Outdoor material in extreme cold weather

[10sacer]

Looking for help from you guys who live and do signs in the frigid cold areas.
What base material would you use for exterior wayfinding and interpretive/educational kiosks that will be permanantly outdoors in sub-freezing temperatures at least 4 months out of the year?
My initial thought was HDPE in 3/4" sheet - but open to suggestions.

 

[Gino]

We just finished a bunch for a customer and we used .125 aluminum and powder coated them. Just about any kinda plastic is gonna expend and contract to a certain degree..... then again so will aluminum, but there's chance of cracking with metal. Our sizes are from 26" x 38" up to 48" x 96" and lots in-between.

 

[JBurton]

The stuff I've seen used to route state park displays is really robust, though I've never used it. Here it lists a brittleness factor at -105F, which sounds pretty extreme...

King StarBoard®

King StarBoard® The Original Marine Grade High-Density Polyethylene Building Sheet

www.kingplastic.com