Elongation and Permanent Set. The material must not stretch 

 excessively when subjected to operational loads, and should return to 

 pre-load lengths after removal of the load. It should be dimensionally 

 stable under varying conditions of load, moisture, and temperature. 

 This stability is important to insure that the boom retains its shape 

 and features while under operational conditions in seawater. 



The elongation capacity of a material can be expressed in terms of 

 percent of original length when stretched to breaking, as determined 

 from FTMS 191 Method 5102, in terms of the stress-strain curve for the 

 material or in terms of its 100% modulus which is the stress required to 

 elongate the material 100% of its original length. 



A relatively low total elongation of a fabric, characterized by a 

 steep stress- strain curve and high 100% modulus, and recovery from 

 elongation are desirable for containment boom material to prevent the 

 boom from losing its shape when subjected to uneven load distribution 

 along the height of its cross section as is normally encountered with a 

 floating barrier subjected to wind, wave, and current forces. The 

 below-water portion of the curtain material subjected to the greater 

 current loads can cause boom failure through loss of draft as the load 

 relieves itself through fabric stretching. 



Required values for the elongation properties of a boom material 

 have not been established. The requirements must, however, be based on 

 boom design. 



Low Density. In emergency spill situations the boom must be de- 

 ployed as quickly and with as few personnel as possible; therefore, the 

 lighter the boom the easier it is to deploy and retrieve. A lightweight 

 material, however, must also have sufficient strength, so lower density 

 material may need to be thicker or bulkier to develop the required 

 strength. The strength-to-weight ratio of a material offers a means of 

 comparing materials for density. 



Nonporous. The material must be impervious to petroleum or its 

 derivatives. No standard test exists for measuring the porosity of the 

 material with respect to oil. However, FTMS 191 Method 5512 measures 

 the resistance of coated cloth to the passage of water under high pressure. 

 This same test can be used for measuring the porosity of the material 

 with respect to petroleum products by substituting the specific petroleum 

 product for the water in the test. This test actually measures the 

 pressure at which the liquid first appears on the other side of the 

 material. 



High Temperature Resistance. In exposure to high temperatures, 

 there must be no appreciable change in the flexibility of the material, 

 and it must not become tacky or block. A boom may be subjected to high 

 temperatures during storage for prolonged periods or during hot water 

 cleaning after use. Temperatures can be expected to be as high as 

 180°F. FTMS No. 191 Methods 5870 and 5872 are standard methods for 

 measuring the effects of high temperature on material flexure and block- 





