applied to all foam floats, especially in seawater. This protection may be a brush of spray 

 coat of polyvinyl-acetate emulsion or dense polyurethane, a fiberglass and resin application, 

 a plaster coating, or concrete encasement of the foam. 



Extruded polystyrene is often preferred to the heat-spanded pellet product (headboard) 

 because it is of uniform quaUty and is completely impervious to water. However, unless 

 specially treated, it can be damaged by petroleum product spills and must be protected by a 

 hydrocarbon -resistant coating where this is a potential hazard. The expanded-peUet product 

 can also be made hydrocarbon-resistant and is usually less costly than extruded polystyrene. 

 If improperly made, it can be penetrated by water and may lack the desired amount of 

 cohesiveness. To reduce costs, some manufacturers have used a less than minumum amount 

 of material and have overexpanded the beads, producing a friable foam with high void 

 content. Unequal heating during manufacture will also produce a foam with various flaws. 

 Adequate density specification and proper heat-expansion techniques will correct both 

 problems. Because of the widespread use of polystyrene for flotation, the following 

 specifications, recommended by the California Department of Navigation and Ocean 

 Development (State of Cahfornia, 1971), are quoted for the guidance of prospective 

 purchasers of polystyrene for flotation of structures in marinas: 



"(1) Materials: Cellular polystyrene may be formed by the expansion of high 



density beads or granules in a mold or directly from the base resin by extrusion. 



The material shall be firm in composition and essentially unicellular. No 



reprocessed materials shall be used. 



(2) Dimensions: Unless otherwise specified, the manufacturers' standard size 

 will be acceptable if incorporated into the design with a minimum of field cutting. 

 The tolerance in each dimension shall be plus 1 inch or minus 0.5 inch. 



(3) Color: As normally suppUed by the manufacturers for the particular 

 type of polystyrene. Variation in color indicative of damage or deterioration will 

 not be accepted. 



(4) Surface Finish: Surface shall be stressed, polished, free from pits, 

 bUsters, cracks, dents, waviness, heat marks, or deep scratches. 



(5) Odor: The material shall be free from any objectionable odor. 



(6) Exterior Coating: In all locations where the waterfront is subject to 

 infestation by marine borers which damage polystyrene, the flotation material 

 shall be protected with an adequate material capable of resisting any anticipated 

 attack by marine organisms. 



(7) Physical Properties: Specimens from polystyrene planks shall conform 

 to the requirements stated below: 



(a) Density: 1.5 pounds per cubic foot (minimum). 



(b) Compressive Strength: 20 pounds per cubic inch minimum at 5 

 percent deflection. 



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