Polybutylene Terephthalate PBT with UV inhibitors

[rmetzger]

I'm exploring this for a possible outdoor use and wanted to get some feedback regarding this material when processed with UV inhibitors. I've seen examples used in automotive application but am unsure if the final product was coated with a paint or other material before going into service to make it suitable

 

[Pud]

PBT is one of the better outdoor materials.

You need to talk to one the zillion manufacturers.


Rgds


Harry

 

[patprimmer]

PBT is inherently fairly UV light resistant. Stabilisers and or UV opaque pigments improve it.

It can be used outdoors with quite reasonable life.

Regards

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[Demon3]

If you want really outstanding UV resistance then I suggest ASA (e.g. Luran S) it last years and years outdoors with no degradation of mechanics or discolouration. Find mechanical data for ASA at

http://www.matweb.com

for instance. In terms of mechanics it's like ABS only it's it contains a much more stable impact modifier than ABS does.

 

[Pud]

Demon3,

Have you got shares in BASF/or work for them?

Only you keep banging on ad nauseum about ASA whenever any UV stability query pops up?

You have not mentioned it's difficult to colour via masterbatches, has same poor solvent resistance as ABS, and (at least in the UK) is more expensive than PBT!!

Oh, and it will process slower than PBT....

Harry

 

[Demon3]

Lol, I have personal experience of ASA so it comes to mind when I know someone needs UV resistance. I have no experience with BT though. Actually ASA should be more chemical resistant than ABS due to the higher acrylonitrile (AN) content in the SAN matrix. That has been measured to be the case, at least for the ASA grades with high AN content. I am interested that you believe ASA will process slower than PBT, I thought normally semi-crytalline polymers like PBT take longer because you have to remove heat so that it crystallises.

 

[Pud]

Hi Demon3,

Perhaps this should be a different thread - apologies to the original poster but it's a bit relevant.....

Processing time is more related to the heat distortion temp - e.g. at what temp can it be ejected from the tool. In the case of PBT (and others!) this it quite a bit higher than the amorphous materials.

fyi, heat contents of some polymers:

ASA 402 J/g
ABS 369 J/g
PBT 283 J/g
PP 557 J/g
PE HD 800 J/g
uPVC 291 J/g

The HDT of PBT is much higher - especially if filled - so can be off the tool much quicker. The heat content is also less (all above for unfilled materials)

Of course, if the mechanical properties are sufficient, then UPVC is another (if not the best) outdoor material. Cheap too, even taking into account the high density.

Regards

Harry

 

[patprimmer]

Come on guys, play nice.

PBT will process considerably faster than ASA, and it does have very good UV resistance.

ASA has a very good reputation for outdoor use, because it has similar properties to ABS but much better UV resistance. ABS has very poor UV resistance, so I think ASA is sometimes overrated because of that comparison rather than a comparison to very good materials re UV.

I would never recommend ASA as a substitute for PBT because of the dramatical difference in many properties.

I posted something like this earlier, but it disappeared. I cannot believe it was red flagged and removed when the quality of the technical issues being disputed is considered.

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.

 

[Demon3]

Thanks for the input Pat. As I mentioned I've no hands-on experience with PBT so it was interesting to get your take on it.

 

[Pud]

Hi Folks,

No offence intended - more like tongue in cheek than foot in mouth!

Apologies to those offended.

Rgds

Harry

 

[Demon3]

No problem, it takes quite a bit to offend me