Optimizing Strength and Versatility of Underwater Adhesion Polymer System
Among the hundreds of commercial adhesives available today, few, if any, have the ability to form strong adhesive bonds in an underwater system. Man-made adhesives have been shown to not work underwater because the glues interact with water rather than forming adhesive and cohesive bonds with the surface of the substrate. However, mussels and oysters naturally produce an adhesive that is unaffected by their watery environment. Examination of this adhesive has shown that shellfish use a mixture of proteins containing 3,4-dihydroxyphenylalanine (DOPA) that crosslink to form glue. Thus, an effort has been made to create a biomimetic polymer that includes DOPA with its unique adhesion mechanisms to increase adhesion underwater. ^ In the creation of a biomimetic adhesive, it is important to make it practical for use outside a controlled experiment. For an underwater polymer, this means the adhesive must be applied and cured completely underwater while demonstrating high adhesive strength. More specifically, during the application process, the polymer must stay in solution and display slightly negative buoyancy attributes as to not sink or float. To study these characteristics, solvent, crosslinker, and filler studies were completed to determine the best combination of additives for optimum adhesion. Experimentally, this was determined to be a solvent combination of 3:1 DMF:EDC with a filler additive of 5 wt.% 70 nm CaCO3. Testing involved changing the angle of the adherents to demonstrate the usefulness of the adhesive within a range of positions. Finally, a comparison study was completed to illustrate the superior adhesion strength of the created system.^
Jonathan Wilker, Purdue University.
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