TNU Journal of Science and Technology
226(06): 3 - 9
http://jst.tnu.edu.vn 5 Email: jst@tnu.edu.vn
water and ethanol-benzene in turn. Then, this treated bagasse powder was put into DESs
including choline chloride and formic acid (1:5 molar ratio) at 70
o
C for 3
hours with magnetic
stirring at 200 rpm. The liquid containing DES-soluble lignin (DESL) was then obtained from the
DESs-bagasse mixture by vacuum-filtering to remove hemicellulose and cellulose. After that, the
DESL
was diluted with ethanol, then centrifuged to isolate lignin. The obtained lignin was
washed and dried to prepare for the next experiment.
2.3. Preparation of PVA/lignin composite films
PVA/lignin composite films were fabricated by the casting method. Firstly, PVA (Mw
205,000 g.mol
-1
) and lignin were put into distilled water successively. Then, the mixture was
magnetically stirred and heated to 90
o
C. After that, this mixture was maintained at 90
o
C with a
stirring time of 180 minutes to make PVA dissolve into hot water completely and lignin disperse
homogeneously in the PVA matrix. After being cooled down to 70
o
C,
the mixture was poured
onto Petri dishes. Next, the mixture was dried in a vacuum oven at about 60
o
C to remove air
bubbles. Then, the mixture is maintained at room temperature for 24h. Finally,
the composites
were removed from the Petri dishes and stored in a desiccator. For this experiment, the additional
amount of lignin in the composite was investigated with 5 wt%, 15 wt%, 25 wt%, 35 wt%, and
45 wt%; thus, the samples were labeled as PL1, PL2, PL3, PL4, PL5 respectively and PL0 was
referred to the pristine PVA sample.
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