On Saturday, December 9, 2000 3:40:23 AM UTC-5, Michael Shell wrote:
Asimov wrote:


The answer is that the plastic breaks down when in contact with vinyl.
I've experienced this problem a number of times when leaving guitar
patch cords on top of plastic equipment for a length of time.

This is a real, and very serious, problem with lots of products.
Vinyl seems to emit a gas which will react with and destroy many substances.
A good example is those vinyl book covers which have turned the outside of
many a book into eternal sticky mush.

I thought that it may be a possibility that the keypad is reacting to the
green
protective PCB coating. The problem with that theory is:

1. The green coating is not degraded in any way.
2. Silicone rubber (and oil) is extremely inert. You have to work to
find something that will pick a fight with it.

It seems from the URL I cited, that silicone oil is trapped in the polymer
matrix during the manufacturing process. If steps are not taken to expel it,
it will leach out years later. Pressure points, which are highest at the
contact areas, tend to squeeze it out. Heat accelerates the process too.
Also, gravity
will tend to work the oil downward. Note that the idea that a soft rubber is
carrying a liquid within it is, in my opinion, creepy.

See a new thread: "my list of most hated design choices"


Mike

Very interesting about Silicone and Vinyl.
Though I find myself cleaning my Bravia remote every few months and this is after putting up with sketchy behavior for a month. The area that is affected the most on any of my present or past remotes seems to only be the Volume and Mute buttons which are used more than any of the others. Don't like listening to the overly load commercials. So maybe there is the rubbing of silicone against vinyl that is in play here. ???

Vinyl seems to emit a gas which will react with and destroy many
substances. A good example is those vinyl book covers which have
turned the outside of many a book into eternal sticky mush.

It's not a gas, it's the plasticizer that keeps the vinyl flexible. I had the
same trouble with textbooks that had a kind "plastic-coated-board" covers. And
I've seen the plasticizer in patch cords attack plastic surfaces.

I am no aware of any plasticizer in the rubbery contacts of remote controls.

I've taken apart the keypad for my Ford. There is a silicone goo in it, which
I assume is there to prevent rust or corrosion.