Evaluation of the durability of elastomeric easy-release coatings

Abstract

Novel coatings have been designed to solve

problems associated with biofouling of marine structures,

particularly ship hulls. The best

candidates to date are multilayered coatings incorporating silicone

rubber technology. These materials are efficient because they exhibit

excellent release properties. However, they are

very soft and tend to be more susceptible to various forms of

mechanical damage.

Fundamental analysis of the durability of these coatings has been done

using standard laboratory tests. Simulative studies are essential to screen

candidates as well as to predict the true life of the systems.

The goal of this project was to develop a testing protocol for the

evaluation of the durability of elastomeric easy release coatings and

to implement it on selected candidate coatings.

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A brushing apparatus was designed and built to simulate the cleaning

processes of ship hulls. Wear was measured with profilometry. The

proposed methodology is valuable to study the processes of wear of the

coatings, to screen various materials and to identify parameters,

either functional or material, which would directly affect their durability.

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Two groups of candidate coatings were tested: the EXS series and the NRL series.

The EXS samples showed better wear resistance than the NRL

samples and showed no dependence on the rotational speed of the

brushes.

The NRL samples showed that increasing the sliding speed

resulted in a decrease in wear.

An increase in the applied load resulted in increased wear for both sample series.

The effect of coating thickness was also investigated and discrimination

between the proposed coatings could not be established because the tips

of the bristles were sharp and irregular.

Scratches matching the path of the brush bristles were observed in the

wear scars of both sample types under all load and speed

conditions.

The NRL samples also exhibited ridges perpendicular to the sliding direction similar to the abrasion pattern.