Thermally and Electrically Conductive Elastomers

[jared4jackie]

Just doing some brainstorming...If you were to make an elastomer thermally and electrically conductive, how would you do it? Thanks.

 

[TheAnswerGuy]

jared4jackie,

I guess that I would try mixing your material copper or aluminum powder.

You will have to do a lot of experimenting since, the metal will have an effect on the elastomer.

I have molded ABS w/aluminum dust for a temperature sensing bulb. Sorry I don't remember the percentage. But it worked!

 

[kenvlach]

1) For a little bit of conductivity (e.g., for anti-static), add polar chemical compounds such as amines, quaternary ammonium compounds, phosphate esters and polyethylene glycol ester. Absorbed water will also help (although otherwise generally detrimental).

2) For a bit more conductivity, add aluminum flake, perhaps with carbon black or metal powder to provide some flake-to-flake connection.

3) For significant conductivity, you need conductive fiber (graphite or metal), plus metal/graphite flake or powder. Of course, you will lose some elongation.

For special purposes, aluminum-coated glass fiber has been used in FRP, but not in elastomers, to my knowledge.

 

[kenvlach]

Here is a source for conductive vinyl & silicone sheeting (with silver, Resistivity 0.001-0.002 ohm-cm, Elongation at Rupture 50%).
They also have conductive silicone caulking, Electrically Conductive Adhesives,Coatings and greases:

http://www.eccosorb.com/catalog/eccoshield/index.asp

 

[patprimmer]

Stainles steel fibres works very well at improving electrical conductivity at low concentrations (Like about 2%) in thermoplastics.

It might work for your application. It is horendously expensive. DSM have some technology in it's use

Regards
pat

 

[JimMetalsCeramics]

Such elastomers exist. They contain metal powders (e. g., silver) which are mixed into the pre-cure rubber before it sets. The outer surface may have to be removed if it forms a continuous rubber outer layer (intefacial segregation).

Of the companies that make these, here is one:

http://www.irmicrolink.com/zoflex.html

 

[kenvlach]

Intrinsically electrically conductive polymers (having a conductive backbone) are mentioned in a recent JOM article:
“Conductive Polymer Coatings for Anodes in Aqueous Electrowinning,” A.M. Alfantazi and R.R. Moskalyk, pp. 49-55. (July 2003).

http://doc.tms.org/ezMerchant/prodtms.nsf/ProductLookupItemID/JOM-0307-49/

[click on PDF for first page]
“This article discusses the potential application of electrically conductive polymers as protective coatings for permanent lead anodes employed in aqueous electrowinning processes. Also presented are results from a preliminary study of the performance of two intrinsically conductive polymers (polyaniline and poly 3,4,5-trifluoro-phenylthiophene [TFPT]) under mild copper electrowinning conditions as conductive and protective coatings on anodic surfaces. The laboratory results indicated that using lead alloy anodes coated with TFPT merits continued research.”

Polyaniline is unusual in that it is ~nonconductive when prepared in alkaline solution, but its conductivity increases by orders of magnitude when prepared at low pH.

“Table I. Conductivities of Some Conductive Polymers*
Polymer Conductivity (S/cm)
Polyacetylene 10²–10⁵ (stretched)
Polythiophene 10²–10⁴
Polypyrrole 10–10³ (stretched)
Poly(p-phenylenevinylene) 10³
Polyaniline 10–150 (heated), 10²–10³
Poly(2,3-ethyldioxythiophene) 10–780 (in nanopores)”

For comparison, metallic lead has a conductivity of 4.8x10⁴ S/cm.
I don’t know which of these are considered elastomers, though.

*Data are from ‘Electrically Active Polymers and Their Application,’ Mary E. Galvin, JOM, vol. 49, no. 3, pp. 52-55 (1997).

 

[shashak]

jared4jackie,

Please see my reply under Polymer engineering FAQ

faq334-704

Thanks!

 

[JimMetalsCeramics]

Despite the last posting, if you want maximum conductivity, micron level aluminum or silver powder will generally mix well and still provide good flexibility in a polymer. I've made such compositions in RTV silicone.

 

[JimMetalsCeramics]

How does S/cm convert to micro-ohm-cm?

 

[kenvlach]

S/cm is a conductivity unit, and micro-ohm-cm is a resistivity unit, hence, there is a reciprocal relationship.
Conductance in siemens, S, is the reciprocal of resistance in ohms (S = mho).
Conductivity units: S/cm = 1/ohm-cm, so S/cm = 10^-6/micro-ohm-cm