Does The molding time affect the quality of the composite Manhole Cover?
Everyone knows that the Composite Manhole Cover is molded by a high-temperature heating machine using a polymer composite material.
Simply put: material quality + processing technology - quality manhole cover
How can I make a high quality manhole cover? The material of the manhole cover is guaranteed. It depends on the processing technology. It is very important to put the prepared materials into the mold and the length of the molding time of the press.
The molding time is also called compression molding heat preservation time. It refers to the time when the material is heated and solidified in the mold after the mold is completely closed or after the last venting and closing of the mold. The role of the molding time in the molding process is mainly to allow the molded body having the cavity shape to have sufficient time to complete the curing. Curing refers to the formation process of a bulk structure during the formation of a thermosetting plastic. From the nature of the chemical reaction, the curing process is a process in which the crosslinking reaction proceeds. However, the "complete curing" of the process does not mean that the crosslinking reaction has proceeded to the end, that is, all the reactive groups that can participate in the crosslinking have all participated in the reaction. This term is technically meant that the crosslinking reaction has been carried out to the appropriate extent and that the overall physical and mechanical properties of the article or other specifically specified properties have met the desired specifications. Obviously, the degree of cross-linking of the product cannot reach 100 ° C and the degree of curing can exceed 100 ° C. The phenomenon that cross-linking is more than required for complete curing is generally referred to as "over-ripening", and vice versa.
The molding time is determined by the curing rate of SMC/BMC molding compound, the shape and wall thickness of the product, the structure of the mold, the molding temperature and the molding pressure, as well as the factors such as pre-compression, preheating and whether the exhaust is formed during molding. Regarding all of these factors, the influence of molding temperature, product wall thickness and preheating conditions on the molding time is significant. Suitable preheating conditions are beneficial to shorten the molding time by speeding up the temperature rising process of the material in the cavity and filling the cavity. When the molding temperature is increased, the molding time is shortened and the thickness of the product wall is increased. Extend the molding time. When the molding temperature and the molding pressure are constant, the molding time becomes a key factor determining the performance of the product. If the molding time is too short, the resin cannot be completely cured, the product is under-cooked, and the mechanical properties are poor, the appearance lacks luster, and warpage and deformation are likely to occur after demolding.Appropriate extension of the molding time not only overcomes the above disadvantages, but also reduces the molding shrinkage of the product and improves its heat resistance, strength properties and electrical insulation properties. However, excessively prolonging the molding time will over-cook the product, which not only reduces production efficiency, increases energy consumption, but also increases the shrinkage rate due to excessive cross-linking, which causes large internal stress between the resin and the filler, and often causes the surface of the product. Dark blistering, severe rupture of the product.
Contact: Elaine Yang
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