Re: electrical hardening

Date: Tue Feb 01 2000 - 17:35:08 EET

In a message dated 00-01-31 18:03:08 EST, you write:

<< has any one ever heard of a liquid material that hardens with an electrial
 current or a plastic material that will float in water.
Dear Mr. Irvin:

There are a number of electrorheological fluids that harden selectively with
application of electrical current. Methods of RP using them have been
investigated, but no practical application has resulted. There may be better
applications for the technology in manufacturing of things like shoe soles
that require different properties in different areas of the part. There are
patents on this stuff and a considerable body of lit. Look under inventor
Ronald P. Reitz.

Most garden variety engineering plastics have a sp g right around 1. I
believe that I have seen some numbers around 0.9, but this is something
you'll have to look in a plastics handbook for. I don't remember where I saw
that, but it's not going to be a common material. Obviously plastics that
have been modified in structure, like foams, have a much lower density and
will readily float. There are other ways of modifying structure, or alloying
plastics with other substances that might result in a floating thermoplastic,
so it depends on your application.


Ed Grenda
Castle Island Co.
19 Pondview Road
Arlington, MA 02474 USA
781-646-6280 (voice or fax) (email)

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