Chemistry Reference
In-Depth Information
Table 2.
Average molecular weights of grafted LDPE at differ-
ent radiation doses, using 30% DEM in the solution.
This fact could be corroborated comparing
the results showed in Table 3, where a
significant reduction in the partial area of
the peak with the highest melting point in
the grafted LDPE is observed, simulta-
neously with an increase in the melting
peak areas of the fractions with higher
branch contents. The maximum area reduc-
tion was observed in the LDPE grafted at
200 kGy. However, this modification could
also be attributed to long-branch genera-
tion, as a consequence of radiation effects,
which are as well able to interrupt the linear
sequences. This fact was evidenced com-
paring the SSA curve of the neat irradiated
LDPE, as shown in Figure 7. Additionally,
no significant changes were observed in the
melting temperatures of each fraction,
which only depended on the chosen self-
seeding temperature.
Radiation Dose
M
n
M
w
PDI
0DEM_0 kGy
8233
158680
19.3
30DEM_30 kGy
13099
239267
18.4
30DEM_50 kGy
20109
387837
19.3
30DEM_100 kGy
28982
410477
14.2
index (PDI) value change only at high
radiation doses, where a reduction in its
value was observed.
The final DSC curves, obtained after
applying the SSA technique, showed the
heterogeneity in the branching distribution,
according to the segregation mechanism
based on similar lengths of linear crystal-
lizable sequences.
[21]
The final SSA ther-
mograms showed nine fractions (Figure 6),
corresponding to the segregation of the
chains as a function of the branching
content. As it is clearly noticed, the area
under the peak with the highest melting
temperature decreases significantly with
the radiation dose, corresponding to the
increase in grafting degree. This fact
indicates that the insertion of DEM pro-
duced an interruption in the more linear
sequences, showing that the grafting occurs
preferentially in secondary carbons.
[21,22,24-25]
Conclusions
The characterization results evidenced the
grafting of LDPE by gamma rays. LDPE
needs high radiation doses in order to
produce high grafting degrees. The gen-
eration of branching and unsaturations in
the LDPE molecular structure depends on
Figure 6.
SSA curves of grafted LDPE at different radiation doses, using 30% DEM in the solution.
