yellowing component in Polyster resin

[niksmith]

A problem which we are presently facing is that orthophthalic polyster resin purchased from two different locations are having two different colours .One is yellowish whereas the other tends towards green . Due to the big difference in the colour the products made from these two locations though identical in process are looking tone wise different . The supplier is at a loss as to why such a difference exists between their polyester an that from another supplier .

Can someone suggest the possible components to check which may be responsible for the resin colour moving towards green .

The resin comes already mixed with stirene and it is in a ratio of around 65 ester to 35 styrene.

Thanks in advance ,
Nik Smith

 

[Demon3]

Actually I don't know the answer. One possibility is that it is not the monomers themselves that are giving colour but the stabilisers (antioxidants) used to prevent polymerisation during transport and storage. Those can give colour. A test would be to pass the monomer through an column from e.g. Aldrich (

http://www.sigma-aldrich.com)

that will remove the stabilisers. Then you can see if the colour remains or not.

 

[TechQA]

1stly, if the brand or grade of the polyester resin are different, it is definitely different unless one of them stole the recipe from the other. I am not well-versed in polyester but doing QA in a colouring house, i am aware that different resin makers have different formulations. They add in different pigments or even spices into their polymerisation stage. This explains the differences in color tones and the 'smell' which you experience during processing.

Demon3 is partly correct on the antioxidants involved in the resin polymerisation. Colours moving towards green could only mean insufficent antioxidants or the material is kept too long or the storage conditions is poor eg humid, wet or temperatures too warm. Hope this helps.