This document summarizes research on grafting acrylamide onto banana fibers to improve their water absorbency properties. It describes extracting banana fibers from plants, pre-treating the fibers, and grafting acrylamide onto the fibers using ceric ammonium nitrate as an initiator. The document outlines experiments to optimize the grafting temperature, monomer concentration, and initiator concentration. After grafting, the fibers undergo hydrolysis and precipitation. The grafted fibers are then tested for percent weight addition and water absorbency to evaluate the grafting process. Safety precautions are also discussed when handling the various chemicals.

1. Acrylamide Grafting on Banana
fibres
Final Year B.Tech Project by
Ketki Chavan
( B.Tech – F.T.P.T.)
(2014)

2. Banana fibres
• Obtained from Pseudo-stem of fully grown banana
plants, usually extracted after harvesting of fruits
and uprooting of the grown plant.
• Chemical Composition:
– Cellulose: 63 to 65%
– Hemicellulose: 20 to 22%
– Lignin: 12 to 16%
(chemical composition varies with the variety of the plant
and geographical conditions where the plant was grown)

3. Characteristics of Banana fibres
• Lignocellulosic fibre
• Strong fibre, high tensile modulus, low
elongation at break
• Average fineness 2400Nm
• Light weight
• Good spinnability
• Strong moisture absorbing ability; absorbs as
well as releases moisture very fast.
• Eco-friendly fibre.

4. Acrylamide Monomer
• IUPAC name: Pro-2-enamide
• Chemical formula: C3H5NO
• Structure: CH2=CH-C=O
NH2
• White odourless crystalline solid
• Water, ether, ethanol and chloroform soluble
• Carcinogenic if inhaled
• Used for Polymer preparation or as Cross-
linking agent. Polyacrylamide is not
carcinogenic.

5. Introduction to Grafting of
cellulosic fibres
A graft copolymer consists of a polymeric backbone with covalently
linked polymeric side chains. In principle, both the backbone and
side chains could be homopolymers or copolymers.
Grafting can be carried out in such a way that the properties of the
side chains can be added to those of the substrate polymer without
changing the latter.
But with other types of grafting, the crystalline nature of the
cellulose, for example, can be largely destroyed. This releases the
natural absorbency of cellulose as well as adding that of the
hydrophic side chains leading to very high water absorbency. This
can be accomplished by a decrystallization procedure after grafting
or, in the case of the hydrolyzed grafted products, by the process
itself.

6. Methods for synthesis of
Graft Copolymers
2 methods:
1. Side chain polymer A could be linked directed
by a suitable chemical reaction to the
backbone polymer B
2. Backbone polymer B could have active sites
such as free radicals or ions formed upon it.
These can then be used to polymerize a
suitable monomer to produce the side chains
of polymer A.

7. • The first method is difficult except in solution and perhaps the
most successful has been by treating "living" polymers to a
suitably reactive backbone. A good example is the
polystyrene- polyvinyl pyridine system where both polymers
have been used as backbones and side chains
• Advantages of this approach:
– Simple Synthetic method
– Fewer problems of homopolymer formation
– Length and number of side chains could be controlled
– Superior properties, including absorbency, because of the
higher degrees of substitution and shorter side chains
• Disadvantages of this approach:
– difficulty of inducing polymer reactions

8. Types of grafting
The second general method is much more successful
and a large number of techniques have been
developed. Essentially, these are free radical processes.
Techniques:
• Chain Transfer Method
• Direct Oxidation
• Initiators for Polysaccharide
• Polysaccharide derivatives as Co-monomers
• Direct Radiation

9. Chain Transfer Method
• In this method radicals are created on the polysaccharide
backbone including cellulose and starch by use of the reactions:
R can be the growing chain of polymers formed by polymerization
with a radical initiator in the presence of the polysaccharide, or by
the primary radical from the initiator itself.
The efficiency of this type of grafting reaction is also greatly
improved by increasing the ratio of polysaccharide to monomers
such as by using a simple swollen system or with the correct choice
of swelling agents.

10. Direct Oxidation
• A number of oxidizing agents have been found to interact with
polysaccharides to form macroradicals which, with monomer,
form graft copolymers. The most successful and best studied
of these is ceric ion. Briefly the reaction is as follows:
• In fact the reaction is much more complicated and the
oxidation-reaction is often preceded by complexing of the
ceric ion by the polysaccharides.
• Other oxidizing agents studied include pentavalent vanadium,
manganese(III) and manganese(IV) ions.

11. Initiators for Polysaccharides
• Initiators such as peroxides or diazonium salts can be
formed directly on the backbone molecules.
Hydroperoxides and peroxides of unknown structure
can be formed by ozonolysis or by treating with
ultraviolet (UV) or high energy radiation in the presence
of air.
• These initiators can then be used to bring about grafting
by decomposing in the presence of monomer. The latter
can be achieved by heat or by the addition of a reducing
agent such as ferrous ammonium sulfate. The use of
reducing agents largely eliminates the concurrent
formation of homopolymer.

12. Polysaccharide Derivatives as
Co-monomers
• A number of vinyl and allyl derivatives of
polysaccharides may be synthesised quite readily.
Direct free radical polymerization of a suitable
monomer in the presence of these derivatives
produces a mixture of grafting and cross-linking.
• With very low degrees of substitution and the
proper choice of reactivity ratios and by the
controlled addition of chain transfer agents
essentially cross-link free grafted products can be
prepared.

13. Direct Radiation
• High energy radiation, both isotopic and with accelerated electrons
brings about grafting directly.
• In the presence of air, radiation can be used to produce peroxides.
• In the absence of air, 2 methods are available:
– Firstly, direct, mutual, irradiation of the polysaccharide in the
presence of the monomer and a suitable swelling agent can be used.
This normally produces a considerable amount of homopolymer
which can be reduced to a very small proportion by various means,
such as increasing the substrate to monomer level, addition of
inhibitors, or using vapour phase addition of the monomer.
– The second method, often termed the pre-irradiation method,
involves irradiating the polysaccharide and adding the monomer,
plus any swelling agent needed, subsequently. This method is very
valuable for monomers such as acrylic acid which polymerize rapidly
with radiation.

14. Cellulose Grafting for Enhanced
Water Absorbency
Cellulose is the key raw material for most commercial absorbent
products. Because of the constant demand to increase the
absorbency of these products, there has been a concomitant
demand for improvement in absorbency of natural and regenerated
cellulose fibres.
The absorbency of cellulose fibres has been improved by
modification of their chemical structure, the known techniques
being:
1. By substituting new chemical groups at the site of the original
hydroxyl groups of the cellulose fibres;
2. By crosslinking cellulose chains into a network structure;
3. By introducing new groups and crosslinking them together; or
4. By grafting side chains onto the cellulose backbone.

15. • While many modified cellulose fibres have greater
absorbency then unmodified cellulose fibres, they gain this
absorbency at the cost of decreased softness and the loss of
other desirable fibrous qualities.
• Therefore, even though many standard techniques of
grafting hydrophilic monomers to cellulose fibres are
possible, not all of them result in the most desirable
superabsorbent fibres.
• The ideal superabsorbent fibre would be the one which
would exhibit substantially enhanced absorbency, while
essentially maintaining the flexibility of the initial fibre
substrate.
• This challenge is being partially met by the introduction of a
combination of ionic and non-ionic monomer grafting
approach, focusing on meeting the requirements of
disposable absorbent products.

16. Cellulose Grafting for Enhanced
Water Absorbency
The grafting techniques for cellulose super-
absorbency are broadly classified under 2 types:
• Saponifiable grafts to cellulose.
• Direct grafting of acrylic and methacrylic acids
to cellulose.

17. • Saponifiable grafts to cellulose:
In this approach monomers such as acrylonitrile,
acrylamide, and various acrylate and methacrylate
esters and their mixtures are grafted, followed by
saponification to sodium polyacrylate or methacrylate.
Non-saponifiable co-monomers are sometimes also
used.
• Direct grafting of acrylic and methacrylic acids:
A direct method is initiation by high energy radiation.
Since these monomers homopolymerize rapidly with
radiation, the pre-irradiation method is the most
convenient. In principle, however, direct irradiation of
cellulose in the presence of monomer could be used
with the monomer in the vapour phase or in solution
containing suitable inhibitors.

18. Materials & Methods
• Materials:
– Banana fibres obtained from CIRCOT, Mumbai.
– Acrylamide AR (monomer)
– Ceric Ammonium Nitrate (initiator)
– Sodium Hydroxide Pellets
– Absolute Alcohol
All supplied by Ami Chemicals of S D Fine Chemicals,
Mumbai.

19. Materials & Methods
• Methods:
1. Pre-treatment of Banana Fibres
2. Grafting
3. Hydrolysis
4. Precipitation

20. Procedure for Pre-treatment
Step 1: Treatment with 0.5% H2SO4 at 40°C for
30 mins. This is for degrading lignin. Treatment
was followed by a hot and cold wash to remove
acid.
Step 2: Scouring of the fibres is done with 5%
NaOH solution at boiling temperature in water-
bath for 4 hours using 1:40 MLR. This is followed
by hot and cold wash to remove alkali and also
assist removal of floating impurities and pseudo
stem residuals.

21. Procedure for Pre-treatment
Step 3: Bleaching of the scoured fibres os done
using following recipe:
• 4 vol H2O2 (50%(w/w))
• 2 g/l Sodium Silicate
• 2 g/l Non-ionic soap
Bleaching treatment is carried out at 85°C for 45
mins using 1:40 MLR. Care must be taken to
avoid fibres to come to the surface so that air
oxidation could be avoided.

22. Procedure for Grafting
• Grafting is carried out in atmospheric conditions & not in inert
N2 atmosphere.
• Variation in Parameters:
(MLR used 1:50)
PARAMATER VALUES
Initiator Concentration (% wt/vol) 0.1, 0.2, 0.4
Monomer Concentration (% wt/vol) 1,2,3
Temperature of Grafting (°C) 30,70,100
Time for Grafting (hrs) 0.5,1,1.5,2,2.5,3

23. PLAN TO OPTIMIZE INITIATOR & MONOMER
CONCENTRATION, TEMPERATURE OF
GRAFTING AND TIME DURATION OF
GRAFTING.

24. Treatments 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Initiator
concentration
(% wt/vol)
0.1 0.2 0.4 0.1 0.2 0.4 0.1 0.2 0.4 0.1 0.2 0.4 0.1 0.2 0.4
Monomer
concentration
(% wt/vol)
1 1 1 2 2 2 3 3 3 1 1 1 2 2 2
Temperature (°C) 30 30 30 30 30 30 30 30 30 70 70 70 70 70 70
Treatment 16 17 18 19 20 21 22 23 24 25 26 27
Initiator
concentration
(% wt/vol)
0.1 0.2 0.4 0.1 0.2 0.4 0.1 0.2 0.4 0.1 0.2 0.4
Monomer
concentration
(% wt/vol)
3 3 3 1 1 1 2 2 2 3 3 3
Temperature (°C) 70 70 70 100 100 100 100 100 100 100 100 100
In all experiments, time duration was kept constant at 2 hours.

25. The conditions which gave samples with good % weight add-on
were analysed [refer results and discussions]
Good values of % weight add-on were observed between
temperatures 70 and 100°C when the monomer concentration
was 2 and 3% wt/vol and initiator concentration was above 0.2%
wt/vol.
Optimising temperature and monomer concentration:
Treatment 28 29 30 31 32 33 34 35
Initiator
Conc
(%wt/vol)
0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2
Monomer
Conc
(%wt/vol)
2 2 2 2 3 3 3 3
Temp (°C) 70 80 90 100 70 80 90 100

26. • Again the samples with max % weigth add-on were treated to
be the optimum and so by maintaining these conditions the
following plan was used for optimization of Time Duration for
Grafting:
Thus a total of 41 samples were prepared and all of them were
Hydrolyzed and Precipitated.
Treatment 36 37 38 39 40 41
Initiator
Concentration
(% wt/vol)
0.2 0.2 0.2 0.2 0.2 0.2
Monomer
Concentration
(% wt/vol)
3 3 3 3 3 3
Temperature
(°C)
70 70 70 70 70 70
Time
(hours)
0.5 1 1.5 2 2.5 3

27. • Procedure for Hydrolysis:
Hydrolysis treatment of the grafted fibres is
carried out using an 8% (wt/vol) NaOH solution
at 70°C for 2 hours in atmospheric conditions.
• Procedure for Precipitation:
Precipitation is done in Absolute Alcohol after
completion of the Hydrolysis treatment.
Use of safety goggles and gloves is a must during
precipitation.

28. Testing procedure
1. Calculation of % Weight Add-on:
• The fibres after bleaching and before grafting are dried
in an oven at 105°C for 30 mins and then weighed. This
weight is abbreviated as Wb.
• The fibres obtained after Hydrolysis and Precipitation
are also dried at 105°C for 30 mins and then weighed.
This weight is abbreviated as Wg.
Now,
% Weight Add-on = [ ( Wg - Wb ) / Wb ] x 100

29. Testing procedure
2. Calculation of Water Absorbency:
1 gm of prepared grafted fibre was immersed in 100ml distilled
water for 1hour to reach the swelling equilibrium at room
temperature. The swollen fibres were filtered through a Nylon
cloth and the remaining fibres were weighed.
The water absorption Q (g/g) is given by;
Q = [ Ws-Wd ] / Wd.
Where, Ws is the swollen weight of the sample.
Wd is the dried weight of the sample.

30. Safety Precautions
• Use of Hand gloves is a must always during the Pre-
treatment procedure for cleaning of banana fibres.
• Use of Hand gloves as well as Safety Goggles and Face
masks during the Grafting Procedure to avoid contact of the
hot fumes to be inhaled or contacted with eyes.
• Continue the procedure of hydrolysis with all the stated
safety measures in point (ii) to avoid contact of the alkaline
fumes to coming into contact with eyes or getting inhaled.
• Use of proper face masks, Safety Goggles and Hand Gloves
is a must during the Precipitation process as Alcohol is
involved in the process and a continuous exposure to the
precipitating medium may cause severe headache and
watering of eyes along with yellowing of hands.

31. RESULTS & DISCUSSIONS

32. Temp, Monomer & Initiator Conc.
Optimization
Sample No. /
Treatment No.
Weight Add-on
(%)
Water Absorbency
(gm/gm of grafted fibre)
1 18 9
2 19 10
3 20 12
4 19 9.3
5 21 12.5
6 23 13
7 25 13.5
8 27 15
9 30 16
Samples: Temp = 30°C; Monomer con = 1,2,3 (% wt/vol);
Initiator con = 0.1,0.2,0.4(%wt/vol)

33. Temp, Monomer & Initiator Conc.
Optimization
10 44 20
11 49.5 21
12 53 23.4
13 51 22
14 52 22.5
15 55 24.6
16 60 27
17 62 27.5
18 64 27.8
Samples: Temp = 70°C; Monomer con = 1,2,3(%wt/vol);
Initiator con = 0.1,0.2,0.4(%wt/vol)

34. Temp, Monomer & Initiator Conc.
Optimization
19 46 20.2
20 48 20.4
21 49 20.8
22 58 26.4
23 59 26.8
24 61 27.2
25 63 27.6
26 65 28
27 66 29.1
Samples: Temp = 100°C; Monomer con = 1,2,3(%wt/vol);
Initiator con = 0.1,0.2,0.4(%wt/vol)

35. Temp & Monomer Conc. Optimization
28 52 22
29 51 22.5
30 53 23.6
31 52 22.1
32 62 27.4
33 63 27.5
34 64 27.8
35 65 28.1
Samples: Temp = 70, 80,90,100°C; Monomer con = 2,3(%wt/vol);
Initator con = 0.2(%wt/vol)

36. Time Duration Optimization
36 44 19.5
37 49 21
38 52 22.1
39 58 26.4
40 63 27.6
41 68 29.5
Samples: Temp = 70°C; Monomer con = 3(%wt/vol); Initiator con = 0.2(%wt/vol);
Time duration = 0.5,1,1.5,2,2.5,3 hours.

37. • Effect of Initiator Concentration:
With constant monomer concentration and temperature it can be
seen that % weight add-on and water absorbency increases with
increase in Initiator concentration. As concentration goes above
0.2% wt/vol it can be seen that there is more amount of grafting
which can be due to more number of active sites available for the
monomer to polymerize.
• Effect of Monomer Concentration:
With constant initiator concentration and temperature it can be
seen that % weight add-on and water absorbency increases with
increase in Monomer concentration upto a limit after which it
decreases. As concentration goes above 2% wt/vol the availability
of initiator gives good extent of grafting but as concentration
increases further above 3% wt/vol, the formation of
homopolymer becomes more prominent than actual grafting
taking place. Thus the absorbency decreases.

38. • Effect of Temperature of Grafting:
Increase in temperature of grafting from 30°C to 70°C gives a drastic
increase in % weight add-on due to increase in extent of grafting. It can
thus be noted that a temperature of minimum 70°C is required for
grafting of Acrylamide onto Banana fibre cellulose. After further
increase above 70°C towards 100°C, there is not much difference in
the % weight add-on, only slight steady increase is seen. This indicated
that a temperature of 70°C is sufficient for grafting rather than moving
to higher temperatures. It was also seen in the cases where monomer
concentration was 3% wt/vol that the fibre grafting taking place at
temperature above 90°C was fast but the homopolymer formation
was comparatively more than the grafted fibre formation. The reason
here can be the higher temperature supporting the quick formation of
homoplymer due to good availability of initiator and monomer rather
than grafting onto the fibre cellulose. Thus higher temperature has
selectivity to formation of homopolymer and thus it can be inferred
that temperature between 70°C to 80°C is sufficient for selective
grafting.

39. • Effect of Time duration of Grafting:
With the conditions for maximum % weight add-on and good
water absorbency obtained in terms of Initiator
concentration, Monomer concentration and Temperature of
Grafting, the time of grafting showed a positive effect on the
% weight add-on and water absorbency value. Increase in
time of grafting at optimized conditions of 0.2% wt/vol
Initiator, 3% wt/vol Monomer and grafting at 70°C, showed a
steady rise in % weight add-on as well as water absorbency.
The increase in time duration of grafting helped completion
of grafting onto fibre to give more weight add-on and thus
increased water absorbency. But time taken more than 3
hours lead to hardening of the copolymer formed, thus
creating a problem in Hydrolysis. Thus the time duration of
Grafting was optimised to 3 hours.

40. Response Surface Diagrams for
% Weight Add-on
• At Temp = 30°C
0.1
0.2
0.4
0
10
20
30
1
2
3
% Weight Add-on when Grafting at 30°C
Monomer Conc
Initiator Conc

41. Response Surface Diagrams for
% Weight Add-on
• At Temp = 70°C
0.1
0.2
0.4
0
10
20
30
40
50
60
70
1
2
3
% Weight Add-on when Grafting at 70°C
Monomer Conc
Initiator Conc

42. Response Surface Diagrams for
% Weight Add-on
• At Temp = 100°C
0.1
0.2
0.3
0
20
40
60
80
1
2
3
% Weight Add-on when Grafting at 100°C
Initiator Conc
Monomer Conc

43. FT-IR Spectra
• Raw Banana fibre
• The absorptions bands at 3600-3100 cm–1 can be assigned to stretching
vibrations and other polymeric associations of hydroxyl groups.
Symmetric stretching at 2913 cm–1 assigned to the CH2 groups present
in polysaccharides. Angular deformations of C–H linkages of aromatic
groups were observed at 858, 761, 668 and 576 cm–1. An overlapping of
peaks was observed between 1654–1327 cm–1 and 1244–1026 cm–1
due to C–C, C=C, OH, CO, CHn, CH, and C–O–C vibrations. These are
generally observed in cellulose, hemicellulose and lignin, suggesting an
aromatic and ethereal character of the sample.

44. FT-IR Spectra
• Bleached Banana fibre
• The differences in the FT-IR spectra of raw and Bleached Banana fibres
are seen clearly. The change in the spectra occurs in between
wavelengths 2913 cm-1 and 1654 cm-1. The removal of hemicellulose
on other impurities after scouring and bleaching is indicated in
between the stated wavelengths.

45. FT-IR Spectra
• Acrylamide-g-Banana fibre:
The FT-IR spectrum shows characteristic broad bands at around 3400
and 1660 cm-1 which can be assigned to –NH2 and carboxamido
groups, respectively. It also shows bands at 2880 and 2940 cm-1 which
can be assigned to –CH2 and –CH3 groups of alkyl chains. Also, the
bands at 2940 and 1060 cm-1 can be assigned to C–O-C ethereal group
of the grafted copolymer.

46. Conclusion
This project was an attempt to utilize Banana fibre α-cellulose as a
source of cellulose to prepare cellulose based SAPs. The procedure
of the project was the optimization of the various parameters
involved in the Graft Copolymerisation process of Acrylamide
Monomer by Free radical Initiation technique using Ceric
ammonium nitrate as the initiator. The parameters considered
were Initiator Concentration, Monomer Concentration,
Temperature of Grafting and Time Duration for Grafting.
The effects of each of the parameters were studied individually as
well as relatively, on the water absorbency of the prepared grafted
fibres. The results obtained showed that the optimum conditions
involved in formation of the most absorbent copolymer were:
• Initiator Concentration: Minimum 0.2% wt/vol
• Monomer Concentration: Upto 3% wt/vol
• Temperature of Grafting: 70°C
• Time duration of Grafting: 3 hours