Polyacrylamide (PAM) is a synthetic polymer commonly used in various industrial and scientific applications. However, polyacrylamide is not typically classified into specific grades based on a grading system. Instead, it is produced in various forms and molecular weights to suit different applications. The properties of polyacrylamide can be modified by adjusting factors like the degree of polymerization, charge density, and crosslinking, among others.

Here are some common types or forms of polyacrylamide:

1. Nonionic Polyacrylamide: This type of polyacrylamide does not contain charged groups and is therefore nonionic. It is used in applications such as water treatment, papermaking, and mineral processing.

2. Anionic Polyacrylamide: Anionic polyacrylamide contains negatively charged groups along the polymer chain, typically carboxylate or sulfate groups. It is used in applications like wastewater treatment, mining, and soil conditioning.

3. Cationic Polyacrylamide: Cationic polyacrylamide has positively charged groups along the polymer chain, such as amino or quaternary ammonium groups. It is used in applications like flocculation, sludge dewatering, and papermaking.

4. Amphoteric Polyacrylamide: Amphoteric polyacrylamide contains both positive and negative charged groups on its polymer chain. It can be used in a wide range of applications, including wastewater treatment, oil recovery, and gel electrophoresis.

Apart from these broad categories, polyacrylamide can vary in terms of molecular weight, which affects its viscosity and performance in different applications. Various molecular weight ranges are available to suit specific needs.

It's important to note that specific manufacturers or suppliers may have their own product lines or proprietary formulations with different names, but the general classification mentioned above covers the common types of polyacrylamide used in various industries.