scission during dissolution even at shorter times than expected [25]. New
approaches have been presented recently to prevent polymer degradation, like
using a better solvent (decaline) for the sample dissolution step at lower
temperatures [26] or by new autosamplers that allow for nitrogen purging of the
vial and precise dissolution time of each sample [27], eliminating the waiting
time for injection of the current systems. The importance of nitrogen purging and
the influence of dissolution time in degradation of the various polyolefins have
been presented recently [28] and can be seen in Fig. 5 for polypropylene.
Fig. 5 Polypropylene degradation during dissolution at high temperature. (a) Shift of MMD
and (b) weight-average molecular mass (M w ) versus dissolution time in TCB with 300 ppm BHT,
with and without nitrogen purge
212
B. Monrabal