The presence of NC reduces the onset of thermal degradation as
a consequence of the higher content of hydroxyl groups, which can
be hydrogen bonded to PLA. On the other hand, the increase of the
char at 500 C indicates that the fraction of PLA that interacts with
NC is also involved in the formation of the residue. Additionally, the
NC may contain some sulfate groups due to the initial acid hydrolysis
treatment (small signal at 1080 cm1 in NC FTIR spectrum),
which could lead to a higher char.
The analysis of the PLABz degradation curve (Fig. 5) shows
a first degradation step in the 100e280 C range (maximum at
137 C) that is explained by the scission of free end carboxylic
groups that are lost as CO2, as it has been described for other
polymers with carboxylic groups [15]. There is another degradation
step between 280 and 370 C (maximum at 355 C), which
corresponds to the degradation of PLA, mainly due to ester
scission.
The lower thermal stability of this intermediate product is the
result of the reduced interactions between carboxylic and hydroxyl
groups, since the last ones are blocked, after the reaction.
The presence of NC reduces the onset of thermal degradation as
a consequence of the higher content of hydroxyl groups, which can
be hydrogen bonded to PLA. On the other hand, the increase of the
char at 500 C indicates that the fraction of PLA that interacts with
NC is also involved in the formation of the residue. Additionally, the
NC may contain some sulfate groups due to the initial acid hydrolysis
treatment (small signal at 1080 cm1 in NC FTIR spectrum),
which could lead to a higher char.
The analysis of the PLABz degradation curve (Fig. 5) shows
a first degradation step in the 100e280 C range (maximum at
137 C) that is explained by the scission of free end carboxylic
groups that are lost as CO2, as it has been described for other
polymers with carboxylic groups [15]. There is another degradation
step between 280 and 370 C (maximum at 355 C), which
corresponds to the degradation of PLA, mainly due to ester
scission.
The lower thermal stability of this intermediate product is the
result of the reduced interactions between carboxylic and hydroxyl
groups, since the last ones are blocked, after the reaction.
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