Plastics, casting

Optics. Good optical properties and low thermal resistance make poly(methyl methacrylate) polymers well suited for use as plastic optical fibers. The manufacturing methods and optical properties of the fibers have been reviewed (124) (see Fiber optics). Methods for the preparation of Fresnel lenses and a Fresnel lens film have been reported (125,126). Compositions and methods for the industrial production of cast plastic eyeglass lenses are available (127). 

Anisotropic material In an anisotropic material the properties vary, depending on the direction in which they are measured. There are various degrees of anisotropy, using different terms such as orthotropic or unidirectional, bidirectional, heterogeneous, and so on (Fig. 3-19). For example, cast plastics or metals tend to be reasonably isotropic. However, plastics that are extruded, injection molded, and rolled plastics and metals tend to develop an orientation in the processing flow direction (machined direction). Thus, they have different properties in the machine and transverse directions, particularly in the case of extruded or rolled materials (plastics, steels, etc.). 

The process interaction in cast plastic products is mainly involved with the curing processes and with mold filling problems. Voids and porous sections are a frequent problem with castings because the mold filling is done at atmospheric pressure, or low pressure, and if the product has thin sections to fill, the flow may be a problem. 

In order for such an extensive project to remain manageable, certain requirements were necessary. Initially the data were confined to TPs, TSs, TPEs, and casting plastics. To be included in this group were the TSEs, reinforced plastics, foams, semifinished products, and others. Polymat completed its initial work in 1989. New plastics products on the market and updated additional information on existing products are continually added. Data no longer available are still accessible to the user in a memory file. 

The properties of polymers may be improved by the presence of appropriately selected additives. With the exception of some cast plastics, such as polymethyl methacrylate (PMMA), and some fibers, such as unpigmented cotton, most commercial polymers are mixtures of the polymer with one or more additives. 

Durcon. A series of cast, plastic, epoxy formulations manufd by the Duriron Co for use in corrosion resistant equipment such as pumps, valves, fans and others Ref CondChemDiet (1961), p426... 

Tabla III. Mechanical and Thermal Properties of Cast Plasticized Polycarbonate Films... 

Indirect tooling methods are many. Examples include cast aluminum, investment metal cast, cast plastics, cast kirksite, sprayed steel, spin-castings, plaster casting, electroforming, room temperature vulcanizing (RTV) silicone elastomer (Chapter 2 Silicone Elastomer), elastomer/ rubber, reaction injection, stereolithography,338 344 (Table 17.4), direct metal laser sintering, and laminate construction. 

The nose and tail caps are cast using either plaster of paris or clear casting plastic. 

Spray the inside of the mold with a casting release agent. Hix and pour liquid casting plastic into the mold until It Is approx. I/A inch deep. Now pour in 3/16" or l/A" Steel ball bearings until you have a layer of them covering the bottom of the mold. Add casting plastic If needed so that the layer of balls is barely covered. Set Che mold a-Slde and let the plastic cure. N0T Plaster of Paris or body putty can also be used to cast the balls in. The ball bearings are the easiest to work with but any metal can be used (nuts, bolts, screws, nails, etc.). 

Although unsaturated polyester resins are often regarded as casting plastics in at least one important use, glass-fiber lamination, they are used as adhesives. The method of binding glass-fiber mats with unsaturated polyesters started in 1942 by U.S. Rubber [1]. 

Plastic tooling ru A term designating structures composed of plastics that are used as tools in the fabrication of metals or other materials including plastics. While they are usually made of reinforced and/or filled thermosets, flexible silicone or polyurethane tools are often used for casting plastics. Common applications of rigid plastics... 

High-impMt copolymer and rubber-modified compound Unfilled with molybdenum disulfide Impact-modified 30% glass fiber-reinforoed EMI shielding (conductive) 30 /o PAN carbon fiber Cast Cast, heat-stabilized Cast, oil-filled Cast, plasticized Cast, Type 612 blend Molding compound... 

Casein plastics can be fabricated in the same manner as cast plastics. The hardening operation, which is considered to be a condensation reaction between the aldehyde and the amino group of the casein molecule, transforms the material from a thermoplastic to a thermosetting condition. Casein plastics are nonflammable and extremely tough. These properties along with its availability in all colors have given casein its widest use in the manufacture of buttons, buckles, etc. The usefulness of the material is somewhat limited by its odor, but more importantly by its absorption of water (7-14% after 24-h water immersion). Because of this hygroscopic nature, casein plastics are not suitable where dimensional stability is desired. Casein plastics are not widely nsed today. 

High-impact Copolymers and Rubber-modified Compounds Unfilled with Molybdenum Disulfide Impact-Modified 30% Glass Fiber-Reinforced EMI shielding (Conductive) 30% PAN Carbon Fiber Cast Cast, heat-stabilized Cast, Oil-Filled Cast, Plasticized Cast, Type 612 Blend Molding Compound... 

In 1872, Baker found that the reaction between phenol and formaldehyde yielded a resinous product. The resin could be formed and cured and thus used for the production of a variety of moulded and cast plastic products. Baekland made the first successful commercial exploitation and the product entered the market in 1909 under the name of Bakelite. This was the first wholly synthetic polymer. Fillers and other additives were used to improve the product. From these first resins, other varieties have been developed so that phenol-formaldehyde resins now designate a group of resins with varying properties made from different phenols and aldehydes. 

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