Injection transfer molding process

Most thermosets are molded with the compression or transfer molding process (tires, dinnerware, electrical components, etc.). Some products, usually iimdler ones, can be made using the injection molding process in specially 1 or modified injection molding machines. Some thermosets are used as Is, applied to sheets or mats of glass and other fibers, and then cured under low) pressure and heat. (Examples are plywood, particle board, structures, etc.)... 

Mathur, R., Advani, S. G. and Fink, B. K., A real-coded hybrid genetic algorithm to determine optimal resin injection locations in the resin transfer molding process . Computer Modeling in Engineering and Sciences, 4(5), 587-602, 2003. 

Figure 1.79 (b) shows the mold for the transfer molding process from the bottom. A press with a separate injection unit is required for molds of this design. Most commonly, these are presses with a hydraulic cylinder that is centrally attached to the mold table. This actuates the transfer piston which is linked to the machine control (transfer press). 

The principal steps of the injection blow molding process are illustrated in Figure 18. The initial step is the injection molding of an inflatable preform. This simultaneously creates a bottle neck with well-defined dimensions and a tube of polymer sealed at one end that will later be inflated. The preform is then transferred to an oven, where the tube is reheated to its softening temperature. The softened preform is then transported to a conventional blow mold, and compressed air is introduced to inflate it. 

The injection blow molding process involves two stages. In the first stage, a plastic part called a preform is made, using a traditional injection molding process. The preform is a precise shape, with precise wall thicknesses. This preform is then transferred to a blow molding station, where it is placed in another mold and held in place by specific features of the preform that mate with the blow mold cavity. Compressed air is then injected into the center of the part, forcing the unsupported walls of the preform tube to stretch and expand outward, until they hit the walls of the second mold. Once the material cools and solidifies, the mold is opened and the part is removed. 

In the manufacture of shaft seals, the molding is the process where the compound and treated metal stamping (phosphated and adhesive applied) are brought together to form the conventional lip type shaft seal. Therefore, it is critical that the compounds used are formulated to suit the molding process. There are three fundamental molding processes in use today compression, injection, and injection/transfer. 

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. 

Resin transfer molding With vacuum assisted RTM, this process can be called infusion molding. RTM usually uses liquid TS plastics that is transferred or injected into an enclosed mold usually at low pressures of about 60 psi (410 kPa) in which reinforcement... 

Thermosets are processed by compression molding, transfer molding and injection molding or by extrusion, depending on their structure. The pressing temperatures are about 150 to 190°C. Corresponding requirements are placed on the pigments. Dyes are often also used to color thermosets. 

Resin transfer molding (RTM) is a hybrid of two polymer processing techniques we have already described transfer molding and reaction injection molding (RIM). The key difference is that a reinforcement is incorporated during molding to create a composite. 

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