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.