If you are looking for a smoother and more durable material than Correx for your poster and display requirements then ABS plastic sheeting is a good alternative.
ABS stands for Acrylonitrile Butadiene Styrene and is a versatile material that is strong and safe to use as a display medium. It has a smooth finish that yields a high definition print appearance. The price is higher than for Correx board, but it is still an affordable option if you are looking for a more durable material.
From our experience printed ABS plastic board have an outdoor durability in excess of three years in South African conditions.