Chemistry Reference
In-Depth Information
(Figure 3). Theses bands were more
pronounced at 200 kGy, evidencing that
the branching reaction can occur addition-
ally as a consequence of radiation effects.
Table 1 shows that the pendant vinyl
groups are consumed during the grafting
reaction, while the amount of trans-vinyl
groups corresponding to long-branch for-
mation increases, which is a consequence of
coupling allylic radicals.
[6]
Additionally, the
content of pendant vinyl groups increase
with the radiation dose at doses higher than
50 kGy, which could be a consequence of
other secondary reactions like branch
scission, as Figure 4 shows. Branch scissions
take place at lower proportions. Thus, their
effect on the molecular-weight distribution
curve is negligible. Additionally, the inter-
connection of the long branches could lead
to crosslinking of the polymeric chains.
Figure 3.
Mechanism of long-chain branching and/or crosslinking: (a) allyl hydrogen abstraction; (b) H abstraction to form
a secondary radical; (c) reaction of products from (a) and (b) to form long branches.
[22]
