colouring pigments and curing temperature 2

[niksmith]

Do the colouring pigments used within a thermosetting resin have an effect on the curing temperature or on the quality of polymerisation which occurs .
I have observed that some colours like red when present in the resin cause the polymerisation to occur to a lesser degree than in a resin which is without any colouring pigment .

Can someone please help me on this or point me to some site which can help me out on this matter .The curing temperature in both cases was the same .

Best Regards,
NIK SMITH

 

[Demon3]

They certainly can have an effect. As one example materials that cure by free radical mechanisms (unsaturated polyesters etc) are affected by such additives if they influence the radicals. For example pigments containing copper or iron can affect radical stability.

It is also well known that fillers and pigments can adsorb and thereby deactivate suring agents in some thermosets. For example sulfonates, carboxlates and amines are readily adsorbed and this will alter the curing rate and properties of the final product.

Typical ways to avoid such problems are to precoat the filler with something inert. Ciba sells epoxies that can be used to deactivate iron containing pigments and fillers.

 

[niksmith]

Thanks for the reply ,Demon 3. I am interested in the effect of the pigments on the polyester resin curing .

Do you mean to say that the epoxy sold by ciba is used to coat the colouring pigments in order to deactivate them . In that case will the pigments still give the colour which they are intended to give once added to the polyester base ?

 

[Demon3]

Yes, even after coating you will get the intended colour but without the interactions with the cure reaction.

 

[niksmith]

Demon3 ,can you please provide the link that will guide to the ciba site with this product which can used with the pigment?

Thank you,
Nik Smith

 

[patprimmer]

Try typing CIBA pigments into google.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[niksmith]

Sorry ,but searching using CIBA pigments into google gives me a whole lot of information but I am not able to find this particular kind of resin . It would be easier if someone could tell me the term CIBA uses for such resins .

Sorry to keep pressing on the matter .Please bear with me .

Best Regards,
Nik Smith

 

[patprimmer]

http://www.cibasc.com/index/search.htm

Took all of 2 minutes to find

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[niksmith]

Hi Patprimmer ,

I understood that you are being sarcastic ,but your link takes me to the CIBA search engine which I already checked yesterday . I used the words pigments ,carrier resin ,epoxy resin to block retarding action of colouring pigments etc etc but couldn't come up with anything substantital .
I hope you understood now .

Kind regards,
Nik Smith

 

[patprimmer]

Go there and try typing in saturated polyester

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[niksmith]

thanks for that tip .it does seem that the technical name for the kind of the resin is ' metal deactivator ' .
I hope this is what demon3 was implying as well .

Will post the results once I make some trials .Presently I am in the process of acquiring this deactivator.

Best Regards,
Nik Smith

 

[Demon3]

Hello,

Sorry for the delay, I have been away at a conference. I looked for the epoxy deactivators that are used for talc containing iron and I didn't find them at Ciba's site either. There are other deactivators like Irganox 1024 which are antioxidants that act by adsorbing to the metal site, e.g. iron or copper. They are used in PE cable formulations where the copper adversely affects the long-term stability of the cable. However, I suspect that these are not appropriate in your case as they neutralise free radicals and may therefore interfere with any free-radical curing.

 

[niksmith]

Demon 3 ,good to see that you are back .Hope the conference went well .
From what you have explained lastly ,it does seem that the metal deactivator will have an effect contrary to what I am expecting . I made a search for the epoxy deactivator with other manufacturer but the term which crops up is again -'metal deactivator' .
Do let me know if there are some other ideas which I could try .

Best Regards,
NIk Smith

 

[Demon3]

OK. Things to try. I will assume that the red pigment is iron based and therfore interacts to retard polymerisation. In that case you can look for a coated pigment ot a non iron-based pigment (e.g. an organic pigment). Pigment specialists such as Clariant may be able to help.