The processing of PP Bottle raw materials is mai […]
The processing of PP Bottle raw materials is mainly to make rubber particles into finished products, which are then melted, flowed and cooled. This is the process of heating and then cooling, as well as the process of changing the plastic from particles to different shapes. Ningbo RUICHANG Commodity Packaging CO , Ltd. will explain the different stages of PP bottle injection molding.
The equipment heater (heater) gradually melts the raw material particles into a fluid stream, which is mainly suitable for temperature regulation of different raw materials. An increase in temperature will tend to accelerate the flow of the feedstock, which may increase efficiency, but may not ensure production, so it must be appropriate. balance.
Another good effect of PP and high thermal cracking characteristics, it is best to make the raw materials in the production process smooth and smooth to the mold, to avoid the lack of filling or reflow phenomenon, the reflow represents the flow of raw materials faster than the yield, and finally, the average The increase in flow efficiency is equal to the increase in MFR, which is one of the methods available for processing, but it also causes an abnormality in the MFR distribution to cause an increase in instability, which may result in an increase in the defect rate.
However, PP final products are not products with high dimensional accuracy due to their application relationship, so the impact is not significant.
Most PP processing relies on a screw to drive fluidity, so the screw design has a large impact. The diameter of the screw affects the output. The compression ratio affects the pressure value and also affects the yield and final product. This also includes a variety of materials. The mixing effect of (color masterbatch, additives and modifiers).
The flow of the raw material mainly depends on the temperature, but the friction of the raw material also generates frictional heat, thereby promoting fluidity. Therefore, the screw compression is smaller than the small drive flow, and the rotation speed must be increased so that the frictional heat energy is larger than the screw having a large compression ratio.
Therefore, it is often said that there is no master of plastic processing, and those who are proficient in machine performance are masters. The heating of the raw materials is not just heating. It must be included in the friction heat and hold time.
Therefore, this is a practical issue, and experience can help solve production problems and improve efficiency. If a particularly good screw mixing is required, a two-stage different screw or twin-shaft screw is sometimes designed and different types of screws are provided to achieve various mixing effects.
3, mold or mold
The plastic reset depends on the mold or mold. Injection molded products are three-dimensional. The mold is also complex and takes into account shrinkage. Others are flat, ribbon and needle continuous product molds. If it is a special shape. To classify, you need to pay attention to the immediate cooling problem.
Most designs of plastic machines are like injection syringes. The screw-driven squeezing force will create a large pressure on the small outlet and increase production efficiency. When the mold is designed to be flat, how to distribute the raw materials evenly over the entire surface, the design of the hanger mold is very important, and the excavation opportunity increases the stable raw material supply of the surimi pump.
4, heat dissipation
In addition to the gate casting material, the injection mold has a cooling water passage cooling material design. Extrusion relies on the cooling water passage in the roll to achieve a cooling effect. In addition to the air knife, the cooling water is sprayed directly onto the air bag, and there is a cooling method such as a hollow blow.
The rework extension of the finished product will enhance the effect. For example, the belt is driven by the front and rear rolls to create a stretch, and the stretched stretch of the finished product is not easily torn, but the transverse direction is easily torn. The molecular weight distribution also affects the elongation during high speed production. All extruded products, including fibers, have unequal elongation. Vacuum and pressure forming can also be considered as another form of extension.
6, shrinkage rate
Any raw material has a problem of shrinkage due to thermal expansion and contraction and internal stresses caused by crystal formation.
In general, thermal expansion and contraction are easier to overcome and can be extended during processing to extend the cooling time and maintain pressure continuously. The crystalline starting material tends to have a larger shrinkage difference than amorphous, and is about one thousandth in terms of PP. 16 years old, but ABS is only four thousandths, the difference is very big. This part should be overcome on the mold or additives often added to reduce shrinkage. Extruded sheets are also often added with LDPE to improve necking problems.