PU color paste factory introduces the causes and solutions of polyurethane sponge yellowing to you

The yellowing of the polyurethane soft foam sponge of auditorium chairs and theater chairs has always been a problem that has puzzled sponge manufacturers and polyol manufacturers for a long time. Many sponge manufacturers, especially some high-end sponge manufacturers, try to improve the anti-yellowing function of sponges by adding antioxidants and light stabilizers, but the results are not obvious. The following PU color paste factory will link the characteristics of polyol and sponge production upstream and downstream, systematically analyze the reasons for sponge yellowing, and discuss the corresponding solutions.

Generally, from the perspective of additives, the yellowing of sponges includes the following four types:

1. In the process of foaming/processing of sponge, thermal oxidation yellowing caused by high temperature

2. Smoke and yellowing caused by touching nitrogen oxides (NOX) in the air

3. Fabric pollution caused by sponge

4. Yellowing caused by the sponge touching ultraviolet rays

These yellowing changes are often directly related to antioxidants. In other words, the presence of antioxidants can positively inhibit some of the above yellowing. For example, the anti-oxidative aging yellowing caused by high temperature during foaming/processing is inhibited by adding antioxidants. However, it can also have a negative effect and promote the occurrence of other species of yellowing, such as: amine antioxidants in contact with nitrogen oxides (NOX, mainly from car exhaust) in the air, or ultraviolet rays, will promote the yellowing of sponges, The antioxidant BHT is the primary cause of fabric pollution.

Generally, polyol manufacturers add a certain amount of antioxidants to polyols in order to ensure the safe production of downstream foam manufacturers in the process of using polyol foaming. At present, the main type of antioxidant used by domestic polyether manufacturers is the compound antioxidant system of BHT and amine antioxidants or phenthianine, and some world-renowned polyether manufacturers mainly use some large molecular weight antioxidants. Hindered phenolic antioxidants, and amine antioxidants.

As a sponge market manufacturer, when getting a polyol, in addition to thinking about safety, cost and foaming function, it seldom evaluates the effect of the antioxidant system in the polyol on the yellowing of the sponge. And this factor, which is often overlooked by us, hides an important reason that affects the yellowing of the sponge.

Under normal conditions, the antioxidants present in the polyols can inhibit the aging and degradation of the polymer due to the high temperature generated by the foam itself during the foam foaming process, which not only ensures the safe production of the foam foaming process , and effectively avoid the problem of yellowing of the core in the process of sponge foaming. However, after the foaming of the sponge is completed, the antioxidants remaining in the sponge can easily lead to the yellowing problem of many sponges.

The anti-yellowing solution for auditorium chairs and theater chair sponges we recommend is: "select high-performance polyethers that do not contain BHT and amine antioxidants"