Fluorosilicone elastomer based on the poly[(3,3,3‐trifluoropropyl)methyl‐siloxane‐co‐(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)methylsiloxane]

Fluorosilicone elastomer based on the poly[(3,3,3-trifluoropropyl)methylsiloxane-co-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane] was studied. First, the synthesis of fluorosilicone polymer based on the poly[(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane] (PNFHMS) was examined by the polymerization of 1,3,5-tris(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-1,3,5-trimethylcyclotrisiloxane (C4F9D3) by sodium hydroxide. On the contrast of the polymerization of the commercially available 1,3,5-tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclotrisiloxane (CF3D3), the polymerization of C4F9D3 with sodium hydroxide resulted in the formation of 1,3,5,7-tetrakis(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-1,3,­5,7-tetramethylcyclotetrasiloxane : [C4F9CH2CH2(CH3)SiO]4 (C4F9D4) as the major product. It was due to the easy occurrence of the depolymerization by the back-biting mechanism, because C4F9D4 is more stable ­than 1,3,5,7-tetrakis(3,3,3-trifluoropropyl)-1,3,5,7-tetramethylcyclotetrasiloxane : [CF3CH2CH2(CH3)SiO]4 (CF3D4). The above result made us to conclude that it was difficult to apply the polymer based on PNFHMS to heat vulcanizable elastomers and to investigate the elastomer based on the poly[(3,3,3-trifluoropropyl)methylsiloxane-co-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane]. C4F9D3 and CF3D3 were co-polymerized successfully by sodium hydroxide and formulated with the silica treated by CF3D3. The use of silica treated with methylsilyl unit failed, because creep-hardening phenomenon occurred. This elastomer was evaluated about some mechanical properties, and the resistance to organic solvents, and a fuel. The advantage that can be detected from the introduction of [C4F9C2H4-(CH3)SiO] unit was that the resistance to the polar solvents such as acetone and dimethylformamide was improved. Copyright © 2001 John Wiley & Sons, Ltd.