Jacketed molds

Epcar EPM. [BFGoodtich/Spec. Polymers] EPM rubber fm molded and extruded prods., wire insulation and jacketing, mold o-rings, bidce components, sidewalls, hose, matting, automotive weatherstripping. 

Jacketed molds heated with hot oil or salts were used in the past. The heat transfer efficiency of these systems was good but the maintenance problems have made these systems uncommon today. Modem machines employ forced air convection ovens to heat the molds. In the majority of industrial machines the ovens are heated by the combustion of a gas, while in smaller machines electricity is normally used. Ovens are provided with blowers and baffles to improve heat transfer. 

It rotates on two perpendicular axes at speeds up to 40 RPM. It is heated in an air oven or by oil in a jacketed mold. The resin is distributed by the force of gravity—the speed is not high enough for centrifugal force. A complete cycle may be 5 to 30 min. Yields are high, because there is no waste of material. 

As higher temperatures are required to process polycarbonate, heat transfer through the mold to the material can be a problem. The best results are achieved using oil-jacketed molds and finer powder than the 35 mesh (500 tm) commonly used for polyethylene. However, bubbles can still occur in parts and it is common to see textured mold surfaces used to disguise their presence. The use of a nitrogen atmosphere can reduce the yellow color caused by degradation. 

Air is the dominant heat transfer medium for rotomolding. It is also the simplest choice from a safety and handling standpoint. Hot liquids, such as oils, could be sprayed on the mold while it is being rotated but hazards and operational problems have precluded their use. Liquid heat transfer medium can be used in jacketed molds, which results in improved heat transfer. The increase in the cost of fabricating jacketed molds makes it difficult to justify their inclusion in commercial operations unless they are required. For example, nylon 6 parts are rotomolded in jacketed molds to avoid oxidation of the polymer. 

The main uses of EPM of EPDM are in automotive appHcations as profiles, (radiator) hoses, and seals in building and constmction as profiles, roofing foil, and seals in cable and wke as cable insulation and jacketing and in appHances as a wide variety of mostiy molded articles. 

The next step involves heating the mold while it is rotating. Molds can be heated by a heated oven, a direct flame, a heat-transfer liquid (either in a jacket around the mold or sprayed over the mold), or electric-resistance heaters placed around the mold. With uniform heat transfer through the mold, the plastic melts to build up a layer of molten plastic on the molds inside surface. 

I even had to cover the metal buttons on my jacket, because I reacted to them. I couldn t stay in my home because of mold and pesticides inside. 

They can be processed by techniques commonly used for thermoplastics, such as extrusion, injection molding, rotational molding, dip, slush molding, and powder and fluidized bed coating,16 and can be expanded into foams.17 Compression and transfer molding of FEP resins can be done, but with some difficulty. Extrusion of PEP is used for primary insulation or cable jackets and for tubing and films. 

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