Carbon Fiber Yellowing

1 min. readlast update: 09.07.2022

To give some background; our carbon fiber is produced by soaking sheets of pure 3x3 twill carbon fiber fabric in epoxy resin. The resin we use is the highest grade available in terms of UV stability and temperature resistance. Our epoxy is rated 30 deg. higher than most use on carbon fiber automotive components. We also use a hindered amine light stabilizer (HALS) to prevent UV yellowing.

Unfortunately all epoxy is susceptible to yellowing under high temperatures. The engine bay in the Veloster N can reach some pretty extreme sustained temperatures, especially on the top side of the intake system, due to tight fitment of the turbocharger and the sloped hood. Heat tends to concentrate in the intake area and, as such, a chemical reaction occurs in the epoxy. The exact process is a bit complex, but essentially the sustained high temperature leads to oxidation of a carbonyl-group in the resin, and this oxidation turns yellow.

This is all a long winded way of saying that this is definitely normal, but we understand that it can be a bit of a shock to see it turning golden-yellow! 

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