Primer adhesion

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

The surface preparation must enable and promote the formation of bonds across the adherend/primer-adhesive interface. These bonds may be chemical (covalent, acid-base, van der Waals, hydrogen, etc.), physical (mechanical interlocking), diffusional (not likely with adhesive bonding to metals), or some combination of these (Chapters 7-9). 

Fig. 2. Peel strength of NBR rubber as a function of HD2 grease contamination level on grit-blasted steel using the. solvent-borne Chcmlock 205/23.3 primer/adhesive and the aqueotis Chemlock 805/855. Adapted from Ref. 12. ...

Major uses of epoxy resins are coatings for appliance finishes, auto primers, adhesive, and in coatings for cans and drums. Interior coatings of drums used for chemicals and solvents manifests its chemical resistance. 

Polyethylene coating on ferrous pipes may be applied by means of one of the following processes circular or ring-type head extrusion, side extrusion and wrapping or powder sintering. The commercially available coating systems also differ further in that the extruded polyethylene may be applied in conjunction with various primer/adhesive systems. 

Primer Chemistry Primer Adhesion Loss in SS (mm i Bond Streneth CMPal Initial After SS Failure... 

Surface Treatment of Polytetrafluoroethylene Primer, Adhesive, Corrosion Inhibiting, -67 to 200°F Primer, Adhesive, Corrosion-Inhibiting, for High Durability Structural Adhesive Bonding... 

Since it was observed that fluorine contamination was a possibility and had potentially detrimental effects as described in Chapter 10, the excellent primer adhesion achieved with Tfs/(Ar) and Tcs/(Ar), shown in Table 31.3, has significant importance in the practical application of the plasma technique without any of the potentially deleterious effects of fluorine-based systems. Argon plasma treatments on both flow system TMS (Tfs) and closed system TMS (Tcs) polymers were then investigated as an additional system modification that could provide strong adhesion without the incorporation of fluorine-containing monomers in the quest to produce chromate-free coatings systems. 

Table 31.3 summarizes the adhesion test results of nonchromated primers [Spraylat EWAE118 (D) and Dexter 10-PW-22-2(X)] to plasma coatings deposited without an anode assembly, which were produced in both flow and closed system deposition processes. As noted in Table 31.3, closed system TMS plasma polymers (Tcs) showed superior primer adhesion performance to similar ones obtained from a flow system (Tfs). Similar to chromated primers, summarized in... 

Table 31.1, tenacious and water-insensitive primer adhesion was always achieved with closed system TMS plasma polymers treated with subsequent Ar plasma applications [Tcs/(Ar)]. 

The corrosion protection of plasma interface-engineered coating systems relies on the tenacious water-insensitive adhesion and good barrier characteristics of the coatings [3]. DC cathodic polymerization and plasma treatment have been demonstrated as efficient in improving the primer adhesion to metallic substrates. 

From the XPS analysis results, it was found that TMS plasma coatings prepared in a closed system have a carbon-rich surface, which is similar to TMS polymers followed by methane plasma deposition, i.e., T/C as described in a flow system. The adhesion study also showed that the T/C plasma treatment on aluminum alloy provided excellent adhesion to spray paint primers. The primer adhesion performance of closed system TMS plasma polymers was also examined. Since the porous surface... 

Structure of IVD A1 coating may conceal the plasma treatment effect on primer adhesion, Alclad 7075-T6 A1 alloy panels were selected as the substrates for adhesion investigation based on the fact that they can provide smooth surfaces while still providing an A1 coating similar to that of IVD A1 coatings. 

In order to produce chromate-free plasma coating systems, the adhesion of closed system TMS coatings to nonchromated primers (Spraylat EWAE118 and Dexter lO-PW-22-2) was also investigated, and the adhesion test results are summarized in Table 32.9. Closed system TMS plasma polymers showed superior primer adhesion performance to those obtained from a flow system. Similar to chromated primers, summarized in Table 32.8, excellent primer adhesion was always achieved with closed system TMS plasma polymers treated with subsequent Ar plasma applications. 

It should be pointed out that excellent primer adhesion was also obtained with TMS plasma polymers from a (TMS-bAr) mixture in a closed reactor system. This result indicated that, to achieve equally good primer adhesion, TMS polymerization with subsequent Ar plasma treatment could be replaced by one process of cathodic polymerization of a (TMS-bAr) mixture. Since the addition of argon to TMS can help stabilize the gas discharge, plasma polymerization of a (TMS + Ar) mixture is very important in the practical operation of plasma deposition process in conjunction with the industrial IVD process. Plasma polymerization of a mixture of TMS and argon in a closed system also has the advantage of being more... 

DC cathodic polymerization of TMS mixed with argon improved the primer adhesion performance of the closed system TMS plasma polymers. Moreover, the addition of a certain amount of argon into the TMS plasma system further increased the plasma coating quality, reflected in the increase in refractive indices. Based on the higher compatibility with the IVD process, the excellent adhesion performance, and the benefit of one process combining TMS plasma polymerization and the postdeposition plasma treatment, DC cathodic polymerization of TMS mixed with argon in a closed system is being considered as a more realistic and favorable approach in practical applications. 

The practice of modifying epoxy resins with liquid polysulphides may not be new but the method of doing so has advanced significantly in recent years to the extent that these systems are being given serious consideration in the design of specialist coatings, primers, adhesives and encap-sulants (Morton International, undated a Rees and Wilford, 1994 Rees et al., 1994). 

Micobond. [Dexter Spec. Coatings] Primers, adhesives. 

A primer adhesive is first applied to a properly prepared concrete surface. A thin coat of epoxy mortar is then applied with a trowel. While this thin coat is still wet, a fiberglass membrane is rolled into the mortar. The edges of the membrane should be overlapped 2 inches. The mortar will squeeze up through the voids in the fiberglass mesh, resulting in adhesive base to which the final epoxy mortar will adhere. While this first application of mortar is still tacky, the second layer of epoxy mortar is applied over the glass cloth. This second layer may then be screeded and leveled. ... 

Nouybond 266 [Air ProdsJPerf. Chems.j Chem. Deserp. Modified polyamidoamine Uses PVC plastisol adhesion promoter for automotive sealants, underbody coatings, and anti-chip primers adhesion promoter for electrodeposition primers used in mfg. of automobiles, tmcks, and buses Features 120 C cure exc. color stabilily Properties Amber clear liq. vise. 5-20 poise amine no. 110-135 Use Level 1-2 parts... 

Uses PVC plastisol adhesion promoter for automotive underbody coatings and anti-chip primers adhesion promoterforelectrodeposilion primers used in mfg. of automobiles, trucks, and buses Features 130 C cure high tens. str. 

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