Result and discussion
66
8- Viscosity
The viscosity of chitosan solutions at different concentrations was measured using a digital
rotary viscosimeter equipped with a spindle operating at a rotational speed of 20 revolutions
per minute and a temperature of 22°C. The chitosan solutions were prepared in a 1% acetic acid
solvent.
Table 18:results of dynamic viscosity of diffe rent solutions of chitosan
[chitosan]= g/ml
0.01
0.008
0.005
Dynamic viscosity mPa.s
1179.4
897.5
631.2
The vertical projection of the line on the y-axis corresponds to the intrinsic viscosity (η), The
calculation method is employed to plot the graph of the relationship between intrinsic viscosity
(η) and concentration (c), as expressed by the equation η = f(c).
Therefore, for x = 0, we obtain the viscosity of the produced chitosan is 74.761 ml/g.
9- Molecular weight
The method employed for calculating the molecular weight necessitates the consideration of
intrinsic viscosity, utilizing the Mark-Houwink equation.
[𝑀] = (𝜂 / 𝐾)^(1 / 𝛼)
where: [M]= molecular weight, (η)= the intrinsic viscosity
The molecular weight of the produced chitosan was determined to be 130 kDa, classifying it as
a medium-molecular weight chitosan. It is important to note that the standard molecular weight
range for chitosan typically falls between 100 and 500 kDa (THOMAS et al., 2020). Therefore,
the obtained molecular weight value of 130 kDa is within the expected range for chitosan.
1179,4
897,5
631,2
y = 107992x + 74,761
R² = 0,9828
dynamic
viscosity
Chitosan concentration (g/ml)
viscosity
Figure 55:Determination of the intrinsic viscosity of chitosan