Bulk-sized boron nitride nanotube (BNNT) reinforced polyurethane (PU) composites at different volume contents have been produced. A large quantity of BNNT fillers are synthesized by a boron ink method. Compared to the neat PU, the 0.5 vol% and 2.0 vol% BNNT reinforced composites show 38.2% and 6.3% increases in compressive modulus, respectively. The relatively less enhanced compressive modulus of the 2.0 vol% composite may be due to the agglomerations of nanotubes at high volume percentages. Contrary to normal behaviour, the composites show decreasing Rockwell (HRR) hardness values with an increasing volume fraction. A large quantity of BNNT fillers are synthesized by a boron ink method. Compared to the neat PU, the 0.5 vol% and 2.0 vol % BNNT reinforced composites show 38.2% and 6.3% increases in compressive modulus, respectively. The relatively less enhanced compressive modulus of the 2.0 vol% composite may due to the agglomerations of nanotubes at high volume percentages. Contrary to normal behavior, the composites show decreasing Rockwell (HRR) hardness values ​​with an increasing volume fraction