Due to the volume change of crystallization during injection molding, the pressure is high, the viscosity difference of melt is small, the interlaminar shear stress is small, and the elastic rebound is large after demoulding. Therefore, the shrinkage of injection molding can be reduced appropriately, and the material temperature is high, the shrinkage is large, but the directivity is small.

When the pressure increases, the melt will be greatly affected by shearing and fluidity, especially PE and POM are more sensitive. Therefore, it is advisable to adjust the pressure during injection molding to control the fluidity. The filling condition can also be properly adjusted by controlling the material temperature, mold temperature, injection pressure and injection speed to meet the molding needs.