Silane, primer system

Wedge test results suggest that the curing process (e.g., percent crosslinking) of the epoxy-polyamide primer system is not affected by the addition of organosilanes, but may be affected by NTMP. The results of substrate surface characterization, adsorption behavior of applied films, and evaluation of candidate inhibitors by chemical, mechanical, and electrochemical test methods are presented. Mechanisms to explain the observed behavior of the various phosphonate and silane polymer systems are discussed. 

In all adhesive joints, the interfacial region between the adhesive and the substrate plays an important role in the transfer of stress from one adherend to another [8]. The initial strength and stability of the joint depend on the molecular structure of the interphase after processing and environmental exposure, respectively. Characterization of the molecular structure near the interface is essential to model and, subsequently, to maximize the performance of an adhesive system in a given environment. When deposited on a substrate, the silane primers have a finite thickness and constitute separate phases. If there is interaction between the primer and the adherend surface or adhesive, a new interphase region is formed. This interphase has a molecular structure different from the molecular structure of either of the two primary phases from which it is formed. Thus, it is essential to characterize these interphases thoroughly. 

This work discusses the structure of films formed by a multicomponent silane primer as applied to an aluminum oxide surface as well as the interactions of this primer with the adhesive and oxide to form an interphase region with a distinct composition and properties. The mecanical properties and durability of adhesive joints prepared using this primer system have yet to be evaluated. 

A. Seth and W.J. van Ooij, in A Novel, Low-VOC, Chromate-Free, One-Step Primer System for the Corrosion Protection of Metals and Alloys (K.L. Mittal, ed.), presented at the Fifth International Symposium on Silanes and Other Coupling Agents, Toronto, Canada, June 22-24,2(X)5 and has been accepted for pubhcation in Silanes and Other Coupling Agents. 

In contrast, hydrolyzed silane compounds, presumably adsorbed as oligomeric films, confer corrosion resistance in both hydrating and Cl environments. These inhibitors can also couple with applied epoxy primer or adhesive formulations to further protect the metal against corrosion by strengthening the metal-epoxide bond. The organosilanes do not appear to affect the curing process, e.g., % crosslinking, of the polymeric epoxy systems. 

Formulated primers. The use of formulated primers in which a silane (or silanes) is blended with a film former, a solvent, and perhaps a hydrolysis catalyst, has been described by Plueddemann [16] and in the Dow Corning trade literature [17]. Primers of this type which contain a film former should not be confused with the previously mentioned silane pretreatment primers, as they deposit a film of measureable thickness and strength. Such formulated primers are required to wet the substrate, be readily wet by the adhesive or coating and should provide a layer of intermediate modulus between substrate and resin system. As with the pretreatment primers a formulated primer can be tailored to both the substrate and the resin. Ageing of formulated primers may be a problem both in the storage container and on the substrate before subsequent coating. 

Substrate cleaning usually involves the light sanding of a clean, dry bonding surface. A primer (urethane or silane) is sometimes used to improve adhesion. Urethanes are generally bonded with a flexible epoxy or a urethane adhesive system. 

Polyurethane Methanol 1. Abrasion followed by brushing. Grit or vapor blast or 280-grit emery cloth followed by solvent wipe. 2. Incorporation of a chlorosilane into the adhesive elastomer system 1% by weight is usually sufficient. Chlorosilane is available commercially. Addition to adhesive eliminates need for priming and improves adhesion to glass and metals. Silane may be used as a surface primer... 

Fortunately, E. P. Plueddemann of Dow Corning Corp. had already developed a primer for polyester films. The primer consists of American Cyanamid Cymel 303, 90 parts Dow Corning silane Z-6040, 10 parts and methanol, 300 parts. Peel tests of Scotchpar bonded to EVA using this primer were excellent. Unfortunately, this system did not perform well in the 7-day cold-water soak test as shown in Table III. 

Chem. Descrip. Methyl trimethoxy silane CAS 1185-55-3 EINECS/ELINCS 214-685-0 Uses Pigment and filler treatment in solv. and water-based systems primer reduces pigment separation and floating improves disp. adhesion promoter... 

Chem. Descrip. Waterborne silane with amine functionality Uses Coupling agent in mineral surface treatment, acrylic coatings and caulks, antifreeze systems, and metal primers Properties Completely sol. in water dens. 1.1 g/ml vise. 4-6 mFa-s- f.p. 

---