Cashew Nutshell Liquid (CNSL) Polyols as a Drop-In Replacement for Petroleum Rigid Polyurethane Foams

Increasing demand for polyurethane materials and the struggle to balance this demand with sustainability have forced researchers to divert from traditional petrochemical-based polyols to alternative biobased polyols originating from renewable feedstocks. While rigid polyurethane foams (RPUFs) made from biobased polyols could potentially replace petroleum-based polyols, their commercial applications are hampered by various challenges such as processability, scalability, slow reactivity, and availability of raw materials. Moreover, limited information exists regarding the applicability of the commercially available biobased polyols as a drop-in replacement for petroleum-based polyols in current RPUF systems. This study addresses the limited research on the direct replacement of petroleum-based polyols with commercially available renewable polyols. In this work, we evaluated RPUFs made from commercially available cashew nut shell liquid (CNSL)-based polyols for their thermal insulation and flammability for building applications. RPUFs were made by systematically replacing a commercial petroleum-based polyol in a commercial spray foam system and comparing the thermal conductivity, mechanical strength, and morphological differences. We demonstrated that the biobased CNSL foams had similar physical properties to the commercial system. We found that all CNSL foams had higher modulus values (14 and 17 kPa) than the commercial foam (3 kPa), with the CNSL foam made with NX-9006 yielding the largest increase in performance among all of the foams tested. Furthermore, we demonstrated that CNSL-based foams can be augmented with various commercial flame retardants, such as expandable graphite (EG), to significantly reduce the linear burning rate (LBR), making them excellent for building insulation applications.