• clocks and piers 



tanker terminal 

 structures 



* port and harbor walls 



Figure 88. Typical uses of molded high 



density polyethylene (courtesy 

 of Schlegel Corporation). 



(2) Fenders and Bumpers . Rubber and high density polyethylene 

 (HDPE) are excellent and widely used materials for fenders and bumpers. 

 High density polyethylene has excellent properties for marine application 

 such as sliding fenders. It has excellent low friction properties, good 

 toughness, and resistance to abrasion and impact damage. High density 

 polyethylene may be cross linked to form a three-dimensional structure to 

 make it even higher in strength. However, its elongation and flexibility 

 properties are reduced as its strength is increased. 



Polyethylene outlasts wood rubbing strips on fenders four to five times, 

 is easily machinable or extrudable, and requires little maintenance. It also 

 has greater fire resistance than wood. This fire resistance can also be 

 enhanced by certain formulation modifications of the polyethylene. 



Rubber, in the form of tires and molded shapes, is utilized with excellent 

 success as rubbing bumpers. Old tires are frequently found in harbors as 

 bumpers for small craft. The energy absorption capacity of old tires is 

 unpredictable and not relied upon for larger vessels. For larger vessels, a 

 chain net of tires over a rubber or HDPE cushion block to provide energy 

 absorption may be used. Figure 89 shows such an application. 



d. Pipe Forms. 



(1) F iber Reinforced Plastic (FRP) . This special pipe is 

 coming into wide usage today. It is often referred to as. RTRP (reinforced 

 thermosetting resin pipe). As mentioned above, thermosetting resins such as 



304 



