Binder carbon fibres

Pitch is a common high temperature binder. The extrudates with green pitch are preoxidized at medium temperatures in order to stabilize the pitch. Crosslinkages are created through the graphene layers in order to transform the fluid state into a solid skeleton in a subsequent high temperature treatment, and prevent the complete pyrolysis of the pitch. This step is similar to the stabilization of carbon fibres, after the melt spinning step [51]. 

Thin sheets of carbon produced in the same fashion as paper from a carbon fibre or graphite and binder slurry. Its conductivity and resistance to corrosion have led to its use as electrodes in electrostatic precipitators. 

Conductive organic coatings consist of a conductive carbon pigment in an organic binder. The most widely used systems have been solvent based. There are also water-based systems which have been developed more recently. One proprietary system uses a nickel coated carbon fibre rather than flaked graphite. 

Otani S, Some properties of a condensed polynuclear aromatic resin (COPNA) as a binder for carbon fibre composites, J Mater Sci, 21(6), 2027, 1986. 

A PAN-based carbon fibre tow coated with a novel, low-cure-temperature thermosetting resin. Hydrosize U-Nyte Set 201 binder. 

Oxygen reduction studies and cyclic voltammetry were carried out at ambient temperature (22 2°C) in 1 cm gas diffusion electrodes as previously described (8). The catalyst, mixed with ca. 50 mass % PTFE as a binder (and Nafion solution in one case), was spread on carbon fibre paper (CFP Toray TGPH090), which was then hot-bond to a Nafion 117 membrane. In the cell, a controlled flow of gas (O2, or N2 for cyclic voltammetry) was passed over the CFP and the membrane was in contact with a 1 M H2S04(aq) solution containing counter and reference (SCE) electrodes. 

Fig. 1. Thermal conductivity (X, W/m K) of glass-carbon fibres EDT-10 on the basis of epoxy binder and AG-4C on the basis of phenoloformaldehyde binder.

It may be supposed that in the test material affected by residual and thermal stresses, which are due to sign-different coefficients of linear expansion for carbon fibre (negative) and for glass fibre and binder (positive), two simultaneous processes take place in the microvolumes around each monofibre. These are formations of overmolecular microfibril structures of higher order and overmolecular binder film structures. 

Thermal properties of glass-carbon fibres depend on the anisotropy of the binder film properties that is caused by thermal stresses, whose value and direction depend on the temperature range and filler composition and which is of a variable nature. 

As shown in Fig. 5 7(b) the solid polymer electrolyte cell comprises a membrane, fuel cell type, porous electrodes and three further components z carbon collector, a platinized titanium anode support and a cathode support made from carbon-fibre paper The collector is moulded in graphite with a fluorocarbon polymer binder A 25 pm thick platinized titanium foil is moulded to the anode side to prevent oxidation. The purpose of the collector is to bnsure even fluid distribution over the active electrode area, to act as the main structural component of the cell, to provide sealing of fluid ports and the reactor and to carry current from one cell to the next E>emineralized water is carried across the cell via a number of channels moulded into the collector These channels terminate in recessed manifold areas each of which is fed from six drilled ports. The anode support is a porous conducting sheet of platinized titanium having a thickness of approximately 250 pm. The purpose of the support is to distribute current and fluid uniformly over the active electrode area. It also prevents masking of those parts of the electrode area which would be covered by the... 

Modem electrodes tend to use carbon-supported catalysts, mixed with PTFE, which are then rolled out onto a material such as nickel mesh. The PTFE acts as a binder, and its hydrophobic properties also stop the electrode from flooding and provide for controlled permeation of the electrode by the liquid electrolyte. A thin layer of PTFE is put over the surface of the electrode to further control the porosity and to prevent the electrolyte passing through the electrode, without the need to pressurise the reactant gases, as has to be done with the porous metal electrodes. Carbon fibre is sometimes added to the mix to increase strength, conductivity, and roughness. Such an electrode is shown in Figure 5.8. 

To improve adhesion of binders to fibres, including carbon fibers, methods of surface treatment by cold plasma were developed. In the course of such treatment, the removal of a weak border layer of the fiber proceeds and the contact between the surface and a binder is improved. At the same time, the number of active centers capable of chemical interaction with a binder increases and the wetting becomes better. It may be expected that pol5mierization under plasma action may also serve as a tool adhesion improvement at the phase border. In spite of the existence of many ways of surface treatment of the reinforcement surface, no model of interaction was proposed which is effective in predicting the t5T)e of reinforcement by surface treatment of a given filler-matrix combination. According to Drzal, the major reason for this lack of theoretical developments is in the over-simplification of the composition and nature of the filler-matrix interface. 

---