EN
The biggest shortcoming of epoxide resins is their yellowing under the effect of light. The resins which turn yellow easily are mainly the cheapest, universally available and widely applied epoxide resins obtained from dian and epichlorohydrin. Until now chemists have not been able to establish the mechanism of their yellowing, although it is well-known that this process depends largely on a chemical structure of resins, their kind and quantity of auxiliary substances (dissolvents, softeners, accelerators, hardening agents and conditions of hardening). A vast number of such products is offered on the market, some of which show very high resistance to yellowing, whilst the resistance of others is very low. The article mentions products with exceptionally high resistance to yellowing under the effect of temperature and also describes light fastness of some epoxide compounds made by Ciba-Geigy. Attention has been paid to the fact that improper hardening reduces light fastness of hardened resins.