What are the main points that affect the quality of plastic

In the production of plastics, there are often many factors that affect the quality of the product. In summary, there are four main points:

1).Plastic material

The complexity of plastic material properties determines the complexity of the injection molding process. The performance of plastic materials varies greatly due to different varieties, different brands, different manufacturers, and even different batches. Different performance parameters may lead to completely different molding results.

2). Injection temperature

The melt flows into the cooled cavity and loses heat due to heat conduction. At the same time, heat is generated due to the shearing effect, which may be more or less than the heat lost by heat conduction, depending on the injection molding conditions. The viscosity of the melt decreases with increasing temperature. In this way, the higher the injection temperature, the lower the viscosity of the melt, and the smaller the required filling pressure. At the same time, the injection temperature is also limited by the thermal degradation temperature and decomposition temperature.

3). Mold temperature

The lower the mold temperature, the faster the heat loss due to heat conduction, and the lower the melt temperature, the worse the fluidity. This phenomenon is especially obvious when using a lower injection rate.

4). Injection time

The influence of injection time on the injection molding process is manifested in three aspects:

(1) To shorten the injection time, the shear strain rate in the melt will also increase, and the injection pressure required to fill the cavity will also increase.

(2) Shorten the injection time and increase the shear strain rate in the melt. Due to the shear thinning characteristics of the plastic melt, the viscosity of the melt is reduced, and the injection pressure required to fill the cavity is also reduced.

(3) Shorten the injection time and increase the shear strain rate in the melt. The greater the shear heating, and the less heat lost due to heat conduction, the higher the melt temperature and the lower the viscosity, the injection required to fill the cavity The pressure should also be reduced.

As a result of the above three conditions, the curve of the injection pressure required to fill the cavity presents a "U" shape. In other words, there is an injection time when the required injection pressure is the smallest.