials, it was also reported that there was a distinct difference in the coloration and impact properties of the UV-stabilized PECT, depending strongly on an exposure variable not often reported in the literature, that of the effect of sunlight reaching the back side of 

The interpretation of this color versus depth versus exposure time data was that there are two obviously different processes having much different sensitivity to wavelength from each other. The one which represents the essentially parabolic 

It is interesting to speculate that these same processes are probably at work in PET itself although there is currently no data reported either to 

With reference back to the GPC data with depth (see above), one concludes that both sets of data are quite consistent and indicate that the short wavelength(s) capable of chain scission and branching are likely also active in color formation. The longer wavelengths responsible for the deeper coloration, however, must not be capable of very much chain scission or chain branching. 

We also note data from atomic force microscopy (AFM) versus depth, carried out by using a diamond tip for scratching patterns into the surface [12], Because of the 2° microtoming method reported, these authors were able to examine the depth profile of brittle behavior in weathered samples with excellent resolution. The data showed a very rapid decrease in the brittleness with depth into the sample which, of course, was a strong function of exposure time. The brittleness was more in line with the IR data (see above) versus depth than the molecular weight data, hence suggesting that some chain scission and branching can be tolerated in the system before it manifests brittle behavior. 

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When GPC analysis was employed to determine the depth profile of the damage [9], the results (Figure 18.11) showed that substantially more damage was... 

Fig. 8.10. (a) The 1.8-MeVHe backscattering spectra for random and (110) aligned Si crystal before and after damage by a 5 x 1014 cm-2, 200-keV B implant at -150°C. (b) The analyzed depth distribution of the disorder and the deposited energy into atomic collisions normalized to the disorder profile at a depth of 5,500 A (after Feldman et al. 1982)... 

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