Scalable manufacturing and reprocessing of vitrimerized flexible polyurethane foam (PUF) based on commercial soy polyols†

Abstract

As the polyurethane foam (PUF) market, especially in the automotive sector, continues to grow, the environmental impacts of its petrochemical demands and end-of-life waste have motivated the industry to look for more sustainable solutions. This study explores the preparation of recyclable PUFs using commercially available soy polyols (Cargill's BiOH), aiming to enable improved thermal reprocessability of flexible PUFs via vitrimer chemistry. A series of “soy-PUFs” was produced by partially substituting petrochemical polyether polyols with 25% or 50% soy polyols in a standard reference formulation. Incorporation of soy polyols resulted in an increase in the stiffness of the resulting foams. Employing a modest amount (∼0.5 wt%) of dibutyltin dilaurate (DBTDL) in the formulations facilitated dynamic covalent bond exchanges in the cross-linked network during a mild “foam-to-sheet” reprocessing process (160 °C), converting malleable PUFs into densified sheet materials (PUS) with proper compactness and mechanical performance (e.g., tensile modulus = ∼50 MPa). Soy-PUFs demonstrated a modestly enhanced stress relaxation behavior, suggesting adequate reprocessing ability. DMA results demonstrated the phenomenon of forming an “intermediate” region between the hard and soft domains of PUSs after reprocessing.

Keywords: Polyurethane foam; Soybean oil; Polyols; Vitrimer chemistry; Reprocessing; Recycling.