Coloring & UV stabilizing ASA resin for use outdoors

[PFHF3]

We have had a part molded for us successfully, for several years, using LG LI-912WH which is a pre-colored white ASA. Our lot sizes are small, approx 350 Kg, Our molder is now telling us the pre-colored resin is no longer available from stock and will require a 3000 Kg min. lot size and a long lead time. They say they can get 500 Kg of natural ASA from stock, but tell us they have had trouble in the past when they colorize natural resin white, the parts turn yellow when exposed to UV. Are there effective UV stabilizers and pigments the molder can add to increase resistance to UV and minimize yellowing?

 

[Demon3]

Hello, I was in charge of ASA technical matters at BASF (their ASS is called Luran S) for some time so I know what you are describing.

1. ASA comes with different UV stabilization packages, i.e. antioxidants so while ASA is UV stable, some grades are far better than others
2. White means adding TiO2, in fact the UV stability of ASA is not that great without it (it helps block the UV), but if you have the wrong grade of TiO2 results will be terrible because some kinds of TiO2 generate free radicals in UV light which cause yellowing and rip the polymer apart giving bad mechanicals too.

So the answer is to try and find someone who can supply you with smaller lots (try BASF, Hitachi and others) and to make sure the stabilization package and TiO2 type are correct in type and concentration. If you have some of your old good material you can have a lab extract the stabilizers to tell you the type and amount in there (e.g. try

http://www.stabilization-technologies.com).

You can color and UV stabilize the natural ASA if you work out the right antioxidants to use and the right TiO2 type to add. TiO2 experts from DuPont, Huntsman or Kronos can probably advise.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[PFHF3]

Thanks for your help. Just so I am clear, do we need a UV stabilizer, antioxidants, and a TiO2 intended for use outdoors?

 

[Demon3]

Yes. You will need a hindered phenol type and a hindered amine type antioxidant plus a couple percent TiO2. Higher molecular weight antioxidants stay in the polymer better (not as easily washed out by rain).

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com