company news about Why white edge iccured when the PPR water pipe is cut?

hen we cut PPR water pipes with pipe scissors, we often see white edges, just like the picture above. Many people say that there is a problem with such water pipes, which is the reason why the material is not good and calcium powder is added. Is that so? Let me tell you about it today.

This phenomenon of white edges on the incision usually occurs on colored water pipes, but it is not easy to see in white PPR water pipes. It is not because the white PPR pipe does not have it, but the white pipe itself is white, so it is not easy to see It appears to have a white border.

So, what is the reason for this white border?

In fact, this phenomenon has a professional term in polymer physics, called "crazing phenomenon".

The crazing phenomenon is a unique property of polymers. It means that under the action of tensile stress, the polymer produces local plastic deformation due to stress concentration in some weak parts of the material, so that it is perpendicular to the stress direction on the surface or inside of the material. The phenomenon of fine grooves or "cracks" with a length of 100 μm, a width of about 10 μm, and a thickness of about 1 μm appears on the surface.

When we cut the PPR water pipe, when the blade cuts the water pipe longitudinally, it will also generate a tensile stress in the transverse direction, which causes the PPR material to produce silver streaks at the incision. To put it more simply, when the PPR material is sheared longitudinally, there is a force in the transverse direction, which pulls the material a bit, and this pulling produces plastic deformation.

What is plastic deformation? Plastic deformation is relative to elastic deformation. Elastic deformation means that it can return to its original state after deformation, while plastic deformation cannot be restored.

Due to the difference in the refractive index of the part where the silver streak occurs is different from that of the normal PPR material, it exhibits a silvery white luster under light irradiation. To make an image metaphor, glass is transparent, but broken into glass slag is the existence of white powder, which will be easier to understand.

A characteristic of the part where the crazing phenomenon occurs is reversibility. It can disappear by itself above the glass transition temperature of the material, which is called "self-healing". So, for the water pipe cut that produces silver streaks, if you blow it with a heat gun for a while, the silver streaks will disappear naturally.

It is a normal physical phenomenon that there is a white edge on the cut of the PPR water pipe. If your scissors are sharp enough, or if you cut fast enough to minimize the lateral stress pull during the undercut, the crazing will be much lessened or invisible.