Robert F. Brady

Mechanical factors favoring release from fouling release coatings.

For some twenty years the marine coatings industry has been intrigued by polymer surfaces with low adhesion to other materials, especially to the biological glues used by marine organisms. Polymers with fouling release surfaces have been made from sundry materials, and their resistance to marine fouling in both static and dynamic tests has been evaluated in the worlds oceans. Although the polymer surface property most frequently correlated with bioadhesion is its critical surface tension (γ?), resistance to fouling is also influenced by other bulk and surface properties of the polymer. This paper reviews the types of bonding associated with polymeric materials used in fouling resistant coatings, describes the removal process in terms of fracture mechanics, and discusses the importance of surface energy, elastic modulus and coating thickness in the release of biofoulants.

Properties which influence marine fouling resistance in polymers containing silicon and fluorine

Our research strives to understand and construct polymer surfaces with no inherent power to interact with other materials, especially with the biological polymers used by marine organisms to bind themselves to objects in the sea. During the past 15 years we have synthesized polymers, formulated them into coatings, and measured their resistance to marine fouling in both static and dynamic testing. The polymer surface property which has been most frequently correlated with bioadhesion is critical surface tension (γc); in fact, a generalized relationship between γc and marine fouling has been known for more than twenty years. However, this behavior is also influenced by other bulk and surface properties of the polymer. This paper presents several alternative interpretations of the relationship between γc and bioadhesion, and uses these insights to develop requirements for polymers which refuse or resist strong bonds to other materials.

Clean hulls without poisons: Devising and testing nontoxic marine coatings

Because this paper marks 50 years since the first Mattiello Memorial Lecture, it begins with a remembrance of the man in whose honor we meet and an appreciation of his character and his contributions to the coatings industry. The body of the paper is concerned with the coating used on a hull of a ship to prevent the accumulation of barnacles and other fouling. The most effective antifouling paint now being used contains toxins and will be forbidden by international regulations within eight years. The ideal replacement will be a nontoxic material that resists the attachment of marine life and encourages the organisms to fall off the ship. This paper describes laboratory and field work during the past 18 years on a variety of fluorinated coatings and silicone coatings with these properties and criteria for formulating successful nontoxic coatings. Silicone and fluorinated coatings frustrate fouling by different mechanisms, and thus the criteria for a successful coating are distinct in important ways.

Elastomeric fluorinated polyurethane coatings for nontoxic fouling control

Nontoxic antifouling coatings have been investigated for many years as possible successors to toxic antifouling paints. Polymers containing fluorine or silicone have been tested and each has been shown to be partially effective for different reasons. This paper describes a new coating which combines the best features of fluorinated and silicone coatings and is non-toxic. Four fluorinated elastomers were prepared and tested for fouling resistance during a full fouling season. The surface energy and mechanical properties of each polymer were measured and correlated to fouling performance. One of the elastomers was shown to foul slowly, clean easily, be durable in the marine environment and organisms bonded to it only weakly. The surface energy, elastic modulus, and thickness of the elastomer may be varied as desired over wide ranges to meet differing performance requirements.

Macrofouling of hydrocarbon polymers which contain variable proportions of crystallinity

The effect of crystallinity on the ability of a hydrocarbon to resist attachment to marine fouling organisms has been investigated. Polymers composed only of carbon and hydrogen were casted or extruded and were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and contact angle measurements. The polymers were immersed in Chesapeake Bay and evaluated at monthly intervals. All materials accumulated barnacles, algae and slime. During periods of most active growth, the polymers required moderate scraping for cleaning, but were restored to their original appearance usually with little or no damage. Fouling of the films was not influenced by their content of crystallinity.