Key Technical Parameters of Polyacrylamide (PAM)

Polyacrylamide (PAM) is a widely used polymer flocculant in water treatment processes due to its low cost, reliable performance, and broad applicability. The main technical parameters of PAM include molecular weight, degree of hydrolysis (or ionic charge), viscosity, and residual monomer content, all of which significantly influence its performance.

1. Molecular Weight

PAM is a linear high-molecular-weight polymer. In the 1970s, typical PAM products had molecular weights of several million, while modern high-performance PAMs often exceed 15 million or even 20 million. Each PAM molecule consists of more than 100,000 acrylamide or sodium acrylate monomers.
Based on molecular weight, PAM can be classified as low (<1 million), medium (1–10 million), high (10–15 million), or ultra-high (>15 million). Generally, a higher molecular weight leads to better flocculation performance.

2. Degree of Hydrolysis and Ionicity

The ionic degree of PAM plays a crucial role in its application. For anionic PAM, this parameter is often referred to as the degree of hydrolysis, while for cationic PAM, it is called ionicity.
The optimal ionic degree depends on the composition of the treated material. For materials with higher ionic strength or more inorganic components, a higher ionic degree PAM should be selected. Modern PAM products are available in a wide range of ionic degrees, allowing users to choose directly without further hydrolysis.
It is important to distinguish between dissolution (a physical process) and hydrolysis (a chemical reaction that releases ammonia gas); they are fundamentally different.

3. Residual Monomer Content

Residual monomer refers to unreacted acrylamide monomers that remain in the product after polymerization. Although PAM itself is non-toxic, acrylamide is mildly toxic, making this parameter particularly important for food and drinking water applications.
According to international standards, the residual monomer content in PAM used for drinking water and food applications must not exceed 0.05%, and leading international manufacturers control it below 0.03%.

4. Viscosity

Because PAM molecules are long and flexible chains, they exhibit resistance when moving in solution, resulting in measurable viscosity. The higher the molecular weight, the greater the viscosity.
Viscosity reflects the internal friction of the solution and can be used to estimate the polymer’s average molecular weight — an important indicator of polymer performance.