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GRP roof tiles are a commonly used building material with the advantages of lightweight, corrosion resistance, and good weather resistance. They are widely used in the roofs and walls of buildings. Ho...
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The SMC insulator is a high-strength, high-insulation, lightweight insulating material. It is primarily composed of quartz, glass fiber, and other materials combined with resin. It finds extensive app...
Everyone knows that the SMC molding process has many advantages, such as: accurate product size, smooth surface, good repeatability of product appearance and size, complex structure can also be molded at one time, and secondary processing does not need to damage the product. It can be said that the SMC material molding process is the most efficient one in the FRP/composite molding process. However, there will also be bad defects in the SMC molding production process, resulting in defective products, mainly in the following aspects.
1. SMC material is short of material during the molding process
Lack of material means that the SMC molded part is not completely filled, and its production parts are mostly concentrated on the edge of the SMC product, especially the root and top of the corner. Analysis of the reasons: the discharge amount is small; the fluidity of the SMC material is poor; the equipment pressure is not sufficient; the curing is too fast.
①After the SMC material is heated and plasticized, the melt viscosity is large, and there is not enough time, pressure, and volume to fill the mold cavity with the melt before the cross-linking and curing reaction is completed.
②The storage time of the SMC molding material is too long, and the styrene volatilization is too much, which causes the flow performance of the SMC molding material to be significantly reduced.
③ The resin paste does not penetrate the fibers. During molding, the resin paste cannot drive the fibers to flow, resulting in material shortage. The most direct solution to the shortage of materials caused by the above reasons is to remove these molding materials when cutting materials.
④Insufficient feeding amount causes material shortage. The solution is to appropriately increase the feeding amount.
⑤ There is too much air and a lot of volatiles in the molding material. The solution is to appropriately increase the number of exhausts; appropriately increase the feeding area, and clean the mold at certain intervals; appropriately increase the molding pressure.
⑥ The pressure is too late, and the molding material has completed cross-linking and curing before filling the mold cavity.
⑦ The mold temperature is too high, the cross-linking curing reaction is advanced, and the temperature should be appropriately lowered.
2. The SMC material has pores during the molding process
①The SMC molding material is wrapped in a lot of air and the volatile content is large, and the exhaust is not smooth; the thickening effect of the SMC material is not good, and the gas cannot be effectively discharged. For the above-mentioned causes, it can be effectively controlled by a combination of increasing the number of exhausts and cleaning the mold.
②The feeding area is too large, and it can be controlled by appropriately reducing the feeding area. In the actual operation process, human factors may also cause trachoma. For example, pressing too early may make it difficult for the gas in the molding material to be discharged, resulting in surface defects of pores on the surface of the product.
3. SMC material is warped and deformed during the molding process
During the resin curing reaction, the chemical structure changes, causing volume shrinkage, and uneven curing makes the product tend to warp toward the side that cures first. Secondly, the thermal expansion coefficient of the product is larger than that of the steel mold. When the product cools, its unidirectional shrinkage is greater than the unidirectional thermal shrinkage of the mold. To this end, the following methods are used to solve it:
①Reduce the temperature difference between the upper and lower molds to make the temperature distribution as uniform as possible.
②Use a cooling jig to limit deformation.
③ Properly increase the molding pressure, increase the structural compactness of the product, and reduce the shrinkage rate of the product.
④ Properly extend the holding time to eliminate internal stress.
⑤Adjust the curing shrinkage of SMC material.
4. The SMC material foams during the molding process
It may be that the material is not fully cured, the local temperature is too high, or the volatile content in the material is large, and air collects between the sheets, causing the semicircle on the surface of the product to bulge.
① Properly increase the molding pressure.
②Extend the holding time.
③ Reduce the mold temperature.
④ Reduce the discharge area.
5. The surface color of the SMC material is uneven during the molding process
①The mold temperature is uneven and locally too high, so the mold temperature should be properly controlled.
②The fluidity of the molding material is poor, resulting in uneven distribution of fibers. Generally, the molding pressure can be increased to increase the fluidity of the melt.
③ In the process of color paste deployment, the pigment and resin are not well miscible.
