One-shot molding

One-shot molding n. A process for molding polyurethane foam in which the reactants, usually an isocyanate, a polyol, and a catalyst, are fed in separate streams to a mixing head from which the mixed reactants are discharged into a mold. The polyol and catalyst are sometimes combined along with other additives prior to mixing, but the isocyanate is always fed separately to the mixing head. 

See also one-shot molding, isocyanate, polyol, polyether foam, reticulated polyurethane foam, and integral-skin molding. 

One-Shot Molding n A process for molding polyurethane foam in which the reactants, usually an... 

In more recent years, molded flexible foam products are becoming more popular. The bulk of the molded flexible urethane foam is employed in the transportation industry, where it is highly suitable for the manufacture of seat cushions, back cushions, and bucket-seat padding. TDI prepolymers were used in flexible foam mol ding ia conjunction with polyether polyols. The introduction of organotin catalysts and efficient siHcone surfactants faciHtates one-shot foam mol ding, which is the most economical production method. 

Consolidation Even though blow molding provides the capability of providing multiple products combined into one, by including hinges the designer has an added feature. The ability to produce many articulated products in one shot has always opened new design... 

An ounce is a unit used to represent the capacity of an injection molding machine, showing the polystyrene equivalent weight of polymer for one shot . 

The reaction shown in Figure 2.6 produces what is referred to as a prepolymer via the production method of choice before the one-shot process was developed. Prepolymers are still commonly used. Small molding operations, elastomers, and hydrophilic polyurethanes involve production of prepolymers. 

A typical formulation for the reaction-injection molding (RIM) process is shown below (one-shot process) ... 

MPX functionality is arranged into three modules, the first of which is the Setup Xpert, a module that allows users to perform a variety of injection-velocity- and pressure-phase-related setup routines to fix certain defects, such as short shots, flash, burn marks, sink marks, etc. The objective of Setup Xpert is to achieve one good molded part with no defects. The basic process is that a user molds a part, then provides feedback to the MPX system regarding molded part quality. The MPX system then processes this feedback along with data being collected from the machine and (if necessary) determines a process change that will improve the result. 

Manufacturing Process. Both prepolymer and one-shot processes are available, but the polymeric isocyanate-based one-shot process is used in preference because of the easy processing due to the low viscosity of the system, relatively low toxicity of polymeric isocyanates, and fewer environmental problems. However, a disadvantage of the one-shot process is a possible risk of shrunken-foam formation due to its higher closed-cell content. In contrast, the TDI-based prepolymer process has advantages including better in-mold flowability and higher open-cell content. 

PU foams were prepared by the one-shot, free-rlse method. A homogeneous liquid mixture consisting of Nlax 31-28, Isonol-100, silicone surfactant DC-193 (Dow Corning), T-12, Nlax A-1 (Union Carbide), trlchlorofluoromethane (Freon llA, E.I. duPont de Nemours Co.), and water was mixed thoroughly with Isonate-143L. It was put Into a cold mold and allowed to free rise. 

This chapter presents an overview of performance plastic polymers in commercial planar and 3-dimensional circuit board products, and describes in detail one approach (two-shot molding) developed as an integrated 3-D circuit manufacturing technology. The distinctions between conventional planar (2-dimensional) circuitry, based on thermoset laminates and "subtractive etching processes, and the enhanced design flexibility afforded by expanded interconnection capacity in three axes are discussed. Specific examples of 3-dimensional interconnect protoypes and products are described and pictured. 

MOLDING/METALLIZATION. Molded thermoplastic circuit board substrates may be rendered selectively conductive by several additive process techniques including conductive polymeric thick film inks (PTF), and semi and fully additive electroless/electrolytic platings. Of the various chemical process methods developed to produce circuitry on a molded plastic substrate, one method practiced by Pathtek, A Kodak Company, combines both "catalytic" and "non-catalytic" resins in a highly automated commercialized two-shot molding/selective metallization process. 

Injection-molding machines are rated by their capacity to mold polystyrene in a single shot. Thus a 2-oz machine can melt and push 2 oz of general-purpose polystyrene into a mold in one shot. This capacity is determined by a number of factors such as plunger diameter, plunger travel, and heating capacity. 

Other developments of one-shot flexible foam systems include direct molding, where the mixture is fed into a mold cavity (with or without inserts such as springs, frames, etc.) and cured by heat. In a typical application, molds would be filled and closed, then heated rapidly to 300°F-400°F (149°C-204°C) to develop maximum properties. 

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