How can I identify a polymer which has a UV stabaliser additive 2

[qbob]

Hi Guy's;
Im looking for a solution to the following problem. We are currently in the design phase of a new project which includes the moulding of an exterior component which must be UV ressistant. The problem is in identifying that the correct materila has been used during the moulding process. Idealy, we would like to find a method of quickly checking parts at various times during production. The material being specified is UV Durethan BKV 30 G H2.0 900116. The material supplier has stated that it could be checked via its melt flow index, thats fine for material varification on delivery but we would like to eliminate the possibility of moulding in the wrong material during production and be able to carry out checks along the way. Any ideas gents?

 

[patprimmer]

MFI is not at all related to UV stabiliser content. I am sorry to say your supplier has fed you a load of garbage.

If you have a method to determine copper content you will be able to relate that to the most common stabiliser used in nylons, although copper based stabilisers tend to discolour the resin so are only used on dull colours.

The pigment system used for colouring can also have a significant effect on the UV stability of the resin, well at least of the resin below the surface layer. The pigment can be checked with reasonable reliability by a spectrophotometer.

Regards
Pat
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[Demon3]

I'm not sure we're all on the same page here. My interpretation is that qbob is confident in the stabilization of the material but wants to make sure that it didn't get switched by mistake at his facility with non uv stabilized material. Pat is right that MFI is certainly not appropriate for that unless your UV stabilized grade has a dramatically different MFI than all other nylons you have in stock.

Your original comment about UV fluorescence makes sense to check whether your material is consistent. It won't tell you if there is the right UV stabilizer but it may tell you whether the your material has not been switched in house for something else.

UV diodes are really cheap and readily available, then I guess all you need are a light detector (probably with a filter so you know you're detecting the right wavelength) and an alarm or printout. I imagine an internet search may turn up something like that off the shelf.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Pud]

We just read the grade number off the bags the stuff comes in.

The rest is good housekeeping and some sort of system.

This requires staff being able to read, of course.

Cheers

H

http://www.tynevalleyplastics.co.uk

 

[Demon3]

I once worked at a bus station in the US during my summer vacations as a student. Some mistakes happened because one guy could not read. He used the fuming sulfuric acid toilet bowl cleaner on the taps / faucets. We couldn't work out why they needed replacing every few months!

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Pud]

Demon3:

You mean you did not have titanium taps? Sheesh, what cheap skates!

H

http://www.tynevalleyplastics.co.uk

 

[Demon3]

My Dad was the manager. He told the guy "don't use Bowl Aid on the faucets" and the guy promised not to. After several months and a thousand dollars in new faucets my Dad asked him, so what are you using on the faucets and he merrily replied, "oh, I use that stuff that fumes". That would be Bowl Aid, contents concentrated sulfuric acid, takes the chrome right off and down to the brass. Expensive chemistry lesson. Nice guy, just couldn't read. Never thought to ask.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[patprimmer]

Harry

It takes staff that can read, want to read and will read and then care enough to actually want to do it right.

Also occasionally the grade numbers can be only very slightly different, like Akulon K222D Wt UN0189 and Akulon K222D Wt QN0189. Same white masterbatch but different additive levels for button white and opaque electrical switch white. Technically the hopper boys mistake but really pretty easy mistake to make.

If it's Durethan BKV 30 GH2.0 900116 vs
Durethan BKV 30 G 900116 and both were in stock, that would be a potential for error that I would worry about

Staff that are prepared to work as a hopper boy who could also be depended upon to reliably differentiate at that level of detail are rare.

If I had both those in stock, I would personally place at least a days supply of the correct material beside that machine every morning.



Regards
Pat
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[patprimmer]

Oh

If I remember correctly, Bayers colour codes that start with 9 are blacks. This might mask UV fluorescence.

Regards
Pat
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[qbob]

Hi Guy's

Back after a well earned but all to short Xmas break. First of all thanks for all your replies!

Demon3 is spot on in the interpretation of the problem. The issue is one of checking that the finished componant is of the correct material. And Pat, yes the material is black. From Demons comments, am I correct in thinking that if I pass the finished part under a UV light it will detect the presence of a UV stabalising additive within the material

 

[patprimmer]

The black will kill the fluorescence from UV stabiliser in the presence of UV light.

Regards
Pat
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[qbob]

Thanks Pat;

Looks like this may be more difficult than I thought

 

[Demon3]

My guess is that the UV detection method will still work. The carbon black will not be able to block all the light before it gets out and to the detector.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[qbob]

Just a quick up date guy's'

Ive been speaking to a new material supplier who appears much more helpful. They have stated that they already do something similar for another customer in china by mixing an additive to the base polymer. They are now speaking to thier supplier of the additive who has already confimed that it can be done with black polymer but the quantity of additive reqired may be prohibitive due the cost.

Ill keep you posted.

 

[patprimmer]

Maybe I missed it, but am I correct in presuming that you use two grades of 30% GF nylon 6 black, one stabilised and one not stabilised.

If so can you use the UV stabilised grade in all jobs.

If you must use both, can you at least use different suppliers so the bags look obviously different and the trade name is different. Failing that can a BIG colour coded patch be attached to every bag as it arrives from the supplier. Can one be in bulk packs and one in 25kg bags or whatever.

Regards
Pat
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[Demon3]

Pat's idea to use only the one grade, the UV stabilized grade is a really nice solution. Normally a UV stabilized grade might cost a little more but you should get a discount for buying a large amount of one grade instead of smaller amounts of two grades. Thus, the change may not cost you anything!

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[patprimmer]

It costs potable water and food contact but that is not likely an issue with GF nylon.

Price premium is typically $0.05/Kg or less.

Regards
Pat
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[qbob]

We have several grades of GF material ranging from 30 - 60%, all black. This will be the first UV stabalised material we have used. The identification of incoming material really isnt an issue, its ensuring that the correct material has been processed. With the best will in the world mistakes are made. We have had this on more than one occasion when the wrong grade (%) has been used and not noticed untill failure in the field (very expensive). So the hope was that we could carry out simple hourly checks during production, ie pass a part under UV light, in order to sleep at night. I like the idea of using UV stabalised material for all jobs and will investigate costs. We have had our original supplier come back to us with a check which can be carried out on the raw material and moulded part by means of a fluid indicator using an ethanol/water mixture, which Im looking into

 

[patprimmer]

Obviously glass % can be checked by part weight.

Regards
Pat
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