Crazing phenomenon of PPR water pipe

The crazing 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. 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 will show a silvery white luster when exposed to light. 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". Therefore, for the water pipe incision that produces silver streaks, blow it with a hot air gun for a while, and the silver streaks will disappear naturally.