Document dnp6jKZvQpqw68L36eke0DLJQ
The irreplaceability of CTFE-based polymers General Comment: Sinochem Lantian is an enterprise specializing in the CTFE series of polymers. CTFE-based polymers is widely used to meet exceptional requirements in the aerospace field, with outstanding chemical resistance, ultra-low temperature resistance, and high barrier properties. Currently, there are no viable alternatives for this application. Therefore, we request an indefinite extension of this use until a feasible alternative is available. The main reasons are as follows: In the aerospace field, the CTFE series of polymers primarily achieve essential properties like ultra-low temperature resistance [1] and high barrier properties [2]. Specifically, when these polymers are applied in certain rocket valve systems, the sealing components in contact with liquid fuel must meet requirements such as not reacting with the liquid fuel, not becoming brittle at ultra-low temperatures, and not causing liquid fuel leakage. Currently available alternatives mentioned in the draft cannot fully replace them.
Table 1: Permeation Resistance Data Comparison
(According to the permeation data in Table 1, whether compared with fluorinated materials or materials produced from non-PFAS sources, PCTFE has the lowest water vapor permeability, at only about 0.2g/m2*day. This represents the excellent density of PCTFE material, making it highly suitable for sealing components in the aerospace field that come into contact with liquid fuel. It prevents liquid fuel from permeating or leaking. In contrast, using other materials would pose the risk of liquid fuel permeation and leakage.)
medium
HCl H2SO4 ClHSO HNO3 H2CrO4
HF NaOH Na2CO3
Cl2 Br2 H2O2 HCOOH CHCl3 CH3COC H3 C6H6
Table 2: Chemical Resistance Data Comparison
Concentrati
on
PCTFE PE PVC PA11 CPE
%
35
112224114334112
98
111234234444234
-
113444444444344
60
111344234444134
50
111234124444344
40
123234114234113
40
111114114123111
Saturation 1 1 1 2 2 4 1 1 4 2 4 4 1 1 3
-
233334244444233
-
111444444444334
30
111114114 - 111
96
113344124344123
-
22- 24- 44- 23- 23-
EP
234 444 444 444 344 233 123 344 444 444 111 233 34-
-
13- 24- 44- 12- 23- 34-
-
233234444123233234
(Looking at the chemical resistance data in Table 2, PCTFE has exceptional corrosion resistance. It does not react with strong bases, strong acids, or most organic solvents. Therefore, it is very suitable for sealing components in the aerospace field that come into contact with liquid fuel. When using other materials produced from non-PFAS sources, their chemical resistance is insufficient, making the sealing components prone to reacting with the liquid fuel, thus contaminating it and even causing leakage, posing a danger.)
Reference: [1] Wei C. Polytrifluorochloroethylene resin. Organo-Fluorine Industry, 1998(03), 5-11. [2] Daikin PCTFE Product Manual.