Fire-retardant, anti-dripping, biodegradable and biobased polyurethane elastomers enabled by hydrogen-bonding with cellulose nanocrystals

Thermoplastic polyurethane(PU)elastomers have attracted significant attention because of their many important industrial applications.However,the creation of fire-retardant and anti-dripping PU elastomers has remained a grant challenge due to the lack of crosslinking and weak interchain interactions.Herein,we report a mechanically robust,biodegradable,fire-retardant,and anti-dripping biobased PU elastomer with excellent biodegradability using an abietic acid-based compound as hard segments and polycaprolactone diol(PCL)as soft segments,followed by physically crosslinking with cellulose nanocrystals(CNC)through dynamic hydrogen-bonding.The resultant elastomer shows the balanced mechanical and fire-retardant properties,e.g.,a tensile strength and break strain of 9.1 MPa and 560%,a self-extinguishing ability(V-0 rating in UL-94 testing),and an anti-dripping behavior.Moreover,the as-developed PU can be completely degraded in 1.0 wt.%lipase solution at 37℃ in 60 days,arising from the catalytic and wicking effect of CNC on PU chains.This work provides an innovative and versatile strategy for constructing robust,fire-retardant,anti-dripping,and biodegradable PU elastomers,which hold great promise for practical applications in electronic and automobile sectors.