anyone do crash tests at -30?

This morning I was taking the car seat out of the car with bare hands, and the feel of -20C plastic made me wonder...does anyone do crash tests at low temperatures?

I've driven a vehicle at sub -40, and it takes a while for the interior to warm up much. It seems possible that a collision could happen while the interior materials were still at -30 or -20.

Most plastics get pretty brittle at cold temperatures...I wonder if a plastic framed seat would be weakened, or if the energy-absorbing foam might not absorb as much energy as it is supposed to.

Anyone know?

My understanding is that yes, manufacturers do in fact subject their seats to cold and hot temperatures and analyze the plastic afterwards.

I don't know the answer specifically with regard to car-seats but I am an Engineer that designed plastic medical devices before becoming a SAHM. Regulations are surely different between FDA regulated devices and transport safety devices. However, they may be similar. We had to simulate every relevant condition. That could affect product and material safety and performance. First we used a simulated aging process to artificially age the device to or beyond the expiration date of the device. We also tested non-aged product with the same protocol. Aging of plastics is typically done with heat but is sometimes done by cycling between hot and cold temperatures. Humidity may also be used. Then, the products, in their original packaging are placed on a vibration table to simulate transportation, and then dropped on sides, edges, and corners from a specific height. Then conditions of use are simulated as closely as possible. Temperature, humidity, chemicals, etc. If it not possible to test at temperature we could use engineering justification and perhaps additional testing. So if the test sled is not in a temperature chamber, they may get the seat to temperature, have test all set up, and then quickly bring seat out and test within so many minutes.

That doesn't answer for the car-seat industry but good engineering practice would...

There is no specific requirement in the CMVSS or FMVSS to the best of my knowledge. Manufacturers may do some plastic testing to cold and hot temperatures, but not necessarily on the sled.