Nano-Engineered Additives for Active Coatings

Researchers with the U.S. Army Research Laboratory (ARL) have developed and are patenting novel additives for coatings systems that spontaneously segregate to the surface of the coating. These macromolecular transports (MTs) can be coupled with traditional additives to control their distribution in a cured film, and the MTs are compatible with a wide range of military and commercial coating chemistries. This autonomous concentration at the surface of the film translates to reduced additive quantities required for desired surface properties (i.e., antimicrobial activity), as well as reduced impact on the bulk properties of the film. Potential applications include, but are not limited to, antifouling coatings for marine applications, pool coatings, coatings for hospitals and wood treatment. ARL has successfully produced a technology that will “float” anti-microbial compounds to the surface of a curing polymer matrix (Figure 2). Self-segregating materials address several issues: decreased additive requirements; minimize mass transport issues; minimize diffusion limitations; minimize impact on physical properties of base coating. Figure 4 shows the impact of MTs with antimicrobial characteristics when dispersed in a thermoplastic polyurethane matrix. The additives clearly reduced the appearance of plaques, and samples have demonstrated 99.9999 % killing efficiency with 1 wt % of additive without negative effects on the base coating. MTs have also been incorporated into various commercial off-the-shelf paints from local home improvement stores. The U.S. Army has developed an inexpensive additive that spontaneously segregates to the polymer/air interface of coating systems which can be chemically modified with desired properties (not solely biocidal) and is compatible with existing coating systems. Concentration of material at the air interface reduces overall additive requirements. By using the MT technology, 10-fold surface concentration enhancements have been observed. This saves money, is better for the environment, and minimizes negative effects on the base coating. While further applications are in development at the Army’s Aberdeen Proving Ground in Maryland, the basic technology offers new ways to enhance the performance of commercial and military coatings. A patent application has been filed. These MTs have the ability to transport a myriad of additives to the air/polymer surface of a coating, allowing the formulation of systems with new performance characteristics and the potential for reduced costs and overall loading requirements.