Injection molding process of commonly used transparent raw materials

Author: MULAN – Plastic Molding Manufacturer

Since transparent injection molded parts require good light transmittance, the requirements for the surface quality of plastic products are relatively strict, and there should be no defects such as streaks, pores, whitening, halo, black spots, discoloration, and poor gloss. In the process of processing, strict requirements are put forward for plastic raw materials, injection molding equipment and injection molds. For example, transparent raw materials commonly used by Mulan injection mold factory: PMMA, PC, PET, etc. 1. When PMMA transparent injection molding is processed, due to the high viscosity and poor fluidity of PMMA plastic, high material temperature and high injection pressure must be maintained in injection molding processing. The influence of injection temperature is greater than that of injection pressure, and the rise of injection pressure High, it is beneficial to improve the shrinkage rate of the product.

The injection temperature range is wide, so the temperature adjustment range of the material is wide, and the manufacturability is good. Therefore, to improve the fluidity of plastics, we can start with the injection temperature. Poor impact performance, poor wear resistance, easy to scratch and brittle, so the mold temperature should be increased to improve the condensation process to improve injection molding defects.

2. PC transparent injection molding processing, because PC material has high viscosity, high melting temperature and poor fluidity, so it is injected at a higher temperature during injection molding processing. Relatively speaking, the material temperature adjustment range is narrow, and the processability is not as good as PMMA. Injection pressure has little effect on fluidity, but due to viscosity, injection pressure still needs to be relatively high, but in order to prevent internal stress, the holding time should be shortened as much as possible. PC injection molded parts have large shrinkage and stable dimensions, but the internal stress of the product is large and easy to crack. Therefore, it is best to improve the fluidity by increasing the temperature instead of pressing, and reduce the mold temperature by increasing the mold temperature to improve the mold structure and post-processing. possibility of cracking.

In the case of low injection molding speed and defects such as ripples at the gate, the temperature of the injection nozzle should be controlled separately, the temperature of the mold should be increased, and the resistance of the runner and gate should be reduced. 3. During PET injection molding, due to the high temperature required for molding, the temperature adjustment range is narrow, but after melting, because of its good fluidity, the processability is poor, so it is necessary to add an anti-dripping device in the nozzle. The mechanical strength and performance after injection molding are not high, and the performance must be improved by stretching process and modification.

Precisely control the mold temperature to prevent deformation. important factor, it is recommended to use a hot runner mold. If the mold temperature is too high, it will cause poor surface gloss and difficult demoulding.