High‐Temperature and Chemically Resistant Foams from Sustainable Nanostructured Protein

Covalently crosslinked protein networks produced from whey protein nanofibrils (PNFs) are demonstrated to be sustainable high‐performance foams that show chemical resistance and mechanical strength, stiffness, and toughness on harsh aging at 150 °C. The aged foams are able to retain their properties at 180 °C for as long as 24 h, far exceeding the properties of most classical petroleum‐based thermoplastics. The foams are further developed into soft foams by the addition of glycerol as a plasticizer. The improvement in the mechanical performance of the foams with aging, which is equivalent to an increase by one order of magnitude in modulus and yield strength, is confirmed to be associated with (iso)peptide crosslinks. The results open the way for using protein‐based foam materials in severe/corrosive environments such as filtration, thermal insulation, and fluid absorption. The protein foams produced are suggested as suitable alternatives to petroleum‐based porous polymers.