2-5-2- Extraction of Lignin
Lignin is extract from sawdust by alkali extraction method. 50g of prepared saw dust was placed into a beaker and
300 ml of NaOH (5M) solution was poured into it then heated about140
o
C for 7 hours. Then the content was filtered
and washed with NaOH 2-3 times. It was heated to evaporate the solvent at 100
o
C during 2 days, to isolate the lignin
from liquid part. And the precipitate was dried in oven at 105
o
C during 2 days.
2-5-3- Lignin Purification
Extracted lignin sample was refluxed with acetic acid for 4 hours, to remove impurities. Then it was filtered and
washed with acetic acid for 2-3 times. Then the solution was heated at 100
o
C for 2 days. Lignin precipitate was cured
in an oven at 105
o
C for 2 days.
2-5-4- Lignin Identification
Lignin was analysed by qualitative methods as, Lignin was treated with phenol and HCl, and greenish blue colour
was obtained. Then lignin was treated with aniline sulphite then it was turned to yellow colour.
2-5-5- Synthesis of Lignin Based PF Resin
20 ml of phenol, 15 ml formaldehyde, 0.5 g of extracted alkali lignin and 0.5 g of sodium hydroxide were placed in
a beaker equipped with a mechanical stirrer. It was heated at 80 ºC for 45 minutes. Setup was
cooled to 40 ºC in order
to stop the reaction. Finally, resin was cured at 110 ºC for 3 hour in an oven.
2-6- Analysis of Synthesized Resin
Mechanical properties
were quantified.
Conductivity
of the resin was determined by conductivity meter.
Density was determine by Mass of unit volume
Total solid content (TSC)
An accurately weighed sample (about 0.5g) was evaporated to dryness at 170°C for 30 min
Gel time
A weighed amount of resin was filled into a test tube and dipped into an oil bath at 130°C.
The increase in viscosity was identified with a glass rod used like a piston. The gel point of the resin was identified as
the instant when the glass rod gets stuck in the resinous mass.
Swelling test
A piece of Rubber was placed in a stoppered bottle containing toluene sufficient quantity to cover the rubber piece.
Swell percentage =
W
after swelling
− W
initial
W
initial
(1)
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