Letter 18069

ABS vs Other Plastics  

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Hello,

I just began to study some of the issues of plating plastics because next year I will do graduate studies (diploma) in Plastics Plating. I have found many papers of plating ABS but a few plating other plastics (PP, PC, PA66). Does ABS have advantages to be plated over other plastics?

Gustavo Quintanar
- Monterrey, N.L. Mexico

Hi Gustavo,

Whereas I know zilch about plating platics, I know a little bit about ABS.

ABS should have better impact properties than most other plastics (except Pe) and is eminently cementable.

Unlike PVC, for instance, you can, if you know how, edge join ABS using cement to achieve high strengths.

I'd imagine, too, that its coeff. of thermal expansion is far less than PP or Pe. In other words the chances of a plated section 'delaminating' should be less. Go check your books.

It is OK for aliphatic solvents but not, like PP, the polar solvents. It's house useage as drain pipe is excellent..

In mining applications they used a MINELINE pipe which is made of ABS ... and the fittings are CEMENTED together. Why ABS? Because of its impact strength and good abrasion resistance.

Freeman Newton - White Rock, B.C. Canada

The reason that most of the processes relate to ABS is because ABS can be etched chemically giving good keying and therefore adhesion. The "B" butadiene component of the ABS is microetched out with chromic/sulphuric and when the plating is pulled off in adhesion testing plastic comes away with the electroplate.

Geoff Whitelaw
- Port Melbourne, Vic., Australia

ABS is acrylonitrile-butadiene-styrene. It is the workhorse of the plastics industry and is used in a myriad of parts. The beauty about it is that it is cheap and easy to metallise. Metallisation is achieved by etching it in chromic acid; this dissolves out the butadiene particles to leave a micropitted surface. The etchant also chemically reacts with the surface of the polymer to give chemically reactive sites. Other chemical etchants, such as permanganate are also known and can be as effective as chromic acid, but they are not as universal. The surface can then be easily metallised by conventional plating on plastics processes. Other plastics can also be treated in this manner and it is possible to get good metal adhesion. The polymers you mention (PP, PC and PA66) are a mixed bag. PP is very difficult to metallise, although it can be done; however, adhesion is not brilliant and it has a large coefficient of expansion,so delamination can be a problem, especially with high thermal cycling. PA66 is a nylon and readily adsorbs water; this makes it dimensionally unstable and not very suitable for wet processing; it also runs the risk of adsorbing chromic acid and this will not do any good to the products long term integrity. PC can be metallised by the above method with a great deal of success, but it is expensive (relatively). Other good plastics are MIPS and HIPS, acetal, etc. However, it is essential that before metallising plastics you are sure the plastic is fit for purpose in the final product. It is also possible to activate plastics by more sophisticated methods such as plasma etching.

Trevor Crichton R&D practical scientist - UK

Dear Sir,

ABS was not only one of the first polymers to be metallized but it is also one of the easiest. It's full name is [A/crylene B/utadiene S/tyrene ] as you see it is acopolymer which contains rubber and that make etching very easy and so the adhesion will be good and that is the key in any satisfactorily plating technique.

Thanks,

RAAFAT ALBENDARY
- CAIRO, EGYPT

Hi, Gustavo,

If you are to graduate on Plating On Plastics(POP) then you should already be aware that ABS is perhaps the only plastic readily available that has three components, one of them (butadiene) is a sort of rubber, the other two are plastic. This rubber is discretely and randomly dispersed in the form of round particles in a matrix formed by the other two components. When you immerse it in the porper chemical only those rubber balls are dissolved leaving tiny rounded pits over the plastic part. Maximum adherence is obtained at those pits where the orifice is smaller that the inside. This creates a mechanical counterlock when metal builts inside them. No other roughening or etching can produce this geometry.

Guillermo Marrufo
Monterrey, NL, Mexico

How can I test to see if the material is ABS or HIPS plastic
thank you,

John
working in shop selling finishing touch - Morristown, New Jersey

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