In the process of PE pipe production, PE pipe manufacturers always produce some pe pipes with rough surface. In order to solve this problem, today I will analyze the reasons for you:
Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.
1. First, remove the roughness caused by moisture. Only for PE new materials.
2. PE pipe roughness only occurs on a very thin layer on the surface, which is also a kind of melt fracture, but it is different from the usual melt fracture. The usual melt fracture is that the entire melt has unstable flow, and the surface roughness only occurs on a very thin layer on the surface of the pipe. The roughness of the pipe is formed in the die section. When the surface of the PE pipe is smooth, the molecules on the surface of the melt must reach a certain degree of relaxation before exiting the mold.
3. Physical explanation of PE pipe surface roughness
A. Roughness is caused by the friction between the melt and the mold surface and has nothing to do with the surface roughness of the mold. This friction is caused by the adhesion between the melt and the metal surface of the mold.
B. Lubricant is needed to finish the surface of PE pipe.
The low-viscosity high-density polyethylene can form a lubricant on the surface of the die as the extrusion progresses. Because the molecular chains of low-viscosity polyethylene have relatively few entanglement points, as the extrusion progresses, under the action of the mold surface, part of the molecular chains will be separated from the melt and "hang" on the surface of the mold to form a lubricant , which is dynamically balanced. For high-viscosity polyethylene, due to the strong entanglement between the molecular chains, the molecular chains are not easily separated from the melt, so effective lubrication cannot be formed, and the surface of the pipe will be very rough.
C. The high-viscosity polyethylene has a rough surface.
Take a molecule from the surface of the melt as the test object. One end of this molecule adheres to the surface of the mold, and the other end is entangled with other molecules, so that force exists at both ends of this molecule. Due to the strong entanglement of high-viscosity polyethylene, the adhesion of the molecule to the mold surface is sliding, and the molecule is "straightened". Once the melt exits the mold, the adhesion between the melt and the mold surface will disappear, and the entanglement between the molecule and the surrounding molecules still exists. Since the molecule has been in a stretched state before exiting the mold, it cannot be bent in time after the exit mold. Only after the exit mold can it be bent. The result of the bending of the exit mold is the formation of pits on the surface of the pipe. To make high-viscosity polyethylene smooth, only additional lubricants are needed. The better method now is to add solid lubricants (polytetrafluoroethylene).
D. The friction between the melt and the die is also the cause of die accumulation.
The above are the reasons for the rough surface of the PE pipe. For these reasons, the corresponding measures can be taken to solve the problem of the rough surface of the PE pipe. We hope to provide you with some help. If you have any demand, please call us for detailed inquiry. We will provide you with professional equipment procurement suggestions and technical guidance.