Epoxy resin Fibres

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

With the exception of epoxy resins, when a resin is fully polymerized it loses any irritant properties. However, associated materials, e.g. glass fibre used as a filler, or the dust from plywood or veneers, may promote initation. Partially-cured resins will retain some uritant properties. Traces of cutaneous or respiratory sensitizers liberated, e.g. by heating or machinery, may be problematic. 

Nowadays the major thermosetting resins used in conjunction with glass fibre reinforcement are unsaturated polyester resins and to a lesser extent epoxy resins. The most important advantages which these materials can offer are that they do not liberate volatiles during cross-linking and they can be moulded using low pressures at room temperature. Table 3.1 shows typical properties of fibre reinforced epoxy. 

Thermal decomposition of the matrix material offers a simple way of recovering the relatively expensive reinforcing fibres from a fibre-reinforced laminate. The epoxy resin matrix was made to decompose by thermal treatment in air or nitrogen, this treatment allowing the carbon fibres to be recovered without damage. 

Glass-fibre-reinforced epoxy resins are also used for chemical plant but are more expensive than the polyester resins. In general they are resistant to the same range of chemicals as the polyesters, but are more resistant to alkalies. 

Epoxy resins find a large number of uses because of their remarkable chemical resistance and good adhesion. Epoxy resins are excellent structural adhesives. When properly cured, epoxy resins can yield very tough materials. They are used in industrial floorings, foams, potting materials for electrical insulations, etc. One of the principal constituents in many of the Fibre-reinforced plastics (FRP) is an epoxy polymer. 

The engines of the Polimotor and Ford projects are in hybrid composites of phenolic resins/glass fibres and epoxy/glass fibres with combustion chambers, cylinders and pistons in metal. This permits the direct contact with hot combustion gases that the polymer could not support. The composite provides the rigidity of the engine. 

Alternatively, an assembly of microelectrodes can alleviate some of the problems associated with the individual microelectrodes. Such a random array of microelectrodes (RAM) comprises about 1000 carbon fibres (each of diameter 5-7 pm) which are embedded randomly within an inert adhesive such as an epoxy resin. (The ends of the fibres need to be widely spaced.) The net result is to generate an electrode system with a superior response time and a current which is IfKK) times that of a single microelectrode. By increasing the current in this way, the sensitivity of measurement is further increased. 

Random array of microelectrodes (RAM) A microelectrode system comprising about 1000 carbon fibres embedded randomly within an inert adhesive such as an epoxy resin. 

Horie. K., Murai, H.. Mita, I. (1977). Bonding of epoxy resin to graphite fibers. Fibre Sci. Technol.9, 253-264. 

Sato N., Kurauchi T., Sato, S. and Kamigaito O. (1986). Fracture mechanism of unidirectional carbon-fibre reinforced epoxy resin composites. J. Mater. Sci. 21, 1005-1010. 

Results are presented of experiments undertaken by Gaiker in the manufacture of sandwich panels containing foam cores based on PETP recycled by a solid state polyaddition process developed by M G Ricerche. Panels were produced with glass fibre-reinforced unsaturated polyester and epoxy resin skins, and allthermoplastic panels with PE, PP, PS and glass fibre-reinforced PETP skins were also produced. EVA hot melt adhesives and thermoset adhesives were evaluated in bonding glass fibre-reinforced PETP skins to the foam cores. Data are presented for the mechanical properties of the structures studied. 

Figure 5.8 — Probe-type sensor based on continuous circulation of a stream containing an acid-base indicator for the batch determination of COj in sea water, (a) Reagent delivery capillary, (d) Reagent exit capillary, (c) Optical fibre from source, (d) Optical fibre to detector, (e) White silicone rubber membrane. (/) White silicone sealant, (g) Epoxy resin, (/i) 0-ring. (/) Sensor housing. (/) Optical cable. (Reproduced from [12] with permission of the American Chemical Society).

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

The preparation of carbon disk-shape UMEs is similar to that of the carbon fibre UME. The only difference is that the active part is sealed on epoxy resin. With this purpose, a micropipette tip (1 mL) is glued to the head-tip of a carbon fibre UME. The carbon fibre is maintained in vertical position with a metal hook and the micropipette tip (1 mL) is filled with epoxy resin. Once the resin is cured, the tip is cross-sectioned with a microtome or a blade. Then, the disk carbon UME is ready. 

Carbon fibres of 7 pm diameter (Donnay, Belgium) epoxy resin (Kit A.R. Spurr, CA) pipette tips mercury copper wires oven. 

The most important polymeric matrices are linear and cross-linked polyesters, epoxy resins and linear and cross-linked polyimides the most important reinforcements are high-performance polymeric fibres and filaments (for polymeric composites), filaments of refractory metals and inorganic materials (E-glass, A12C>3, B, BN, SiC and Carbon) and whiskers (fibrillar single crystals of A1203, B4C, WC, SiC and C, exclusively for reinforcement of metals). 

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