What is LCP injection molding？

1. LCP material treatment process (liquid crystal polymer)

Focus: LCP material should be dried before use, the temperature is about 150 ℃, the time is about 4~6 hours, the content of the remaining moisture of LCP material after dehumidification should be below 0.02%, the dew point is kept at -35 ℃.

Note: It is recommended to use a vacuum dehumidifying dryer, not a general dryer. Because the vacuum dehumidification dryer can extract moisture from LCP material, while the general dryer can not completely extract the moisture from the material, it is difficult to achieve the required quality of products.

2. LCP material injection molding process


The following issues should be noted when molding.

①Adopt proportional back pressure to make the feeding more accurate and stable.

② Large products can use large back pressure, small products with small back pressure.

③Large products with small back pressure will also have relatively small density and poor surface gloss.

④High sensitivity injection system and automatic V-P (V injection pressure, P holding pressure) conversion function to make the products precise and stable. In case of need (such as very precise products), it is recommended to install pressure sensors at the mold cavity gate to make the V-P switching closer to the actual.

(6) The holding time of beer plane products should not be too long, otherwise it will easily cause warping and deformation of products and generate stress.

(7) LCP material stays in the material tube for too long or the residual amount is too much to make the LCP material overcooked, and there will be bubbles on the surface of the products, generally open the mold within 3 seconds after the melt of the material tube, and ensure the residual amount is within 5mm.

⑧ If the machine is stopped and started again, the waste material should be shot out.

LCP material has good fluidity, so the filling time is relatively short, and the crystallization molding speed is faster, so the molding cycle is relatively short.

3. LCP material special injection molding machine selection overview

    It is necessary to choose a special injection molding machine for LCP material.

    The screw needs to be made of a material with better wear resistance.

    The screw head should be made of a structure that prevents backflow.

    The need for a more sophisticated temperature control system.

    The nozzle section needs to be specially designed.

    Responsive filling and injection system.

    The capacity of injection tube should be matched with the weight of the product, not too much or too little.

4. LCP material special mold process focus

①The mold design of LCP products is very critical, the mold inlet should use ordinary open nozzle, not hot nozzle, if the product with hot nozzle is easy to blister, that is, the temperature is too high and easy to cause the product to overfire.

② general mold temperature at about 140 ℃, the upper (before) mold temperature should be higher than the lower (after) mold, because the upper (before) mold temperature is high molten rubber fluidity is not easy to cause cold glue, the lower (after) mold temperature is low products are easy to crystallization molding, the upper (before) lower (after) mold temperature difference of not more than 15 ℃.

③In the choice of mold temperature, in order to shorten the molding cycle and prevent phi, a lower mold temperature should be chosen; if the products are required to have high dimensional stability, reduce the generation of joints and underfilling problems, a higher mold temperature should be chosen.

5. Pressure and speed

The most suitable pressure must depend on the material, the shape of the product, the mold design (especially direct gates, runners, gates) and other molding conditions. But LCP without any grade has a very low melt viscosity, so the pressure is lower than normal thermoplastic resin.

It is better to use low pressure at the beginning of molding and then slowly increase the pressure. Roughly, the molded products can be molded at 15MPa-45MPa. In addition, the curing time of LCP is relatively fast, so it is easy to get good results if the speed is fast.

6.Molding cycle time

The molding cycle depends on the size, shape, thickness, mold structure and molding conditions of the molded product. As mentioned above, LCP has good flowability, so its filling time is short and curing speed is fast, so we can get a short molding cycle. The representative molding cycle time is 10 seconds-30 seconds.