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What is the reason for the peeling of plastic products?

Views: 94 Author: WJM Publish Time: Origin: WJM

Looking at the three major reasons for peeling of plastic products

1: caused by plastic pollution during injection molding

When the plastic is polluted, this is very simple, the ABS plastic and the PC plastic are not sufficiently blended, and there are pollution sources in the middle, which leads to the delamination of the ABS plastic and the PC plastic, and finally leads to the peeling of the plastic.

PVC

2: Caused by improper mold design during injection molding

During injection molding, if it is found that the mold design is improper and the shell wall is too thin, in the case that ABS plastic and PC plastic are fully integrated, if the design is too thin, the plastic shell may also be delaminated, which will eventually lead to the phenomenon of plastic peeling.

macbook case (4)

3: The injection molding process fails to meet the requirements during the injection molding process.

If the process is immature, the rupture of the fluid and the separation of the two phases will occur under high high shear, and then the phenomenon of delamination and peeling will occur.

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Focus on fluid rupture

The main reason for peeling is nothing more than caused by the injection molding process. This is understandable. When the plastic product has been formed, the peeling rarely occurs now. Unless the quality of the plastic is too poor, it will not occur again after molding. Skin phenomenon. Let's analyze the reasons

The ultimate cause of plastic peeling is melt rupture. After the rupture, the temper phenomenon we see will appear. So why is there melt rupture?

When PC plastic and ABS plastic are polymerized, a polymer is formed. This plastic cup is extruded for injection molding, or we can say that before being injected into injection molding, the polymer plastic extruded through the die and gate at this time has a smooth At the same time, it has a uniform shape, and the fluid shear at this time is relatively normal.

When the fluid shear force increases, the shear stress also increases at the same time. When the two of them increase to a certain required value, the extruded plastic will have adverse reactions at this time, and the surface of the extrudate will lose its luster. We touch the plastic with our hands. The surface of the casing will feel rough.

When the fluid shear force increases again, the extrusion rate of the extrudate increases again. At this time, there will be many irregular nodes on the surface of the extruded plastic product, sometimes there will be distortion, and sometimes there will be The most unimaginable phenomenon of the slub pattern is the occurrence of fracture and fragmentation. The result is that the plastic is broken into pieces, column segments, and the plastic zero boundary point that appears at this time is called melt fracture.

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From the above three points, we can draw some conclusions

1: When the shear stress is low, the plastic particles will have a small disturbance, and this small disturbance will have little effect after the injection molded product.

2: When the shear stress changes, when they become larger, the instability of the plastic particles increases. It can be seen that the fusion of ABS plastic and PC plastic is unstable and the uncertainty increases with the increase of temperature.

3: When the shear stress rises to a certain level, it will reach the zero boundary point, which will cause the rupture of the fluid

Summarize

An important reason for peeling: PC plastic and ABS plastic can only be partially fused. As the temperature increases, the degree of fusion becomes higher. After reaching a certain temperature, the degree of fusion becomes lower. Melting point rupture occurs.


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