Tuning of antifouling active PDMS domains tethered to epoxy/amine surface

Abstract

Biocides in marine coatings provide superior antifouling properties, although harmful effects on the eco system are inevitable. Environmentally friendly polydimethylsiloxane (PDMS) alternatives rely on biorepulsion, but inherently lack in durability due to their low E-Modulus making them unsuited for mechanical cleaning. We employ the commercially available 2K epoxy-amine system Beckopox™ EP 128 and Beckopox™ EH 637, which we modify with Bis(3-aminopropyl) terminated polydimethylsiloxane. This approach incorporates a robust 2K epoxy resin as a basis for reactive PDMS species combining the environmentally benign biorepulsion with mechanical stability. The immiscibility between epoxy and PDMS phases causes a spontaneous separation process thereby forming circular PDMS enriched surface domains as verified via EDX. A Key factor in improving the antifouling performance is to carefully tune the interstitial domain distances and ensure domain formation over the whole surface. Since control over these parameters has proven to be challenging, we introduce an amphiphilic polyglycol-PDMS compatibilizer (COMP) to the system specifically fit to balance out the internal interfacial tensions. Prepared coatings have shown to withstand even high-pressure cleaning with no sign of significant erosion. The use of 5.1 wt% COMP guarantees surface coverages up to 60%. Further domain control is gained by the variation of the time between application and cured state (pre-curing time). Specific topography and interstitial distance design were correlated to the coatings antifouling performance under real-life conditions in the North Sea (Norderney, Germany). Retardation of the biological growth is demonstrated to be present for 117 days after submersion until foulants settlement matches the control.