Abstract: Prepare an extruded polymeric foam using a foamable polymer composition that contains a polymer composition with styrene-acrylonitrile copolymer, a blowing agent composition with only 1,1,1,2-tetrafluoroethane (74-78 weight-percent), carbon dioxide (13-16 weight-percent) and water (7-9 weight-percent) where the concentrations are relative to total blowing agent weight, and less than 0.5 weight-percent filler based on foamable polymer composition weight by using an extrusion foaming process with a foaming temperature of 120-125 degrees Celsius to produce a polymeric foam having a density of 29-37 kilograms per cubic meter and a vertical compressive strength in kilopascals having a magnitude exceeding 520 less than the product of the magnitude of the foam density in kilograms per cubic meter and 25.9.

Abstract: Prepare an alkenyl-aromatic foam having good surface quality, high thermal insulating properties and low density using an extrusion method by expanding a foamable polymer composition of an alkenyl-aromatic polymer composition containing less than 20 weight-percent covalently bonded halogens and having a polydispersity of less than 2.5 and a water solubility greater than 0.09 moles per kilogram and 2.2 moles per kilogram or less at 130 degrees Celsius and 101 kilopascals pressure and 0.8-2 moles per kilogram of a blowing agent containing 0.4 moles per kilogram or more of a chlorine-free fluorinated blowing agents and water at a concentration of at least 0.22 moles per kilogram; wherein moles per kilogram are relative to kilograms of alkenyl-aromatic polymer. The resulting foam has a density of 64 kilograms per cubic meter or less and a thermal conductivity of 32 milliwatts per meter-Kelvin or less after 180 days.