silicone in automotive industry?

[aart2]

hello, my name is aart schmid and i am working on a door sealing device. our customer produces doors and he also sells to the automotive industry. he states that silicone is unacceptable as a material because the automotive industry doesn't accept this material in the production environment (painting).
our silicone supplier states that after post curing silicone rubber the volatile molecules are fixed up to temperatures of 200 deg Celcius.
is this good enough, or isn't it?
Hope someone can help me,
Aart

 

[Chumley]

As far as painting goes silicone doesn't bond well with paints used in automotive applications. That would cause corrosion problems at any point where metals are joined as far as creating a structural panel then painted after fabrication. When silicone out gasses during the cure it can discolor or etch the surface of some glossy paints.

Are you talking about using silicone as a door/window sealing gasket or some other sealing "device"? It's unclear from your post what the purpose of the device is and how it is used.

Chumley

 

[aart2]

Well Chumley, first of all: thank you for replying.
I will try to explain the application of the product:
We make a sealing device for fire and smoke-prevention doors. These doors are used in all kinds of environments. One of the environments in which it will be used is in the automotive industry. Our customer produces these doors.
So the product will not be used in the cars, but in the factory buildings.
I want to find some inside-information from the automotive-industry, because one of the requirements is that the materials used have to be accepted by the automotive industry. It is (too) easy to say that we should't use silicone rubber (like our customer does), because the temperatures during the testing of the smoke-prevention doors will exceed 200deg Celcius, and, unless we use silicone-rubber it is very hard to find a material that can withstand these conditions.
This is why I want to know if post-cured silicone rubber is an acceptable material according to the automotive-industry?

 

[rhc]

Hi aart2. My understanding of silicone elastomers and paint is that even a minute amount of rogue silicone plays havoc in a paint shop. The paint tends to form "fish eyes".
Testing a silicone elastomer sealed fire door anywhere near panels that later are to be painted probably is not a good idea.

 

[JonnyRochester]

Petrolium melts silicon real quick.

Sometimes they add silicon to paint to make it more flexable, but also have to add something else so it won't go funny.

 

[aart2]

Well OK, but my main goal is to find a sealing material with certain properties (hardness app. 50-70 shore A, maximum service temperature 200 deg Celcius etc, etc)which also is accepted by the automotive industrie to be used in the factories.
The problem in using silicone materials is that the versatile molecules that evaporate from the material can cause problems in area's where electronic circuits are made, or in area's where parts are painted.
What I have heard is that there is a method to postcure silicone, in order to make sure that no versatile molecules will evaporate. (Philips (consumer electronics) seems to use this type of silicone in electric razors.)
I want to find out if this postcured silicone can be used in the automotive industry (more specifically: area's where electronic circuits are made and area's where parts are painted).

My idea by submitting this thread was to get reactions from people within the automotive industry who have to do with painting and/or electronic area's and who are able to tell me if they know something about this material and if it's used more often in the industry,
Aart

 

[Speedy]

aart2,

If you properly post-cure the silicone then you should not have problems with volatiles.

I worked on a project previously where an injection moulded silicone product was causing skin reactions. It transpired that this was due to inadequate post-curing. We increased the time in the oven ensuring that the products were evenly spaced apart. This solved the problem.

Hope this is of some help.

Speedy

 

[Glueguy]

Silicone has gotten a bad name due to its curing process. Most silicones free acetic acid, which will prevent painting, corrode brass & copper, and a few other minor effects. If heated over 150F degrees most will release formaldehyde fumes. Most Silicones will degrade catalytic devices used to burn unused VOC's. If auto industries are leary, I can't fault them. Are you limited to silicone or do you sell an equivalent product in a urethane base??

I hope I've helped. John Schrock

http://www.glubie.com

 

[aart2]

dear all,
this problem is not a problem anymore.
Our customer has exaggerated the requirements for the material a little. After doing a little testing ourselves we have found that temperatures will not exceed 160deg C, and the product doesn't have to meet any strength requirements at this temperature anymore: the only important thing is that the door still prevents draught of (hot) air, and can be opened without the use of tools.
So now we can use a TPE sealing profile.
Thanks to all who took time to help me,
Aart

 

[gluesniffer]

in my experience even the vulcanised silicones can transfer at least 16 atom % pdms Poly dimethyl siloxane just on room temperature contact. Which is enough to affect the wettability of any substrate to which you want to paint or bond. so there is a room temeperature issue.

If you were only worried about the high temperature issues ie during a fire I would suggest that there would be more pollutants in the atmosphere by then for your customer to be worried about form all the other combustable materials.

A way around the problem would be to try a material called Viton which can be used to either coat the exisiting rubber or just make the seals out of this material.

 

[poepatterson]

THERE IS A GASEOUS DEPOSITION THAT CAN SEAL MOST ANY ELASTOMER INCLUDING OUT GASSING. AUTOMOTIVE FOLKS USE A LARGE AMOUNT OF SILICONE PRODUCTS.

JOHN PATTERSON