Prepare an extruded polymeric foam using a thermoplastic polymer composition of styrene-acrylonitrile copolymer having a copolymerized acrylonitrile comonomer content of 20 weight-percent or less, a mean acrylonitrile comonomer content that exceeds its median acrylonitrile comonomer content and an average copolymerized acrylonitrile comonomer distribution having a breadth at half-height that is greater than 2.5 weight-percent as measured at half peak height of a copolymerized acrylonitrile comonomer distribution curve for the styrene-acrylonitrile copolymer.
