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My vehicle built in '08 suffered extreme damage to the dashboard, it permanently melted and is now sticky to the touch even when cool.

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Presumably this is why so many vehicle owners use covers to block the sunlight when parked. I never liked the idea of these, they seem like a hassle that better engineering could fix.

Have there been recent manufacturing / vehicle design improvements across the automotive industry so future cars will be resistant to high temperatures? Or is this still a common problem? If so, what fundamental trait of car interior materials causes this issue to be either so hard or so expensive to solve?

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    $\begingroup$ I think it is the type of plastic selected according to the economic class for the type of the car - the more expansive of a car the better material used, also the flexibility of the plastic for ease of fitting and installation. In certain models, vinyl was used too. $\endgroup$
    – r13
    Aug 19, 2021 at 19:15
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    $\begingroup$ Reminds me of a story of the reflections from a building "melting" a parked car: bbc.co.uk/news/uk-england-london-23930675. What I would say is that the plastics in cars tend to be "hard" plastics that are expensive and hard to recycle. Going cheap or "green" may compromise their ability to survive the crazy extremes some of them will go through in their lives. $\endgroup$ Aug 20, 2021 at 9:13
  • $\begingroup$ @RalphBolton I remember that article. I actually had read this version, which had the more sensational description of Death Ray :-) It mentioned that the temperature (in London nonetheless) would reach 60 deg celcius $\endgroup$
    – NMech
    Aug 20, 2021 at 10:17

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The main problem is that there are many constraints for the material of a dashboard. Namely (just a few that pop to mind - I will update later if I forgotten any important ones):

  • good UV resistance
  • good thermal stability (low coefficient of expansion)
  • high melting point
  • good surface
  • coming in different shape
  • machinable (in order to take a nice shape)
  • flame retardant (Pete W addition)
  • able to withstand common cleaners like bleach and peroxide (Pete W addition)
  • and cheap.

When there are so many constraints its difficult to find a material/solution that satisfies perfectly all needs. (A wise friend said to me constantly "quickly, done correctly, cheaply, pick any two", I guess this is applicable in this instance its just with more constraints)

One final note, since cars are sometimes (IMHO more often than not) sold more on looks rather than the durability of the dashboard (keep in mind that the owner's handling is also a factor here), the compromise tends to be the aesthetics over durability.


Another factor why this is not permanently solved is, that car companies want to "innovate" (notice the ""). Sometimes that means that they try a "new" and "better" material. Sometimes a driver for the decision, (especially in car markets that are potentially huge), they might make a deal to use that "new" and "better" (but unproven) material in their cars for a reduced cost. That benefits the car maker (because they get a material at a lower cost), and the material producers because they find a potentially large market. The problem is that durability testing of the dashboard is not something that can be completed in the timescales that a new car is designed nowadays. So sometimes, the buyer of the car gets the short straw.

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  • $\begingroup$ The Hyundai probably tended to cheap $\endgroup$
    – Tiger Guy
    Aug 19, 2021 at 16:35
  • $\begingroup$ Lean would say that "quickly, done correctly, cheaply, pick any two" is false and that quick and correct means cheap. $\endgroup$
    – Tiger Guy
    Aug 19, 2021 at 16:35
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    $\begingroup$ also flame retardant, and able to withstand common cleaners like bleach and peroxide. They end up with some weird polymer blends $\endgroup$
    – Pete W
    Aug 19, 2021 at 21:40
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    $\begingroup$ "good UV resistance" - Windscreen glass offers UV protection against UVB and ~75% UVA. A poor quality OEM windscreen, or an aftermarket replacement may not offer a significant amount of protection against UV. $\endgroup$ Aug 20, 2021 at 10:06
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    $\begingroup$ @skipey_richie that 25% can still be too much after 10 years in a sunny country, if the owner leaves the car consistently in the sun. My understanding is that the cracks are mainly from the UV (rather that the heat intensity). However, I don't have any hard scientific data to back it up, so I might be wrong. $\endgroup$
    – NMech
    Aug 20, 2021 at 10:10
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It's not a common problem.

My car made in 2005 does not have this problem and a car I had that was made in 1968 did not have the problem...

It has happened when some manufacturers have used a "new" material and it proves not to survive the UV - especially in some countries as they get more sun than others.

As for the aluminum foil shown in the window - it works much better to reduce the temperature when put on the outside of the screen - if you want to keep the interior temperature down, which is why people use them, then don't let the energy get inside the cabin...

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    $\begingroup$ Putting it on the inside still reflects most of the solar energy and it can't blow away. $\endgroup$
    – user253751
    Aug 20, 2021 at 9:13
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    $\begingroup$ @user253751 doesn't blow away in winter when used to stop the frost settling on the windscreen, so why would it blow away in summer? Mine has straps to fix it down - works fine whether it is windy or not. Have you actually used one? $\endgroup$
    – Solar Mike
    Aug 20, 2021 at 9:19
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    $\begingroup$ @SolarMike I've used one but never seen one with straps. Mine was a flimsy thing with absolutely the minimum material possible, meant to fold up easily for storage (and probably also for cost reasons). It had the approximate aerodynamics and build quality of a plastic grocery bag, and even if strapped down I would have expected it to tear at the straps immediately. (But it worked fine when in a very sheltered place, like inside a car). $\endgroup$ Aug 20, 2021 at 14:59
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I want to add to the answers above the other side of the story, the car's history of sun exposure and maintenance.

Some cars are parked mostly under the shade or indoors. Some are parked in harsh climates and exposed to extreme sunlight without even so much a window left a crack open to reduce the heat.

I have a car that was exposed mostly to the sun coming from the driver side over many years and the dashboard shows small cracks on that side.

Sometimes one uses the wrong chemicals to polish the dashboard, they may look nicer while the built-in UV resistive coat is being compromised.

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