Why is UGLI™ Hybrid made out of cardboard? A Why is UGLI™ Hybrid made out of cardboard? Truthfully cardboard is a very good heat resistant material. The burning point of cardboard starts around 450 deg. F. where as many plastics start to melt at 140 degrees. Back to Top Post navigationPrevious post: I heard the UGLI™ oven is made of cardboard. Will it catch fire?Next post: How durable is the UGLI™ hybrid cardboard case?