Fluorinated-pitch chemical crosslinking

For mechanical test such as tensile test and flexural test, the impregnation of polymer-blend to the carbon fiber was carried out several soakings of the fiber in the polymer-blend dispersion consists of PTFE (98.2 wt%) and fluorinated-pitch (1.8 wt%). A sheet of chemical crosslinked pre-forming sample was prepared under the pressure at around 20 MPa and then heat-treated at 350 °C 5 °C for 30 minutes. Samples were irradiated by EB up to 1000 kGy at 335 °C 3 °C in nitrogen gas atmosphere. 

Chemical Crosslinking of PTFE using Fluorinated-Pitch... 

The first degradation step of fluorinated-pitch should be induced crosslinking reaction in PTFE molecules. That is, the crosslinking would be occurred in PTFE molecules through thermal chemical reaction with decomposion of fluorinated-pitch without EB irradiation. 

Table I shows the mechanical properties of the carbon fiber-reinforced PTFE (PTFE composite non-crosslinked) and the carbon fiber-reinforced PTFE with fluorinated-pitch (PTFE / FP composite thermo-chemical crosslinked). For the tensile test with a direction of 45 ° for plane-woven carbon fabric, the tensile strength of the PTFE / FP composite was about 2.3 times higher than that of the non-crosslinked PTFE composite. Moreover, the Young s modulus of the crosslinked composite was about 2.6 times higher than that of the PTFE composite. The tensile strength and Young s modulus are results of 0 ° or 90 ° direction for the fabric reflected the carbon fiber strength and the modulus.

The synergistic crosslinking was carried out, that is, EB-crosslinking treatment was performed after thermo-chemical crosslinking treatment of PTFE with fluorinated-pitch (1.8 wt% additive). The thermal properties of obtained crosslinked PTFE were examined by DSC analysis shown in Table II. The melting and the crystallization temperatures of radiation-crosslinked PTFE (RX-PTFE), thermo-chemical-crosslinked PTFE (CX-PTFE), synergetic-crosslinked PTFE (thermo-chemical and radiation SX-PTFE) shift to lower temperatures, compared with PTFE. 

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