How to resist yellowing of polyurethane foam sponge?

How to resist yellowing of polyurethane foam sponge?
The yellowing of polyurethane soft foam sponge has been a long-standing problem for sponge manufacturers, and polyol manufacturers. Many sponge manufacturers, especially some high-grade sponge manufacturers, have tried to improve the anti-yellowing performance of sponges by adding antioxidants and light stabilizers, but the results are not significant. C汽巴精化，作为世界上知名的抗老化添加剂供应商，研发了IRGASTAB?series of antioxidants, especially its revolutionary production IRGASTAB?PUR 68, fundamentally for the sponge yellowing to provide a set of solutions, this paper will be combined with the polyols and sponge production of upstream and downstream characteristics of the sponge, a systematic analysis of sponge yellowing causes, and elaborates on the corresponding solutions.

Usually, from the point of view of additives, sponge yellowing includes the following four kinds: – sponge foaming / processing, due to high temperature caused by thermo-oxidative aging yellowing
-Air fumigation yellowing caused by exposure to nitrogen oxides (NOx) in the air.
-Fabric contamination caused by sponge
-Yellowing caused by sponge exposure to ultraviolet rays.
And these yellowing, often and antioxidant there is a direct relationship. In other words, the presence of antioxidants, both may have a positive inhibition of some of the above yellowing, for example: sponge foaming/processing process of high temperature caused by thermo-oxidative aging yellowing is through the addition of antioxidants to be inhibited; However, it may also play a negative role in the promotion of other types of yellowing, for example: amine antioxidants in the air in the contact with nitrogen oxides (NOx, mainly from automobile exhaust), or ultraviolet light, will promote the yellowing of sponges. or UV rays, will promote sponge yellowing; and antioxidant BHT, is the main causative agent of fabric contamination.

Usually, polyol manufacturers will add a certain amount of antioxidant in polyol, its purpose is to ensure that the downstream foam manufacturers, in the use of polyol foaming process safety production. At present, domestic polyether manufacturers mainly use antioxidant type for BHT and amine antioxidant or phenol thiocyanate compound antioxidant system; while a well-known international polyether manufacturers mainly use some large molecular weight hindered phenolic antioxidant, and amine antioxidant, such as the vapor bar’s IRGANOX 1135 (large molecular weight hindered phenolic antioxidant), and IRGANOX 5057 (amine antioxidant) belongs to the large molecular weight hindered phenolic antioxidant, and amine antioxidant. IRGANOX? 5057 (amine antioxidant) belong to this system.

As a manufacturer in the sponge market, when we get a polyol, we seldom evaluate the effect of the antioxidant system in the polyol on the yellowing of the sponge, except for the considerations of safety, cost and foaming performance. And this often overlooked factors, but hides an important reason for the impact of sponge yellowing.
Usually in the ideal state, the presence of antioxidants in the polyol, in the sponge foaming process, can play a role in inhibiting the high temperature generated by the foaming itself on the polymer aging degradation, not only to ensure the safety of the sponge foaming process, but also effectively prevent the sponge foaming process of the core of the yellowing problem. However, with the completion of sponge foaming, residual antioxidants in the sponge is prone to cause many sponge yellowing problems.