Alkenyl aromatic polymer foams and processes for preparing same

Disclosed is an insulative, bimodal aromatic polymer foam structure having microscopic pinholes in the cell walls to enhance the flexibility of the foam structure. Further disclosed is an insulative, bimodal alkenyl aromatic polymer foam structure containing carbon black. Further disclosed is a process for making low density alkenyl aromatic polymer foams prepared with a halogen-free blowing agent of carbon dioxide, lower alcohol and water. The cell size can be effectively controlled by controlling the amount of water in the blowing agent.