A foam material having one glass transition temperature (Tg) and made from an immiscible composition having at least two glass transition temperatures (Tg) by an extrusion process wherein said composition (C) comprises at least one polyarylene (P1) polymer, wherein more than 50% by moles (moles %) of the recurring units of said (P1) polymer are recurring units (R1) consisting of an arylene group, wherein said arylene group is a hydrocarbon divalent group consisting of one core composed of one benzene ring or of a plurality of benzene rings fused together by sharing two or more neighboring ring carbon atoms, said benzene ring being optionally substituted, wherein each of said arylene group is bound to two other arylene groups of neighboring recurring units (R1) through a first C—C bond (E1) and a second C—C bond (E2), wherein at least 20 moles % of recurring units (R1) are kink-forming arylene units (R1-b), the remainder being rigid rod-forming arylene units (R1-a) different from aryleneR1_b units, wherein in said aryleneR1_a units the bond (E1) and the bond (E2) are co-linear and anti-parallel towards each other, said (P1) polymer being present in composition (C) in an amount of below 75% by weight (wt. %) and above 10 wt. % based on the total wt. % of (P1) polymer and (PPSU) polymer, and (ii) at least one polyphenylsulfone polymer, said (PPSU) polymer being present in composition (C) in an amount of below 90 wt. % and above 25 wt. % of based on the total wt. % of polyarylene (P4) polymer and (PPSU) polymer.