Confused By Apparent Slip Agent in ABS

[Chaldaean]

Hello All,

We are pad printing a company logo on some ABS Bayer Lustran 348.

We are having trouble getting the pad printing to stick to the part (after the ink cures, it can be removed with a fingernail) and we have identified (via FTIR) a fatty acid most like Erucamide. According to Bayer, this "slow bloom slip agent" is not an ingredient in their ABS base material.

To combat this Erucamide (which propagates to the surface of the part over time), we are wiping all the plastic parts with Isopropyl Acetate prior to printing in an attempt to remove the surface contaminant.

Do any of you have experience with Ercuamide (sources of and techniques for removing it)?

Thanks!

- Josh

 

[Demon3]

You won't be able to remove it.

How did it get there is Bayer didn't add it? Is that a component of for example your mold release spray?

Be careful wiping ABS, solvent can destroy it via environmental stress cracking.

First check to make sure what your mold release is. After all, that is a chemical designed to prevent adhesion.

Get another grade from another company, Dow or BASF.

There are additive that improve adhesion, contact for example Cray Valley (Jeremy Austin is my contact person there).

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Chaldaean]

Dr. DeArmitt, thank you very much for your reply!

Firstly, to answer your question, we are a medical device manufacturer and mold release is not permitted on our product; the "no mold release" statement is noted on our drawings (I even have a signed letter from the president of the molder we work with that states no mold release is introduced).

Yes, I am stumped where this surface contaminant is coming from. I did query lustran-polymers.com and they relayed that Erucamide is not within their formula. They did state that Lustran ABS 348 contains an external lubricant "AWAX" (a.k.a. N’N Ethylene bisstearamide); perhaps that is what is giving us the trouble.

Your advice to try another supplier makes sense and I will definitely look into additives that promote adhesion (I assume these additives are mixed in with the base material).

Again, thank you very much for your reply; I appreciate it.

 

[patprimmer]

Are you adding a colour master batch.

Unless it's a smaller shop with a CEO who works also at shop floor level regularly, despite what company CEOs like to think, once it gets down to shop floor level, staff do break procedures at times if it makes life easier for them.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[prdave00]

I assume your nit using reveling pellets, but is this virgin resin from INEOS/ Bayer or is it being compounded to add pigments or other fillers/additives. I was curious and it looks like Erucamide is a typical additive in LLDPE. Is it possible there is some cross contamination from a previous molding job? Maybe the hopper wasn't cleaned or the system not purged?

 

[prdave00]

Sorry. Start of first sentence should have been "I assume you're not using reground pellets".

I also realize this might be what Pat was getting at.

 

[Chaldaean]

Pat, yes, colorant is added to make an off-white color. The Certificates of Analysis from the plastics compounder (a company called Compounding Solutions out of Lewiston, ME) note that the final product is 0.999% colorant (I believe it is four different pigments mixed together).

I'll keep your advice about CEO vs. Shop Floor in mind as well, Pat. A site visit to the molder is an option.

prdave00, yes, as these are medical devices, regrind is not permitted. Your thought about cross-contamination in the hopper is a great one and I will follow up on that.

I would estimate that our losses in production scrap and time spent on this ink adhesion issue are in the tens of thousands of dollars at this point. We are very interested in finding root cause and I thank you all for your help.

 

[patprimmer]

My tip is that it will be a diluent in the pigments used for the colour or as a component in the colour master batch.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Pud]

My money's on Pat's horse.

http://www.tynevalleyplastics.co.uk

 

[Demon3]

I agree, the additive is probably in the color masterbatch. Masterbatchers love to add that as it helps processing and because it's so cheap so they can make lots of money selling a masterbatch full of cheap waxes. I've seen masterbatches with 30-50% wax.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[prdave00]

Chaldaean,

Let me know what you find out. I'm interested since the mold shop we contract with for our some surgical instruments has used Compounding Solutions for their needs (including adding barium sulfate to Lustran). I guess there is nothing barring them from using pigments/additives containing fatty acids (unless CFR Title 21 explicitly prohibits it), but it would be nice to find out what's in the compounded resin to also support biocomp data.

I had some parts shot from natural Lustran 348 resin. The attached file attempts to show the off-white color of it against a white background. I'm also aware that INEOS offers a Sno-White color. Have you considered switching to a resin that isn't compounded by another supplier? I guess it might be too late if your trying to save an existing batch.

 

[Demon3]

Adding any filler to ABS results in horrible mechanicals. I've tried it and even fine, well dispersed filler results in a huge drop in impact resistance and elongation to break. Be careful.

The effect occurs in all ABS but in some types it's less of a problem than in others. I just presented on this very topic in a webinar yesterday (for SpecialChem).

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Chaldaean]

Pat, Pud and Dr. DeArmitt, thanks for opinion on the potential diluent; much appreciated.

prdave00, I'll surely keep this thread updated with the findings and thanks for the photo of the natural Lustran 348. I did see that INEOS offers the "sno white" color and this would be a good option to relay to our customer once the ink adhesion benefits are proven out.

I'd be very interested in shooting some samples with a resin that isn't compounded (the molder that we work with has also said they would support this activity).

Would I obtain this sno-white Lustran 348 directly from INEOS or another supplier?

Dr. DeArmitt, concerning the mechanics of the parts, we ultrasonically weld them together after pad printing, so I am interested to see how the weld results of our current compounded material compare to unadulterated, un-compounded material.

Again, I thank you all for your time and expertise. This is great information.

 

[Demon3]

Filled ABS of any type will have very poor properties compared to ABS without filler.

Pigment in the ABS acts the same as filler and lowers the impact resistance significantly.

Are you interested in "snow white" ABS because it would be pure, without additives? In that case don't bother. Pure, uncolored ABS is a beige colour, not white. Any white ABS you buy has had TiO2 pigment added and so it could have your unwanted wax present because TiO2 is often added in a masterbatch containing waxes and dispersants.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Demon3]

If you want ABS without color or additives ask for "natural".

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[prdave00]

I've always had the mold house source the resin except when we were molding in house, but then I was buying compounded resin (typically from Foster Comp). Our ops guy referred me to Ashland Chemicals (

http://www.ashland.com/)

if you want to order a 50 lb bag or you could call INEOS and have them either refer you to a distributor or a local sales office.

You should heed Chris's warning and make sure that fatty acids like Erucamide aren't being introduced in the compounding of their "sno-white" colored offering. There probably is a very good chance that pigments like titanium dioxide (TiO2), Ti-Pure R-101 for example, are added. I say better to be safe than sorry, so I would call the INEOS and confirm specifically about it. That resin may pass the "medical grade" test but not the pad print test.

Per their data sheet: "Lustran® ABS 348 resin is an injection molding grade of ABS (Acrylonitrile butadiene styrene). It is a medium impact, high-gloss ABS, available in natural (000000), snowhite (012002), and selected colors."

 

[Demon3]

Also note that even pure ABS with nothing added can contain lots of surfactant that can ruin your adhesion. That's because the impact modifier is made by emulsion polymerization where you add surfactant like stearic acid or similar.

I know that as I worked on that topic for some years at BASF who make ABS.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry