Synthesis and properties of polyurethane foams prepared from heavy oil modified by polyols with 4,4′-methylene-diphenylene isocyanate (MDI)

► Polyurethane foams could not be directly prepared from heavy oil for its low hydroxyl number. ► After modification, heavy oil increased its hydroxyl number to 564.5 mg KOH/g. ► Furthermore, the secondary alcohol hydroxyl was the main product. ► The compressive strength of foams increased 32% by adding 10% activated heavy oil. ► However, adding 100% activated heavy oil would weaken the properties of PU foams.