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GRP tile is a new type of composite material, composed of glass fiber and resin. It not only has the high strength, hardness and transparency of glass, but also has some advantages of plastic, such as...
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BMC insulation is a thermoset composite material consisting of staple fiber reinforcements, fillers, resins, and additives. These components are blended to form a flowable mixture that can be processe...
In the SMC moulding process, three elements need to be focused on, namely mold temperature, mold pressure, and mold time control.
1. Mold temperature control
The mold temperature is the temperature of the SMC molding temperature, which determines the conditions of heat transfer from the mold to the material inside the mold cavity, and has a decisive influence on the material's melting, flowing, and curing process. Curing cross-linking reactions do not begin simultaneously in the inner and outer layers of the material.
2. Mold pressure control
Mold pressure is usually expressed in terms of mold pressure (MPa). The role of mold pressure in the SMC molding process is to close the mold and densification of the material, as well as to promote the flow of melt and balance the force generated by the volatilization of low molecular material in the mold cavity. Molded materials with a large compression ratio consume more energy to densify, thus requiring a higher mold pressure to mold the bulk material than the molded blanks, and SMC/BMC developed materials have a higher pressure than molded powders. Molded materials with high melt viscosity and fast cross-linking rate, as well as products with complex shapes, thin walls, depths, or large areas, need to overcome greater resistance to flow to fill the mold cavity, thus requiring a higher molding pressure.
3. Mold time control
Molding time, also known as compression moulding holding time, is the time between when the mold is completely closed, or after the last outgassing has closed the mold, and when the mold is open when the material is heated and cured in the mold. The role of the compression time in the molding process is to allow enough time for the molded material, which has obtained the shape of the mold cavity, to cure. Curing refers to the process of forming the body structure of thermosetting plastics when they are molded, and the process of curing is a cross-linking reaction from the nature of chemical reactions.
Mold time is determined with the SMC / BMC molded plastic curing rate, the shape and wall thickness of the product, the structure of the mold, the mold temperature and mold pressure level, as well as pre-pressing, preheating, and molding whether the exhaust and other factors, in all of these factors to mold temperature, product wall thickness and preheating conditions on the molding time of the most significant impact.
Appropriate extension of molding time can reduce the molding shrinkage of the product and make it heat resistance, strength properties, and electrical insulation properties are improved. However, the excessive extension of the molding time will make the product over-ripe, not only to reduce production efficiency, increased energy consumption and will be due to excessive cross-linking to increase the shrinkage will lead to greater internal stress between the resin and filler, but also often make the product surface dark blistering, serious product breakage will occur.
