long-term water absorption studies. This is comparable to the water absorp- 

 tion of conventional epoxy glass-reinforced laminates. Consequently, 

 organotin epoxy laminates have been fabricated using the "shell" concept. 

 Organotin epoxy glass-reinforced laminates have demonstrated significant 

 antifouling effectiveness at Miami Beach, Florida. 



In addition to the epoxy resin formulation described above, organotin 

 epoxy formulations based on cycloaliphatic epoxies , novolac resins, and low 

 molecular weight bisphenol-A epoxy resins have been prepared. Studies lead- 

 ing to optimization of the antifouling effectiveness of these materials are 

 now under way. Of the best antifouling and structural formulation, organo- 

 tin epoxy preimpregnated (prepreg) glass tapes were manufactured by a com- 

 mercial company in 1978. Although the use of prepreg tape may not be 

 planned for the construction of the cold water pipe or warm water intake 

 screens, "filament-wound" amd "molded" techniques for the preparation of 

 glass-reinforced organotin plastic have been examined for Navy use in sea- 

 water piping systems. Both are considered feasible, and their subsequent 

 application as antifouling GRP could see use in a developmental OTEC plant. 

 The cost of inherently antifouling GRP pipe is difficult to estimate. 

 Development of the concept is now at an early stage. Successful completion 

 of the presently funded programs for development and application of these 

 materials would lead to a field evaluation of prototypes in the early 

 1980's. The method used to manufacture the GRP pipe and intakes would be 

 important in determining the cost estimate. Cost would either be equal to 

 or greater than fabrication costs of these two components from conventional 

 GRP. It appears that the "shell" fabrication method would be the more 

 cost effective. 



W. R. Graner mixed organotin compounds into polyester and epoxy resins 

 and used them to fabricate glass-reinforced laminates. He achieved only 

 short-term antifouling effectiveness. More recently 90-10 Cu-Ni flakes 

 were mixed into conventional polyester resins which then were used as gel 



1 TO 



coats on glass-reinforced polyester laminates. Short-term antifouling 

 protection was observed. Slime attachment to the gel coat was suggested to 

 be the major factor in reducing the effectiveness of the polyester gel coat; 

 mechanical cleaning was proposed to extend the service life of this coating. 



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