• Liquid polyurethane is commonly utilized by many people and companies for a variety of purposes, ranging from arts and crafts to underground covering for pipes. It can be used to make molds of almost any shape and size. Since the mixture is liquid, it can be poured, sprayed or even brushed. Its advantages are numerous, including ease of use, low viscosity and abrasion resistance. Even with all these benefits, there are still many disadvantages that accompany the use of liquid polyurethane.
  
  

Sticks to Surfaces

• When it comes to creating arts and crafts projects around the home, one of the keys is that the materials should be easy to use. When using a mold that is liquid, one of the difficulties can be handling the liquid, ensuring that it is only used on the areas desired. Liquid polyurethane has the added problem in that not only is it liquid and therefore spills easily, it also adheres to surfaces freely. Having one of the worst release properties---especially when compared to alternative types of rubbers such as silicone---it can be extremely difficult and messy to use.
  
  

Moisture

• Although often forgotten, moisture can wreak havoc on the application of some types of moldings. As a result, liquid polyurethane cannot be used in just any environment. The mixture is extremely sensitive to moisture in the air, so using it in an atmosphere that is humid can create problems with the mixture. The same applies to cold weather, where application of liquid polyurethane can result in problems. Applying liquid polyurethane in an environment that is anything but dry and warm can result in the mixture bubbling.
  
  

Limited Life

• Unlike paints and silicone moldings, another drawback with liquid polyurethane is that the mixture cannot be saved under normal circumstances. The limited shelf life is due to its sensitivity to moisture after exposure to air. For consumers who need to store liquid polyurethane, there are a few products available that can extend the shelf life of unused portions.