2.1.8.2. Absorbency Under Load (AUL) - BADA

3.9.Ⅰ. Effect of Particle Size
The dependency of particle size on the equilibrium swelling ratio of the EDTAD- AP hydrogel
were measured by sieve analysis. The results showed that the water absorption rate was increased
with decreasing particle size. Decreases in particle size caused to increases in the surface area per
unit of hydrogel mass and led to rapid water absorption. Moreover the water desorption rate
increased slightly with decreasing particle size for the same reason. In this study, the maximum
results were obtained by use the average mesh size 25-30 for determination of swelling behavior of
the AP hydrogel.
3.10.Ⅰ. FTIR-Spectroscopy analysis of AP- Superabsorbent
Figure 30 shows the FT-IR spectra of unmodified albumin protein (a), EDTAD-modified AP (b)
and EDTAD-AP hydrogel (c), in the frequency region from 700 to 4000 cm −1 .
In spectra the broad band at 3100–3300 cm −1 due to O–H stretching, an additional peak at 2950-
3200 cm −1 occurs due to the N─H stretching of amino acids. Amide I and amide II bands illustrate
two important bands of the protein infrared spectrum, so the stretching band observed at 1640 cm −1
can be attributed to amide I (RCONH2) and the peak at 1550 cm −1 is due to amide II (RCONHR')
in albumin protein (Fig.30a).
The EDTAD-modified protein carries carboxylate functional groups which are verified by a strong
band at 1730 cm −1 (Fig.30b,30c).Moreover ,the medium band detected at 1522 cm −1 can be
allocated to N-H bending coupled with C-N stretching [14] . The AP-hydrogel compared with
unmodified and EDTAD-modified albumin protein indicates an important peak at 2360 cm −1
(medium), that might be due to anti-symmetric stretching ─NCO (Fig.30c), because of the
rearrangement mechanism.
56