What causes PU (Polyurethane sealants) failure and how can we avoid it?

Polyurethane (PU) sealant is a flexible adhesive and sealing compound used in a variety of industries such as construction, automotive, and manufacturing. PU sealant, like any other material, might fail under certain situations or for certain causes. Here are some of the most typical reasons why PU sealant fails:


Note :- Because PU sealants are not food grade materials and have a strong odour, they cannot be used in permanently submerged situations. 

1. Inadequate Surface Preparation: Inadequate surface preparation is one of the most prevalent reasons of PU sealant failure. Surfaces that are to be sealed must be clean, dry, and free of dust, grease, oil, and pollutants. Failure to adequately prepare the surface may prevent the sealant from sticking effectively.

2. Poor Adhesion: PU sealants must adhere well to the substrates they are sealing. The sealant may fail if it does not adhere adequately. This might occur as a result of inadequate surface preparation, mismatched substrates, or inappropriate application processes.

3. Incompatible Substrates: Some materials may not cling well to PU sealants. It is critical to verify that the sealant is compatible with the substrates on which it is applied. Otherwise, it may fail to connect adequately.

4. Infiltration of Moisture or Contaminants: PU sealants are susceptible to moisture during the curing process. Moisture infiltration into the sealant before it has fully set might result in diminished adhesion and failure. Contaminants such as dirt or oil might also impair the sealant’s function.

5. Improper Mixing: Before application, some PU sealants require two-part mixing. If the components are not combined correctly or in the precise amounts, the sealant may fail to cure properly.

6. Incorrect Application Temperature: PU sealants frequently have temperature ranges suggested for application and curing. If the sealant is put outside of these temperature ranges, it may fail to cure properly.

7. Excessive Stretching or Movement: Although PU sealants are flexible and can allow some movement, excessive stretching or movement beyond their limitations might cause them to fail. In such circumstances, a sealer designed for high-movement joints may be necessary.

8. UV Exposure: Some PU sealants are not UV-resistant and may deteriorate over time when exposed to sunshine. They may fail if used in outdoor situations without sufficient UV protection.

9. Ageing and Weathering: PU sealants can degrade over time owing to exposure to weather, chemicals, and other environmental variables. This can result in decreased performance and, eventually, failure.

10. Using Low-Quality or Expired Sealant: Using low-quality or expired PU sealant might lead to premature failure. Use sealants from recognised manufacturers and keep track of their expiration dates.

It is critical to follow the manufacturer’s directions for correct application, substrate compatibility, and climatic conditions to ensure the long-term effectiveness of PU sealants. Regular inspection and maintenance can help discover early symptoms of sealant breakdown, allowing for prompt repairs or replacements.

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