2.1.8.2. Absorbency Under Load (AUL) - BADA

2.1.8.1. Centrifuge Retention Capacity (CRC)
The retention capacity was approximately determined by weight 0.03 g of the dried hydrogel in a
non-woven pouch (6 × 4 cm). Then this closed pouch was placed in both water and 0.9% sodium
chloride (Normal saline) for 30 min at 25±2° C and allowed to dip into liquids. The swollen pouch
was removed from the water and saline solution and placed on a sieve (100-mesh) in order to
remove the excess water for 5 min and then centrifuged in the centrifuge tube (Viva spin 20,
Sartorius Biolab product), at 250 × g force for 5 min. The retention capacity of the protein
hydrogel was calculated by using the equation (2) [17] .
Weight of swollen gel after centrifuge – weight of dried gel
CRC = (2)
Weight of initial protein superabsorbent
2.1.8.2. Absorbency Under Load (AUL)
The absorbency under load (AUL) is a test method which measures the ability of a superabsorbent
material to absorb different liquids under an applied load or controlling force in order to various
absorbent products such as pad and diapers.
A high value of AUL depends on high hydrogel strength and the high hydrogel strength can
maintain a more hydrogel mass during swelling, even at high concentrations of superabsorbent
material. The superabsorbent polymer with superior hydrogel strength has been achieved by
increasing the degree of crosslinking.
In general in the superabsorbent polymer when the AUL value, as a function of the degree of
crosslinking is increased the retention capacity, as a reciprocal function of the degree of
crosslinking is reduced at the same time [17] (Fig.16).
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