Effect of carbon black on adhesion to plastics in solventborne 2K polyurethanes

These studies show that when the pigment volume content (PVC) of carbon bla ck particles increases in polyurethanes (PUR), NCO consumption increases, a nd the extent of H-bonded C=O species near the film-substrate (F-S) interfa ce is enhanced. During crosslinking, polyurea (PUA) is produced, and its co ncentration levels near the F-S interface are diminished for unpigmented co atings, whereas for the same system containing carbon black, the PUA format ion is enhanced. Although the presence of carbon black particles at the F-S interface results in diminished adhesion of 2K PUR to acrylonitrile-butadi ene-styrene (ABS), adhesion is also affected by the presence of OH and C=O functionalities on ABS, which are potential sites for H-bonding to PUR. Str onger hydrogen donor affinity of N-H functionalities in PUA as compared to the N-H groups on PUR leads to increased H-bonding in the presence of carbo n black. Enhanced intermolecular H-bonding in PUR due to the presence of ca rbon black particles competes wit the F-S interfacial H-bonding that promot es adhesion.