Processing and properties of rigid polyurethane foams based on bio-oils from microwave-assisted pyrolysis of corn stover

A new kind of rigid polyurethane (PU) foam was synthesized from the oil phase of bio-oils from microwaveassisted pyrolysis of corn stover. The recipes for the PU foams consisted of polyol-rich bio-oils, water as blowing agent, polyethylene glycol (PEG) as both polyol donor and plasticizer, diphenylmethane-4,4'-diisocyanate (polymeric MDI) as cross-linking agent, silicon-based surfactant, and tin-based catalyst. The mechanical properties of rigid foams were measured with universal testing machine (Instron4206). The effects of individual ingredients on the physical and mechanical properties of the foams were studied. It was found that water content, bio-oil content, and isocyanate dosage were important variables in making PU foams in terms of mechanical strength, density, and cellular structure. Under optimal conditions, the compression strength of the prepared PU foams reached 1130 kPa with a density of 152.9 g/L. The results show that bio-oils are potential renewable polyol sources for making rigid PU foams.