Mold material carbonizing

Recently, thermoplastic composites such as GMT and LFT are becoming more and more popular in the automotive industry whereas thermoset molding compounds have been the principal molding materials. Carbon fibers are increasing their share even in the automotive industry in spite... 

Carbon Composites. In this class of materials, carbon or graphite fibers are embedded in a carbon or graphite matrix. The matrix can be formed by two methods chemical vapor deposition (CVD) and coking. In the case of chemical vapor deposition (see Film deposition techniques) a hydrocarbon gas is introduced into a reaction chamber in which carbon formed from the decomposition of the gas condenses on the surface of carbon fibers. An alternative method is to mold a carbon fiber—resin mixture into shape and coke the resin precursor at high temperatures and then foUow with CVD. In both methods the process has to be repeated until a desired density is obtained. 

Recently, results of careful experiments were reported by Ito et a/.101 They claimed that formic acid, formaldehyde, and methanol, which had been previously reported as photoelectrochemical reduction products of carbon dioxide, were observed also by photolysis of cell materials, such as electrolytes, including 15-crown-5 ether, and epoxy resin, which has often been used as the molding material of semiconductor electrodes in aqueous solutions. Previously reported reduction products were obtained also under nitrogen with (Table 4) and without (Table 5) a p-GaP photocathode under illumination. These precise experiments under improved conditions, where no photolytic products were observed, gave the result that the main reduction product of carbon dioxide at a p-GaP photocathode in aqueous electrolytes was formic acid. Thus, many kinds of products reported in previous papers83,97,100 were suggested to be due to photolysis of cell materials. 

By the addition of glass fibers, textile fibers, or chopped fabrics to crosslinkable polymers molding materials are produced with increased tensile strength, stiffness, and thermal stability compared to the filler-free polymers. The so-called reinforcing fillers, like carbon black, have good adhesion to the matrix due to their nonpolar structure and their characteristic geometry. 

Asbestos-reinforced organic binders (thermoplastics, duroplasts and elastomers) are widely utilized e.g. hardenable molding materials on the basis of asbestos-reinforced phenol or melamine resins for the manufacture of insulating components for combustion engines, components for electrical installations, cogwheels etc. Possible fiber substitutes are glass fibers, carbon fibers and other synthetic fibers (e.g. aramide fibers) and non-fiber fillers such as calcium carbonate, clay or talcum. 

C being a direct consequence of the nanostructure. Thus, Carbon-AeroSand composites have a high potential as a new core and mold material for foundry applications (Chap. 36). 

Molding. The precursor polymer is often combined with other materials such as solvents to obtain the desired molding and carbonization characteristics. Some of these compositions and processes are considered proprietary by the manufacturers. 

Castings are produced by different molding processes green sand, air-set sand, resin-bonded sand, rammed graphite, investment, etc. The corrosion resistance of an as-cast surface is a function of the moulding process, pouring temperature, and mold surface treatments or mold washes. Carbon pick-up and mold reactions are just two of the factors that influence corrosion resistance. The corrosion resistance of most machined surfaces will be independent of the molding process provided that 1/16-1/8 in. of material is removed. 

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