Method for identifying residual trace NCO of high-viscosity PU resin

The invention provides a method for identifying residual trace NCO of high-viscosity PU (polyurethane) resin. The method comprises the following steps: S1, adding a polyamino oligomer with the mass fraction of 0.01-10% into the high-viscosity PU resin; and S2, observing whether gel appears or the viscosity is obviously increased so as to judge whether the PU resin also contains NCO. According to the method for identifying the trace amount of residual NCO in the high-viscosity PU resin, the characteristic that amido can quickly react with NCO is utilized, and a multi-amido oligomer is selected, so that the multi-amido oligomer can fully react with a trace amount of NCO groups and can quickly react to generate cross-linked macromolecules; as the cross-linked polymer has insoluble substances, the cross-linked polymer can be separated out from a system to form observable gel, so that the generated gel is observed as a judgment basis for judging whether trace NCO is contained in the high-viscosity PU resin, and th