Nowadays, TDI or MDI are chosen to be the main raw materials for most PU products, whether curing agent, soft and hard foaming, elasticity, PU leather or PU paint. However, either for TDI or MDI, its benzene ring in TDI and MDI directly connects to different isocyanester groups, and the pi bond gets conjugate with nearby NCO. Under the influence of light, heat, oxygen, especially ultraviolet radiation, it can cause ammonia ester linkage decomposition and generate aromatic amine, on which the benzene nucleus rearranges after oxidation. This would generate chromophoric groups which cause the yellowing on the final PU products. The human eye is very sensitive to color, usually a few PPM of colored impurities will lead to the appearance of yellow products.
To solve the yellowing problem, the most essential method is to use HDI or IPDI instead of TDI and MDl as raw materials without direct connection between benzene ring and NCO. But the price of these raw materials has such shortcomings: the price is more expensive, poor chemical resistance, rigidity is not enough… . This greatly restricts the promotion of HDI on PU.
Another solution is to fill inert gas in the process of production and storage to isolate the contact with oxygen as much as possible. The more effective method is to add antioxidant and UV absorber, which can effectively prevent and delay the occurrence of PU yellowing.
YIHOO HN130 is an amine anti-yellowing agent. It’s used as a gas stabilizer in the production process, has good selectivity to nitric oxide (NO) and nitrogen dioxide (NO2), and effectively prevent yellowing caused by gas fumigating.
YIHOO HN130 is widely used in PU moulding materials, footwear materials, plastics, polyurethane fibers and polyurethane coatings, greatly extending the service life of the products.
You are always welcome to contact us for inquiries!
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Email: yihoo@yihoopolymer.com
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Post time: Nov-22-2021