Influence of Graphene Oxide Contents on Mechanical Behavior of Polyurethane Composites Fabricated with Different Diisocyanates.

The exceptional behavior of graphene has not yet been entirely implicit in the polymer matrix. To explore this fact in the present work, two series of Polyurethan (PU) composites were synthesized. The structural modification was observed by the use of two different diisocyanate of methylene diisocyanate (MDI) and hexamethylene diisocyanate (HMDI) in hydroxylterminated polybutadiene (HTPB) by using I,4 Butane diol (BD) as the chain extender. The variation in hard segment up to 25 (wt.%) in both series led to significant changes in the mechanical behavior of graphene oxide (GO) induced composites. Both series were prepared by an in situ polymerization process. Fourier transform infrared (FTIR) analysis showed a peak in the region of 1700 cm-1, which confirmed the conversion of the NCO group into urethane linkages. Thermal gravimetric analysis (TGA) revealed a thermal stability up to 450 °C @ 90% weight loss. The swelling behavior showed the optimum uptake of 30% of water and 40% of dimethyl sulfoxide (DMSO) with aliphatic diisocyanate. The values of storage modulus (E'), complex modulus (E*), and compliance complex (D*) were observed up to 7 MPa, 8 Mpa, and 0.7 MPa-1, respectively. The degree of entanglement (N) values were calculated from DMA and were found in the range of 1.7 × 10-4 (mol/m3). Phase segregation of PU was observed by scanning electron microscopy (SEM), elucidating the morphology of composites.