ABS: how does working temperature affect its properties

[Mendiriv]

We have made two series of ABS pipes by extrusion. On our second series material appearance result yellowish and more fragile. Our supplier says this is because they used a lower temperature for the second lot:
* is it really possible that this happens to ABS under these conditions?
we don't think there was used other material than ABS as the flammability test says it is so, but we are suspecting our supplier might have used recycled material.
* what would ABS look like if it was recycled?
i hope someone can help us with this.
thank you very much in advance.

 

[Demon3]

ABS is made of SAN with particles of polybutadiene rubber in it to add impact resistance.

The SAN is heat resistant and not affected by recycling.

That type of rubber is unstable to heat and UV light. If you took ABS that had been used in an application and recycled it, it could be brittle and yellow.

Recycling fresh scrap from extusion, that has not been used in an application should not be too bad because the rubber survives extrusion well. I have done this exact experiment myself when I worked at BASF. You might lose up to 10% impact resistance by extruding twice in a row but it would not ruin the ABS.

If the ABS was contaminated with another polymer, that would make it brittle too. For example, if it was made from recycled material where the ABS still had some other polymers left in it.

If the rubber is ruined from oxidation, you could see it by FTIR spectroscopy. Look for a carbonyl peak at around 1700-1800cm-1.

Hope that helps.

Chris DeArmitt

"Knowledge has no value except that which can be gained from its application toward some worthwhile end."
Think and Grow Rich - Napoleon Hill

 

[Mahlo]

ABS can be used between ?25 and 60 °C as its mechanical properties vary with temperature. The properties are created by rubber toughening, where fine particles of elastomer are distributed throughout the rigid matrix.

http://www.mahloamerica.com

 

[patprimmer]

Embrittlement temperature and heat deflection temperature have nothing to do with thermal degradation in processing. The OPs question related directly the effect on properties of processing conditions or the use of regrind.

I agree with everything Chris says, but would like to expand a little.

As ABS is a terpolymer, the various components can be adjusted to give substantially different properties. Also there are several manufacturing methods for producing ABS that do have an impact on the range of properties obtainable. From memory, high temperature grades are rated at 90 deg C and can be used at higher temperatures for short term low load.

The probles the OP is concerned about could be caused by:-

Incorrect grade of ABS.
Useing regrind of low quality.
Contamination in material.
Excessive shear in processing.
Overheating during processing.
Different colour or masterbatch formulation.


Regards
Pat
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