The typical stack is plastic substrate / UV base coat / vacuum aluminum / UV top coat. The metal layer is only tens of nanometers thick and carries almost no stress, so once the base coat delaminates the whole stack peels.
Injection molded parts often carry mold release residue, films such as PET and BOPP have low surface energy, and the thermal radiation during metallizing adds further interfacial stress.
The classic failure is the boiling water test: blisters in the top coat and haze in the metallized layer after 30 minutes, which is interfacial hydrolysis.
KM2130's alkyl segments absorb the strain between substrate and metal layer, while phosphate groups anchor to polar groups or residual oxides on the plastic surface, forming a bridge.
KM2160's high functionality gives a dense network in the top coat, improving scratch and chemical resistance while retaining adhesion to the metal layer.
The division of labor is clear: the base coat must bond and flex, the top coat must resist abrasion.