8 Nanocomposites Based on Thermosetting Polyurethane Matrix. . .
119
8.2.1.4 Reduction of MWCNT Surface Acidic Groups
MWCNT-hemin and MWCNT-ox samples (100 mg) were sonicated in dry THF
(50 ml) to obtain a dispersion. Lithium aluminium hydride (LiAlH 4 ) in THF (1 M,
10 ml) was added under a nitrogen atmosphere, and the mixture was refluxed
for 4 hrs. After cooling, excess LiAlH 4 was decomposed with careful addition
of MeOH. Reduced samples (MWCNT-hemin-red and MWCNT-red, respectively)
were stirred in HCl in order to remove trace decomposition products and then
washed thoroughly in water and dried at 100 ◦ C. Samples were checked for the
generation of additional fulvic acids through the reduction step, but none were
detected.
8.2.1.5 Surface Group Analysis
All samples were titrated according to the Boehm method [11, 17]. MWCNT samples (50 mg) were sonicated in sodium bicarbonate, (NaHCO 3 ), sodium carbonate
(Na 2 CO 3 ) and NaOH solution (0.01 M, 20 ml, with 0.1 M NaCl) and stirred for
8 hrs. Samples were separated through centrifugation, and the supernatant was
filtered through 0.2 μm PTFE filters to ensure all MWCNTs were removed. Aliquots
(5 ml) were titrated against HCl (0.01 M, with 0.1 M NaCl) using a pH meter to
monitor the reaction. Titration analysis was repeated three times. Solutions were
stored under nitrogen and were checked to ensure that atmospheric carbon dioxide
had not affected the titration [18].
8.2.1.6 Polyurethane Nanocomposite Preparation
A PU network, to be used as the polymer matrix for nanocomposite preparation,
was synthesised from poly(oxypropylene glycol) (PPG) with M w = 2.000 g mol −1
and adduct of trimethylolpropane (TMP) and toluene diisocyanate (TDI) using a
two-step method, as described previously [28]. The adduct and PPG were used in a
molar ratio of 2:3. The synthesized PU matrix is depicted by the formula:
C
C 2 H 5
C
C
C
HNOCOCH 2
HNOCOCH 2
HNOCOCH 2
CH 3
- NHCOO
CH 2 OCONH
CH 2 OCONH
- NHCOO
CH 3
CH 3
CH 2 OCONH
CONH
[
]
n
n
]
[
C O N H
H 3 C
H 3 C
CONH
[
]
n
H 3 C
CH 2 CH O
CH 3
CH 2 CH O
CH 3
CH 2 CH O
CH 3
- NHCOO
Samples of the nanocomposites were prepared according to the procedures
described in the previous work [26]. To prepare the nanocomposites, MWCNTs, as
119
8.2.1.4 Reduction of MWCNT Surface Acidic Groups
MWCNT-hemin and MWCNT-ox samples (100 mg) were sonicated in dry THF
(50 ml) to obtain a dispersion. Lithium aluminium hydride (LiAlH 4 ) in THF (1 M,
10 ml) was added under a nitrogen atmosphere, and the mixture was refluxed
for 4 hrs. After cooling, excess LiAlH 4 was decomposed with careful addition
of MeOH. Reduced samples (MWCNT-hemin-red and MWCNT-red, respectively)
were stirred in HCl in order to remove trace decomposition products and then
washed thoroughly in water and dried at 100 ◦ C. Samples were checked for the
generation of additional fulvic acids through the reduction step, but none were
detected.
8.2.1.5 Surface Group Analysis
All samples were titrated according to the Boehm method [11, 17]. MWCNT samples (50 mg) were sonicated in sodium bicarbonate, (NaHCO 3 ), sodium carbonate
(Na 2 CO 3 ) and NaOH solution (0.01 M, 20 ml, with 0.1 M NaCl) and stirred for
8 hrs. Samples were separated through centrifugation, and the supernatant was
filtered through 0.2 μm PTFE filters to ensure all MWCNTs were removed. Aliquots
(5 ml) were titrated against HCl (0.01 M, with 0.1 M NaCl) using a pH meter to
monitor the reaction. Titration analysis was repeated three times. Solutions were
stored under nitrogen and were checked to ensure that atmospheric carbon dioxide
had not affected the titration [18].
8.2.1.6 Polyurethane Nanocomposite Preparation
A PU network, to be used as the polymer matrix for nanocomposite preparation,
was synthesised from poly(oxypropylene glycol) (PPG) with M w = 2.000 g mol −1
and adduct of trimethylolpropane (TMP) and toluene diisocyanate (TDI) using a
two-step method, as described previously [28]. The adduct and PPG were used in a
molar ratio of 2:3. The synthesized PU matrix is depicted by the formula:
C
C 2 H 5
C
C
C
HNOCOCH 2
HNOCOCH 2
HNOCOCH 2
CH 3
- NHCOO
CH 2 OCONH
CH 2 OCONH
- NHCOO
CH 3
CH 3
CH 2 OCONH
CONH
[
]
n
n
]
[
C O N H
H 3 C
H 3 C
CONH
[
]
n
H 3 C
CH 2 CH O
CH 3
CH 2 CH O
CH 3
CH 2 CH O
CH 3
- NHCOO
Samples of the nanocomposites were prepared according to the procedures
described in the previous work [26]. To prepare the nanocomposites, MWCNTs, as