Four Concepts Of Injection Products

Next, I will tell you about the relevant content of injection products, come and have a look!

1. Mobility

We all know that different thermoplastics have different processing properties, shrinkage properties and physical properties. For crystalline plastics, when the processing temperature is higher than the melting point, its fluidity is better, the cavity can be filled quickly, and the injection pressure required is smaller. For amorphous plastics, its fluidity is poor, so the injection speed is slow and the pressure required is also high.

When designing the mold, the mold designer can use the fluidity of the plastic as the basis for calculating the size of the runner system. This can not only avoid material waste, prolong the injection molding cycle, but also avoid filling difficulties due to the size of the runner system being too small and pressure retention problems.

2. Shrinkage

When a thermoplastic is transformed from a molten state to a solidified state, its volume will shrink to varying degrees. In general, the shrinkage rate of crystalline plastics ranges from 1.0% to 3.0%, and that of amorphous plastics ranges from 0.4% to 0.8%, so the shrinkage rate and shrinkage range of crystalline plastics are larger than that of amorphous plastics, and more Vulnerable to molding process. After the crystalline plastic is demoulded, it can crystallize at room temperature and continue to shrink. The shrinkage depends on the thickness and temperature of the product. The thicker the product, the greater the shrinkage.

3. Rheology

What is rheology? Rheology refers to the relationship between stress, deformation, deformation rate and viscosity during processing. According to the rheology of plastics, plastics can be divided into two types: shear-sensitive plastics and heat-sensitive plastics. Common shear-sensitive plastics include ABS, PS, PE, PP, POM, etc. The viscosity of this plastic will decrease rapidly as the shear rate increases. Common heat-sensitive plastics include PC, PA, PMMA, etc. This kind of plastic has a strong dependence on temperature. The higher the temperature, the faster the viscosity will drop.

From the perspective of high molecular polymers, the shear rate has an impact on the viscosity of the above two plastics. The increase of the shear rate can reduce the viscosity of the melt to varying degrees and cause the melt to produce a "shear thinning" phenomenon. , the rheology of injection molded products will also change accordingly.

4. Orientation effect

The plastic melt will produce an orientation effect during the flow process, and the orientation effect can affect the performance of the injection molded product. What is the orientation effect? The macromolecules of the plastic melt are stretched under the action of external force, and then arranged parallel to each other along the flow direction. This arrangement will freeze in the solid product before the plastic cools and solidifies, forming an orientation effect. The orientation effect will weaken the integrity of the product, resulting in uneven shrinkage and warpage of the injection molded product.

Cixi Haofeng Mold Technology Co., Ltd. is a professional OEM Injection Products Processing Factory. If you need it, you can click the official website to contact us. We are willing to answer you for more information.