Polyester fibers by definition are composed of at least 85% by 

 weight of an ester of a dihydric alcohol and terephthalic acid [17]. 

 Polyester fibers are more dimensionally stable than nylon or acrylic 

 (Orion) , have a high tensile strength and high elastic recoveries from 

 small deformations [8]. The elastic modulus is much higher than that 

 for corresponding nylons. Another feature of the polyester fibers is 

 the retention of mechanical properties when wet. They also absorb 

 little water and have excellent resistance to most chemicals and organic 

 solvents as well as good weathering characteristics. Polyester fiber is 

 much more ultraviolet resistant than nylon. 



Glass fibers exhibit nearly all of the properties desirable in a 

 fiber suitable for containment boom with the exception of stiffness. 

 The fibers are much more rigid than any of the other manmade or natural 

 fibers. Glass fibers when used in a situation requiring large flexures 

 tend to cut themselves as they rub against each other. For this reason 

 these fibers are generally used in rigid plastic situations rather than 

 in coated fabrics that will be subjected to continuous flexing. 



As a result of the examination and comparison of the properties of 

 the manmade and natural fibers, nylon and polyester fibers appear to be 

 the most appropriate for use as a substrate for coated material for 

 containment boom. The acrylic and modacrylic fibers also exhibit all 

 the necessary characteristics but have much lower strength-to-weight 

 ratios than either nylon or polyester. Polyester has an advantage over 

 nylon because of the greater dimensional stability and better water 

 absorption characteristics. 



Coating Materials 



Nearly all coating materials used in any quantity today are synthetic. 

 Coatings can be generally categorized as rubber or plastic. Plastic 

 materials by definition contain at least one polymeric substance of 

 large molecular weight that is shaped by flow during processing but is a 

 solid in its finished state [20]. Rubbers are materials capable of 

 recovering from large deformations quickly and forcibly and have been 

 modified such that they are essentially insoluble in boiling solvents. 

 These definitions are not mutually exclusive. Materials having proper- 

 ties of both plastic and rubber are generally classified as rubber. 



Another term used in a broader sense is elastomer. Elastomers are 

 substances capable of being stretched to twice their original length at 

 standard conditions and, once the stretching force is removed, return 

 almost immediately to their original length. Thus, many plastic and 

 rubber materials can be considered elastomers. 



The number of different plastics and rubber materials being used 

 commercially in coated fabrics is extremely large and to discuss the 

 attributes of each of them would be a time consuming task and would not 

 add significantly to this report. As stated in MATERIAL REQUIREMENTS, 

 for a coating to be suitable for use in a containment boom, it must be 

 resistant to degradation from oil or other petroleum products it may 



16 



