Hybrid Fluorosilicones for Aircraft Fuel Tank Sealants. Part 4. Synthesis of Fluorocarbon and Fluorocarbon Ether Hybrid Fluorosilicone Polymers

摘要

Two fluoroether silicone (FES) elastomeric polymers were synthesized, and cured research samples were delivered to AFML for evaluation. These polymers were based on the -(CF2)2O(CF2)NO(CF2)2- (n = 2,5) backbone unit. A one-step synthesis of I(CF2)2O(CF2)2O(CF2)2I from commercially available starting materials was demonstrated: about 110 g of this fluoroether was prepared, and over 500 g of I(CF2)2O(CF2)5O(CF2)2I was synthesized. Coupling studies of the alpha, omega-diiodoperfluoroethers have shown: (1) A good yield (71%) of dimer and trimer is produced by photolysis of I(CF2)2O(CF2)5O(CF2)2I/Hg/C7F16; (2) Fair yields (ca. 40%) of dimer and trimer are produced by heating copper-bronze powder with the ether, but some hydrogen endblocked materials are also produced; (3) Heating with Hg or Cu(Hg) produces mercury-inserted fluoroether oligomers. The following samples of LS/FCS-210 copolymer sealants were prepared and submitted to AFML for evaluation: 1 pound LS/FCS-210 (0.9/1.0), unformulated, 1 pound LS/FCS-210 (0.9/1.0), formulated, Research sample LS/FCS-210 (1-1.2/1.0), unformulated, Research sample LS/FCS-210 (1.5/1.0) unformulated. In addition, Dow Corning Corporation has attempted to prepare samples of alternating LS/FCS-210 copolymers having the following ratios: 1/1, 1.5/1, 2/1. Analyses are pending.