Compression molding, plastics

Figure 14.1 Schematics of compression molding plastic materials...

Chrysler specified a modified polymethyl methacrylate (PMMA) laminating resin for the body panels of the high-performance sports car, the 400 bhp 10 cylinder Dodge Viper, which went on sale in January 1992. The transition from styling to production took only three years. The decision to use glass fiber reinforced PMMA resin, molded by resin transfer, was a fundamental departure from established Chrysler practice, where previously all main exterior bodywork had been in sheet metal. However, at expected sales of 3000 a year and a unit price of about 50,000, sheet metal would not have been viable and the annual volume was too low to justify injection or compression molded plastics. 

A large proportion of the amino resin produced is used as compression-molded plastics, with or without carrier materials such as cellulose. Amino resins are less colored and less light sensitive then phenolic resins, but they are more sensitive to humidity and temperature. Urea formaldehyde resins can be employed up to temperatures of 90° C and melamine formaldehyde resins up to 150°C. The urea formaldehyde resins are particularly suitable for rapidsetting compression molding materials. Of course, aniline formaldehyde resins must be used as pre-cross-linked products, since no aromatic nucleus condensation occurs in the absence of acid catalysts and a postcuring with... 

Spritzprflgen compression modulus Kompressionsmodul compression-molded plastic part... 

The only standardized test is the wet-treeing test for cable, EIC CS5-79, of the Association of Edison Illuminating Company. Both initiation and rate of wettree growth are important. Among other accepted techniques, one uses a compression-molded plastic specimen with sharp conical depressions, which are filled with water or electrolyte. The pie-plate specimen is then placed in water and different voltages are appUed between the water in the specimen and the surrounding water. The number, size, and nature of the trees, eg, bush, fan, bow-tie, etc, are observed periodically. The complexity of such observations. 

A film is placed in a compression mold. Plastic is extruded onto the film. Often times a reinforcing layer such as glass fiber matt is added. The mold is closed. The heat from the extruded plastic will heat the film for forming. The film provides a class A surface part. Films such as polyvinalinedifloride/acrylic, polyester, ionomer, and ASA have been used. 

Keywords recycling, cross linking, compression molding, plastics foaming, chemical blowing agents. 

PCTFE plastic is available in products that conform to ASTM 1430-89 Type 1 (Grades 1 and 2) and is suitable for processing into parts that meet MIL-P 46036 (Federal Specification LP-385C was canceled 1988). Standards for fabricated forms are available for compression molded heavy sections (AMS-3645 Class C), thin-walled tubing, rod, sheet, and molded shapes (AMS-3650). PCTFE plastics have been approved for use in contact with food by the FDA (55). 

Eoamable compositions in which the pressure within the cells is increased relative to that of the surroundings have generally been called expandable formulations. Both chemical and physical processes are used to stabilize plastic foams from expandable formulations. There is no single name for the group of cellular plastics produced by the decompression processes. The various operations used to make cellular plastics by this principle are extmsion, injection mol ding, and compression molding. Either physical or chemical methods may be used to stabilize products of the decompression process. 

Wet System Compression M olding. Wet system compression molding was the first high volume method for manufacturing reinforced plastic parts, in such appHcations as the Chevrolet Corvette, industrial trays, tote boxes, luggage, refrigerator liners, and other commercial appHcations. 

Arc Extinguishing Plastics 1964 E Injection or compression molded and extruded Fuse tubing, lightning arrestors, circuit breakers, panel boards... 

Some plastics, such as the TSs and in particular the TS-RPs (RTSs), can produce products with exceptionally tight tolerances that practically meet zero tolerances. In injection or compression molding of relatively thin to thick and complex shapes, tolerances can be held to less than 0.001 in. or to even zero, as can also be done using hand layup RP fabricating techniques. 

TS plastic products that are injection, transfer, or compression molded combine thick and thin sections relatively easily since the hardening process is a chemical reaction (Chapter 6). Annular shapes are best made by compression to gain best dimensional control and freedom from distortion. In the compression process, the molding compound is compressed and reduced to the plastic state in the mold. During this process, portions of the material may lie in hard forms in the mold while other portions are flowing rapidly with great force. 

The TS plastic compression-molded products will have a higher shrinkage when ... 

PVC, PVA, PVAC, Copolymers) organosols forms available including hard and flexible types. Properties are highly dependent on plasticizer used. May be injection, extrusion, compression molded, vacuum formed. Low cost. antistatic sheet and hose, RF gaskets, heat-shrinkable tubing. 

Some specialized uses of PETN are summarized below. Expendable cartridges for small arms are made by coating unglazed grains or single base smokeless powder with PETN, spraying with plasticized thermoplastic binder and compression molding to the desired shape (Ref 99). Tucker et al (Ref 85) describe a spark detonator without primary expls. Secondary... 

The behavior of plastic structures under compression plays a critical role in numerous applications. It has been recognized that the buckling of metals under elevated temperatures presents important distinctions from the classical Eulerian case, [11]. During an experimental study, [12], buckling times were registered for a range of compressive loads applied to the top of compression molded and annealed thermoplastic samples (see Fig. 2). A typical time - load dependence is shown in Fig. 3. 

Pf pressure at the tip of the screw for an injection-molding plasticator (Eq. 10.22) Q extrusion rate in kg/h O specific rate in kg/(h-rpm) for Eq. 10.21 R compression rate in the helical direction Pjs belt sheave reduction Rg speed reduction for the gearbox S support distance from the fixed end of the barrel shear strength of the material used for the screw t plasticating time in seconds (Eq. 10.21)... 

Mixed, or commingled, plastics must be dealt with differently to find end uses. Several technologies exist for mixed plastics, such as the ET/1 extrusion process from Advanced Recycling Technology of Belgium and a compression-molding process from Recycloplast of West Germany. At... 

An important step in the manufacture of any plastic product is the fabrication or the shaping of the article. Most polymers used as plastics when manufactured are prepared in pellet form as they are expelled from the reactor. These are small pieces of material a couple of millimeters in size. This resin can then be heated and shaped by one of several methods. Thermoset materials are usually compression molded, cast, or laminated. Thermoplastic resins can be injection molded, extruded, or blow molded most commonly, with vacuum forming and calendering also used but to a lesser extent. 

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