TW EASTERN CHEM SINGAPORE PTE.LTD
Analysis of the Reasons for the Decrease of Viscosity and Flocculation Effect of Polyacrylamide Solution
Polyacrylamide
(PAM) needs to be dissolved into liquid to be used. Viscosity and flocculation
effect of PAM solution often decrease in the use process, which affects the use
effect. Here, we sum up a few reasons below.
1: Storage
time:
With the increase of storage time, the
more degradation of PAM solution, the lower the viscosity and the worse the
flocculation effect. Generally speaking, anionic PAM solution can be stored for
seven days and cationic PAM solution can be stored for 24 hours. This is due to
the hydrolysis of amide group and the increase of hydroxyl content. Especially
the effect of cationic group is more obvious. The increase of rigidity of
molecular chain is the result of the removal of NH3 from amide group to imide
group.
2:
Temperature:
When the temperature of 0.1% PAM solution
reaches 80-90 C, the molecular weight of 18 million will degrade to about 5
million in 2-4 hours. With the increase of temperature, the degradation will be
faster and faster. The performance is stable at room temperature of 25 C.
3:
Mechanical effects:
Stirring can improve the dissolution rate
of PAM powder. But it will cut the molecular chain of polyacrylamide with high
stirring speed. It is suggested that the stirring speed should be controlled at
60 rpm on-line, and high-strength stirring equipment and high-speed conveying
equipment should not be used.
4. The
influence of light:
Illumination increases temperature, which
leads to degradation of polyacrylamide. Direct exposure to ultraviolet light
also causes rapid degradation of solubility. The molecular weight of PAM decreases by 30-50% after direct irradiation
for 3-5 hours under intense light.
5.
Impurity effect:
It is better to use neutral water to
dissolve PAM powder. The hardness of water or impurities will affect the
viscosity and use effect of PAM.