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Material for Instrument Window

Material for Instrument Window

(OP)
We are currently working with a customer on an instrument cluster assembly.  Their design calls for a flat piece of plastic as the window in the front.  What materials are generally used for this?

Options we are exploring:
1)polycarbonate with anti-scratch coating on the outside with anti-fog coating on the inside
Pro: impact resistant
Cons: yellows over time, scratches somewhat easily

2)acrylic with anti-anti scratch on the outside and anti-fog on the inside
Pros: Scratch Resistant, does not weather
Cons: so far difficult to find someone that can anti-fog coat,  

What are the pros and cons of either option?  Is an anti fog coating needed(or used in industry) for a totally sealed unit?  I have talked to suppliers and a lot are saying it is tough to get an anti fog coating to adhere to acrylic.

RE: Material for Instrument Window

As far as I know acrylic is always used unless there is a potential head impact situation. This is for reasons of optical clarity, scratch resistance, resistance to some very commonly used personal care chemicals and resistance to UV light and cost.

I never saw a requirement for anti fog.

With the heat generated from the instruments, I never saw fog as an issue.

Regards

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RE: Material for Instrument Window

(OP)
yeah, it seems our customer is more accustomed to glass and is new to using a plastic material for this.  

I am not sure about the anti-fog either, as its a sealed unit with a large PCB in it so it should generate a lot of heat.  

I have not yet found a supplier that can coat acrylic sheets in an anti-fog coating, something about it won't adhere properly.  I have talked to people that anti-fog molded components, but they said you have to match the right acrylic resin to the anti-fog coating in order to get proper adhesion.  

Is there anywhere else i can find information on what is normally used for this sort of thing?

RE: Material for Instrument Window

Extra con for polycarbonate: low chemical resistance

I don't think yellowing would be that much of a problem as long as you work with the material supplier on an appropriate grade.

Extra con for acrylic: low fracture toughness


Regards,

Cory

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RE: Material for Instrument Window

(OP)
does anyone have any other thoughts on this?

still unable to find a supplier that can supply acrylic with an anti fog coating.  The customer is currently using a polycarbonate with an anti-fog coating(or so they say...) on the inside, and that is why they asked for it.   

And yes, from those who i have talked to already, it seems PC options would not really weather with the new grades and coatings available.  

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