come in contact with under operational conditions. Resistance to oil is 

 generally an inherent property of the material that cannot be changed by 

 the addition of plastic or other modifiers. This requirement was used 

 to initially screen the variety of materials available [21,22]. Further 

 screening was accomplished by considering general weathering and flexural 

 properties to obtain the list of candidate coating materials contained 

 in Table 3 [17]. The coatings impart much of the physical and chemical 

 resistive properties to the complete material with the exception of 

 strength which is usually determined by the woven fabric substrate. 

 Table 3 also contains information on the properties of these coatings as 

 published by the manufacturers [22]. 



Nearly all of the coatings indicated in Table 3 would be suitable 

 for use on containment boom. Many of them offer exceptionally good 

 characteristics. For instance, the Viton and Teflon have excellent 

 resistance to most oils, fuels, and many aliphatic and aromatic hydro- 

 carbons, are virtually unaffected by weather and high temperatures, and 

 have outstanding abrasion resistance [17,21,22], Perhaps the main 

 technical drawback to Viton or Teflon is their high specific gravity 

 which would make a containment boom heavy and difficult to handle. 

 Teflon also presents some problems in processing because of its low 

 coefficient of friction and its nonadhesive character. On the nontechni- 

 cal side, the specific gravity coupled with the high price of the elastom- 

 ers makes its use almost prohibitive. 



The polyester elastomer Hytrel [22] also exhibits nearly all the 

 properties required in a coating material for containment booms. It's 

 use would necessarily be restricted to substrate other than polyester 

 although use without reinforcing substrate is possible because of the 

 high tensile strength of this material. 



Polyurethanes also exhibit extremely high tensile strength and can 

 be used without a reinforcing substrate although they can be combined 

 with polyester or nylon fabrics to obtain a coated fabric possessing 

 nearly all the requirements for containment booms [22,23], Polyurethanes 

 generally have either a polyester or polyether base. Polyester-based 

 urethanes do not perform well in the presence of moisture and are not 

 recommended [11]. On the other hand, the polyether-based urethanes 

 exhibit good resistance to moisture. This resistance improves as the 

 coating thickness increases; with thicker material the flexibility is 

 reduced. The stiff er material may impair the wave conformance capability 

 of the containment boom. 



Poly (vinyl chloride) (PVC) can be made to have all the qualities 

 required in a containment boom material through the addition of plastici- 

 zers to improve its flexibility and resistance to ultraviolet light and 

 oxidation [17]. A problem with materials that use plasticizers is that 

 the plasticized plastics are subject to swelling after prolonged exposure 

 to oils resulting in shortened operational life of the material. 



17 



