Do you know the cause of yellowing of nylon fabrics?

White or light-coloured textiles made from nylon and elastane fibres and their blends are particularly susceptible to yellowing, which can occur during the dyeing and finishing process, in storage or hanging in shop windows, or even at home. There are many possible causes of yellowing, such as the fibres themselves, which are prone to yellowing (material-related), or the chemicals used on the fabric, such as residues of oils and softeners (chemical-related).
Often further analyses have to be carried out to find out the causes of yellowing, how the processing conditions are set up, which chemicals should be used or only which ones, what influences interact to cause yellowing, how the fabrics are packaged and stored etc.
We mainly focus on high heat yellowing and storage yellowing of nylon, polyester and elastane blends such as Lycra, Dorlastan and Spandex.
Gas fading:
--NOx fumes from sizing machines
-NOx fumes from storage
--Ozone exposure
Temperature:
--High heat moulding
--High temperature moulding
-Elasticiser and high temperature treatment
Packaging & Storage:
--Phenol and amine related yellowing (Light):
--Fading of dyestuffs and fluorescent essences
--Degradation of fibres
Micro-organisms:
--Damage by bacteria and moulds
Miscellaneous:
--Interrelationship between softeners and fluorescents.

Translated with DeepL.com (free version)