The solution to the yellowing of polyurethane foam?

The solution to the yellowing of polyurethane foam?

 

Polyurethane foam is now used in many industrial fields. Polyurethane foam materials have a series of characteristics such as light weight, elasticity, fast pressure-sensitive fixing, easy use, free bending, ultra-thin volume, and reliable performance. However, some users have found that it will turn yellow and become more and more ugly after using it for a long time. Is there no way to improve it?

 

Why does polyurethane foam turn yellow?

 

At present, most of the polyurethane foam products are directly connected to the isocyanate group by the benzene ring. Under the action of light, heat, oxygen, especially ultraviolet rays, the urethane bond will be decomposed to form an aromatic amine. After oxidative rearrangement of the benzene nucleus of PU, it generates chromophores such as an awake structure, so that the PU foam products produced are prone to yellowing.

 

How to solve the problem of yellowing of polyurethane foam?

The most essential method is not to use TDI and MDI, but to use benzene rings such as HDI or IPDI instead of directly connecting with NCO as raw materials. However, these raw materials have such disadvantages as follows: the price is relatively expensive, the chemical resistance is poor, and the rigidity is not enough, which restricts the use of HDI in PU.

 

Another solution is to fill the inert gas in the production and storage process to isolate the contact with oxygen as much as possible. A more effective method is to add antioxidants and UV absorbers, which can effectively prevent and delay the yellowing of PU foam. There are many kinds of antioxidants, and the selection of suitable products requires certain technical support and experience accumulation.