High-quality mold surface

A reasonably high quality of surface finish can be achieved (depending on mold cavity quality) and a form of in-mold coating system can also be employed to achieve Class A finishes. 

Zinc alloy (kirksite) high-quality molds can be made from cast zinc alloys, offering good non-porous surfaces but are relatively heavy, with lower heat conductivity than aluminum, requiring closely spaced cooling channels. 

The heat resistance and water-white color of melamine polymers make them ideally suited for use in the home as high-quality molded dinnerware melamine-surfaced decorative laminates find wide application in the home. The decorative pattern may be a solid color, a wood grain, or any design. 

The machining of press tools of large sheet metal parts such as car parts or injection molding tools of large plastic products needs the removal of a large quantity of material to produce high quality 3D surfaces. Productivity is enhanced by reducing the control of... 

Injection-compression molding first injects the material into a partially opened mold, and then squeezes the material by closing the mold. Injection-compression molding is used for polymer products that require a high quality surface finish, such as compact discs and other optically demanding components because it practically eliminates tangential molecular orientation. 

Experience has shown that the finish on the part surface is a direct function of the mold finish, and that the mold finish is a direct function of the quality of the mold material. Excellent results have been obtained using high-quality, nickel-plated, tool steel molds and electroformed nickel shells. 

Polyurethane RIM (PU-RIM) was selected for the Initial RIM application of automotive fascia not only because 1t provides the required damage resistance and other performance requirements, but also because the reactivity of the urethane raw materials, Isocyanate and polyol, provide acceptable productivity. Because the urethane mnomers can be nucleated, high quality sink free surfaces that are suitable for automotive exteriors are produced at the time of demold. Little, 1f any, post mold surface repair 1s needed 1n preparation for painting the RIM part. 

Internal mold release technology is well developed for nylon RIM systems while it is being developed for urethanes. Most urethanes require application of a mold release agent, a wax, a soap or a silicone, after every shot. Many mold releases cannot be added to the urethane reactant streams or the tanks because they react with the urethane chemicals. These reactions have caused problems of build-up in the mold, even with spray-on mold releases, necessitating periodic shutdowns to scrub the mold surfaces. Some newer systems use a third component stream to Introduce mold release at the mix head. Newer Internal mold release systems permit from 0 to 50 urethane shots to be made between applications of external mold release spray to the tool. Monsanto s nylon RIM system contains an internal mold release that is paintable. In certain applications where a high quality smooth show surface is required on a part, a... 

As in other molding methods, these molds must be constructed from corrosion-resistant metals. Rusting and pitting can be avoided by plating the mold with nickel to athickness of 10-50 pm.1 1 The plate must be devoid of pinholes to enhance the durability of the nickel coating and produce high quality surface parts. 

RTM is compatible with a variety of thermosetting polymers including polyester, vinyl ester, epoxy, phenolic, modified acrylic, and hybrid polyester-urethane. A convenient typical viscosity of thermoset precursors is in the range of 0.2-0.6 Pa s. The RTM process has the following advantages (i) emissions are lower than in open-mold processes such as spray-up or hand lay-up (ii) it can produce parts faster, as much as 5-20 times faster than open-mold techniques (iii) the mold surface can produce a high quality finish (iv) complex mold shapes can be achieved and... 

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