When cutting PPR water pipes, it is often seen that the cut has a white edge. Many people think that this is a problem with the quality of the water pipe. But is it really so? IFAN will explain it for you.
The white edge phenomenon 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 the length of 100 μm and the width of about 10 μm appear on the surface or inside of the material perpendicular to the stress direction. The phenomenon of microscopic grooves or "cracks" with a thickness of about 1 μm.
When cutting the PPR water pipe, the blade cuts the water pipe longitudinally, and a tensile stress is also generated in the transverse direction. This force causes the PPR material to produce crazing at the incision, that is, plastic deformation. Because the refractive index of the part where the white edge phenomenon occurs is different from that of the normal PPR material, it will show a silvery white luster when exposed to light. A feature of the part where the white edge phenomenon occurs is reversibility. It can disappear by itself above the glass transition temperature of the material, which is called "self-healing". Therefore, for the water pipe incision that produces silver streaks, blow it with a hot air gun for a while, and the white edge will disappear naturally.
