How do chlorinated poly(olefins) promote adhesion of coatings to poly(propylene)?

The mechanism by which chlorinated poly(olefin) (CPO) primer coatings promote adhesion of paints to poly(propylene) and thermoplastic poly(olefins) (TPO) has been examined by surface characterization techniques including electron spectroscopy for chemical analysis (ESCA), time-of-flight secondary ion mass spectrometry (ToFSIMS) and transmission electron microscopy (TEM). The coatings, their interfacial failures, and taper-cut cross sections were studied, using both waterborne and solventborne CPO primers. The results were then correlated with peel strength and crosshatch adhesion tests. CPO primers do not penetrate deeply into the poly(olefin) substrates, but are quite mobile following application of the topcoat. Solventborne CPO's generally showed adhesive failure at the CPO/poly(olefin) interface when dried at ambient temperatures. Test results are also reported for waterborne CPO adhesion promoters.