Page 315 - Handbook of Adhesives and Sealants

Primers and Adhesion Promoters 277

ment steps. 35 Typical dosage is 0.2% by weight of the polymer. They
can also be used to treat aluminum alloys for adhesive bonding.
Zirconate coupling agents have a structure very similar to titanates.
Zirconium propionate is used as an adhesion promoter in printing ink
formulations for polyolefins that have been treated by corona-
discharge. The coupling agent is believed to form hydrogen bonds with
the nitrocellulose in the ink. Surface COOH groups seem to be the
most likely attachment site to the polyolefin surface. Like the titan-
ates, zirconate coupling agents are useful in improving the dispersion
characteristics of fillers in polymer systems. Other examples of zircon-
ate coupling agents and their applications are shown in Table 7.9.
Chrome complexes have been formed as adhesion promoters by the
reaction of chromium chloride with methacrylic acid. The chromium
oxide portion of the adhesion promoter reacts with a substrate while
the methacrylic portion reacts with a free radical curing outer layer.
Chrome based adhesion promoters are commonly used as a primer for
aluminum foil to increase the strength and durability of aluminum/
polyethylene interfaces. 25 The polyethylene is typically extrusion
coated as a hot melt onto the treated aluminum for applications as
diverse as packaging and communications cable shielding. Other types
of coupling agents include 1,2-diketones for steel, 38 nitrogen hetero-
cyclic compounds such as benzotriazole for copper, 39,40 and some cobalt
compounds for the adhesion of brass plated tire cords to rubber. 41

References
1. Comyn, J., Adhesion Science, (Cambridge: Royal Society of Chemistry, 1997) at
27–28.
2. Krieger, R. B., ‘‘Advances in Corrosion Resistance of Bonded Structures’’, in Proc.
Nat. SAMPE Tech. Conf., vol. 2, Aerospace Adhesives and Elastomers, 1970.
3. Kuhbander, R. J. and Mazza, J. J., ‘‘Evaluation of Low VOC Chromated and Non-
chromated Primers for Adhesive Bonding’’, 38th Annual SAMPE Symposium, May
1993 at 785–795.
4. Sweet, D. E., ‘‘Metlbond X6747 100% Water Based Primer for Aerospace Bonding
Applications’’, 38th International SAMPE Symposium, May 1993 at 1241.
5. Lindner-Meyler, K. and Brescia, J. A., ‘‘Effectiveness of Water Borne Primers for
Structural Adhesive Bonding of Aluminum and Aluminum Lithium Surfaces’’, J. of
Adhesion Science and Technology, vol. 9, no. 1, 1995 at 81–95.
6. Foister, R. T., Gray, R. K., et al., ‘‘Structural Adhesive Bonds to Primers Electro-
deposited on Steel’’, J. Adhesion, vol. 24, 1989 at 17.
7. Reinhart, T. J., ‘‘Novel Concepts for priming Metallic Adherends for Structural Ad-
hesive Bonding’’,in Adhesion 2, K. W. Allen, ed. (London: Elsevier Science Publish-
ers, 1978).
8. Davis, G. D., Whisnant, P. L., et al., ‘‘Plasma Sprayed Coatings as Surface Treat-
ments of Aluminum Adherends’’, 41st International SAMPE Symposium, March
1996 at 291–301.
9. Clearfield, H. M., et al., ‘‘Surface Preparation of Ti-6Al-4V for High Temperature
Adhesive Bonding’’, J. Adhesion, 29, 81 (1989).
10. Okamoto, Y., and Klemarczyk, P. T., ‘‘Primers for Bonding Polyolefin’’ J. Adhesion,
40 (1993) at 81.
11. Yang, J. and Garton, A. J., J. of Applied Polymer Science, 48 (1993) at 359.