Oligomeric adhesion promoter

Because of this reactivity, primer solutions are formulated as very dilute (typically 0.1 vol %) solutions and used quickly. In industry, however, it is usually not practical to make a fresh APS solution for each application. Therefore, there is some concern as to how oligomerization will affect the adhesion promoting efficiency of such primer solutions over a typical 8-hour shift. 

Solutions with APS monomer concentrations below 0.01 vol % do not yield acceptable coupling, especially after T H stress. Residual monomer concentration in highly-oligomerized solutions does not appear to be solely responsible for adhesion promotion. 

Most anaerobic adhesive formulations are based on oligomeric acrylic esters, inherently low-toxicity materials. Various formulations contain additives such as adhesion promoters or cure components, and after excessive or repeated skin contact may cause skin irritation in sensitive persons. Adhesives should be washed away with water after skin contact. Nonaque-ous hand cleaners assist in removal of adhesive. Skin contact should be avoided by the use of appropriate application equipment. 

Urethanes Urethane adhesion promoters are used widely to bond PVC to polyester, nylon, and other fabrics, including sized glass fiber. In multicoat operations, the additive is used only in the first coat. With, polyester fabric, the isocyanate component in urethane formation can be used alone. Solvent or plasticizer solutions of oligomerized toluene diisocyanate (TDl) are available under the trade names Vulcabond (Akzo Nobel), Vanchem HM-50 (Vanderbilt), Thanecure T9 (TSE Industries), and Desmodur (Bayer). For improved resistance of the bond to heat and moisture, products based on bisphenyl diisocyanate (MDl) are also used. These include Vanchem HM-4346 and Rubinate 9480 (Huntsman). These are typically used at 3-7 phr levels in plastisols for coating polyester fabric. The second or subsequent coats should contain titanium dioxide and UV light stabilizer for outdoor service. With translucent products, an aliphatic isocyanate such as Desmodur N-lOO or TMl META (Cytec) should be used. 

Highly self-oligomerized 0.1 vol% APS solutions promote adhesion as do those with very low amounts of self-oligomerization. Formation of covalent Si—O bond with the mineral surface may not even be required to promote adhesion. Possibly, only hydrogen bonding or van der Waals interactions are sufficient. Such ideas have been discussed previously [6]. 

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