Mold inching

Impact Failure. Standard notched Izod impact measurements have been made over wide temperature ranges on specimens cut from compression molded %-inch thick sheets of BPA polycarbonate and two BPA carbonate-silicone block polymers (Figure 4) (see Table I for compositions and properties). In the homopolymer a ductile-brittle transition occurs at 0° to —15°C, as reported previously (4, 5). Introduction of 15 and 25% silicone lowers the transition to —45° and —110°C (block polymers A and B). As indicated in Table I, this increase in toughness at low temperature is accompanied by the reduction of modulus and yield stress. 

The important tensile modulus (modulus of elasticity) is another property derived from the stress-strain curve. The speed of testing, unless otherwise indicated is 0.2 in./min, with the exception of molded or laminated TS materials in which the speed is 0.05 in./min. The tensile modulus is the ratio of stress to corresponding strain below the proportional limit of a material and is expressed in psi (pounds per square inch) or MPa (mega-Pascal) (Fig. 2-7). 

On another occasion, upon addn of tri-methyl phosphite to anhyd Mg perchlorate, the mixt expld with injury to the operator (Ref 12a). Anhyd Mg perchlorate was added to a mixt of Bu acrylate and acrylonitrile, and the mixt polymerized in a 2.75 inch mold to give an illuminating flare of 2 miilion CP (Ref 14)... 

Table XII. NBS Smoke Chamber Data for Electroless Nickel on Injection Molded Polycarbonate (1 /8 inch thickness)...

Coating with Bulk Polybutadiene. E-glass fabric was embedded In Firestone s Diene 35 NFA using procedures very similar to those used to prepare peel test specimens. Rubber, which had been mill-mixed with 0.05% dlcumyl peroxide, was premolded between Mylar sheets to the desired thlckness(0.308, 0.151, or 0.100 cm) and size ( 30.5 X 18 cm) by molding for 1 hour at 60 C. and 40,000 lbs/5" ram. Fabric was cut so that the final size was at least one Inch smaller than the rubber sheets In all directions. A sandwich was made from the fabric and two premolded rubber sheets of the same thickness and about half the total thickness of the final sandwich. The sandwich was cured In a press for 2 hours at 150°C and 5000 lbs/5" ram. In the cured specimen the fabric was embedded In the center of the molded specimen (0.15 -0.40 In thick). Samples were Immensed In alkali before cutting to size for tensile tests. 

Injection molding requires the barrel temperature to be about 350°C with a barrel pressure in excess of 138 MPa. The mold is maintained at 110°C to ensure uniform flow and high definition, and to discourage an uneven index of refraction, birefringence. The CD is about four one-hundredths of an inch (0.5 mm) thick. For prerecorded CDs, the PC is compression-molded on a stamper imprinted with the recorder information. This takes about 4 sec. Once the clear piece of polycarbonate is formed, a thin, reflective aluminum layer is sputtered onto the disc. Then, a thin acrylic layer is sprayed over the aluminum to protect it. The label is then printed onto the acrylic surface and the CD is complete. This process is described later in greater detail. 

For the cement stabilization option, a facility would be constmcted to dewater and treat the wastes. There would be a 7- to 21-day staging period of wastes for quality assurance operations. An online rate of 250 days a year was assumed. It is estimated that cement stabilization would result in a volume factor increase roughly 3.75 times the total volume of waste treated. This increase in volume is necessary to immobilize technetium present in the wastes and to achieve a final waste form that could withstand pressures of 500 pounds per square inch (psi). The cement would be placed in 4-ft by 4-ft by 8-ft steel containers that would serve as a mold and to facilitate the handling of the finished blocks (D114432, Appendix A). 

Sample Temperature Rise Owing to Irradiation. A temperature rise of 2.9°C. during irradiation was found at the center of 0.033-inch thick water-cooled polystyrene samples for a beam current of 10 fxa. This temperature was measured several times, using thermocouples compression-molded into the center of the samples. The thermocouple leads entered the sample from the direction shown in Figure 1. Several different thermocouple junction sizes were used, with the same measured results. 

Samples for irradiation crosslinking were prepared by milling in the antioxidant, followed by compression molding. Sample dimensions were 6 X 7 X 0.083 inch. Details of the milling and compression molding procedures are given in Table II. 

Press type. Pasadena Hydraulics, Inc., Model P-210 Mold cavity. 6 X 7 X 0.083 inch Press temperature. 180°C. 

Polyethylene. The most straightforward process for the production of polymers from ethylene is that of the direct polymerization of the olefin. The polymerization process usually requires pressures and temperatures of 15,000 to 30,000 pounds per square inch and 200° to 300° C., and may be effected in either gas or liquid phase reactions (9). The polymer of molecular weight above 20,000 is the white, translucent plastic, polyethylene, widely used in electrical insulation, packaging material for foods, cosmetics and pharmaceuticals, liners for paper bags, etc. Articles molded from polyethylene are semirigid or rigid, depending on their thickness, but in thin films the material has excellent flexibility, even at relatively low temperatures. 

Since the materials have a very soft plasticity rating, or inches of flow on spiral mold, the materials are all molded in special transfer molding presses and specially designed transfer molds. Because an acid catalyst and glass or mineral fillers are used to make the compound, these materials may have an adverse effect on the hardened steel mold with the result that there may be excessive runner and gate wear. 

The compounds were mixed on a two-roll mill at 320°F. for 8 minutes, then molded into test plaques at 340°F. and 1500 p.s.i. Samples for mechanical testing, hardness, compatibility, and Clash-Berg temperature were 0.075 inch thick while carbon black volatility and extractions were performed on 0.010 inch films. All testing was in accordance with ASTM specifications, and results are summarized in Tables II through V. 

Milled sheets were molded into 6 inch discs 35 mils thick by preheating 1 min., pressing 1 min. at a temperature between 115° and 205°C. according to the thermal plasticity requirements of the different compositions, and cooling 1 min. under pressure before removing from the mold. Pure Hycar 1032 was too rubbery to form good moldings and was therefore cast into film from 20% solution in methyl ethyl ketone. 

An artist wants to create a metal sculpture using a mold so that his artwork can be readily mass-produced. He wants his sculpture to be exactly 6 inches tall. Should the mold also be 6 inches tall Why or why not ... 

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