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Defects and causes analysis of BMC products

Defects and causes analysis of BMC products

Send:2018/10/11 12:05:57


  It is due to the presence of gas in the pressurized BMC substrate that leads to the surface protuberance of work in process.

  Possible causes and possible causes of corrective measures and possible causes of corrective measures and corrective measures:

  1. The "dry glass fiber" in the BMC raw material causes the voids in the molded plastics layer, which may expand into bubbles when formed. In order to completely rectify, it is necessary to change the process or reduce the content of glass fiber when preparing BMC.

  2. BMC raw materials are contaminated by moisture, press oil, lubricant or exterior demoulding agent. When heated during molding, they may turn into steam and form bubbles. Calcium carbonate and stearate are hydrophilic substances, so they are easy to be contaminated with water.

  3. The chance of capturing air should be minimized, depending on the area and location of the BMC paving. In fact, reducing the area of the paving is effective by placing it in the center of the mold like a pyramid, which forces the air to escape in front of the BMC flow during the molding.

  4. When closing to the final size, should try to slow down the closing speed, lower closing speed will reduce the agitation of materials and weaken the opportunity to capture air.

  5. the lower closing speed, if combined with lower mold temperature, can lead to flat flow and less gel, and also reduce the chance of capturing air, but the curing time must be lengthened.

  6. It is effective to reduce the pressure of the mold, to form a flat flow of material and to reduce the chance of capturing air.

  7. check the parallelism of the mold installation and the parallelism of the press itself. Because of the mold installation level will cause material flow agitation (uneven flow) will increase the opportunity to capture air.

  8. excessive initiator or inhibitor can cause gel and uneven flow. Similarly, low shrinkage additives can also cause gas production. At the moment, it is necessary to improve the formulation of BMC.

  9. The viscosity of the material greatly affects the material flow, so to adjust it to the appropriate range, usually pay attention to the different viscosity level will affect the location and frequency of the bubble.

  10. Variable cross-section and variable thickness parts of the product can change the flat material flow, and the thick cross-section can not get sufficient heat and pressure when curing, so it can be reviewed from the product design.

  11. Usually, the air captured in the molding will cause meat shortage, spontaneous combustion and bubbles in the product. Therefore, proper discharge flying edge is necessary to facilitate the exhaust.

  12. excessive dry and stiff materials cause unstable flow of material, leading to gel, pinholes and bubbles.



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