Chemistry Reference
In-Depth Information
Fig. 5.20
TG (A) and DTG (B) curves of XG; TG (C) and DTG (D) curves of XG-g-PMA [
62
]
O
O
O
O
O
O
O
CH
2
CH
2
CH
2
O
CH
2
CH
2
O
CH
2
CO
H
3
C-C
C
H
3
C-C-COOH
HOOC-C-CH
3
H
3
C-C
C-C-CH
3
C-CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
O
O
O
-H
2
O
-CO
2
H
3
C-C-COOH
HOOC-C-CH
3
H
3
C-C
C
O
C
C-CH
3
H
3
C-C
C
C-CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
Fig. 5.21
Schematic representation of degradation of XG-g-PMA [
62
]
copolymer of XG with methacrylic acid shows different thermal behaviors from XG
(Fig.
5.20
)[
62
].
XG shows a single step thermal degradation process started at about 232
C, and
nearly 45 % weight loss occurred between 200 and 310
C, and the final decompo-
sition temperature (FDT) is 316
C. The 60 % of XG was degraded at 600
C. The
weight loss rate of graft copolymer increased with increasing the temperature up to
250
C, and two
T
max
are obtained at 243.9 and 343.58
C. The FDT is 452
C,
which is much higher than XG. The weight loss in the range of 150-250
C is due to
the formation of anhydride with elimination of H
2
O molecule from the two
neighboring carboxylic group of the grafted chains. The second
T
max
is attributed
to the decarboxylation of the anhydrides formed earlier (Fig.
5.21
). The change of
thermal behaviors confirmed the formation of grafted copolymer.
Differential scanning calorimetric analysis (DSC) is a useful technique to
explain the formation of graft copolymers. The endothermic or exothermic peaks
of the gum could be changed after grafting reaction due to the increased interaction
between the main chains of gun and the grafted polymer chains.
