All plastics are brittle at deep freezer temperatures and boxes must be handled without physical impact while cold.
PP (polypropylene) is one of the most suitable plastics for cold storage and recommended down to -80C.
PC (polycarbonate) is recommended down to -190C.
Treated cardboard can be used for storage of samples at ultra low temperatures.
No brittleness temperature effect makes cardboard superior at lower temperatures down to -80C.