Water-borne oligomers

Emulsion polymerization usually leads to high MM products and in many cases to MMDs somewhat narrower than found in polymers produced in homogoieous free-radical polymerizatioa The mechanisms of particle nucleation and radical aitry operative in emulsion polymerization, however, also lead to the formation of short water-borne oligomers (c. 2-20 monomo- units d Jending on the polarity of the monomer). The characterization of these tdigomeric species is of considerable importance from a mechanistic point of view [162-168]. 

The same plasma polymer deposited in a closed-system reactor has a graded elemental composition with a carbon-rich top surface, and the oligomer content is much lower [10], both of which increase the level of adhesion. The adhesion of the same water-borne primer is excellent and survives 8 h immersion in boiling water. When this surface is treated with O2 plasma, the adhesion does not survive 1 h of boiling, while the dry tape test still remains at the level of 5. The water-sensitivity of adhesion depends on the chemical nature of the top surface as depicted by XPS data shown in Figure 28.12. Water-insensitive tenacious adhesion, coupled with good transport barrier characteristics, provides excellent corrosion protection, as supported by experimental data [1-4], and constitutes the basic principle for the barrier-adhesion approach. 

The Clean Air Act demands the elimination of organic solvents use, hence a number of plasticisers and solvents (such as methylene dichloride (MEK), toluene, xylene) are classified as hazardous, which led to development of new, environment compliant systems to develop, such as water borne systems, or use of rapidly curable/dryable oligomers (i.e., printing inks use oligomeric bis acrylates, polyester acrylates and polyurethane acrylates, which can be crosslinked quickly by UV light with the aid of certain sensitisers). 

Chem. Descrip. Reactive epoxy-functional siloxane oligomer in water Uses Adhesion promoter between inorg. materials (glass, minerals, metals) and org. polymers (thermosets, thermoplastics, elastomers) surface treatment aid for mins. reinforcement aid for glass fibers primer for glass and metals surface modifier for org. materials additive for water-borne polymers... 

---