Perspex or polycarbonate ?

[sgr143]

I'd like to replace the hinged plastic cover over the engine control panel in the cockpit. The current one is supposedly clear plastic but is so crazed that it's hard to see through. The panel is 4mm thick, about 50mm x 160mm, hinged (two hinges) on the top (long ) edge. Various companies offer plastic cut to size for not much dosh - but having nearly ordered a bit of perspex I was wondering if polycarbonate would be better.

( [edit] - checking their elastic moduli, PMMA is quoted as 2.4-3.4 GPa, and PC about 2.6 GPa, so from the stiffness point of view I should think there's not much in it. PC would be rather tougher, though.)

Thoughts?

 

[macd]

For that sort of application, I'd suggest there's little need for the additional strength of polycarbonate, and no need at all for its lesser scratch-resistance.
Note that Perspex is simply one of many brand names. Acrylic sheet is the generic.

 

[Minchsailor]

Perspex has allegedly better UV resistance than polycarbonate.

 

[Rafiki]

In the past I have dispensed with a hinged cover and instead used a small piece of that thick clear plastic you see used in warehouse doors that forklifts drive through. You can cut with a knife and screw into place using the same old screw holes. Many suppliers on ebay, and very cheap so buy twice or three times what you want and when it goes milky after 4 or 5 years cut another piece off and replace.
Andrew

 

[Seashoreman]

In the past I have dispensed with a hinged cover and instead used a small piece of that thick clear plastic you see used in warehouse doors that forklifts drive through. You can cut with a knife and screw into place using the same old screw holes. Many suppliers on ebay, and very cheap so buy twice or three times what you want and when it goes milky after 4 or 5 years cut another piece off and replace.
Andrew

What term or phrase would you use to search for this?

 

[macd]

What term or phrase would you use to search for this?

Vinyl, perhaps?
(The stuff used for, say, sprayhood windows is somewhat thinner than for the application Rafiki mentions but, I think, essentially the same stuff.)

 

[thinwater]

Strataglass, Reaglite, Crystal Clear, O'Sea.

These are clear vinyl window materials used in dodgers. IF you are going to mount with punched holes, go at least 40 mil. I suggest getting a scrap from a canvass shop.

 

[Robin B]

Crazing is caused by the tension releasing in extruded acrylic. Cast acrylic will have far less tension in it, so will craze lots less.
Extruded: much more even thickness; will craze. Cheaper and more uniform.
Cast: more uneven due to not coming out of rollers - quite a lot of difference in a big sheet; more stable and therefore less prone to crazing. More expensive.

 

[jwilson]

Mine is in a fairly vulnerable position. After the fourth replacement of acrylic/perspex after breakages though boots etc. kicking it, put in polycarbonate. So far so good.

My understanding though is that polycarbonate is much easier to scratch than acrylic, though far tougher. Spent some time years ago behind one inch thick polycarbonate, in an environment where bullets might just arrive.

 

[Robin B]

Yes, polycarbonate is easier to scratch but tougher, does not shatter. Will also go cloudy over time, even with anti UV coating although takes longer.

 

[Dull Spark]

I broke the hinge on mine and was about to buy a new hinge and acrylic sheet from Hindleu when I succeeded in repairing with araldite.

https://www.hindleys.com/perspex-clear.html

If you buy from them, please let us know the result.

Good luck!

 

[C08]

Yes, polycarbonate is easier to scratch but tougher, does not shatter. Will also go cloudy over time, even with anti UV coating although takes longer.

Yes my wheelhouse front window in UV stable, top quality Polycarbonate sheet went quite cloudy after only a couple of years. My side windows in Acrylic are still crystal clear.

 

[GHA]

Yes my wheelhouse front window in UV stable, top quality Polycarbonate sheet went quite cloudy after only a couple of years. My side windows in Acrylic are still crystal clear.

Fitted UV stable polycarbonate side windows in 2010 in Trinidad, a few tiny little star chips on the outside but no clouding whatsoever.

 

[C08]

Fitted UV stable polycarbonate side windows in 2010 in Trinidad, a few tiny little star chips on the outside but no clouding whatsoever.

Interesting - mine was Makrolen.

 

[Rafiki]

What term or phrase would you use to search for this?

Here is one on ebay:

https://www.ebay.co.uk/itm/Clear-Fl...=item3a6fab9ebf:g:tD8AAMXQBNlRgMYN:rk:18:pf:0

 

[LittleSister]

Note also that some common polishes trigger crazing on certain clear plastics (acrylics?). I can't remember the details, but hopefully someone in the know will be along shortly to clarify which types.

(Previous owner of my car (or the garage) has used the wrong polish on the clear cover of the speedo etc., resulting in extensive crazing.

 

[pawl]

if you can find a supplier who will supply a small enough sheet or offcut, why not use acrylic coated polycarbonate and have the best of both worlds. avoid using silicone based polish on polycarbonate.

 

[Greenheart]

Fitted UV stable polycarbonate side windows in 2010 in Trinidad, a few tiny little star chips on the outside but no clouding whatsoever.

Interesting. I'm wondering what the best cover might be for a not-quite waterproof solar panel. Presumably, the last thing I'll want is UV resistance, although it needs not to mist over. What's the least UV-resistant covering, which is nevertheless robust? Just glass?

The panel gives enough power that I can live with some reduction of output from the screening effect of the clear cover. I guess a thinner pane or sheet will reduce the loss accordingly?