The shelf - life of polyacrylamide can vary depending on several factors:

1. Solid polyacrylamide

 - Under normal storage conditions (in a dry, cool, and well - ventilated environment, away from direct sunlight and high - temperature sources), solid polyacrylamide powder or granules generally have a shelf - life of about 2 years. If the storage environment is humid, the product may absorb moisture, which can lead to caking and affect its performance. High temperatures can also accelerate the degradation of polyacrylamide, reducing its effective shelf - life.

2. Liquid polyacrylamide

 - Liquid polyacrylamide has a relatively shorter shelf - life compared to the solid form. Usually, in a suitable storage environment (room temperature, protected from light), the shelf - life of liquid polyacrylamide is about 6 months. Liquid products are more prone to microbial contamination, especially in warm and humid conditions. Microbial growth can cause changes in the viscosity and chemical properties of polyacrylamide, reducing its effectiveness for applications such as water treatment or oil recovery.

It is not recommended to use polyacrylamide after it expires for the following reasons:

• Deterioration of flocculation effect: During storage, the molecular chain of polyacrylamide will gradually break and degrade. As time goes by, the molecular weight decreases, which will seriously affect its flocculation performance in water treatment or other applications, resulting in the inability to effectively adsorb and bridge impurity particles, making it difficult for the treated water quality to meet the expected standards.
• Changes in solubility properties: Expired polyacrylamide may be difficult to dissolve, or the solution may agglomerate and become turbid after dissolution, and it is impossible to form a uniform and stable solution. This will not only affect normal addition and use, but may also clog pipes and equipment, affecting the smooth progress of the production process.
• Generation of harmful substances: When stored for a long time and under poor storage conditions, polyacrylamide may undergo chemical changes and generate some substances that are harmful to the environment or subsequent use. For example, in drinking water treatment, if expired products are used, these harmful substances may enter the drinking water and pose a potential threat to human health.